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VAV Terminal Control Applications Application Note

1. Discharge Hot Deck Air Setpoint CFM Setpoint lt gt Discharge Air Prop Band VAVGR12B Figure 24 Discharge Air Low Limit Schedule 70 VAV Terminal Control Applications Application Note Water System Flush Configurations that control water valves and that are targeted for VAV1xx 1 controllers include logic to simplify the processes of flushing and balancing building heating water systems Incremental proportional and two position normally open and normally closed heating outputs are affected by this feature Flush logic does not control multiple stage heating outputs but does control single stage configurations since the HVAC PRO heating questions use the same answer for both single stage and two position normally closed valves Note Do not activate this feature in configurations controlling single stage electric heat If activated single stage heat energizes and if an insufficient volume of air flows over the coil overload protection is tripped This may require replacement of fusible links This feature uses two configurable and adjustable parameters Table 21 Water Flush which is a binary data point is used to select either the appropriate heating command or the value of an analog data point Flush Position to be sent to the heating output logic When Water Flush has a value of one or enable the Flush Position value is sent to the incremental proportional and two position heating control logic Tabl
2. The Temporary Occupancy pushbutton is built into the TE 6400 Zone Sensor The button is wired in parallel to the zone temperature sensor When pushed it momentarily shorts out the zone sensor which signals the controller to enable the Temporary Occupancy mode and sets Temp Occ Status and Occupied Status to on Notes Holding the TE 6400 Temporary Occupancy button in for more than 1 5 seconds initiates Failsoft and results in nuisance alarms at the Zone Terminal or the supervisory system because of zone sensor unreliability You cannot cancel Temp Occ When the Temporary Occupancy button is pressed during Unoccupied or Standby modes the TMZ1600 instructs the controller to go into Temporary Occupancy Mode When the TMZ1600 receives acknowledgment from the controller that it is in Temporary Occupancy mode then the LCD Temporary Occupancy symbol will come on and the Occupied Comfort Setpoint will be enabled for the duration of the Temporary Occupancy time If the controller does not sense an Occupied condition when the Occupancy timer expires the controller will be released back to the previous mode either Unoccupied or Standby However if the Temporary Occupancy button is pressed again during the Temporary Occupancy time period and the controller does not sense an Occupied condition it will return its previous mode either Unoccupied or Standby For more information on the TMZ1600 see the Room Sensor with LCD Display TMZ1600
3. gt Baseboard Prop Band Prop Band Actual Setpoint disch 3 Figure 20 Discharge Temperature Reset Integral Discharge Temperature Control A deadband is utilized in discharge temperature control for stabilization The default discharge temperature deadband is 2 F Discharge temperature error is evaluated This error is used to hold or slowly vary the percentage of cold deck from the calculated discharge flow setpoint Actual Disch Flow Setpt less any ventilation provided by the hot duct HD Min Vent to any minimum ventilation provided by the cold duct CD Min Vent in order to control discharge temperature The cold duct flow setpoint is determined by multiplying the percentage by the Flow Span Range Actual Disch Flow Setpt HD Min Vent CD Min Vent and then adding that value to CD Min Vent The hot duct flow setpoint is determined by subtracting the resultant cold duct flow setpoint from the Actual Disch Flow Setpoint Overriding the cold deck via the preset does not affect the hot deck setpoint VAV Terminal Controller Applications Application Note 65 Discharge temperature is evaluated as shown in Table 20 Table 20 Discharge Temperature If This is True Do This If the discharge temperature is greater than setpoint plus Increment of CD deadband If the discharge temperature is within the setpoint the Hold of CD deadband If the discharge temperature is less than setpoint minus Decrement of CD deadband The
4. DAR Cold Deck Flow Sensor Inc Damper Cold Deck Flow Sensor Cold Deck Flow Sensor Inc Damper Cold Deck Flow Sensor UDF Prop Damper Damper Control Damper Control Damper Control Constant Volume Separate Dampers DAR DAR DAR DAR DAR DAR Cold Deck Flow Sensor Inc Damper Cold Deck Flow Sensor Cold Deck Flow Sensor Inc Damper Cold Deck Flow Sensor UDF Prop Damper Damper Control Damper Control Damper Control Constant Volume Linked Dampers Single Duct Indep Cold Deck w Conver Dependent sion Hot Deck Damper Control Incr Damper Damper Control Incr Damper Incr Damper Damper Control Damper Control Damper Control 104 Group Para Cont meter Point Default Location Value Cold Deck Damper Control Cont Cold Deck Flow Setpts Discharge Set Points Cold Dk BD 236 Override Cold Dk ADF 236 Preset Cold Dk ADF 191 Prop Band Cold Dk AO 8 Setpt Occ CD ADF 144 Clg Max Occ CD ADF 143 Clg Min Occ CD ADF 145 Htg Min Unocc CD ADF 149 Clg Max Unocc CD ADF 148 Clg Min Unocc CD ADF 150 Htg Min Constant Volume Setpts Occupied ADF 143 Flow Setpt Unoccu ADF 144 pied Flow Setpt Warmup ADF 145 Flow Setpt Actual ADF 36 Disch Setpt Low Disch ADF 172 Setpoint Disch ADF 139 Reset Band Disch Air ADF 194 Deadband DA ADF 200 Tempera ture Tuning Actual ADF 25 Disch
5. Hot Dk ADF 35 0 0 cfm Average Average Flow Error Flow Error Flow Error Diag Diag Hot Dk ADF 34 0 0 Actuator Actuator Runtime Hours Runtime Runtime Diag Diag Temp Error ADF 32 0 0 F Average Average Temp Error Temp Error Diag Diag Zone Temp ADF 243 9600 Moving Moving Filter Value Ticks Temp Error Temp Error Volume Damper Config Vol Dmp ADF 158 0 35 sq ft Damper Area Control Vol Dmp ADF 22 5 0 Incr Damper Damper DB Vol Dmp ADF 159 2 25 Damper Mult Control Vol Dmp ADF 141 2 0 Min Incr Stroke Damper Time Volume Damper Control Vol Dmp AO 4 0 0 Incr Damper Damper Cmd Vol Dmp ADF 142 50 cfm Damper Deadband Control Vol Dmp ADF 15 0 0 cfm Damper Flow Control Vol Dmp ADF 192 16 Damper Integ Time Control Vol Dmp BD 236 0 0 Damper Override Disable Control Vol Dmp ADF 236 0 0 cfm Damper Preset Control Vol Dmp ADF 191 1600 Damper Prop Band cfm Control Vol Dmp AO 8 0 0 cfm Damper Setpt Control Continued on next page 112 Group Para Cont meter Point Location Volume Damper Setpts Occupied cfm Unoccu pied cfm Warmup cfm ADF 143 ADF 144 ADF 145 Warmup Damper Setpts Warmup Bbd Min Warmup Clg Max Warmup Clg Min Warmup Htg Max Warmup Htg Min ADF 157 ADF 154 ADF 153 ADF 156 ADF 155 Water System Maintenance Flush Position Water Flush ADF 239 BD 239 Zone Cooling Setpoints Actual Clg Setpt Clg Integ Time Clg Integ Time Clg Prop Ban
6. Max Unocc ADF 180 0 000 DAR Cooling cfm Minimum Unocc ADF 1814 100 000 DAR Heating cfm Max Warmup ADF 154 400 000 DAR Cooling cfm Max Warmup ADF 155 100 000 DAR Cooling cfm Minimum Warmup ADF 156 200 000 DAR Heating cfm Max Occupied ADF 143 400 000 DAR Flow Setpt cfm Unocc ADF 144 100 000 DAR Flow Setpt cfm Warmup ADF 149 400 000 DAR Flow Setpt cfm Warmup ADF 210 100 000 DAR Heating cfm Minimum Unocc ADF 211 0 000 DAR Heating cfm Minimum Occ ADF 212 100 000 DAR Heating cfm Minimum Continued on next page Group Para Cont meter Box Minimum Set Pts Occ CD Min Vent Occ HD Min Vent Unocc CD Min Vent Unocc HD Min Vent Warmup CD Min Vent Warmup HD Min Vent Cold Deck Config Cold Dk Box Area Cold Dk Damper DB Cold Dk Mult Cold Dk Stroke Time Cold Dk Velocity Point Location ADF 145 ADF 179 ADF 150 ADF 183 ADF 152 ADF 153 ADF 158 ADF 22 ADF 159 ADF 141 ADF 27 Cold Deck Damper Control Cold Dk Damper Cmd Cold Dk Deadband Cold Dk Flow Cold Dk Integ Time AO 4 ADF 142 ADF 15 ADF 192 Continued on next page VAV Terminal Controller Applications Application Note 103 Default Value 0 000 cfm 0 000 cfm 0 000 cfm 0 000 cfm 0 000 cfm 0 000 cfm 0 35 sq ft 5 0 2 25 2 0 Min Calculated 0 0 50 cfm 0 0 cfm 16 Pressure Indep DAR DAR DAR DAR DAR
7. 50 0 cfm 0 0 cfm 16 0 0 0 Disable 800 0 cfm 0 0 cfm 0 0 cfm Calculated 30 0 Minute 0 Off 30 0 Minute 00 00 Hr Mn 00 00 Hr Mn 1 On 0 Unocc 1 0 Minute Pressure Pressure Dependent w Independent Feedback Exhaust w Incremental Damper Exhaust w Incremental Damper Exhaust Exhaust UDF Exhaust Exhaust w Incremental Damper Exhaust Exhaust Exhaust Exhaust Exhaust Exhaust Exhaust UDF Boost Mode Boost Mode Temporary Occupied Mode Occupied Mode Occupied Mode Occupied Mode Always Power Fail Restart Boost Mode Boost Mode Temporary Occupied Mode Occupied Mode Occupied Mode Occupied Mode Always Power Fail Restart Pressure Dependent w o Feedback Boost Mode Boost Mode Temporary Occupied Mode Occupied Mode Occupied Mode Occupied Mode Always Power Fail Restart VAV Terminal Controller Applications Application Note 91 Pressure Pressure Dependent Dependent Group Point Default Pressure w w o Cont Parameters Location Value Independent Feedback Feedback Modes Cont Restart Status BD 21 0 Off Power Fail Power Fail Power Fail Restart Restart Restart Shutdn Box Close BD 230 0 Off Shutdown Shutdown Shutdown Command Shutdn Box Open BD 229 0 Off Shutdown Shutdown Shutdown Command Shutdown Status BD 23 0 Off Shutdown Shutdown Shutdown Standby Command BD 228 0 Off Standby Standby Standby Mo
8. 8 1577 16 16 45 8 2463 16 16 45 8 3548 16 16 45 8 4827 16 16 45 8 6309 16 16 45 Supply Band Integ Time VAV1xx 0 EDA 2040 or M9104 Supply Deadband 17 10 10 10 39 24 24 24 69 42 42 42 109 65 65 65 157 94 94 94 213 128 128 128 279 167 167 167 VAV1xx 1 EDA 2040 or M9104 Supply Deadband 10 10 10 10 24 24 24 24 42 42 42 42 65 65 65 65 94 94 94 94 128 128 128 128 167 167 167 167 VAV1x1 x EP 8000 Supply 37 Deadband 10 10 10 24 24 24 42 42 42 65 65 65 94 94 94 128 128 128 167 167 167 38 VAV Terminal Control Applications Application Note Exhaust Boxes The controller uses flow differential to set the relationship between the supply and exhaust control loops Figure 6 A flow differential greater than zero provides a negative room pressure A flow differential less than zero provides a positive room pressure You can select separate occupied and unoccupied differential setpoints This allows you to change zone pressurization simply by changing modes For single duct applications the exhaust setpoint tracks the sum of the supply flow and the differential setpoint Dual Duct applications substitute total flow hot deck and cold deck for the supply flow Note Shutdown does not directly affect the exhaust damper control loop During shutdown the exhaust damper continues to track the supply flow Calculate the
9. Parallel Flow ong On Off Proportional Temp Flow w SP w SP il w SP i w SP v v v y Select exhaust damper output type None Binary outputs Analog output Binary outputs incremental prop control incr control control with diag with diag d y y gt Type of heating for the application None Baseboard heat only Box heat only Both baseboard and box heat Select type of baseboard heat Select type of baseboard heat Incremental Normally Normally Proportional Incremental Normally Normally Proportional open valve closed valve open valve closed valve pw Select type of box heat Incremental Proportional Normally Normally closed 2 stages 3 stages open valve valve single stage v Go To Common Single Duct B SDFLOW Figure 25 Single Duct Configuration Flowchart Part I 80 VAV Terminal Control Applications Application Note Select the damper output type M Binary Outputs Analog Output incremental control proportional control Type of heating for the application v v v v v None Baseboard heat only Box heat only Both baseboard e and box heat Select type of baseboard heat Select type of baseboard heat Incremental Normally Normally Proportional Incremental Normally Normally Proportional d open valve closed valve open valve closed valve 4 Yy Select type of box heat Normally Norma
10. Single Single Zone Zone Setpt Setpt www johnsoncontrols com Published in U S A
11. Supply Detta P 4005 Area FlowHood cfm Example The flow hood reading 300 cfm The Supply Delta P 0 10 inches W C The Area 0 349 sq ft 300 Calculation results outside the range of 0 5 to 13 indicate likelihood of other problems See the Airflow Test and Balance Concerns topic in this section x 2 Supply Multiplier 0 10 0 005 ke sl 2 06 Supply Multiplier Metric SI Calculation for Delta P Sensor Two methods are available The first Fixed Flow Coefficient Method is applicable to all pressure independent paths and adjusts Supply Multiplier to compensate for the fixed value 4005 flow coefficient The second method User Defined Flow Method applies to User Defined Flow paths using Delta P sensors These paths allow user definition of the flow coefficient 1 Fixed Flow Coefficient Method Each variable can be converted to metric as shown below Supply Delta P pascals 248 84 Delta P inches W C Supply Area sq meters 0 0929 a Area sq ft Supply Flow liters sec 0 4720 flow hood reading cfm Example Convert Supply Delta P Als Use the Analog Input modify screen to change high output range for the Delta P sensor to readout in pascals as shown below 124 42 248 84 0 5 inches W C for 0 5 inch sensors 373 26 248 84 x 1 5 inches W C for 1 5 inch sensors VAV Terminal Controller Applications Application Note 31 The other two variables can be converted as shown below Exa
12. The mode generator also selects which flow setpoint schedule supplies the flow proportional integral loop during the Occupied Unoccupied Warmup Standby Shutdown and Auto Zero modes The temperature control loop sequencer compares the zone temperature to the zone setpoint and produces a 0 to 100 output command The output command feeds into the flow setpoint reset schedules to provide a supply flow setpoint during the Occupied Unoccupied and Warmup modes The flow control loop compares the supply flow setpoint from the reset schedule to the actual flow calculated from the differential pressure input and produces a 0 to 100 command to the damper The user defined flow path allows the user to define the flow sensor type and ranging In addition to differential pressure measurement this allows use of linear and non linear sensors with outputs ranged in flow or velocity The user must enter the appropriate constants for the sixth order polynomial to linearize the sensor Then the user enters the flow coefficient box area and indicates whether the box area should be used in the calculation Box area is used to calculate flow loop tuning parameter values so the area must be accurately entered even when not required to calculate flow Setting the flow coefficient to 0 zero disables square root extraction For more information regarding flow control parameter formulas see previous topics in this document beginning with the Flow Loop Tun
13. Typically VAV box manufacturers provide a pressure switch to lock out electric heat in the absence of inlet static pressure but this does not ensure adequate airflow The logic is provided for staged and 2 position heating options since both may control electric heat The function provided depends on the main box strategy selected e In pressure independent boxes box heat is enabled when the measured flow is greater than the presently selected heating minimum flow setpoint minus 1 25 times Supply Deadband Box heat is disabled when the flow drops below the presently selected heating minimum flow setpoint minus 1 5 times Supply Deadband VAV Terminal Controller Applications Application Note 53 In pressure dependent with feedback boxes with incremental binary damper box heat is enabled when the measured actuator position is greater than the presently selected heating minimum position setpoint minus 1 25 times Damper Deadband Box heat is disabled when the actuator position drops below the presently selected heating minimum position setpoint minus 1 5 times Damper Deadband In pressure dependent with feedback boxes with analog damper outputs there is no feedback Since the analog output and corresponding actuator is proportional feedback is not required No additional logic is used to enable box heat in this application because damper position feedback is not provided and because analog actuators respond quickly In pressure dependent
14. accuracy differential pressure meter VAV Terminal Controller Applications Application Note 13 e Perform a duct traverse as detailed in 1997 ASHRAE Handbook Fundamentals Chapter 14 I P Edition VAV Application Logic A collection of logic modules has been created specifically for the VAV application These logic modules fall into three categories e shared modules for both Single Duct and Dual Duct applications e Single Duct application modules e Dual Duct application modules The modules are loaded into a downloadable program in the order shown below in Table 1 Each set of modules has options that are selected by the user during the Question and Answer session Table 1 User Selected Options Module Name Module Type Shared Single Duct Dual Duct Module Module Modules Shutdown Mode X Power Fail Restart Mode Occupied Unoccupied Mode Temporary Occupied Mode x x Xx Xx Boost Warmup Mode X X Setpoint Calculation X x lt Temperature Control Loops X X Damper Control Pressure Independent X Pressure Dependent X without Feedback Pressure Dependent with X Feedback Pressure Independent X Cold Deck w Pressure Independent Hot Deck Constant Volume Separate X Dampers Constant Volume Linked X Dampers Single Duct Conversion X Ind Cold Deck with Dep X Hot Deck Fan Control X Exhaust Box Control X Baseboard Heat X Box Heat Control X Lighting Control X 14 VAV Terminal Control Applications Application
15. four hours This parameter is not modifiable by the user If a large value persists over time it is an indication of a malfunction in the zone temperature control loop Single and Dual Duct Moving Average Zone Temp Error The Moving Average Zone Temperature Error is available in the single duct pressure independent or dual duct pressure independent constant volume separate dampers incremental actuator path The following parameter shows up in the VAV Box Diagnostics group while in the Commissioning mode e Moving Avg Zone Temperature error xxxx Deg F VAV Terminal Controller Applications Application Note 75 Conditions for Moving Average Zone Temperature Computing There are situations during which this diagnostic will be suspended They are when the e zone temperature sensor is unreliable e mode is not Occupied or Standby e mode is in Shutdown Box Open or Close The Moving Average Zone Temperature Error stops changing if the zone temperature sensor becomes unreliable The diagnostic resumes automatically when the sensor is again reliable The zone sensor indicates the standard unreliable value under the Analog Input grouping 76 VAV Terminal Control Applications Application Note Procedure Overview Table 22 Using VAV Applications To Do This Follow These Steps Calculate User Defined Flow Range the input in units of the input signal Parameters for Other voltage Determine if Auto Zero will be used Non Linear Sensors to z
16. 1 Figure 9 Control Sequence for Pressure Dependent Systems without Actuator Feedback VAV Terminal Controller Applications Application Note 47 Mode of Operation Generator Occupied Temporary Occupied Standby Boost Unoccupied Power Fail Restart Shutdown Warmup Cooldown Summer Winter Setpoint Selector Zone Cooling Setpoint Zone Heating Setpoint Temperature Control Loop Cooling Prop Band Baseboard Heat Prop Band Box Heating Prop Band Cooling Integration Time Heating Integration Time Box Heating Baseboard Heating Cooling Command Command Command 0 to 100 0 to 100 Y t Summer Winter Mode Damper Logic 4 Cooling or Heating Command 0 to 100 Analog Output or 0 100 Y Incremental Actuator Controller Actuator Stroke Time min 0 10 VDC Damper Deadband Minimum Position Damper Open Damper Close pd1gem 1 Figure 10 Pressure Dependent without Actuator Feedback Control Logic Pressure Dependent Single Duct Control Logic with Feedback Figure 12 illustrates pressure dependent with feedback control logic The mode of operation generator selects which zone cooling and heating temperature setpoints are used during the selected mode of operation The mode generator also selects which reset schedule supplies the incremental actuator controller during the Occupied Unoccupied and Central System Warmup modes 48 VAV Terminal Control Applications Application Note The tempe
17. 1 to 3 Stage Box Heat Inc Valve Box Ht Command AO7 0 0 Incremental Incremental Incremental Box Heat Box Heat Box Heat Box Ht Deadband ADF 172 5 0 Incremental Incremental Incremental Box Heat Box Heat Box Heat Box Ht Stroke Time ADF 173 1 50 Incremental Incremental Incremental Minute Box Heat Box Heat Box Heat Damper Control Damper Command AO 8 0 0 Incremental Incremental Damper Damper Damper Deadband ADF 142 2 0 Incremental Incremental Damper Damper Minimum Pos ADF 140 10 0 Used Continued on next page 90 VAV Terminal Control Applications Application Note Group Cont Parameters Exh Box Configuration Exh Damper Deadband Exh Stroke Time Exhaust Box Area Exhaust Mult Exhaust Velocity Exhaust Box Setpoints Unocc Exhaust Diff Exhaust Damper Control Exhaust Command Exhaust Deadband Exhaust Flow Exhaust Integ Time Exhaust Override Exhaust Prop Band Exhaust Setpt Exhaust Setpt AO Fan Configuration Fan Velocity Modes Boost Ovrd Time Boost Status Occ Ovrd Time Occ Start Time Occ Stop Time Occupied Command Occupied Status Restart Delay Continued on next page Point Default Location Value ADF 24 ADF 164 ADF 166 ADF 167 ADF 27 ADF 169 AO 3 ADF 165 ADF 17 ADF 187 BD 235 ADF 185 ADF 235 AO 5 ADF 27 ADF 175 BD 15 ADF 174 ADI 225 ADI 226 BD 227 BD 22 ADF 184 1 25 2 0 Minute 0 35 sq ft 2 25 Calculated 200 0 cfm 0 0
18. 5 AO 5 Continued on next page VAV Terminal Controller Applications Application Note 105 Default Value 200 0 cfm 200 0 cfm 5 0 2 0 Min 0 35 sq ft 2 25 Calculated 0 0 50 cfm 0 0 cfm 16 0 0 Disable 1600 cfm 0 0 cfm 0 0 cfm Pressure Indep Exhaust Control Exhaust Control Incremental Exhaust Incremental Exhaust Exhaust Control Exhaust Control UDF Incremental Exhaust Exhaust Control Exhaust Control Exhaust Control Exhaust Control Exhaust Control Exhaust Control Exhaust Control Constant Volume Separate Dampers Exhaust Control Exhaust Control Incremental Exhaust Incremental Exhaust Exhaust Control Exhaust Control UDF Incremental Exhaust Exhaust Control Exhaust Control Exhaust Control Exhaust Control Exhaust Control Exhaust Control Exhaust Control Constant Volume Linked Dampers Exhaust Control Exhaust Control Incremental Exhaust Incremental Exhaust Exhaust Control Exhaust Control Incremental Exhaust Exhaust Control Exhaust Control Exhaust Control Exhaust Control Exhaust Control Exhaust Control Exhaust Control Indep Single Cold Duct Deck w Conver Dependent sion Hot Deck Exhaust Control Exhaust Control Incre mental Exhaust Incre mental Exhaust Exhaust Control Exhaust Control Incre mental
19. Dampers Discharge Air Low Limit Discharge Air Low Limit Discharge Air Low Limit Discharge Air Low Limit Boost Mode Boost Mode Temporary Occupied Mode Occupied Mode Constant Volume Linked Dampers Boost Mode Boost Mode Temporary Occupied Mode Occupied Mode Indep Single Cold Duct Deck w Conver Dependent sion Hot Deck Boost Boost Mode Mode Boost Boost Mode Mode Tempo Temporary rary Occupied Occupied Mode Mode Occupied Occupied Mode Mode 108 Group Para Cont meter Modes Cont Occ Stop Time Occupied Command Occupied Status Restart Delay Restart Status Shutdn Box Close Command Shutdn Box Open Command Shutdown Status Standby Command Temp Occ Status Warmup Command Point Location ADI 226 BD 227 BD 22 ADF 184 BD 21 BD 230 BD 229 BD 23 BD 228 BD 14 BD 225 Occupied Damper Setpts Occ Bbd Min Occ Clg Max Occ Clg Min Occ Htg Max Occ Htg Min ADF 147 ADF 144 ADF 143 ADF 146 ADF 145 Continued on next page Default Pressure Value Indep 00 00 Occupied Hr Mn Mode 1 On Occupied Mode 0 Unocc Always 1 0 Power Fail Minute Restart 0 Off Power Fail Restart 0 Off Shutdown 0 Off Shutdown 0 Off Shutdown 0 Off Standby 0 Off Temporary Occupied Mode 0 Off Always 0 0 cfm 500 0 cfm 100 0 cfm 100 0 cfm 100 0 cfm VAV Terminal Control Application
20. Exhaust Exhaust Control Exhaust Control Exhaust Control Exhaust Control Exhaust Control Exhaust Control Exhaust Control 106 Group Para Cont meter Hot Deck Config Hot Dk Box Area Hot Dk Damper DB Hot Dk Mult Hot Dk Stroke Time Hot Dk Stroke Time Hot Dk Velocity Point Location ADF 162 ADF 23 ADF 163 ADF 160 ADF 160 ADF 26 Hot Deck Damper Control Hot Deck Min Pos Hot Dk Damper Cmd Hot Dk Deadband Hot Dk Flow Hot Dk Integ Time Hot Dk Override Hot Dk Preset Hot Dk Prop Band Hot Dk Setpt ADF 140 AO 3 ADF 161 ADF 16 ADF 198 BD 237 ADF 237 ADF 197 AO 7 Continued on next page Default Value 0 35 sq ft 5 0 2 25 2 0 Min 2 0 Min Calculated 2 0 0 0 50 cfm 0 0 cfm 16 0 0 Disable 0 0 cfm 1600 cfm 0 0 cfm Pressure Indep Hot Deck Flow Sensor Inc Damper Hot Deck Flow Sensor Hot Deck Flow Sensor Inc Damper Hot Deck Flow Sensor UDF Prop Damper Damper Control Damper Control Damper Control Damper Control Damper Control Damper Control Damper Control VAV Terminal Control Applications Application Note Constant Volume Separate Dampers Hot Deck Flow Sensor Inc Damper Hot Deck Flow Sensor Hot Deck Flow Sensor Inc Damper Hot Deck Flow Sensor UDF Prop Damper Damper Control Damper Co
21. Flow Setpt Continued on next page 0 0 Disable 0 0 cfm 1600 cfm 0 0 cfm 500 0 cfm 100 0 cfm 0 0 cfm 400 0 cfm 100 0 cfm 0 0 cfm 400 0 cfm 200 0 cfm 400 0 cfm Calculated 55 0 F 60 0 F 2 0 F 0 025 0 0 cfm Pressure Indep Damper Control Damper Control Damper Control Damper Control Used Used Used Used Used Used DAR DAR DAR DAR DAR DAR VAV Terminal Control Applications Application Note Constant Volume Separate Dampers Damper Control Damper Control Damper Control Damper Control Used Used Used DAR DAR DAR DAR DAR DAR Constant Volume Linked Dampers Used Used Used Single Duct Conver sion Indep Cold Deck w Dependent Hot Deck Damper Control Damper Control Damper Control Damper Control Used Used Used Used Used Used Group Para Cont meter Exhaust Box Setpts Occ Exhaust Diff Unocc Exhaust Diff Exhaust Config Exh Damper Deadband Exh Stroke Time Exhaust Box Area Exhaust Mult Exhaust Velocity Point Location ADF 168 ADF 169 ADF 24 ADF 164 ADF 166 ADF 167 ADF 29 Exhaust Damper Control Exhaust Command Exhaust Deadband Exhaust Flow Exhaust Integ Time Exhaust Override Exhaust Prop Band Exhaust Setpt Exhaust Setpt AO 5 ADF 165 ADF 17 ADF 204 BD 235 ADF 203 AO
22. Incr Prop N C N O N C N O N C N O Zone Cooling Setpoints Actual Clg Setpt ADF 21 0 0 F Always Always Always CLG INTEG TERM ADF 42 0 0 Used Clg Integ Time ADF 133 1000 0 Always Always Always Clg Prop Band ADF 132 10 0 F Always Always Always COOLING PROP ADF 38 0 0 Used CMD Occ Clg Setpt ADF 129 72 0 F Separate Separate Separate Heating and Heatingand Heating and Cooling Cooling Cooling Setpts Setpts Setpts Stby Clg Setpt ADF 130 74 0 F Separate Separate Separate Heating and Heatingand Heating and Cooling Cooling Cooling Setpts Setpts Setpts Unocc Clg Setpt ADF 131 80 0 F Separate Separate Separate Heating and Heatingand Heating and Cooling Cooling Cooling Setpts Setpts Setpts Zone Heating Setpoints Actual Htg Setpt ADF 20 0 0 F Always Always Always Basebd Prop Band ADF 137 10 0 F Baseboard Baseboard Baseboard Heat Both Heat Both Heat Both Heat Heat Heat Basebd Prop Band ADF 177 0 0 F No Heat Box No Heat Box No Heat Box Heat Heat Heat BASEBD PROP ADF 40 0 0 Baseboard Baseboard Baseboard CMD Heat Heat Heat Box Ht Prop Band ADF 138 10 0 F Baseboard Baseboard Baseboard Heat Box Heat Box Heat Box Heat Both Heat Both Heat Both Heat Heat Heat Warmup Warmup Warmup Winter Box Ht Prop Band ADF 138 20 F No Heat No Heat No Heat Warmup Warmup Warmup HEATING PROP ADF 39 0 0 Used Used Used CMD HTG INTEG TERM ADF 41 0 0 Used Used Used Continued on next page 96 VAV Terminal Cont
23. Note Auto Zero x X Shutdown All VAV configurations have two shutdown options Shutdown Box Open and Shutdown Box Closed When either Shutdown mode is enabled all outputs to fans and heating are turned off Integration timers are set to 0 to eliminate windup when the system is put back into control Depending on the strategy selected the damper is controlled as defined in Table 2 Table 2 Damper Control During Shutdown Duct Type VAV Control Strategy Box Open Box Closed Single Duct Pressure Independent with and without Occ Clg Max Flow Setpoint 0 Open User Defined Flow Pressure Dependent 100 Open 0 Open Dual Duct Pressure Independent with and without HD Occ HD Htg Max 0 Open User Defined Flow CD Occ CD Clg Max 0 Open CV Sep Dampers with and without User HD Occ Flow Setpoint 2 0 Open Defined Flow and Discharge Air Reset CD HD 0 Open CU Linked Damper Occ Flow Setpoint 0 Open Single Duct Conversion Occ Clg Max 0 Open Pressure Independent Cold Deck HD 100 open 0 Open w Dependent Hot Deck CD Occ CD Clg Max 0 Open Pressure Independent Discharge Air Reset HD Occ Htg Max 0 Open CD Occ Clg Max 0 Open Occ Clg Max is Occupied Cooling Maximum Consider using Shutdown instead of de energizing Occupied during the Unoccupied period if supply fans are off and no temperature control is required VAV Terminal Controller Applications Application Note 15 Power Fail Restart This mode allows you to disab
24. Occ Clg Setpoint e Ifthe setpoint of the remote sensor becomes unreliable when in Occupied or Warmup the controller uses Occ Setpoint e Ifthe room sensor becomes unreliable the controller sets the box heat and baseboard heating commands to 0 for proportional only temperature control or integrates them to 0 for proportional integral zone control The controller sets the flow setpoint to minimum for proportional only zones For proportional integral zones calling for cooling when the temperature sensor becomes unreliable the present flow setpoint calculated from the flow reset schedule is held Starved Box Flow Saturation Flag for Single Duct Systems The Starved Box Point is a feature that warns when a zone calls for 100 flow in the Occupied mode for approximately 10 minutes Starved box is included in all single duct control strategies You can view and trend this data point at the network level to diagnose a potential problem before zone occupants actually complain of discomfort For the pressure independent strategy the flow saturation function analyzes the output of the proportional integral control routine that controls the VAV box damper When the Damper Command is equal to 100 Starved Box is set to Yes Once the Damper Command drops below 99 Starved Box is set to No VAV Terminal Controller Applications Application Note 21 If you trend the saturation flag for a VAV box and find it to be on for extensive periods of tim
25. Setpoint gt lt gt 1 3 Zone Baseboard Comfort 1 3 Zone Prop Band Prop Band Zone Prop Band Actual Setpoint a disch 2 Figure 19 Discharge Temperature Reset Integral Discharge Temperature Control A deadband is utilized in discharge temperature control for stabilization The default discharge temperature deadband is 2 F Discharge temperature error is evaluated This error is used to hold or slowly vary the percentage of cold deck from the calculated discharge flow setpoint Actual Disch Flow Setpt less any ventilation provided by the hot duct HD Min Vent to any minimum ventilation provided by the cold duct CD Min Vent in order to control discharge temperature The cold duct flow setpoint is determined by multiplying the percentage by the Flow Span Range Actual Disch Flow Setpt HD Min Vent CD Min Vent and then adding that value to CD Min Vent The hot duct flow setpoint is determined by subtracting the resultant cold duct flow setpoint from the Actual Disch Flow Setpoint Overriding the cold deck via the preset does not affect the hot deck setpoint Discharge temperature is evaluated as shown in Table 19 Table 19 Discharge Temperature If This is True Do This If the discharge temperature is greater than setpoint plus Increment of CD deadband If the discharge temperature is within the setpoint the Hold of CD deadband If the discharge temperature is less than setpoint minus Decrement of CD d
26. a reset condition The software time clock is synchronized to realtime when communicating with HVAC PRO Release 5 1 or later A permanently connected Zone Terminal ZT can also do time scheduling If communication to the ZT fails however the controller remains in last mode commanded If you do not require a backup schedule leave these two parameters at 00 00 Then if the controller loses communication it defaults to always occupied Default parameters for this mode are shown in Table 7 22 VAV Terminal Control Applications Application Note Table 7 Backup Daily Schedule Default Parameters Backup Occupancy Default Values Occupied Command Off Occupied Start Time 00 00 Occupied Stop Time 00 00 Occupied Status Off Temperature Setpoint Options The configuration Question and Answer tree segment in Figure 4 illustrates the selections available for zone temperature setpoints Define Setpoint Type v v Separate heating and Single setpoint cooling setpoints with bias v v Define Remote Al Points Define Remote Al Points None Cooling heating Warmer cooler TMZ Digital None Remote Warmer cooler TMZ Digital setpoints adjust room sensor setpoint adjust room sensor setptops Figure 4 Temperature Setpoint Options All VAV terminal control configurations use three sets Occupied Standby and Unoccupied of temperature setpoints for both heating and cooling Separate Heating and Cooling Setpoints The Separate Heati
27. discharge temperature control loop can be tuned by adjusting the deadband Disch Air Deadband and an integration time parameter DA Temperature Tuning DA Temperature Tuning has a default value of 0 025 which provides a rate of change in the cold deck flow of 2 of the Flow Span Range each 1 5 seconds The value for other rates can be calculated as DA Temperature Tuning 0 05 rate Hot and Cold Deck Flow Control Loops Independent proportional plus integral control loops are utilized to position each deck damper Proportional band integration time and deadband parameters are available to tune each deck Recommended values based on deck inlet area and damper stroke can be found in other sections of the manual 66 VAV Terminal Control Applications Application Note Constant Volume Linked Dampers The hot and cold dampers are linked together and modulated by one actuator These dampers modulate to maintain the temperature setpoint schedule per mode of operation The second actuator throttles the box outlet to maintain the constant volume setpoint The hot and cold deck dampers are controlled with one actuator mechanically linked to each damper The damper actuator is controlled directly from the zone temperature within the zone heating or cooling setpoints These setpoints also establish the control limits The VAV box opens to full heat when the zone temperature is at the heating setpoint and opens to full cooling when at the cooling se
28. effect of the damper position on space temperature is nonlinear and the space temperature controller has no control over the actual airflow to the space For example if a number of boxes on a branch duct are closing the resulting inlet pressure at the boxes remaining open increases causing more air to flow into the spaces served Thus VAV box flow is dependent on duct static pressure 6 VAV Terminal Control Applications Application Note Pressure Independent An improved VAV box control strategy employs cascaded Proportional Integral control loops The zone temperature loop samples space temperature and resets the airflow setpoint between the minimum and maximum flow settings This airflow setpoint is used by the airflow loop which samples airflow via a Differential Pressure Transmitter DPT in the box inlet and modulates the damper to control the flow Thus the VAV box flow is independent of duct static pressure The engineering basis for this method of control is that the temperature of a space with a constant load is linearly proportional to the flow of conditioned air into the space It also requires that the consulting engineer has accurately determined the required maximum and minimum flow for each space based on heating and cooling loads Airflow Measurement Common flow measurement methods applicable to VAV terminal unit control are e differential pressure based on the pressure difference created by the motion of air A
29. minimum fresh air volume requirements In colder climates exterior zones may require some form of heating Staged electric heat two position or modulated hot water coil are used to heat the air entering the zone All dual duct systems have a separate hot deck and cold deck Air supplied to the zone may be from the hot or cold deck Within the comfort zone the box may supply a blend of both decks Commonly called a VAV box this mechanical equipment modulates airflow to the space with the Johnson Controls VAV controller It is a commercially manufactured box with a control damper inlet and outlet connections and options such as flow pickups return air plenum inlet heating coil and fan A dual duct box has inlets control dampers for warm and cold air The control damper is usually a butterfly type blade The damper is controlled by rotating its shaft through a full stroke of either 90 60 or 45 degrees depending on the manufacturer Box manufacturers rate their boxes for a range of air flow based on inlet size and 1 inch W C inlet duct static pressure Pressure Dependent A VAV box control strategy where the amount of air delivered to the space is dependent upon the inlet duct static pressure as well as control damper position Pressure dependent control does not use a device to measure inlet pressure as a means to determine flow The space temperature control loop directly positions the damper Drawbacks to this system are that the
30. no feedback boxes box heat is delayed by an adjustable amount following a transition from Shutdown Box Closed You should also use the Power Fail Restart logic with this strategy to delay the heat stages following a controller reset For single stage heat the default minimum on time is 0 because hysteresis is established by the differential compare used to control the single stage Heat is turned on when the Heating Command exceeds the Box Heat On Setpt and it is turned off when the Heating Command falls below one half the Box Heat On Setpt For two and three stage heating applications the default minimum on time is 0 5 minutes AS VAV1xx 1 controllers contain logic to cancel the minimum on timer during Shutdown Box Closed and Auto Zero In older AS VAV1xx 0 controllers this needs to be changed to 0 0 to prevent the minimum on time from holding the heat on when there is no flow 54 VAV Terminal Control Applications Application Note VAV Dual Duct Applications Pressure Independent Decks with and without User Defined Flow Figure 16 illustrates pressure independent control logic The mode of operation generator selects which zone cooling and heating temperature setpoints are used during the selected mode of operation The mode generator also selects which flow reset schedule supplies both the hot and cold deck damper actuator during the Occupied Unoccupied and Warmup modes The zone proportional integral loop compares the zone tem
31. of other problems See the Airflow Test and Balance Concerns topic in this section Supply Multiplier Calculation for Sensors Ranged in Velocity or Flow In these applications the Supply Multiplier has a nominal value of 1 0 and can be adjusted slightly to match controller flow indication with the reading obtained from a flow hood Supply Flow present Supply Multiplier Supply Multiplier pply Pp Flow Hood reading Example The flow hood reading 300 cfm The Supply Flow 320 cfm The present Supply Multiplier 1 0 320 1 0 300 Supply Multiplier 1 067 Supply Multiplier Airflow Control Settings This section explains the key airflow parameters settings Figure 5 illustrates the basic inputs outputs and parameters that surround the control logic Supply Supply Box Area Multiplier sq ft Constant Differential Pressure Airflow Supply Damper FEST RE Calculation Flow 0 100 FEE Command Incremental Open Control Supply Prop Band Logic 7 Damper S Module Closed Supply Integration TIme control Actuator Time PI Temperature Supply Deadband or Control Command 0 to 100 Airflow ehre AO Reset u Minimum cfm Schedules SE We Setpoint Setpoint Device Maximum cfm _ Setpoint VAVCFM 2 Figure 5 Pressure Independent Control Logic for the Damper Actuator VAV Terminal Controller Applic
32. of flexible duct composed of wire reinforced plastic membrane may distort flow patterns and cause inaccurate flow indication This effect can be avoided if a three diameter length of straight duct is connected between the flex duct and the box inlet Extremely low air velocity this condition may be caused by attempting to control at a very low flow or it may be the result of an oversized box The minimum velocity generally accepted to accurately and reliably control VAV box flow is 400 fpm Airflow pickup problems the pickup may be blocked or partially blocked by debris in the duct Pickups could also have plugged ports or internal leaks between the high and low pressure sides of the sensor Pickup performance may suffer when the device is not perpendicular to the duct walls Differential pressure sensor calibrated without allowing one hour warmup 12 VAV Terminal Control Applications Application Note Factors Affecting the Balancer s Flow Reading The following factors may cause errors in the air balancer s flow reading Flow hood accuracy is specified by the manufacturer and may be anywhere from 5 of full scale to 3 of reading on the better instruments Periodically check flow hood calibration Find out When was it last calibrated On what type of diffuser was it last calibrated Calibrating the hood with one type of diffuser and then taking measurements on a different type of diffuser results in less
33. output pulse time for incremental actuators The VAV 1xx 0 has a minimum pulse time of 1 5 seconds and the VAV1xx 1 has a minimum pulse time of 0 5 seconds The equations that follow were used to set the defaults based on the controller minimum pulse time and the different actuator stroke times available Flow Loop Tuning Process The default tuning parameters found in Table 15 were established to ensure stable control As a result the defaults may provide a sluggish damper control loop in some cases Normally flow loop tuning is not required or recommended If you feel it is necessary the proposed process for increasing the responsiveness of the damper control loop is to adjust only the Supply Prop Band A good starting point is to cut the Supply Prop Band in half and watch the performance of the loop 36 VAV Terminal Control Applications Application Note Flow Loop Tuning Equations Note Stroke time used in the calculation must be in seconds but programmed in the controller in minutes Supply Prop Band 4520 x Box Area Supply Integ Time 0 136 Stroke Time For Incremental Damper Actuators High Supply Deadband EE for VAV1xx 0 with StrokeTime EDA 2040 High Supply Deadband JOIN Supp Acer for VAV1xx 1 with StrokeTime EDA 2040 or M9104 Low Supply Deadband maximum High Supply Deadband 2 5 or 120 Supply Area Supply deadband should fall within the above limits based on resolution and noise level For A
34. provides overdrive logic to ensure the position of the control device When the output reaches 99 the output drives 1 5 times the stroke time of the actuator to cause the device to reach its 100 position stroke time plus 50 The command must drop below 90 before the overdrive at 99 re occurs Whenever the output drops below 1 the output will be driven for 1 5 times the stroke time to cause the device to reach its 0 position The command must rise above 10 before overdrive at less than 1 will be repeated Upon controller reset incremental outputs are driven for 1 5 times the programmed stroke time to synchronize the actuator and controller calculated positions Heating values are driven closed Dampers are driven open to avoid supply duct over pressure conditions Pressure Independent Control Flow Loop Tuning Parameters HVAC PRO automatically calculates new flow tuning parameters when an upgrade of an existing VAV is performed Alternately the user can force a calculation by selecting Recalculate Flow Tuning Parameters in the Action menu Use Table 15 and the equations that follow to set the default tuning parameters for the Damper Control Flow Loop Three different controller scenarios are described e VAVI1xx 0 with an EDA 2040 Actuator e VAVI1xx 1 with an EDA 2040 Actuator or M9104 Actuator e VAVI1x1 x with an EP 8000 Transducer high volume model The key difference between the VAV1xx 0 and the VAV1xx 1 is the minimum
35. the curve and fewer points on the more linear portions If the manufacturer did not supply a graph plot the results so that you can see the knees When you have a sufficient number of data points select the two columns and using Excel Chart Wizard create an X Y plot Make sure that the first column is on the chart s X axis Open the chart and select the points plotted 78 VAV Terminal Control Applications Application Note 7 10 From the Insert menu select Trendline In Excel this will cause options to be displayed Select the polynomial function and choose an order of 6 which usually gives the best fit Also mark the options which place the function and R correlation coefficient on the chart Click on the OK button and the Trendline polynomial function and R value should be added to the plot The correlation coefficient is an indication of how well the function fits your data a value of 1 indicates a perfect fit However if you did not provide enough data points you may get a good R value but not a function that accurately linearizes the sensor To test this find a few additional points on the curve and apply the function and compare the results Build the controller configuration Normally square root extraction will not be required so the Flow Coefficient should be set to 0 0 and there will be no airflow pickup gain so the Supply Multiplier should be set to 1 0 Set the Supply Box Area to accurately reflect
36. the hot and cold deck Because of a certain zone temperature the hot deck control point could be 300 cfm which would dictate a 200 cfm control point for the cold deck When the zone temperature is half way in between the heating and cooling setpoint the control point for the hot and cold decks would be 250 cfm each This strategy does not provide minimum flow setpoints for either deck For this capability use the Pressure Independent strategy and set the flow setpoint appropriately The user defined flow path allows the user to define the flow sensor type and ranging In addition to differential pressure measurement this allows use of linear and non linear sensors with outputs ranged in flow or velocity The user must enter the appropriate constants for the sixth order polynomial to linearize the sensor Then the user enters the flow coefficient box area and indicates whether the box area should be used in the calculation Box area is used to calculate flow loop tuning parameter values so the area must be accurately entered even when not required to calculate flow Setting the flow coefficient to 0 zero disables square root extraction 58 VAV Terminal Control Applications Application Note Increasing Output Commands Cold Deck Flow Setpoint Occupied Unoccupied Warmup Hot Deck Increasing Zone Temperature Comfort Zone Actual Heating Setpoint Actual Cooling Setpoint VGRP 12 1 Figure 17 Control Sequence for C
37. two parameters e Controller Runtime e Actuator Runtime The Controller Runtime is the total time the controller has been running in hours since the last reset The Actuator Runtime is the total amount of time the incremental actuator has been pulsed open or closed since the last controller reset The display is also in hours The incremental actuator Duty Cycle can be computed by dividing the actuator runtime by the controller runtime 72 VAV Terminal Control Applications Application Note Single Duct Dual Duct This diagnostic is available only in the pressure independent incremental actuator path See Figure 25 in this document to locate the diagnostic question The parameters for single duct applications are grouped under VAV Box Diagnostics as seen in the Commissioning mode e Controller Runtime Xxxxx Hrs e Actuator Runtime Xxxxx Hrs This diagnostic is available only in the pressure independent or constant volume separate dampers incremental actuator path See Figure 28 in this document to locate the diagnostic question The parameters for dual duct applications are grouped under VAV Box Diagnostics as seen in the Commissioning mode e Controller Runtime Xxxxx Hrs e Hot Dk Runtime Xxxxx Hrs e Cold Dk Runtime Xxxxx Hrs Single Duct Dual Duct VAV Terminal Controller Applications Application Note 73 Moving Average Flow Error This diagnostic indicates the flow error of the damper control loop in the VAV box I
38. 1 0 Proportional Series Fan Fan Speed ADF 160 75 0 Proportional Series Fan Series Fan Series Fan Setpt ADF 199 1 Htg Series Fan On Off w SP Series Fan Proportional w SP Series Fan ADF 198 0 0 Htg Series Fan Differential On Off w SP Series Fan Proportional w SP Staged Heat Box Ht Command AO7 0 0 Staged Box Staged Box Staged Box Heat Heat Heat Heat Stage 1 Percent ADI 234 5 Staged Box Staged Box Staged Box Heat Heat Heat Number of Heat BD 233 2 2 Staged Box 2 Staged Box 2 Staged Box Stages Heat Heat Heat Number of Heat BD 233 3 3 Staged Box 3 Staged Box 3 Staged Box Stages Heat Heat Heat Supply Box Configuration Damper Deadband ADF 22 1 25 Incremental Damper Dmp Stroke Time ADF 141 2 0 Minute Incremental Incremental Damper Damper Supply Box Area ADF 158 0 35 sq ft Used Supply Mult ADF 159 2 25 Used Supply Velocity ADF 26 Calculated UDF VAV Terminal Controller Applications Application Note 93 Point Default Parameters Location Value Supply Damper Control TMZ Setpoint Range Unocc Damper Setpts cfm INTEG TERM ADF 36 0 0 cfm DAMPER CMD ADF 37 0 0 cfm Damper Command AO 4 0 0 Damper Position ADF 35 0 0 Supply Deadband ADF 142 50 0 cfm Supply Flow ADF 15 0 0 cfm Supply Integ Time ADF 182 16 0 Supply Override BD 236 0 0 Disable Supply Prop Band ADF 180 1600 0 cfm Supply Setpt ADF 236 0 0 cfm Supply Setpt ADF 25 0 0 cfm Supply Setpt AO AO 8 0 0 cfm Low Setpoint Limit ADF 127 65 F High Setpoint Limi
39. 4 VAV Terminal Control Applications Application Note Conditions for Moving Average Flow Computing There are situations during which this diagnostic will be suspended They are when the e Delta P sensor is unreliable e mode is not Occupied or Standby e mode is in Shutdown Box Open or Close Note Because of memory constraints the unreliable sensor check is included only in the VAVxxx 1 dual duct applications It is always included with all single duct applications The respective single or dual duct diagnostic values stop changing if the Delta P sensors become unreliable The diagnostics resumes automatically when the Delta P sensors are again reliable The Delta P sensor indicates the standard unreliable value under the Analog Input grouping Moving Average Zone Temperature Error This diagnostic indicates the zone temperature error of the space being controlled by the VAV box It is founded upon a published statistical process control equation exponential weighted moving average The name has been shortened to moving average The equation supplied in Release 4 00 and 5 00 of HVAC PRO is not supported in Release 6 00 The equation provided below is supported in Release 6 00 and later The complete zone temperature equation implemented is Moving Average new measured temp zone setpt moving average old temperature filter value moving average old The temperature filter value is a constant whose value is set to
40. DPT senses the pressure difference across a multiple port airflow pickup which typically amplifies the velocity pressure e thermal Ge hot wire based on the rate of cooling due to the flow of air over a hot body Two basic types are in use a single point duct insertion probe vs a flow through device which samples via the multiple port airflow pickup We recommend differential pressure sensing Reasonable flow measurement accuracy can be obtained at velocities above 400 fpm feet per minute and down to perhaps 200 fpm Given today s technology the temperature effect of the pressure sensor is by far the greatest contributor to error in indicated flow Thus a pressure sensor having a minimal effect due to temperature and or maintained at a relatively constant ambient temperature is desired For example using a 1 5 inch W C sensor with a temperature coefficient of offset of 0 06 of span per F a temperature variation of 3 F and an airflow pickup gain or K factor of 2 78 the flow indication error due to temperature will be less than 5 at 400 fpm and 10 at 200 fpm Also since the largest effect is upon the sensor zero this can be compensated for by an auto zero algorithm Airflow Pickup VAV Terminal Controller Applications Application Note 7 Although thermal types initially have better accuracy at low velocity they sustain a shift in calibration over time as dirt is accumulated on the sensor Additionally hot wire i
41. F Exhaust Ranging L6 ADF 226 0 0 UDF Use Exhaust Area BDF 241 1 Yes UDF Fan AZ Offset ADF 191 0 005 UDF Fan Flow Coef ADF 220 4005 UDF Fan Ranging LO ADF 211 0 0 UDF Fan Ranging L1 ADF 221 1 0 UDF Fan Ranging L2 ADF 222 0 0 UDF Fan Ranging L3 ADF 223 0 0 UDF Continued on next page VAV Terminal Controller Applications Application Note 89 Pressure Pressure Dependent Dependent Group Point Default Pressure w w o Cont Parameters Location Value Independent Feedback Feedback Analog Input Configuration Cont Fan Ranging L4 ADF 224 0 0 UDF Fan Ranging L5 ADF 225 0 0 UDF Fan Ranging L6 ADF 226 0 0 UDF Use Fan Area BDF 242 1 Yes UDF Auto Zero Configuration Auto Zero Cmd BD 226 0 Off Used Auto Zero Duration ADF 188 6 5 Minutes Used Auto Zero Enable BD 232 1 Enable Used Auto Zero Start Time ID 227 00 00 Used Auto Zero Status BD 18 0 Off Used Auto Zero Stop Time ID 228 00 00 Used Basebd Inc Valve Basebd Command AO 6 0 0 Incremental Incremental Incremental Baseboard Baseboard Baseboard Heat Heat Heat Basebd Deadband ADF 170 5 0 Incremental Incremental Incremental Baseboard Baseboard Baseboard Heat Heat Heat Basebd Stroke Time ADF 171 1 500 Incremental Incremental Incremental Minute Baseboard Baseboard Baseboard Heat Heat Heat Box Heat Box Heat On Setpt ADF 200 1 Htg Box Heat Box Heat Box Heat N O N C N O N C N O N C 1 Stage 1 Stage 1 Stage Box Ht Delay Time ADF 201 1 Minute Box Heat N O N C
42. JAHNSON Technical Bulletin CONTRELS Issue Date April 4 2003 VAV Terminal Control Applications Using VAV Applications cccccceceeeeeeeeeeeeeeeeeeeeeeeeeeseeeeeeeaeeeeeeeeeneeeees 2 Introduction s eese Eeee sE Eeo Tse EEEE EEEE EEEE EEEE a E Aai da 2 eege ee 3 Variable Air Volume VAV Controller 220 ccseeeecececcceeeeeeeeneeeeeeeeeeeeeeeesenseeseeeeeeeeetensenes 3 VAV System Operation Theory 2 2 ccccccccceccceeeeseeneseuecceceseeeneseesecceceeeneeeeeeeseeeeeedenenenseeees 4 VAV Application LOGIC tege ees d n det eege ee eebe ee 13 VAV Single Duct Applications ssssseeene ere EEN 43 VAV Dual Duct Applications sees EEN 54 Water System FIUSN EE 70 Controller Diagnos te 71 Procedure OVGRVIOW eege eege eege 76 Detailed Frocegduresg eege eege saknis uniana 77 Calculating User Defined Flow Parameters for Other Non Linear Sensors 77 Creating a VAV Single Duct Application W u sssseeeeeeeeern ne eeeee nr rn rrrrrnnne 78 Creating a VAV Dual Duct Application ssssssseeerer nerne renerne renerne 82 Troubleshooting GE 86 Point Assignments and Parameters sssssseseseseenennnnnnnnnnnnnnnnnnnnnennnnnennnnes 87 Single Duct Default Point Assignments Summary ceeeeeeeeeeeeeee eee eeenttaeeeeeeeeeeeeeeae 87 Dual Duct Default Point Assignments Summary 97 2003 Johnson Controls Inc www johnsoncontrols com Code No LIT 6375120 Sof
43. Runtime Controller Runtime HD Filter Value ADF 149 ADF 148 ADF 151 ADF 150 ADF 241 ADF 33 ADF 31 ADF 30 ADF 242 Continued on next page Default Value 0 35 sq ft 0 35 sq ft 0 0 cfm 2 25 2 25 Calculated 0 0 cfm 400 0 cfm 0 0 cfm 100 0 cfm 100 0 cfm 1200 Ticks 0 0 cfm 0 0 Hours 0 0 Hours 1200 Ticks Pressure Indep Total Deck Flow Sensor Total Deck Flow Sensor Total Deck Flow Sensor Total Deck Flow Sensor Total Deck Flow Sensor UDF Moving Avg Flow Error Average Flow Error Diag Actuator Runtime Diag Actuator Runtime Diag Moving Avg Flow Error VAV Terminal Control Applications Application Note Indep Single Cold Duct Deck w Conver Dependent sion Hot Deck Constant Volume Linked Dampers Constant Volume Separate Dampers Total Deck Flow Sensor Total Deck Flow Sensor Total Deck Flow Sensor Total Deck Flow Sensor Total Deck Flow Sensor UDF Used Used Used Used Used Moving Avg Flow Error Average Flow Error Diag Actuator Runtime Diag Actuator Runtime Diag Moving Avg Flow Error VAV Terminal Controller Applications Application Note 111 Indep Constant Constant Single Cold Volume Volume Duct Deck w Group Para Point Default Pressure Separate Linked Conver Dependent Cont meter Location Value Indep Dampers Dampers sion Hot Deck VAV Box Diagnostics Cont
44. Staged sequencing of Box Heat Stage 2 Continued on next page 88 VAV Terminal Control Applications Application Note Point Point Point Name Description Type Index Cont Binary BO 6 Htg Stage 3 3 Staged sequencing of Box Heat Stage 3 ee Box Heat Close Incremental control for Box Heat Box Heat On Off control with Normally Open Valve Box Heat On Off control with Normally Close Valve Htg Stage 2 2 Staged sequencing of Box Heat Stage 2 BO 7 Baseboard Open Incremental control for Baseboard Heat BO 8 Baseboard Close Incremental control for Baseboard Heat Table 25 Single Duct Default Parameter Assignment and Related Features Pressure Pressure Dependent Dependent Point Default Pressure w w o Group Parameters Location Value Independent Feedback Feedback Analog Input Configuration Supply AZ Offset ADF 190 0 005 User Defined Flow Supply Flow Coef ADF 213 4005 UDF Supply Ranging LO ADF 212 0 0 UDF Supply Ranging L1 ADF 214 1 0 UDF Supply Ranging L2 ADF 215 0 0 UDF Supply Ranging L3 ADF 216 0 0 UDF Supply Ranging L4 ADF 217 0 0 UDF Supply Ranging L5 ADF 218 0 0 UDF Supply Ranging L6 ADF 219 0 0 UDF Use Supply Area BDF 240 1 Yes UDF Exhaust AZ Offset ADF 191 0 005 UDF Exhaust Flow Coef ADF 220 4005 UDF Exhaust Ranging L1 ADF 221 0 0 UDF Exhaust Ranging LO ADF 211 1 0 UDF Exhaust Ranging L2 ADF 222 0 0 UDF Exhaust Ranging L3 ADF 223 0 0 UDF Exhaust Ranging L4 ADF 224 0 0 UDF Exhaust Ranging L5 ADF 225 0 0 UD
45. Table 27 Default Dual Duct Parameter Assignments Para Group meter Analog Input Config Hot Dk AZ Offset Hot Dk Flow Coef HD Ranging LO HD Ranging L1 HD Ranging L2 HD Ranging L3 HD Ranging L4 HD Ranging L5 HD Ranging L6 Use HD Area Cold Dk AZ Offset Cold Dk Flow Coef CD Ranging LO CD Ranging L1 CD Ranging L2 CD Ranging L3 CD Ranging L4 CD Ranging L5 CD Ranging L6 Use CD Area Point Location ADF 209 ADF 213 ADF 211 ADF 214 ADF 215 ADF 216 ADF 217 ADF 218 ADF 219 BDF 233 ADF 234 ADF 220 ADF 212 ADF 221 ADF 222 ADF 223 ADF 224 ADF 225 ADF 226 BDF 234 Continued on next page Default Value 0 005 4005 0 0 1 0 0 0 0 0 0 0 0 0 0 0 1 No 0 005 4005 0 0 1 0 0 0 0 0 0 0 0 0 0 0 1 No Pressure Indep User Defined Flow UDF UDF UDF UDF UDF UDF UDF UDF UDF UDF UDF UDF UDF UDF UDF UDF UDF UDF UDF Constant Volume Separate Dampers User Defined Flow UDF UDF UDF UDF UDF UDF UDF UDF UDF UDF UDF UDF UDF UDF UDF UDF UDF UDF UDF Constant Volume Linked Dampers Single Duct Indep Cold Deck w Conver Dependent sion Hot Deck 100 VAV Terminal Control Applications Application Note Indep Constant Constant Single Cold Volume Volume Duct Deck w Group Para Point Default Pressure Separate Linked Conver Depe
46. Technical Bulletin LIT 6363110 Notes Boost mode is not used with the TMZ1600 The Temporary Occupancy button will not function if the Temporary Occupancy time in the controller has been overridden by an N2 device 18 VAV Terminal Control Applications Application Note Boost If you have not configured Temporary Occupancy mode in your application you may configure the TE 6400 pushbutton for Boost mode Boost mode allows you to quickly set the controller to full heating or cooling within an area A popular application for Boost mode is a conference room where the number of people entering the room changes quickly causing major load variations in the space The Boost pushbutton which is the same pushbutton used for Temporary Occupancy is built into the TE 6400 Zone Sensor The button is wired in parallel to the zone temperature sensor When pushed it momentarily shorts out the zone sensor which signals the controller to enable Boost mode and sets Boost Status to on Note Holding the TE 6400 Zone Sensor button in for more than 1 5 seconds initiates Failsoft and results in nuisance alarms at the Zone Terminal or the operator workstation because of zone sensor unreliability When you enable Boost mode Boost Ovrd time and Boost Status points are added to the parameter table The timer starts when you release the zone sensor momentary button The timer restarts each time an occupant pushes the button Note Boost does not activate
47. VAV provides all point and control information to the rest of the network The devices communicate through the N2 Bus HVAC PRO Release 6 00 or later allows you to configure the Variable Air Volume controller with more ease simplicity and application flexibility than ever before Refer to the Getting Started on HVAC PRO chapter of the Leer e Guide to HVAC PRO LIT 6375040 for information on using the windows environment general information pertaining to starting HVAC PRO and hardware software requirements HVAC PRO Release 6 00 or later allows a VAV controller application to be downloaded with one sideloop A sideloop is a control loop where an input controls an unused output in addition to the VAV controller s main strategy For example you may want to control a humidifier based on return air humidity Since the VAV controller does not offer a humidity loop a sideloop could accomplish this task This sideloop strategy could provide an occupied setpoint and an optional unoccupied setpoint Moreover you could disable the output either from the On status of the controller s Shutdown mode or the Off status of a binary input interlock in order to prevent the humidifier from operating when no air is flowing through the VAV box If more than one sideloop is required HVAC PRO Release 5 10 or later allows downloading of a VAV terminal control configuration to a UNTI In 1 The VAV controller cannot be downloaded as a point multiple
48. accurate values Multiple diffusers served by a single VAV box when the flow hood is placed over one diffuser the hood may present an restriction causing less flow from the measured diffuser and more flow from the others In this case the balancer s sum of the readings taken at all diffusers served by the box will be less than the actual flow Error caused by slotted diffusers a slotted diffuser is easy to visually identify as it normally consists of from one to three slots each about one inch wide and two or more feet long Tests show that hood readings of slotted diffusers may be as much as 40 erroneous Perform airflow measurements for slotted diffusers using a velocity probe type of instrument rather than a hood The diffuser manufacturer s literature will specify how to measure airflow and what instrument to use Error caused by balancing damper proximity to diffuser a balancing damper mounted directly to the diffuser may cause turbulent flow patterns entering the hood and result in erroneous hood indication Use of a hood not matched to diffuser size a balancing hood consists of a flow meter and a variety of hoods designed to fit different diffuser sizes The flow meter can be interchanged among the hoods but generally the hood must completely cover the diffuser You may take two additional measurements to help find the cause of flow reading discrepancies Verify the controller differential pressure reading with a high
49. ace the static pressure in the air handling system changes It is the job of the controller at the air handler to modulate the supply fan providing the needed amount of airflow to each VAV box by maintaining the static pressure setpoint VAV systems are most easily understood by first considering them as cooling applications As the zone temperature increases and if the AHU is supplying cool air the VAV controller opens the VAV box damper to allow more cool air to reach the space The specific amount of air volume required to maintain a particular zone temperature setpoint is dictated by the size of the space and the internal and external heat loads In addition since the size of the VAV box dictates its maximum cooling capacity a VAV box s performance is dependent upon the mechanical engineer s correct box sizing for each zone If the installed unit is too small insufficient cooling results and at high flow rates audible noise may be emitted If the installed unit is too large proper control may be difficult to attain since a small change in damper position causes an excessive change in airflow Today boxes may be oversized to allow for quiet operation or reserve cooling capacity VAV Terminal Controller Applications Application Note 5 Single Duct Systems Dual Duct Systems VAV Terminal Unit Many single duct systems are cooling only When the zone temperature is below the setpoint the damper is open only slightly to provide the
50. alculation in Pressure Independent Actuator Pos Actuator feedback in Pressure Dependent with Feedback Al 5 Exhaust Delta P Pressure Differential for Exhaust Flow calculation Fan Delta P Pressure Differential for Fan Flow calculation Al 6 Box Supply Temp Box Supply Temperature Sensor for standalone Warmup in Pressure Dependent with Feedback and in Pressure Independent Binary BI 1 Occupied Occupied Unoccupied mode selection Inputs ez Standby Standby command BI 3 Shutdn Box Open Shutdown mode with Box Open command BI A Shutdn Box Close Shutdown mode with Box Close command Analog AO1 Damper Command Supply Flow Damper control Outputs Exhaust Command Exhaust Damper control AO 1 Series Fan Series Fan control AO 2 Box Heat Box Heat control Binary BO 1 Lights On Momentary output for lighting Outputs BO 2 Lights Off or BO 5 6 Momentary output for lighting BO 1 Damper Open Incremental control for Supply Flow Damper BO 2 Damper Close Incremental control for Supply Flow Damper BO 3 Series Fan On Off control for Series Fan Parallel Fan On Off control for Parallel Fan Exhaust Open Incremental control for Exhaust Damper BO 4 Exhaust Close Incremental control for Exhaust Damper Baseboard Heat On Off control with Normally Open Valve Baseboard Heat On Off control with Normally Close Valve Htg Stage 1 3 Staged sequencing of Box Heat Stage 1 BO 5 Box Heat Open Incremental control for Box Heat Htg Stage 1 2 Staged sequencing of Box Heat Stage 1 Htg Stage 2 3
51. ampers Disch Air Reset In the following paths Flow Coefficient is a parameter that is adjustable by the user Single Duct Pressure Independent User defined flow Dual Duct Pressure Independent User defined flow and CV with separate dampers User defined flow Supply Box Area Area in square feet of inlet duct where the air flow pickup is located Area may be calculated from 3 1416 1 where r is the inlet radius in feet for circular inlets See Table 12 User Defined Flow VAV Terminal Controller Applications Application Note 27 Table 12 Box Area Values for Common VAV Boxes Size in Diameter Square Feet 4 Inches 0 087 6 Inches 0 196 8 Inches 0 349 10 Inches 0 545 12 Inches 0 785 14 Inches 1 068 16 Inches 1 396 Assumes circular inlet with no constrictions This feature extends support to a wide variety of flow sensors Sensor types supported are Differential pressure Linear velocity sensor Linear flow sensor Non linear velocity and flow sensors which can be fit to a sixth or lower order polynomial equation This flexibility is facilitated by the following additional user adjustable parameters Supply AZ Offset prior to calculating flow removes the 0 005 offset caused by Auto Zero Supply Ranging LO through Supply Ranging L6 intercept and coefficients for polynomial Terms 1 through 6 Supply Flow Coef coefficient for conversion of pressure to velocity i e 4005 for flow in cfm and pressur
52. ating Heating and and and and and Cooling Cooling Cooling Cooling Cooling Setpts Setpts Setpts Setpts Setpts Unocc Clg ADF 131 80 0 F Separate Separate Separate Separate Separate Setpt Heating Heating Heating Heating Heating and and and and and Cooling Cooling Cooling Cooling Cooling Setpts Setpts Setpts Setpts Setpts Zone Heating Setpoints Actual Htg ADF 20 0 000 F Used Used Baseboard Used Used Setpt Heat Basebd ADF 137 10 F Baseboard Baseboard Baseboard Base Baseboard Prop Band Heat Heat Heat board Heat Heat Basebd ADF 137 Ok Prop Band Htg Integ ADF 139 1000 Used Used Baseboard Used Used Time Heat Htg Integ ADF 139 0 Used Time Htg Prop ADF 138 10 F Used Used Baseboard Used Used Band Heat Htg Prop ADF 138 Ort Used Band Occ Htg ADF 134 68 000 F Separate Separate Separate Separate Separate Setpt Heating Heating Heating Heating Heating and and and and and Cooling Cooling Cooling Cooling Cooling Setpts Setpts Setpts Setpts Setpts Stby Htg ADF 135 66 000 F Separate Separate Separate Separate Separate Setpt Heating Heating Heating Heating Heating and and and and and Cooling Cooling Cooling Cooling Cooling Setpts Setpts Setpts Setpts Setpts Unocc Htg ADF 136 62 000 F Separate Separate Separate Separate Separate Setpt Heating Heating Heating Heating Heating and and and and and Cooling Cooling Cooling Cooling Cooling Setpts Setpts Setpts Setpts Setpts 114 VAV Terminal Control Applications Application Note Group Para Point Def
53. ation valve is sequenced prior to resetting the discharge flow from heating minimum to heating maximum as shown in Figure 18 Tuning is facilitated by a proportional band Basebd Prop Band which must have a negative value to produce the reverse acting heating ramp Also the radiation control loop uses the zone integration time 60 VAV Terminal Control Applications Application Note Discharge Temperature and Flow Reset The zone proportional band is divided into three equal segments to reset the discharge temperature and flow As shown in Figure 19 the outer segments are used to reset the discharge flow between the heating maximum and minimum and the cooling maximum and minimum In the inner one third called the comfort zone flow is reset between the heating and cooling minimums For configurations with radiation the discharge flow setpoint is held constant while the radiation is modulated Discharge temperature is reset in the comfort zone as shown in Figure 19 CFM CFM Heating Maximum i i d Cooling Maximum Hot Deck Heating Minimum Cooling Minimum Cold Deck EE PEA on Hot Deck Minimum EE AEE E E ENEE Cold Deck Minimum gt lt gt 1 3 Zone Baseboard Comfort 1 3 Zone Prop Band Prop Band Zone Prop Band Actual ge disch 1 Figure 18 Discharge Flow Reset VAV Terminal Controller Applications Application Note 61 Temperature Discharge Reset Band Discharge Low Limit
54. ations Application Note 33 Minimum Airflow Parameter Adjustment Usually the specifying engineer or balancing contractor determines the minimum airflow setpoint necessary to provide adequate ventilation Many box control configurations provide multiple minimum setpoints In addition to the cooling minimum airflow boxes with heat and or sequenced baseboard radiation have heating and or baseboard minimum setpoints Often all need to be set to the same value Be sure to set each minimum flow setpoint appropriately as the defaults will not likely be correct for the zone Pressure independent minimum setpoints are expressed in the units of flow measurement Pressure dependent minimum setpoints are expressed in percent damper open Required minimum airflow is based primarily on the expected maximum number of occupants in the zone the minimum amount of outside air contained in the supply air building skin leakage and zone exhaust flow ASHRAE Standard 62 recommends 20 cfm of outside air per occupant in commercial buildings Typically zone airflow minimums are between 10 50 of the maximum When ventilation air is not required such as during unoccupied periods or when other sources exist the minimum may be set to zero providing tight shutoff Flow Measurement Sensor Selection For standard applications use the 1 5 inch W C DPT 2000 series sensor This provides resolution of 0 00024 inches W C for controlling at very low flows For other
55. ault Pressure Cont meter Location Value Indep Zone Set Points Actual ADF 21 Calculated Disch Air Zone Setpt Reset Only Actual ADF 20 Calculated DAR Zone Bias Zone Prop ADF 132 10 0 DAR Band Zone Integ ADF 133 500 DAR Time Ticks Zone ADF 146 0 0 F DAR Dead band Occ Bias ADF 134 2 0F Single Zone Setpt Occ Setpt ADF 129 70 0 F Single Zone Setpt Stby Bias ADF 135 4 0 F Single Zone Setpt Stby Setpt ADF 130 70 0 F Single Zone Setpt Unocc Bias ADF 136 ont Single Zone Setpt Unocc ADF 131 71 0 F Single Setpt Zone Setpt Zone Temp Damper Config Zone Dmp ADF 161 5 0 Deadbd Zone Dmp ADF 160 2 0 Stroke Minute Time Zone Temp Damper Control Zone Tmp AO7 0 0 Dmp Cmd JSHNSON CONTR LS Controls Group 507 E Michigan Street P O Box 423 Milwaukee WI 53201 Constant Volume Separate Dampers DAR DAR DAR DAR DAR Single Zone Setpt Single Zone Setpt Single Zone Setpt Single Zone Setpt Single Zone Setpt Single Zone Setpt Constant Volume Linked Dampers Single Zone Setpt Single Zone Setpt Single Zone Setpt Single Zone Setpt Single Zone Setpt Single Zone Setpt Used Used Used Indep Single Cold Duct Deck w Conver Dependent sion Hot Deck Single Single Zone Zone Setpt Setpt Single Single Zone Zone Setpt Setpt Single Single Zone Zone Setpt Setpt Single Single Zone Zone Setpt Setpt Single Single Zone Zone Setpt Setpt
56. chart Part III 81 82 VAV Terminal Control Applications Application Note Creating a VAV Dual Duct Application To create a VAV dual duct application l 2 3 4 Answer the questions as they are presented The sequence of From the File menu select New Select Application Group gt VAV Applications Select Application gt Dual Duct questions and answers is shown in Figure 28 See the Key Concepts section for more information on individual options within the question answer path VAV Terminal Controller Applications Application Note 83 Select the VAV control strategy mA Pressure Constant Volume with Pressure C V with Pressure C V with Independent separate dampers Independent separate dampers Independent separate dampers User Defined User Defined Discharge Discharge Flow Flow Air Reset Air Reset k Define discharge air low limit No Yes v y Select the damper output type v v Binary Outputs Analog Output incremental control proportional control Define flow sensor locations Define flow sensor locations Hot and cold Hot deck and Cold deck and Hot and cold Hot deck and Cold deck and deck flow total flow total flow deck flow total flow total flow v v v Define diagnostics I x None Actuator Moving Moving Runtime and Runtime Moving All of runtime avg flow avg zone moving avg and
57. d Clg Prop Band Occ Clg Setpt ADF 21 ADF 133 ADF 133 ADF 132 ADF 132 ADF 129 Continued on next page Default Value 400 0 cfm 200 0 cfm 400 0 cfm 100 0 cfm 100 0 cfm 100 0 cfm 500 0 cfm 100 0 cfm 100 0 Open 0 Disable 0 0 F 1000 10 F 0 F 72 0 F Pressure Indep Baseboard Heat Incr N O N C Baseboard Heat Incr N O N C Used Used Used Separate Heating and Cooling Setpts VAV Terminal Control Applications Application Note Constant Volume Separate Dampers Baseboard Heat Incr N O N C Baseboard Heat Incr N O N C Used Used Used Separate Heating and Cooling Setpts Constant Volume Linked Dampers Used Used Used Used Used Separate Heating and Cooling Setpts Indep Single Cold Duct Deck w Conver Dependent sion Hot Deck Used Used Used Used Used Used Used Used Used Used Used Separate Separate Heating Heating and and Cooling Cooling Setpts Setpts Continued on next page VAV Terminal Controller Applications Application Note 113 Indep Constant Constant Single Cold Volume Volume Duct Deck w Group Para Point Default Pressure Separate Linked Conver Dependent Cont meter Location Value Indep Dampers Dampers sion Hot Deck Zone Cooling Setpoints Cont Stby Clg ADF 130 74 0 F Separate Separate Separate Separate Separate Setpt Heating Heating Heating He
58. de Mode Mode Starved Box BD 16 0 No Always Always Always Summer Winter BD 231 0 Used Summer Temp Occ Status BD 14 0 Off Temporary Temporary Temporary Occupied Occupied Occupied Mode Mode Mode Warmup Command BD 225 0 Off Always Always Always Warmup Status BD 17 0 Off Warmup Warmup Warmup Occupied Damper Setpts Occ Bsbd Min ADF 147 100 0 cfm Baseboard Heat Both Heat Occ Bsbd Min ADF 147 20 0 Baseboard Heat Both Heat Occ Clg Max ADF 144 90 0 Used Occ Clg Max ADF 144 500 0cfm Used Occ Clg Min ADF 143 20 0 Used Occ Clg Min ADF 143 100 0 cfm Used Occ Htg Max ADF 146 20 0 Box Heat Both Heat Occ Htg Max ADF 146 100 0 cfm Box Heat Both Heat Occ Htg Min ADF 145 20 0 Box Heat Both Heat Occ Htg Min ADF 145 100 0 cfm Box Heat Both Heat Parallel Fan Flow Parallel Fan Flow ADF 163 0 0 cfm Parallel Fan Flow Continued on next page Continued on next page 92 VAV Terminal Control Applications Application Note Pressure Pressure Dependent Dependent Group Point Default Pressure w w o Cont Parameters Location Value Independent Feedback Feedback Parallel Fan Temp Fan Start Setpt ADF 199 1 Htg Parallel Fan Temp Parallel Fan Flow Parallel Fan Temp w SP Parallel Fan Flow w SP Fan Differential ADF 198 0 0 Htg Parallel Fan Temp w SP Parallel Fan Flow w SP Proportional Series Fan Fan Area ADF 161 1 0 sq ft Proportional Series Fan Fan Flow ADF 16 0 0 cfm Proportional Series Fan Fan Flow Mult ADF 162
59. deadband prop band and integration time for the exhaust box using the formulas in the Flow Loop Tuning Equations topic in this section of the document Note You should use one half the value of the prop band found from the equation to ensure the exhaust box responds more quickly than the supply box VAV Terminal Controller Applications Application Note 39 Supply Exhaust Velocity Velocity Pressure Pressure Flow Calculation Flow Calculation Box Area sq ft Box Area sq ft Flow K Factor Flow K Factor Supply Flow Exhaust Differential Logic Occupied Differential Unoccupied Differential Exhaust Setpoint Flow Control Loop J Auto Zero S Exhaust Prop Band a Exhaust Exhaust Integration Flow Exhaust Deadband Analog Output Incremental Actuator Controller 0 100 Actuator Stroke Time min Auto Zero Mode 0 10 VDC Damper Open Damper Close pl4gem 1 Figure 6 Exhaust Damper Control Logic 40 VAV Terminal Control Applications Application Note Auto Zero Use the Auto Zero feature to calibrate the Delta P sensor which is used to measure air flow The points used for Auto Zero are shown in Table 16 Table 16 Auto Zero Default Parameters Auto Zero Parameter Default Value Auto Zero Enable Enabled Auto Zero Command Off Auto Zero Duration 6 5 minutes Auto Zero Start Time 00 00 Hr Min Auto Zero Stop Time 00 00 Hr Min Auto Zero Status Off The controller performs the Auto Zero featu
60. des of operation If you define the Parallel Fan without setpoints the fan starts during unoccupied when the Htg Cmd gt 1 and stops below 1 If you define the Parallel Fan with setpoints w SP then the fan starts when the Htg Cmd gt Fan Start Setpt and stops when the Htg Cmd lt Fan Start Setpt Parallel Fan Differential The Parallel Fan Setpt defaults to 1 and the Parallel Fan Differential defaults to 0 You must adjust these parameters to the required values 52 VAV Terminal Control Applications Application Note Table 18 Parallel and Series Fan Status per Mode of Operation Mode of Operation Occupied and Fan Type Standby Unoccupied Shutdown Parallel Fan Temp Cycled per Box Cycled at Off Heating Unoccupied Box Temperature Heating Setpoint Setpoints Parallel Fan Flow Cycled per Flow Cycled at Off Setpoint Unoccupied Box Heating Setpoint Series On Cycled at Off Proportional Unoccupied Box Heating Setpoint Series On Off On Cycled at Off Unoccupied Box Heating Setpoint On when heating command is greater than Fan Start Setpoint Note Fan and heat control outputs operate independently when overridden Box Heat Box heat support includes incremental proportional two position valve actuators and one to three stages of electric heat Electric heat control for non fan powered boxes contains logic to avoid heat operation with inadequate airflow which otherwise could trip electrical overload protection
61. e you can diagnose the zone by following the steps below 1 Check the damper linkage to ensure the box can fully open 2 Check the static pressure near the box inlet to ensure that enough air is being delivered to the zone to maintain the maximum flow requirements 3 Check the zone cooling setpoint to ensure that it is realistic in comparison to the conditioned air being delivered to the space Lighting Logic Interlock Lighting logic interlock integrates lighting control as a start stop output to control a momentary lighting relay GE RR 7 relay On a transition to Occupied or Temporary Occupied mode the controller commands the lights on On transition to Unoccupied mode the lights blink two minutes before they turn off If you need to directly override the lighting circuit issue either the on or off command through the lights on binary output Backup Daily Schedule If you selected N2 Software Command as the Occupied mode source this feature provides a backup schedule maintains the controller s schedule If the network loses communication with the controller for more than ten minutes the controller reverts to the backup daily schedule as established in the parameter table Two parameters are used Occupied Start Time and Occupied Stop Time Note The software clock that operates inside the VAV controller is not battery backed It resets to 00 00 whenever you apply power to the controller or the controller goes through
62. e 21 Water System Flush Parameters Group Parameter Address Default Water System Water Flush BD 239 0 Disable Maintenance Water System Flush Position ADF 239 100 Htg Maintenance Note These parameters appear in all VAV configurations capable of controlling a heating valve but due to memory constraints of older controllers the associated logic is not loaded in VAV1xx 0 devices Flush has the highest priority and operates in all modes of controller operation VAV Terminal Controller Applications Application Note 71 Controller Diagnostics Duty Cycle HVAC PRO Release 5 10 or later provides three kinds of controller diagnostics These diagnostics are operator selectable or any combination thereof during the Question and Answer session The three diagnostics are e Actuator Runtime e Moving Average Flow Error e Moving Average Zone Temperature Error The logic for accomplishing these diagnostics is included as part of the controller download As a result the collection of these performance diagnostics continues until the controller is reset either from the N2 Bus or by local power cycling Since these diagnostics are for determining controller performance and do not directly contribute to control strategy they should be selected as memory permits in the VAVxxx 0 controllers Sufficient memory for all diagnostics and control logic is available in the VAVxxx 1 controllers Actuator Runtime This diagnostic consists of
63. e Dampers System Hot Dk Damper Cmd Hot Deck Damper control in Pressure Independent and Constant Volume Separate Dampers System Vol Dmp Damper Cmd Control for Damper controlling the total Air Flow in Constant Volume Linked Dampers System Zone Tmp Dmp Cmd Linked Damper control in Constant Volume Linked Dampers System Damper Command Damper control in Single Duct Conversion Exhaust Command Exhaust Damper control A point index of zero causes HVAC PRO to assign the first available point Continued on next page 98 VAV Terminal Control Applications Application Note Point Type Point Cont Index Point Name Description Binary BO 0 Lights On Momentary output for lighting Outputs Lights Off Momentary output for lighting BO 1 Cold Dk Open Incremental control for Cold Deck Damper in Pressure Independent and Constant Volume Separate Dampers System Damper Open Incremental control for Damper in Single Duct Conversion Zn Tmp Dmp Open Incremental control for Linked Dampers in Constant Volume Linked Dampers System BO 2 Cold Dk Close Incremental control for Cold Deck Damper in Pressure Independent and Constant Volume Separate Dampers System Damper Close Incremental control for Damper in Single Duct Conversion Zone Dmp Close Incremental control for Linked Dampers in Constant Volume Linked Dampers System BO 3 Ht Cl Changeover Changeover control from heating to cooling and vice versa in Single Duct Conversion Hot Dk Open Incremental control f
64. e in inches W C 1291 for flow in liters s and pressure in Pascal s Use Supply Area when set to Yes State 1 this binary flag causes the area parameter to be used as a multiplier in the flow equation The entire equation is Supply Flow Supply Box Area Flow Coefficient Maximum polynomial function Supply Delta P Supply AZ Offset 0 Supply Multiplier Supply AZ Offset is defaulted to 0 005 and can be set to 0 0 if Auto Zero will not be used The maximum function assures a positive value 28 VAV Terminal Control Applications Application Note The Supply Ranging parameters default values disable polynomial curve fits and thus are appropriate for differential pressure linear velocity and linear flow sensors LO and L2 through L6 are set to a value of 0 000 and L1 is 1 000 This reduces the equation to Supply Flow Supply Box Area Flow Coefficient Maximum Supply Delta P Supply AZ Offset 0 Supply Multiplier For a sensor having an output scaled in velocity or flow zeroing the Flow Coefficient disables square root extraction giving the following formula Supply Flow Supply Box Area Maximum Supply Delta P Supply AZ Offset 0 Supply Multiplier Rename the analog input to something more appropriate such as Supply Velocity Input along with unit and range changes required by the sensor Set the Supply Multiplier to an initial value of 1 000 For a linear flow sensor als
65. ea Cold Deck Multiplier Cooling Minimum Box Heat Minimum Cooling Maximum Box Heat Maximum Baseboard Minimum Setpoint Setpoint Prop Band Prop Band Integration Integration Deadband Deadband Hot Deck Damper Command Analog Output Incremental Actuator Control Incremental Actuator Control Actuator Stroke Time minimum Actuator Stroke Time minimum 0 100 Analog Output CA0 YDE Cold Deck Open Cold Deck Close Hot Deck Open Hot Deck Close 010 VDE pl3gem 1 Figure 16 Dual Duct Pressure Independent Separate Dampers Control Logic VAV Terminal Controller Applications Application Note 57 Constant Volume Separate Dampers with and without User Defined Flow The Separate Damper Constant Volume control strategy Figure 17 uses two separate damper actuators to modulate the hot and cold deck respectively The control algorithm controls the temperature in the zone and maintains a constant flow by proportionally resetting the hot and cold deck flow setpoints in response to the zone temperature The zone heating and cooling setpoints set the zone temperature limits for full hot deck or cold deck flow Whenever the zone temperature is between these limits the hot and cold deck flow setpoints reset equally but in opposite directions in response to the zone temperature change and thus maintain a constant volume airflow For example a 500 cfm constant volume setpoint establishes a 0 500 cfm range for
66. eadband 62 VAV Terminal Control Applications Application Note The discharge temperature control loop can be tuned by adjusting the deadband Disch Air Deadband and an integration time parameter DA Temperature Tuning DA Temperature Tuning has a default value of 0 025 which provides a rate of change in the cold deck flow of 2 of the Flow Span Range each 1 5 seconds The value for other rates can be calculated as DA Temperature Tuning 0 05 rate Hot and Cold Deck Flow Control Loops Independent Proportional plus Integral control loops are utilized to position each deck damper Proportional band integration time and deadband parameters are available to tune each deck Recommended values based on deck inlet area and damper stroke can be found in other sections of the manual Constant Volume Separate Dampers Discharge Air Reset DAR of Temperature This strategy utilizes a terminal unit discharge air temperature sensor and a temperature reset schedule to provide tight zone control and stable discharge over a wide range of hot and cold deck supply air temperatures and space loads The reset strategy is particularly well suited to cold air systems where the cold deck temperature may be less than the minimum desired air temperature delivered to the occupied space Baseboard radiation control may optionally be integrated to eliminate the effects of cold walls in exterior zones Proportional plus integral control is utilized in the z
67. ed by a single binary output with minimum On Off timers that can be set in the BO Modify screen The Proportional Series Fan uses a single analog output to the S66 speed controller The S66 has built in startup logic that sets the fan at 100 for five seconds The VAV controller turns the fan on by setting the analog output to the Fan Speed parameter value The analog output is set to 0 to turn the fan Off If you define the Series Fan without setpoints the fan starts during unoccupied when the Htg Cmd gt 1 and stops below 1 If you define the Series Fan with setpoints w SP then the fan starts when the Htg Cmd gt Series Fan Setpt and stops when the Ho Cmd lt Series Fan Setpt Series Fan Differential The Series Fan Setpt defaults to 1 and the Series Fan Differential defaults to 0 You must adjust these parameters to the required values The Parallel Fan is also referred to as fan assist The fan is off during the Shutdown and Auto Zero modes The Parallel Temp Fan is cycled on when Warmup is inactive and the internal zone heating command is greater than the value of the Fan Start Setpoint parameter defaulted to 1 The Parallel Flow Fan is also cycled on during Occupied and Standby mode whenever the flow setpoint is below the Parallel Fan Flow parameter value The supply deadband is used as a differential to turn the fan off Table 18 summarizes the relationship between the parallel and series fan types with the different mo
68. ero the sensor If so range the analog input to read 0 when flow is zero Determine the Supply AZ Offset by subtracting 0 005 from the sensor offset voltage Create a spreadsheet with two columns Enter the analog input voltage in the left column and the required readout values in the right column From the sensor manufacturer or test data determine 12 or more points on the curve When you have a sufficient number of data points select the two columns and using Excel Chart Wizard create an X Y plot Open the chart and select the points plotted From the Insert menu select Trendline From the options that display select the polynomial function and choose an order of 6 Mark the options which place the function and R correlation coefficient on the chart Click OK Build the controller configuration If the polynomial function result is in units of velocity set Use Supply Area to Yes State 1 Test the results in a controller with a real sensor in operating conditions against a reference measuring instrument of known accuracy Create a VAV Single Duct From the File menu select New Select Application Application Group gt VAV Applications Select Application gt Single Duct Answer the questions as they are presented Create a VAV Dual Duct From the File menu select New Select Application Application Group gt VAV Applications Select Application gt Dual Duct Answer the questions as they are presented VAV Terminal Co
69. fort band is effectively adjusted Software logic prevents use of biases less than 0 15 ensuring a minimum 0 3 comfort band between the Actual Heating and Actual Cooling Setpoints Actual Heating and Actual Cooling Setpoints are read only parameters that display the values presently used by the control loops See Table 9 for the Single Setpoint default values Table 9 Single Setpoint with Biases Mode Setpoint Setup Bias Resulting Resulting Values Values Actual Actual Heating Cooling Setpoint Setpoint Occupied 21 C 70 F 1 C 2 F 20 C 68 F 22 C 72 F Standby 21 C 70 F 2 C 4 F 19 C 66 F 23 C 74 F Unoccupied 22 C 71 F 5 C 9 F 17 C 62 F 27 C 80 F 24 VAV Terminal Control Applications Application Note Occupant Adjustments There are three options for providing occupant adjustment of the heating and cooling setpoints of a variable air volume controller e The first option is to provide setpoints that are only adjustable over the N2 or through a Zone Terminal There is no local adjustment hardware e The second option is to provide a TE 6400 with remote setpoints for use in Occupied mode When separate heating and cooling setpoints are chosen the TE 6400 provided will have a separate adjustment for heating and cooling setpoints When single setpoint is used the TE 6400 provided has a single remote setpoint The default range is 18 3 to 29 4 C 65 to 85 F This range can be modified fr
70. g L2 Exhaust ADF 230 0 0 UDF UDF Ranging L3 Exhaust ADF 231 0 0 UDF UDF Ranging L4 Exhaust ADF 232 0 0 UDF UDF Ranging L5 Exhaust ADF 233 0 0 UDF UDF Ranging L6 Use BDF 2441 1 No UDF UDF Exhaust Area Auto Zero Config Auto Zero BD 226 0 Off Always Always Always Always Always Cmd Auto Zero BD 232 1 Enable Always Always Always Always Always Enable Auto Zero ADI 227 00 00 Used Used Used Used Used Start Time Hr Mn Auto Zero BD 18 0 Off Always Always Always Always Always Status Auto Zero ADI 228 00 00 Used Used Used Used Used Stop Time Hr Mn Auto Zero ADF 188 6 5 Prop Prop Prop Prop Prop Time Minute Damper Damper Damper Damper Damper Duration Basebd Inc Valve Setpts Basebd AO 6 0 0 Baseboard Baseboard Baseboard Base Baseboard Command Heat Heat Heat board Heat Heat Basebd ADF 170 5 0 Baseboard Baseboard Baseboard Base Baseboard Deadband Heat Heat Heat board Heat Heat Basebd ADF 171 2 0 Baseboard Baseboard Baseboard Base Baseboard Stroke Minute Heat Heat Heat board Heat Time Heat 102 VAV Terminal Control Applications Application Note Indep Constant Constant Single Cold Volume Volume Duct Deck w Group Para Point Default Pressure Separate Linked Conver Dependent Cont meter Location Value Indep Dampers Dampers sion Hot Deck Box Flow Set Pts Occ ADF 144 500 000 DAR Cooling cfm Max Occ ADF 143 100 000 DAR Cooling cfm Minimum Occ ADF 177 400 000 DAR Heating cfm Max Unocc ADF 149 200 000 DAR Cooling cfm
71. if the temperature is in the comfort zone between the heating and cooling setpoints as shown in Figure 3 Boost cancels when the Boost Ovrd time expires or the temperature falls into the comfort zone Default parameters for this mode are shown in Table 6 Table 6 Boost Default Parameters Boost Parameters Default Values Boost Ovrd Time 5 00 minutes Boost Status Off VAV Terminal Controller Applications Application Note 19 Temperature Control Loop Output A 100 lt 4 p Heating Boost No Boost Cooling Boost Zone 0 gt Temperature i Sensor Input Actual Heating Setpoint Actual Cooling Setpoint boostmode Figure 3 Control Sequence for Boost Mode Warmup A warmup cycle can be initiated by an N2 command or through a supply air temperature sensor per VAV box The VAV controller must be in Unoccupied mode before warmup can be initiated The supply sensor can be configured to automatically initiate the Warmup mode if it senses that the supply air temperature is 5 F greater than the zone sensor During Warmup mode the central system supplies either return air or hot air to the zones to bring the building to occupied conditions Zone temperature setpoints are set to their occupied values Box heating and parallel fans are shut down Baseboard heating is available Pressure independent zones have separate flow setpoints for Warmup For pressure dependent zones without actuator feedback the controller positions
72. ing Equations topic in this section 44 VAV Terminal Control Applications Application Note CFM i Heating i i Cooling Maximum i Maximum Cooling Heating Minimum Minimum l t Baseboard Minimum Increasing 0 Zone a gt gt a La gt Temperature Box Baseboard Comfort Cooling Heating Prop Zone Prop Prop Band Band Band Actual Heating Setpoint Actual Cooling Setpoint VGRP15 1 Figure 7 Pressure Independent Sequence VAV Terminal Controller Applications Application Note 45 Mode of Operation Generator Occupied Temporary Occupied Al Al Standby Boost Unoccupied Power Fail Restart Remote Warmer Shutdown Warmup Setpoints Cooler Adjust Auto Zero or I Supply Setpoint Selector Delta P Zone Cooling Setpoint Zone Heating Setpoint Flow Calculation Supply Box Area sq ft Supply Mult Temperature Control Loop Cooling Prop Band Baseboard Heat Prop Band Box Heating Prop Band Cooling Integration Time Heating Integration Time Box Heating Baseboard Heating Cooling Command Command Command 0 to 100 0 to ee 0 to 100 Flow Setpoint Calculation Cooling Min Box Heat Min Cooling Max Box Heat Max Baseboard Min Supply Flow Supply Setpoint Flow Control Loop Y Setpoint Prop Band Supply Integration Deadband Incremental Actuator Control Analog Output Actuator Stroke Time min 0 100 Damper O
73. is desirable amplification in pneumatic flow controllers provides the force necessary to displace diaphragms Flow Multiplier VAV Terminal Controller Applications Application Note 9 Users of digital systems usually expect flow to be accurately calculated and displayed thus the exact pickup gain or K factor must be provided to the control algorithm In VAV applications we use the name Flow Multiplier for pickup gain Velocity pressure is expressed as Pvetocity Paitterential Flow Mult The equation for flow in English system units is Flow Area 4005 Prelocity where flow is in cfm area is in sq ft and Pyetocity is in inches W C Combining the two equations results in Flow Area 4005 Paitferential Flow Mult Note For metric equivalents of these equations in I s see the Airflow Calculations for Pressure Independent Applications topic later in this section Flow Multipliers for most currently manufactured VAV boxes are listed in the OEM Reference Manual FAN 638 and Appendix B VAV Controller Flow Calculation Constants LIT 6375185 in this manual These gains are for use with dead ended devices like differential pressure transducers As box designs change from time to time and also because some controls companies specify flow pickups other than what is normally supplied by the box manufacturer the published gains may not apply to existing boxes being retrofit with new controls In these cases or when using a f
74. l band a 0 100 hot deck damper command is generated In addition the control routine uses a hot deck minimum position expressed as 0 100 open The minimum position value establishes a hot deck position that is maintained even during cold deck operation Hot Deck Min Pos defaults to 2 Increase this when the hot deck is the only source of outdoor air for ventilation Heating Command 100 Hot Deck Hot Deck Minimum 0 Cold Deck Cooling Minimum Cooling Maximum Cold Deck Cold Deck Heating Minimum 4 Hot Deck Baseboard Prop Band Prop Band Actual Heating Setpoint Comfort Zone Cold Deck Prop Band Actual Cooling Setpoint x vgrp 1 Figure 23 Pressure Independent Cold Deck with Pressure Dependent Hot Deck VAV Terminal Controller Applications Application Note 69 Discharge Air Low Limit Logic The discharge air sensor option can be used with the Pressure Independent or Constant Volume Separate Damper Strategies This discharge air sensor automatically maintains the low limit setting The low limit logic may be required when the cold deck supply temperature uses 45 to 50 F air from an ice storage system The discharge air low limit automatically overrides the cold deck flow setpoint command and resets the hot deck volume to make up the difference The limiter utilizes proportional plus integral control CFM Cold Deck CFM Setpoint
75. le all outputs of the controller whenever it first receives power or resets This is useful when you are using multiple controllers in a building and you want to spread out the times when each controller energizes as part your energy management strategy You may stagger the restart delay timers per zone per floor or per area Typically a power fail restart delay is required on VAV boxes that have electric heat and or fans Power fail restart holds the controller in Shutdown Box Open mode for the time equal to the Restart Delay Default parameters for this mode are shown in Table 3 Table 3 Restart Delay Default Parameters Restart Delay Parameters Default Values Restart Delay 1 0 minute Restart Status Off When the value of the Restart Status parameters is On a Restart is in progress Note Regardless of the Power Fail Restart option the controller drives incremental damper actuators full open and incremental valve actuators full closed for 1 5 times their individual stroke times following a controller reset This is required to synchronize the incremental actuators with the controller Occupied Unoccupied Standby All box configurations provide three sets of zone temperature setpoints Occupied is the normal operating mode for occupant comfort while Unoccupied is used when the zone is vacant Note Use Unoccupied instead of Shutdown when supply air is available and or some level of temperature control is required during the U
76. lls more air from the plenum VAV box fans are of two types as shown in Figure 13 and Figure 14 and as described in Table 17 Volume Damper and Actuator IS Primary Duct Air p Air Flow Pickup Secondary Plenum Air Fan Flow Adjust Or e D Outlet e Fan Delta P a vduc 1 Optional Heating Coil Figure 13 Single Duct VAV Box Series Fan VAV Terminal Controller Applications Application Note 51 Volume Damper and Actuator IS Primary Fan Flow Duct Air Adjust Ze e e CJ Air Flow a Outlet e e Pickup ee Optional Heating Coil Secondary Plenum Air p vavduc Figure 14 Single Duct VAV Box Parallel Fan Note When used the Fan Delta P pickup is attached to the fan inlet cone Table 17 Single Duct VAV Box Fan Types Type Series Fan Parallel Fan Description The Series Fan is off during the Shutdown and Auto Zero modes The fan is always on during the Occupied and Standby modes and is cycled on during the Unoccupied and Warmup modes when the zone requires heating Before the fan is turned on the damper is driven closed for the Auto Zero Duration time to ensure that the fan is not spinning backward The on off Series Fan is controll
77. lly closed Incremental Proportional open valve __valve single stage 2 stages 3 stages v e y Y vr y Go To Common Single Duct B Figure 26 Single Duct Configuration Flowchart Part Il SDA1FLOW VAV Terminal Controller Applications Application Note Common Single Duct B Is lighting required y No Yes v y y Power fail restart logic y No Yes y y Use box supply temperature for warmup cooldown during the Unoccupied mode v No Yes y Define Sat type Separate heating and Single setpoint cooling setpoints with bias v Define Remote Al Points Define Remote Al Points wl l None Cooling heating Warmer cooler TMZ Digital None Remote Warmer cooler TMZ Digital unused setpoints adjust room sensor unused setpoint adjust room sensor v y y y gt Define Occupied mode I Software N2 Command Hardware BI Point Both with BI Backup Y Y Both can activate y Define Standby mode I Software N2 Command Hardware BI Point Both with BI Backup v v Both can activate y Define Shutdown mode y Software N2 Command Hardware BI Point Both with BI Backup v Both can activate Y Do you want the Temporary Occupied feature l No Yes Do you want Boost mode OS NOTE BDOS No Yes Ee L gt d Ser COMONFLO Figure 27 Single Duct Configuration Flow
78. low through device like a hot wire sensor contact the box manufacturer and calculate the correct pickup gain as shown below Instead of pickup gain box manufacturers will provide a number that represents the flow in cfm at 1 inch W C differential pressure and combines the gain inlet area and the constant 4005 This number can also be estimated from the graph normally attached to the side of the VAV box These graphs plot flow against differential pressure although it is often incorrectly labeled velocity pressure Calculate Flow Mult as follows 2 4005 Area Flow Mult Pgitterential Flow for flow in cfm area in sq ft and P 10 inches W C 10 VAV Terminal Control Applications Application Note During test and balance the Flow Multiplier may be adjusted to match the controller flow indication with the balancer s reading However if the two readings differ by more than 20 everyone is better served by investigating the cause of the difference Airflow Test and Balance Concerns Pressure independent VAN control jobs frequently require an accuracy within 5 10 of actual flow and indicated flow The balancing contractor must adjust and certify the flow rates specified by the consulting engineer Sometimes the balancer s readings disagree with flow indicated by the VAV controller When airflow readings disagree a problem may exist or some fact of the air delivery system may not be known or unders
79. m Damper Deadband Control Supply ADF 15 0 0 cfm Damper Flow Control Supply ADF 192 16 Damper Integ Time Control Supply BD 236 0 0 Damper Override Disable Control Supply ADF 236 0 0 cfm Damper Preset Control Supply ADF 191 1600 Damper Prop Band cfm Control Supply AO 8 0 0 cfm Damper Setpt Control TMZ Setpoint Range Low ADF 127 65 F Applicable Applicable Applicable Applicable Applicable Setpoint only if only if only if only if only if Limit configured configured configured configured configured with TMZ with TMZ with TMZ with TMZ with TMZ Digital Digital Digital Digital Digital Room Room Room Room Room Sensor Sensor Sensor Sensor Sensor High ADF 128 78 F Applicable Applicable Applicable Applicable Applicable Setpoint only if only if only if only if only if Limit configured configured configured configured configured with TMZ with TMZ with TMZ with TMZ with TMZ Digital Digital Digital Digital Digital Room Room Room Room Room Sensor Sensor Sensor Sensor Sensor Continued on next page 110 Group Para Cont meter Total Dk Config Total Dk Box Area Total Dk Box Area Total Dk Flow Total Dk Mult Total Dk Mult Total Velocity Unocc Damper Setpts Point Location ADF 158 ADF 162 ADF 19 ADF 159 ADF 163 ADF 28 Unocc Bbd ADF 152 Min Unocc Clg Max Unocc Clg Min Unocc Htg Max Unocc Htg Min VAV Box Diagnostics CD Filter Value Cold Dk Flow Error Cold Dk
80. mote VAVHDWMD DBF and VAVHDWMD NDX Setpoint question with any of the are available on The Advisor Replace the following existing files in the C Winpro Data directory Upgrade the affected controllers Note the e None application revision does not change e Cooling Heating setpoints Permanent Solution e Warmer Cooler adjust 1 Install HVAC PRO Release 7 03 This applies to any VAV Single Duct 2 Upgrade the affected controllers Note the application or any of the following application revision does not change VAV Dual Duct applications e pressure independent e constant volume with separate dampers e constant volume with linked dampers e single duct conversion e independent cold deck e dependent hot deck pressure independent user defined flow e constant volume with separate dampers user defined flow VAV Terminal Controller Applications Application Note 87 Point Assignments and Parameters Single Duct Default Point Assignments Summary Table 24 shows the HVAC PRO default hardware point assignments and options for single duct configurations Table 24 Single Duct Default Point Assignments Point Point Point Name Description Type Index Analog Al Zone Temp Zone Temperature sensor measured value Inputs A7 Cooling Setpoint Cooling Setpoint potentiometer Warm Cool Adjust Warm Cooling Adjust potentiometer Al 3 Heating Setpoint Heating Setpoint potentiometer Al 4 Supply Delta P Pressure Differential for Supply Flow c
81. moving avg flow the error temp error flow error avg zone and zone above temp error temp error i v Is there an exhaust box No Yes Select baseboard heat None Incremental Normally open valve Normally closed valve Proportional Vv Go To Common Dual Duct D DDFLOW Figure 28 Dual Duct Configuration Flowchart Part I 84 VAV Terminal Control Applications Application Note A gt Constant volume Single duct with linked dampers conversion l Binary Select the damper output type e Outputs Analog Output incremental control proportional control Is there an exhaust box y No Yes v y Select baseboard heat a Ind cold deck with dep hot deck Select the damper output type y Binary Outputs Analog Output incremental control proportional control None vY Incremental Normally open valve Normally closed valve Proportional Go To Common Dual Duct D DDFLOW2 Figure 29 Dual Duct Configuration Flowchart Part Il Common Dual Duct D VAV Terminal Controller Applications Application Note Is sek eet Power fail restart logic No Yes v y Define setpoint type Separate heating and Single setpoint cooling setpoints with bias Define Remote Al Points Define Remote Al Points T None Cooling heating Warmer cooler TMZ Digital None Remo
82. mple Calculate Metric Supply Multiplier Supply Delta P pascals 248 84 0 1 24 8 Supply Area sq meters 0 0929 0 349 0 0324 Supply Flow liters sec 0 4720 300 141 6 4005 Area Supply Multiplier Supply Delta P 0 005 x Flow D 2 Supply Multiplier 24 8 0 005 ke 20 8 Note For this method the Supply Multiplier typically falls between 14 25 and 33 25 If the user selected one of the paths that allow user defined flow sensors i e single duct pressure independent user defined flow the flow coefficient 4005 is user definable Use the appropriate flow coefficient for your application 2 User Defined Flow Method This method is the same as that for the English calculation except that all values can be ranged directly in metric system units Supply Multiplier Maximum Supply Delta P Supply AZ Offset 0 Flow Coefficient Area Flow Hood Reading The maximum function selects the greater of the two values the sum of Supply Delta P and Supply AZ Offset or zero to prevent a negative result Example The flow hood reading 400 liters s The Supply Delta P 210 0 Pascal s The Area 0 031 sq meters The Flow Coefficient 1291 The Supply AZ Offset 0 005 x 2 Supply Multiplier Maximum 210 0 0 005 OF aor 400 0 Supply Multiplier 2 102 32 VAV Terminal Control Applications Application Note Results outside the range of 0 5 to 13 indicate the likelihood
83. nalog Damper Actuators Supply Deadband 120 Supply Area for VAV1x1 x with EP 8000 Supply Deadband must be greater than this result based on noise level The user can select the constant HVAC PRO uses in the above noise calculation by choosing VAV Flow Deadband from the Action menu Refer to the Recalculating Flow Tuning Parameters procedure in the Testing and Receiving Data from Controllers chapter of the HVAC PRO User s Manual in this manual for detailed information about this procedure Wide 120 default for worst case process noise Medium 84 Narrow 48 for typical process noise This sets the defaults for use when manually forcing a recalculation or when the calculation is performed during an upgrade Note The tuning value will not change until Recalculate Flow Tuning Parameters is selected VAV Terminal Controller Applications Application Note Table 15 Damper Control Flow Loop Tuning Parameters Duct Diameter Supply Area 4 inches 0 087 sq ft 6 inches 0 196 sq ft 8 inches 0 349 sq ft 10 inches 0 545 sq ft 12 inches 0 785 sq ft 14 inches 1 068 sq ft 16 inches 1 396 sq ft Damper Stroke Time 90 De 60 sec 90 sec 120 sec 330 sec 60 sec 90 sec 120 sec 330 sec 60 sec 90 sec 120 sec 330 sec 60 sec 90 sec 120 sec 330 sec 60 sec 90 sec 120 sec 330 sec 60 sec 90 sec 120 sec 330 sec 60 sec 90 sec 120 sec 330 sec Prop Supply 8 393 16 16 45 8 886 16 16 45
84. ndent Cont meter Location Value Indep Dampers Dampers sion Hot Deck Analog Input Config Cont Total Dk ADF 235 0 005 UDF UDF AZ Offset Total Dk ADF 213 4005 UDF UDF Flow Coef Total ADF 211 0 0 UDF UDF Ranging LO Total ADF 214 1 0 UDF UDF Ranging L1 Total ADF 215 0 0 UDF UDF Ranging L2 Total ADF 216 0 0 UDF UDF Ranging L3 Total ADF 217 0 0 UDF UDF Ranging L4 Total ADF 218 0 0 UDF UDF Ranging L5 Total ADF 219 0 0 UDF UDF Ranging L6 Use Total BDF 233 1 No UDF UDF Area Total Dk ADF 235 0 005 UDF UDF AZ Offset Total Dk ADF 220 4005 UDF UDF Flow Coef Total ADF 212 0 0 UDF UDF Ranging LO Total ADF 221 1 0 UDF UDF Ranging L1 Total ADF 222 0 0 UDF UDF Ranging L2 Total ADF 223 0 0 UDF UDF Ranging L3 Total ADF 224 0 0 UDF UDF Ranging L4 Total ADF 225 0 0 UDF UDF Ranging L5 Total ADF 226 0 0 UDF UDF Ranging L6 Use Total BDF 234 1 No UDF UDF Area Exhaust AZ ADF 240 0 005 UDF UDF Offset Continued on next page Continued on next page VAV Terminal Controller Applications Application Note 101 Indep Constant Constant Single Cold Volume Volume Duct Deck w Group Para Point Default Pressure Separate Linked Conver Dependent Cont meter Location Value Indep Dampers Dampers sion Hot Deck Analog Input Config Cont Exhaust ADF 227 4005 UDF UDF Flow Coef Exhaust ADF 210 0 0 UDF UDF Ranging LO Exhaust ADF 228 1 0 UDF UDF Ranging L1 Exhaust ADF 229 0 0 UDF UDF Rangin
85. ng and Cooling Setpoint option provides direct access to each of the six setpoints but often this requires the user to remember to change both a heating and a cooling value Since HVAC PRO Release 5 1 application logic prevents the heating loop setpoint from being higher than the cooling loop setpoint If this is attempted the Actual Heating Setpoint is forced to 0 3 less than the Actual Cooling Setpoint This logic is not loaded in configurations built for the Revision A controllers due to memory constraints See Table 8 for the separate setpoint default values VAV Terminal Controller Applications Application Note 23 Table 8 Separate Heating and Cooling Setpoint Defaults Separate Heating Cooling Setpoint Defaults Values Occupied Cooling Setpoint 22 C 72 F Standby Cooling Setpoint 23 C 74 F Unoccupied Cooling Setpoint 27 C 80 F Occupied Heating Setpoint 20 C 68 F Standby Heating Setpoint 19 C 66 F Unoccupied Heating Setpoint 17 C 62 F Actual Heating Setpoint Wu Actual Cooling Setpoint FAN kkk Displays current controller value Single Setpoint with Bias With Single Setpoint only one value must be changed to adjust the zone Three setpoints and three biases provide flexibility The Actual Heating Setpoint is calculated by subtracting the present mode s bias from the present mode s temperature setpoint Similarly the values are added to determine the Actual Cooling Setpoint In this way the entire com
86. ngle Zone Setpt Single Zone Setpt Single Zone Setpt VAV Terminal Controller Applications Application Note 97 Dual Duct Default Point Assignments Summary Table 26 shows the HVAC PRO hardware point assignments and options for dual duct configurations Table 26 Default Dual Duct I O Assignments Point Point Type Index Point Name Description Analog Al1 Zone Temp Zone Temperature sensor measured value Inputs al 2 Cooling Setpoint Cooling Setpoint potentiometer Warm Cool Adjust Warm Cooling Adjust potentiometer Al 3 Heating Setpoint Heating Setpoint potentiometer Al 4 Vol Dmp Delta P Pressure Differential for total Air Flow calculation in Constant Volume Supply Delta P Pressure Differential for Supply Air Flow calculation in Single Duct Conversion Cold Dk Delta P Pressure Differential for Cold Deck Air Flow calculation in Pressure Independent Total Dk Delta P Pressure Differential for Total Air Flow Al 5 Hot Dk Delta P Pressure Differential for Hot Deck Air Flow calculation in Pressure Independent Al 6 Exhaust Delta P Pressure Differential for Exhaust Flow calculation Dis Air Temp Discharge Air Temperature sensor Binary BI 1 Occupied Occupied Unoccupied mode selection Inputs ez Standby Standby command BI 3 Shutdn Box Open Shutdown mode with Box Open command BI A Shutdn Box Close Shutdown mode with Box Close command Analog AO Cold Dk Damper Cmd Cold Deck Damper control in Pressure Independent and Outputs Constant Volume Separat
87. noccupied period Standby mode is entered into from Unoccupied Standby can provide intermediate temperature setpoints Standby is applicable to conference rooms and other intermittent use areas An occupancy sensor or the Temporary Occupancy feature can be used to switch from Standby to Occupied 16 VAV Terminal Control Applications Application Note Temporary Occupancy Temporary Occupancy mode allows you to set the controller to Occupancy mode for a user defined time period then return to Unoccupied mode During Temporary Occupancy mode the controller maintains occupied temperature setpoints For VAV applications you may need to monitor the Occupied Status data point to turn on the central system or maintain records for tenant billing When you enable the Temporary Occupancy mode Occ Ovrd time and Temp Occ Status Points are added to the parameter table The timer starts when you release the Temporary Occupancy button The timer restarts each time an occupant pushes the button Default parameters for this mode are shown in Table 4 Table 4 Temporary Occupancy Default Parameters Temporary Occupancy Default Values Parameters Occ Ovrd Time 30 00 minutes Temp Occ Status Off VAV Terminal Controller Applications Application Note 17 Table 5 describes the Temporary Occupancy mode in the TE 6400 and TMZ1600 room sensors Table 5 Room Sensor Functions in Temporary Occupancy Mode Room Sensor TE 6400 TMZ1600 Description
88. nsertion probes have the disadvantage of sensing at a single point in the air stream Flow through types may use in line air filters but as the filters become loaded with dirt their pressure drop will increase causing an apparent sensor calibration shift Further this shift can affect both the sensor sensitivity and zero A change in sensitivity cannot be compensated for by an auto zero algorithm and requires verification at two or more points for recalibration This device is usually located in the inlet of a pressure independent box to sample the airflow The pickup may be a molded plastic cross shape or a pair of rings or straight sections of 1 4 inch diameter aluminum or copper tubing Several examples are shown in Figure 1 Sensing Ports Cross Tubes Squared Rings Straight Tubes vav1 Figure 1 Common Flow Pickups as Viewed Looking into the Box Inlet Functionally the pickup consists of two manifolds having an equal number of symmetrically located ports The high side manifold ports face upstream and the low side ports open downstream Each manifold averages the samples from its multiple ports These give a better indication of average pressure than a single port pickup can provide when the air velocity is not uniform across the duct area Non uniform velocity is common in VAV installations typically caused by turns other transitions or sagging flex duct within three diameters upstream of the flow pickup Among multiport device
89. ntained See the Auto Zero topic in this section VAV Terminal Controller Applications Application Note 11 Error caused by turns or transitions in hard duct or sags in flexible duct within close proximity to the flow pickup These conditions may result in non uniform air velocity across the duct area at the flow pickup location If this occurs the velocity at the pickup sampling ports may not represent average air velocity To complicate matters the velocity profile may change at different flow rates This may be indicated during air balance if flow is verified at both minimum and maximum Calculate the pickup gain Flow Mult necessary for the controller indicated flows to match the balancing contractor s readings at both minimum and maximum If the resulting flow multipliers are significantly different i e by more than 10 either the duct transition is causing a problem or the box is operating in a region of non linear pickup behavior To avoid problems caused by flow pickup proximity to transitions ensure that there is a minimum of three duct diameters of straight unrestricted duct upstream of the airflow pickup unless otherwise stated by the box manufacturer The flow profile problem can be corrected by installing turning vanes in the offending duct section or changing the duct configuration to provide greater separation between the transition and pickup and by eliminating sags in flexible duct The spiral pattern on the interior
90. ntrol Damper Control Damper Control Damper Control Damper Control Damper Control Constant Volume Linked Dampers Indep Single Cold Duct Deck w Conver Dependent sion Hot Deck Incr Damper Damper Control Incr Damper Incr Damper Group Para Cont meter Hot Deck Flow Setpts Occ HD Clg Min Occ HD Htg Max Occ HD Htg Min Unocc HD Clg Min Unocc HD Htg Max Unocc HD Htg Min Wrmup HD Clg Min Wrmup HD Htg Max Wrmup HD Htg Min Low Limit Setpoints Dis Air Deadband Dis Air Integ Time Dis Air Low Limit Dis Air Prop Band Modes Boost Ovrd Time Boost Status Occ Ovrd Time Occ Start Time Point Location ADF 179 ADF 177 ADF 176 ADF 183 ADF 181 ADF 180 ADF 153 ADF 156 ADF 155 ADF 194 ADF 193 ADF 172 ADF 173 ADF 175 BD 15 ADF 174 ADI 225 Continued on next page VAV Terminal Controller Applications Application Note 107 Default Value 0 0 cfm 500 0 cfm 100 cfm 0 0 cfm 300 0 cfm 100 0 cfm 0 0 cfm 500 0 cfm 100 0 cfm 1 0 F 200 58 0 F 3 0 F 30 0 Minute 0 Off 30 0 Minute 00 00 Hr Mn Pressure Indep Used Used Used Used Used Used Used Used Used Discharge Air Low Limit Discharge Air Low Limit Discharge Air Low Limit Discharge Air Low Limit Boost Mode Boost Mode Temporary Occupied Mode Occupied Mode Constant Volume Separate
91. ntroller Applications Application Note 77 Detailed Procedures Calculating User Defined Flow Parameters for Other Non Linear Sensors Note The following discussion reference functions of Microsoft amp Excel Version 5 0 or later To calculate user defined flow parameters for other non linear sensors l Because the linearization is accomplished with process code rather than within the analog input range the input in units of the input signal which will generally be voltage Determine if Auto Zero will be used to zero the sensor which is recommended If so range the analog input to read 0 when flow is zero For example if the sensor output voltage range is 0 7 to 5 0 VDC for 0 to 4100 fpm the AI could be ranged as follows e Input Low 0 7 Output Low 0 0 e Input High 5 0 Output High 4 3 e Units VDC sensor voltage relative to the Input Low Determine the Supply AZ Offset by subtracting 0 005 from the sensor offset voltage Supply AZ Offset 0 7 0 005 Supply AZ Offset 0 695 Create a spreadsheet with two columns Enter the analog input voltage in the left column and the required readout values in units of fpm in this example in the right column From the sensor manufacturer or test data determine 12 or more points on the curve Better results will be obtained with 20 to 30 points For sensor curves having more than one knee a greater number of points will be required Select more points on the knee of
92. o set the binary parameter Use Supply Area to No State 0 further reducing the formula to Maximum Supply Delta P Supply AZ Offset 0 Supply Multiplier Supply Flow Note The Supply Box Area must be accurately defined even though not required for the flow equation because the area is used by HVAC PRO to calculate flow loop tuning values VAV Terminal Controller Applications Application Note 29 Table 13 User Defined Flow Parameter Values and Analog Input Definition for Various Flow Sensors Parameter Sensor Type Delta Linear Linear Staefa Kreuter Kreuter Pressure Velocity Flow FK V32 CEE 4841 CEE 4841 default Non linear Non linear Non linear Velocity Velocity Velocity Date Code lt Date Code gt 9315 9315 Supply AZ Offset 0 005 0 005 0 005 0 695 0 005 0 995 Supply Ranging LO 0 0 0 0 0 0 0 0 0 0 0 0 Supply Ranging L1 1 0 1 0 1 0 475 32 120 3 28 309 Supply Ranging L2 0 0 0 0 0 0 973 3 45 699 67 159 Supply Ranging L3 0 0 0 0 0 0 540 81 130 71 16 896 Supply Ranging L4 0 0 0 0 0 0 151 23 33 6 44 134 Supply Ranging L5 0 0 0 0 0 0 17 066 2 627 13 764 Supply Ranging L6 0 0 0 0 0 0 0 546 0 0 1 143 Supply Flow 4005 0 0 0 0 0 0 0 0 0 0 Coefficient Use Supply Area Yes State 1 Yes State 1 No State 0 Yes State 1 Yes State 1 Yes State 1 Supply Multiplier 2 25 1 0 1 0 1 0 1 0 1 0 Al Suggested Supply Supply Supply Supply Sensor Supply Sensor Supply Sensor Name Delta P Velocity In Flow In Span Vol
93. of three locations cold deck hot deck and discharge the non measured variable is internally calculated Discharge flow measurement at low velocity may be less reliable unless the flow pickup is located at least three duct diameters downstream from the box outlet making installation of the discharge flow pickup by the box manufacturer impractical Single setpoint provides for a zone temperature setpoint for each of the modes Occupied Unoccupied and Standby A bias is also provided for each of the three modes In this configuration the bias value establishes the zone control deadband The deadband defines the range of zone temperatures above and below setpoint where no control action takes place allowing the zone to float Thus energy savings may be realized by using a larger bias during unoccupied periods for example The controller defines the deadband to be the zone setpoint bias For stable control and expected component life a bias of at least 0 1 should be used Internally the control offset is set to 50 so the control can function above and below setpoint Zone control loop tuning parameters for proportional band and integration time are available The proportional band uses a positive value for direct action The output from the zone control loop or Zone Command is a value of 0 to 100 which is used by the discharge temperature and flow reset schedules When baseboard control is included and heating is required the radi
94. om the AI Modify screen e The third option is to provide a TE 6400 Zone Sensor with a warmer cooler setpoint adjustment The warmer cooler adjustment is active during all modes of operation Occupied Unoccupied Standby and Warmup The default range provides 5 F adjustment from the setpoint This 5 F range can be modified from the AI Input Modify screen Note If any setpoint potentiometer becomes unreliable the controller automatically uses the default values entered in the setpoint table Zone Temperature Loop Tuning Parameters Default tuning parameter values are shown in Table 10 These are appropriate for typical zones and the TE 6400 Table 10 Zone Temperature Defaults Zone Temperatures Defaults Values Cooling Proportional Band 5 5 C 10 F Cooling Integration Time 1000 ticks Baseboard Proportional Band 5 5 C 10 F Box Heat Proportional Band 5 5 C 10 F Heating Integration Time 1000 ticks Ticks are a controller time interval equal to 1 5 seconds If Baseboard mode is selected In addition there are fixed 0 3 control deadbands below the Actual Heating Setpoint and above the Actual Cooling Setpoint When the Zone temperature is within these deadbands no proportional control action takes place and integration if used in the respective temperature loop is held at its last value VAV Terminal Controller Applications Application Note 25 Even when there is no box heat the Box Heating Prop
95. one temperature loop and in the individual hot and cold deck flow control loops Control of discharge temperature and flow is provided by multi variable control logic Airflow setpoints are in terms of discharge flow For example if cooling design calls for 800 cfm of 42 F cold deck plus 200 cfm of 107 F hot deck in order to produce 1000 cfm of 55 F air flow to the space the flow setpoint should be set to 1000 cfm To meet ventilation requirements a minimum air flow may be established on just one deck or on both decks Although the hot and cold inlet locations are recommended flow may be measured at any two of three locations cold deck hot deck and discharge The non measured variable is internally calculated Discharge flow measurement at low velocity may be less reliable unless the flow pickup is located at least three duct diameters downstream from the box outlet making installation of the discharge flow pickup by the box manufacturer impractical Zone Control VAV Terminal Controller Applications Application Note 63 Single setpoint provides for a zone temperature setpoint for each of the modes occupied unoccupied and standby A bias is also provided for each of the three modes In this configuration the bias value establishes the zone control deadband The deadband defines the range of zone temperatures above and below setpoint where no control action takes place allowing the zone to float Thus energy savings may be reali
96. ons Application Note Each controller upgraded in ascending address order is assigned the next higher schedule until the four times have been applied Then the schedules are re applied N2 Address Start Time Stop Time 1 01 00 01 01 2 01 15 01 16 3 01 30 01 31 4 01 45 01 46 5 01 00 01 01 6 01 15 01 16 7 01 30 01 31 tc Note The controller time clock is set by Companion Facilitator NCM or N30 when communication is established Without a network the time of the most recent reset is considered to be 00 00 hours or midnight e Delta P sensor may become negative as a result of drifting Note Previous releases of HVAC PRO configurations would also trigger when the Zone Temperature changed by more than 5 degrees e Flow is less than one third of the Occupied mode cooling maximum flow setpoint and 24 hours have passed with the Auto Zero Enabled since the last Auto Zero Note This method is useful when the main AHU is turned off during unoccupied times Every day when the AHU turns off the 24 hour timer expires and the flow goes to zero the Auto Zero is triggered VAV Terminal Controller Applications Application Note 43 VAV Single Duct Applications Pressure Independent Single Duct Control Logic User Defined Flow Figure 8 illustrates the pressure independent control logic The mode of operation generator selects which zone cooling and heating temperature setpoints are used during the selected mode of operation
97. onstant Volume Separate Dampers Pressure Independent Discharge Air Reset DAR of Temperature and Flow This strategy utilizes a terminal unit discharge air temperature sensor and flow and temperature reset schedules to provide tight zone control and stable discharge over a wide range of hot and cold deck supply air temperatures and space loads The reset strategy is particularly well suited to cold air systems where the cold deck temperature may be less than the minimum desired air temperature delivered to the occupied space Baseboard radiation control may optionally be integrated to eliminate the effects of cold walls in exterior zones Proportional plus integral control is utilized in the zone temperature loop and in the individual hot and cold deck flow control loops Control of discharge temperature and flow is provided by multi variable control logic Zone Control VAV Terminal Controller Applications Application Note 59 Maximum heating and cooling airflow setpoints are in terms of discharge flow For example if cooling design calls for 800 cfm of 42 F cold deck plus 200 cfm of 107 F hot deck in order to produce 1000 cfm of 55 F air flow to the space the Maximum Cooling flow setpoint should be set to 1000 cfm To meet ventilation requirements a minimum air flow may be established on just one deck on both decks or on discharge flow Although the hot and cold inlet locations are recommended flow may be measured at any two
98. or Hot Deck Damper in Pressure Independent and Constant Volume Separate Dampers System Vol Dmp Open Incremental control for Damper controlling the total Air Flow in Constant Volume Linked Dampers System BO4 Hot Dk Close Incremental control for Hot Deck Damper in Pressure Independent and Constant Volume Separate Dampers System Vol Dmp Close Incremental control for Damper controlling the total Air Flow in Constant Volume Linked Dampers System BO 5 Exhaust Open Incremental control for Exhaust Damper BO 6 Exhaust Close Incremental control for Exhaust Damper BO 7 Basebd Open Incremental control for Baseboard Heat Basebd Heat On Off control with Normally Open Valve Basebd Heat On Off control with Normally Close Valve BO 8 Basebd Close Incremental control for Baseboard Heat Note In the above table Table 26 the Point Names are repeated for different features due to the default assignments by HVAC PRO and based on the Question and Answer session If the default location for a given feature is used by another feature then HVAC PRO tries to assign the next available location for the given feature If the default location for a given feature is zero then HVAC PRO assigns the first unused location for the feature A user can move the point locations to avoid the No Target Device warning Please refer to the HVAC PRO User s Manual for a more detailed description of moving point locations VAV Terminal Controller Applications Application Note 99
99. ortional Band may require a valid value It is used to calculate the flow setpoint for Warmup in Pressure Independent to modulate the damper in Winter mode for Pressure Dependent without Feedback and to calculate position setpoint in Warmup for Pressure Dependent with Feedback The Heating Integration Time applies to both baseboard and box heat if present in the application Flow Setpoint Options Every effort has been made to keep I O points and parameters the same as previous releases of HVAC PRO Release 4 0 or later but because of changes to the flow control algorithm you cannot override the calculated flow setpoints directly from the network A new Supply Preset ADF Analog Data Float has been defined which overrides the Supply Setpoint within the controller logic whenever the Supply Flow Override is enabled See Table 11 Table 11 Damper Control Duct Type Default Value Single Duct Supply Preset 0 0 Supply Flow Override Disable Dual Duct Cold Dk Preset 0 0 Cold Dk Override Disable Hot Dk Preset 0 0 Hot Dk Override Disable Note The supply setpoint address has not changed from previous revisions The Supply Preset is only necessary for applications that override the supply setpoint Monitor only applications do not require any changes 26 VAV Terminal Control Applications Application Note Airflow Calculations for Pressure Independent Applications The VAV controller uses two key parameters in converting differential p
100. pen Damper Close 0 10 VDC pl2gem 1 Figure 8 Pressure Independent Single Duct Control Logic 46 VAV Terminal Control Applications Application Note Pressure Dependent Single Duct Control Logic without Feedback Figure 10 illustrates the pressure dependent control logic The mode of operation generator selects which zone cooling and heating temperature setpoints are to be used by the temperature control loop during the selected mode of operation The temperature control loop compares the zone temperature to the zone setpoint and produces a 0 to 100 output command to the damper actuator In Summer mode the actuator opens the zone damper on an increase in zone temperature within the cooling prop band from the minimum position to 100 Once the zone temperature falls below the cooling setpoint the damper is held at minimum position If you set up the system in Winter mode or Central System Warmup mode the reverse action takes effect as shown in Figure 9 The damper deadband adjustment measured as damper open percentage should not be set lower than 2 or greater than 10 This deadband defines the minimum damper position increment in percent of stroke time Damper Open 100 Winter or Warmup Summer Minimum Position Increasing 0 Zone La EJ E lt t z Temperature Box Heating Baseboard Comfort Zone Cooling Prop Band Prop Band Prop Band Actual Heating Setpoint Actual Cooling Setpoint VGRPH2
101. perature to the zone setpoint and produces 0 to 100 output commands The output commands for heating and cooling feed into separate hot and cold deck reset schedules which provide flow setpoints The damper control uses prop band integration time deadband and stroke time to modulate the damper and thus maintain the flow setpoint To calculate default values see flow loop calculations in the Flow Loop Tuning Equations topic in this section The hot and cold deck flows reset between the zone heating and cooling setpoints The cold deck is automatically reset between its minimum cooling flow setpoint and minimum heating flow setpoint The hot deck is also automatically reset between its minimum heating flow setpoint and minimum cooling flow setpoint This allows for smooth transitions of airflow as the zone temperature requirements switch between heating and cooling The user defined flow path allows the user to define the flow sensor type and ranging In addition to differential pressure measurement this allows use of linear and non linear sensors with outputs ranged in flow or velocity The user must enter the appropriate constants for the sixth order polynomial to linearize the sensor Then the user enters the flow coefficient box area and indicates whether the box area should be used in the calculation Box area is used to calculate flow loop tuning parameter values so the area must be accurately entered even when not required to calc
102. rature control loop compares the zone temperature to the zone setpoint schedule and produces a 0 to 100 output command The output command feeds into the reset schedule to provide a damper command during the Occupied Unoccupied and Central System Warmup modes The damper command from the reset schedule is compared to the actual position feedback Once the actual and damper commands are within the damper deadband the actuator stops driving The damper deadband defaults to 2 of damper stroke This means that once the incremental actuator controller falls into the deadband range it will not drive the actuator until there is a 2 difference between the damper commanded position and the actuator feedback Notes A 2K ohm feedback potentiometer on the damper actuator is recommended for the actuator position feedback When this strategy is used with an analog damper control output position feedback is not used See Figure 12 Damper Open Box Heating Maximum Baseboard Cooling Heating i Cooling Maximum Minimum Minimum i SS A Baseboard Minimum lt gt a gt Increasing Box Heating Baseboard Cooling Zone Prop Band Prop Band Prop Band Temperature Actual Heating Setpoint Actual Cooling Setpoint VGRPH4 1 Figure 11 Control Sequence for Pressure Dependent Systems with Actuator Feedback Actuator Position Feedback VAV Terminal Controller Applications Application Note Mode of Opera
103. re by overdriving the damper and valve actuators closed for the Auto Zero Duration in minutes During this time the Auto Zero Status value is On When the dampers are fully closed new values are calculated and stored into the AI offset table in the controller s nonvolatile memory for Delta P sensors Note The Auto Zero duration must be set one minute longer than the longest stroke time of the incremental dampers and actuators to allow the Delta P sensor to settle Auto Zero sets the AI offset to produce a Delta P reading of 0 005 inches W C and prevent the Delta P value from going negative This 0 005 inches W C is subtracted from the AI value before being passed to the flow calculation VAV Terminal Controller Applications Application Note 41 Trigger Conditions for Auto Zero Activating Auto Zero while the controller is synchronizing incremental outputs causes improper Analog Input offsets to be computed The following conditions trigger Auto Zero Override to On the Auto Zero Command Auto Zero Enable Enable AND Start from controller based Auto Zero Schedule Auto Zero Enable Enable AND Delta P sensor goes negative Auto Zero Enable Enable AND Flow lt 1 3 Occupied Mode Cooling Maximum Flow Setpoint AND 24 hours have passed since last Auto Zero The controller based schedule usually provides the best solution ensuring flow sensors are zeroed once per day Choose the Auto Zero trigger that best serves your applica
104. ressure inputs to airflow Supply Box Area and Supply Multiplier Both apply to any single or dual duct system with a pressure independent path The OEM Technical Manual FAN 638 or Appendix B VAV Controller Flow Calculation Constants LIT 6375185 of this manual provides the flow multiplier also known as K constant or pickup gain values for most OEM boxes Also see the Airflow Measurement topic in this section for an explanation For the purposes of this discussion parameter names from the single duct supply box flow calculation are referenced Exhaust box and dual duct flow calculations have similar but different parameters The controller uses the following equations to determine the airflow The displayed Delta P is reduced by 0 005 introduced by Auto Zero If Supply Delta P gt 0 005 Supply Delta P Supply Delta P 0 005 or else Supply Delta P 0 0 SupplyDeltaP SupplyMultiplier SupplyFlow SupplyBoxArea FlowCoefficient Where Supply Flow airflow calculated in cubic feet per minute cfm Supply Delta P differential pressure inches W C Supply Multiplier K airflow pickup gain Flow Coefficient is fixed at 4005 in the following paths Single Duct Pressure Independent Dual Duct Pressure Independent Constant Volume with separate dampers Constant Volume with linked dampers Single Duct conversion ind cold deck with dep hot deck Pressure Independent Disch Air Reset and CV with separate d
105. rol Applications Application Note Group Cont Parameters Zone Heating Setpoints Cont Htg Integ Time Htg Integ Time Occ Htg Setpt Stby Htg Setpt Unocc Htg Setpt Zone Setpoints Occ Bias Occ Setpt Stby Bias Stby Setpt Unocc Bias Unocc Setpt Point Default Location Value ADF 139 ADF 178 ADF 134 ADF 135 ADF 136 ADF 134 ADF 129 ADF 135 ADF 130 ADF 136 ADF 131 1000 0 0 0 68 0 F 66 0 F 62 0 F 2 F 70 F 4 F 70 F 9 F 71 F Pressure Pressure Dependent w Independent Feedback Baseboard Heat Box Heat and Both Heat No Heat Separate Heating and Cooling Setpts Separate Heating and Cooling Setpts Separate Heating and Cooling Setpts Single Zone Setpt Single Zone Setpt Single Zone Setpt Single Zone Setpt Single Zone Setpt Single Zone Setpt Baseboard Heat Box Heat and Both Heat No Heat Separate Heating and Cooling Setpts Separate Heating and Cooling Setpts Separate Heating and Cooling Setpts Single Zone Setpt Single Zone Setpt Single Zone Setpt Single Zone Setpt Single Zone Setpt Single Zone Setpt Pressure Dependent w o Feedback Baseboard Heat Box Heat and Both Heat No Heat Separate Heating and Cooling Setpts Separate Heating and Cooling Setpts Separate Heating and Cooling Setpts Single Zone Setpt Single Zone Setpt Single Zone Setpt Si
106. s usually the cross and ring types perform better than straight tubes because the sensing ports are more distributed across the duct area 8 VAV Terminal Control Applications Application Note What the Air Flow Pickup Measures Upstream Air Flow gt Sensing Static Pressure Port e Downstream 5 Sensing 7 Port gt Pickup High r Static Pressure Pressure Manifold Pickup Low Area of Increased Velocity f and Decreased Pressure Pressure Manifold Duct Wall vav2 Figure 2 Interaction of the Pickup and Air Stream Referencing Figure 2 the upstream ports are exposed to total pressure In order to sense true static pressure the pickup must have openings that are perpendicular to the direction of flow Instead the low pressure ports open downstream and the passing air exerts a pull on these openings resulting in a pressure less than static Since velocity pressure equals total minus static pressures Pvelocity Ptotal P static and the differential pressure is total minus downstream pressures Paditferential P total P downstream If downstream is less than static then the pressure difference across the pickup must be greater than velocity pressure Thus the velocity pressure is amplified by this effect The amount of amplification or gain of the pickup is determined by its aerodynamic design and the flow characteristics of the box inlet and varies among box manufacturers in the range of 1 5 to 3 5 Th
107. s Application Note Constant Volume Separate Dampers Occupied Mode Occupied Mode Always Power Fail Restart Power Fail Restart Shutdown Shutdown Shutdown Standby Temporary Occupied Mode Always Constant Volume Linked Dampers Occupied Mode Occupied Mode Always Power Fail Restart Power Fail Restart Shutdown Shutdown Shutdown Standby Temporary Occupied Mode Always Single Duct Conver sion Occupied Mode Occupied Mode Always Power Fail Restart Power Fail Restart Shut down Shut down Shut down Standby Tempo rary Occupied Mode Always Used Used Used Used Used Indep Cold Deck wi Dependent Hot Deck Occupied Mode Occupied Mode Always Power Fail Restart Power Fail Restart Shutdown Shutdown Shutdown Standby Temporary Occupied Mode Always VAV Terminal Controller Applications Application Note 109 Indep Constant Constant Single Cold Volume Volume Duct Deck w Group Para Point Default Pressure Separate Linked Conver Dependent Cont meter Location Value Indep Dampers Dampers sion Hot Deck Supply Box Config Damper ADF 22 5 0 Incre Deadband mental Control Dmp ADF 141 2 0 Min Incre Stroke mental Time Control Supply Box ADF 158 0 35 sq ft Damper Area Control Supply ADF 159 2 25 Damper Mult Control Supply Damper Control Damper AO 4 0 0 Incr Command Damper Supply ADF 142 50 cf
108. sensor types refer to the Airflow Calculations for Pressure Independent Applications topic in this section Damper Actuator Selection Table 14 below shows the optimum incremental actuators chosen for good control depending on the controller version Short stroke time may be required by specifications for smoke purge and this may dictate the controller and actuator selection Table 14 Optimum Incremental Actuators Minimum EDA 2040 M9104 Controller Output Pulse Stroke Time Stroke Time seconds minutes minutes AS VAV1xx 0 1 5 2 1 5 2K F W lt AO3 AS VAV1xx 1 0 5 1 1 5 8K F W gt DO2 34 VAV Terminal Control Applications Application Note Selection of the proper stroke time for the damper actuator is critical for maintaining stable and accurate control This is because damper positioning resolution is determined by dividing damper drive time by the minimum controller output pulse length For example a two minute actuator used with the AS VAV1xx 0 provides output resolution of 80 steps if the total damper travel is 90 However 60 or more steps are needed because in practice control resolution is reduced by the following factors e Flow does not vary linearly with damper position e Some box dampers travel only 45 or 60 e When boxes are oversized resolution is lost on the damper positioning unless duct static pressure is reduced e Differential pressure transducer ranges do not typically match the requiremen
109. t ADF 128 78 F Unocc Bsbd Min ADF 152 0 0 cfm Unocc Bsbd Min ADF 152 0 0 Unocc Clg Max ADF 149 50 0 Unocc Clg Max ADF 149 400 0 cfm Unocc Clg Min ADF 148 0 0 cfm Unocc Clg Min ADF 148 20 0 Unocc Htg Max ADF 151 20 0 Unocc Htg Max ADF 151 100 0 cfm Unocc Htg Min ADF 150 20 0 Continued on next page Pressure Pressure Dependent Dependent Pressure w w o Independent Feedback Feedback Used Incremental Damper Used Used Used Used Used Used Used Used Applicable Applicable Applicable only if only if only if configured configured configured with TMZ with TMZ with TMZ Digital Room Digital Room Digital Room Sensor Sensor Sensor Applicable Applicable Applicable only if only if only if configured configured configured with TMZ with TMZ with TMZ Digital Room Digital Room Digital Room Sensor Sensor Sensor Baseboard Heat Both Heat Baseboard Heat Both Heat Used Used Used Used Box Heat Both Heat Box Heat Both Heat Box Heat Both Heat 94 VAV Terminal Control Applications Application Note Group Cont Parameters Unocc Damper Setpts Cont Unocc Htg Min VAV Box Diagnostics Actuator Runtime Average Flow Error Average Temp Error Controller Runtime Flow Filter Value Zone Temp Filter Value Warmup Damper Setpts Warmup Bsbd Min Warmup Bsbd Min Warmup Clg Max Warmup Clg Max Warmup Clg Min Warmup Clg Min Warmup Htg Max Warmup Htg Max Warmup Htg Min Warmup Htg Min Wa
110. t is founded upon a published statistical process control equation exponential weighted moving average The name has been shortened to moving average The complete flow equation implemented is Moving Average new measured flow flow setpoint E moving average old flow filter value moving average old The flow filter value is a constant whose value has been set to 30 minutes This parameter is not modifiable by the user If a large moving average value persists over time it is an indication of a malfunction in the damper control loop The Moving Average Flow Error is available in the single duct pressure independent incremental actuator path The following parameter shows up in the VAV Box Diagnostics group while in the Commissioning mode e Moving Avg Flow Error Xxxx cfm The Moving Average Flow Error Diagnostic is also available for dual duct pressure independent or constant volume separate dampers incremental actuator applications Under the VAV Box Diagnostics grouping the following parameters display if this diagnostic is selected e Moving Avg CD Flow error Xxxx cfm e Moving Avg HD Flow error xxxx cfm Note Three possibilities in placing flow sensors on dual duct boxes include 1 separate cold and hot duct 2 total and cold duct and 3 total and hot duct When either 2 or 3 are selected one of the flow errors computes from the total even though the parameter implies calculation from each deck 7
111. te Warmer cooler TMZ Digital unused setpoints adjust room sensor unused setpoints adiust room sensor p p d y v y v p Define Occupied mode a Software N2 Command Y Hardware BI Point Both with BI Backup v LU Both can activate y Define Standby mode L Software N2 Command V Hardware BI Point Both with BI Backup y y Both can activate Define Shutdown mode Y Software N2 Command LG Hardware BI Point Both with BI Backup Both can activate Do you want the Temporary Occupied feature No Yes Do you want Boost mode No Lo Yes 3 COMFLO2 Figure 30 Dual Duct Configuration Flowchart Part III 86 VAV Terminal Control Applications Application Note Troubleshooting The following are descriptions of known problems and their solutions Table 23 Troubleshooting VAV Controllers Error Condition Problem Solution Second When building certain applications Workarounds use either Occupancy with HVAC PRO Release 7 02 a e When configuring or commissioning a VAV Heating second nuisance Occ Htg Setpoint box with HVAC PRO only adjust the top Occ Htg is loaded in the HVAC PRO Occ Htg Setpoint The second one in the list Setpoint When parameters window This only has no effect Using occurs when a user selects i HVAC PRO Separate Heating and Cooling e The corrected database files Release 7 02 Setpoints and answers the Re
112. ter System Maintenance Flush Position Continued on next page Point Default Location Value ADF 150 ADF 31 ADF 33 ADF 32 ADF 30 ADF 244 ADF 243 ADF 157 ADF 157 ADF 154 ADF 154 ADF 153 ADF 153 ADF 156 ADF 156 ADF 155 ADF 155 ADF 239 100 0 cfm 0 0 Hours 0 0 0 0 0 0 Hours 1200 Ticks 9600 Ticks 100 0 cfm 20 0 100 0 cfm 20 0 100 0 cfm 20 0 90 0 500 0 cfm 20 0 100 0 cfm 100 Open Pressure Pressure Dependent w Independent Feedback Box Heat Both Heat Actuator Runtime Diag Average Flow Error Diag Average Temp Error Diag Actuator Runtime Diag Moving Avg Flow Error Moving Avg Zone Temp Error Baseboard Heat Both Heat Used Used Box Heat Both Heat Box Heat Both Heat Baseboard or Box Heat Incr Prop N C N O Baseboard Heat Both Heat Used Used Box Heat Both Heat Box Heat Both Heat Baseboard or Box Heat Incr Prop N C N O Pressure Dependent w o Feedback Baseboard or Box Heat Incr Prop N C N O VAV Terminal Controller Applications Application Note 95 Pressure Pressure Dependent Dependent Group Point Default Pressure w w o Cont Parameters Location Value Independent Feedback Feedback Water System Maintenance Cont Water Flush BD 239 0 Disable Baseboard or Baseboard or Baseboard or Box Heat Box Heat Box Heat Incr Prop Incr Prop
113. the duct are at the measuring point If the polynomial function result is in units of velocity set Use Supply Area to Yes State 1 Test the results in a controller with a real sensor in operating conditions against a reference measuring instrument of known accuracy Creating a VAV Single Duct Application To create a VAV single duct application l 2 3 4 From the File menu select New Select Application Group gt VAV Applications Select Application gt Single Duct Answer the questions as they are presented The sequence of questions and answers is shown in Figure 25 See the Key Concepts section for more information on individual options within the question answer path VAV Terminal Controller Applications Application Note 79 Select the VAV control strategy Pressure Independent Pressure Dependent Pressure Dependent Pressure without feedback with feedback Independent v User Defined Gowa E gt Select the a output type lt lt Binary Outputs Analog Output incremental control proportional control Define Diagnostics y v None Actuator Moving Moving Runtime Runtime Moving All of runtime avg avg and moving and moving avg the flow error zone temp avg avg flow and above error flow error zone temp zone temp error error D A Se Select igh type I l I N Series Series Parallel Parallel Series On Off Series Proportional Parallel Temp
114. the zone damper open until the zone temperature heating command is less than 1 Pressure dependent zones with actuator feedback have a separate damper position setpoint for Warmup Summer Winter Pressure dependent without feedback zones have a Summer Winter mode to reverse controller action In Summer mode the actuator opens the zone damper on an increase in zone temperature within the cooling prop band from the minimum position to 100 Once the zone temperature falls below the cooling setpoint the damper is held at minimum position In Winter mode the reverse action takes effect The actuator opens the damper on a decrease in zone temperature within the heating prop band 20 VAV Terminal Control Applications Application Note Failsoft In the event that a sensor becomes unreliable Failsoft is a software controlled feature that causes controller outputs to go to a prescribed position to minimize discomfort in VAV applications e Ifthe differential pressure sensor becomes unreliable the damper drives to 100 It is important to select the proper range for the differential pressure sensor Oversized VAV boxes may cause an over range reading which causes Failsoft to lock the damper full open e If warmer cooler adjust of the room sensor becomes unreliable the reported value defaults to 0 F e If heating cooling setpoints of the remote sensor become unreliable when in Occupied or Warmup the controller uses Occ Htg Setpoint and
115. tion If Auto Zero cannot be used then an instrumentation quality pressure transducer may be required The controller may be triggered to begin the Auto Zero when Command the Auto Zero Command point On The Auto Zero command can be sent from the HVAC PRO Companion Facilitator N30 GPL Graphic Programming Language Time Schedule or PMI Person Machine Interface operator command This Auto Zero Command is useful for hospitals and laboratories that are always occupied and need to be scheduled from the Metasys headend This method is also useful if the box dampers leak significantly because you can command Auto Zero when the supply fan is off When Auto Zero Enable is set to Enable and any of the following occur Start request from the controller based Auto Zero schedule The controller based schedule can be programmed manually or automatically To manually set this up command the Auto Zero Start Time to the desired time and Auto Zero Stop Time to one minute after the Start Time Note You must save the configuration before proceeding The default time of 00 00 disables this controller based scheduling To automatically program controller based scheduling use the HVAC PRO Upgrade feature to upgrade all VAV controllers on the N2 Bus The upgrade feature applies an Auto Zero schedule with four different times between 01 00 a m and 01 46 a m to prevent all devices from auto zeroing at once 42 VAV Terminal Control Applicati
116. tion Generator Occupied Temporary Occupied Standby Boost Unoccupied Power Fail Restart Shutdown Warmup Setpoint Selector Zone Cooling Setpoint Zone Heating Setpoint Integration Time Constant Temperature Control Loop Cooling Prop Band Baseboard Heat Prop Band Box Heating Prop Band Cooling Integration Time Heating Integration Time Box Heating Baseboard Heating Cooling Command Command Command 0 to 100 0 to 100 0 to 100 1 Damper Position Reset Schedule Cooling Min Box Heat Min Cooling Max Box Heat Max Baseboard Min 49 Cooling or Heating Command 0 to 100 Analog Output Incremental Actuator Controller Actuator Stroke Time min Damper Deadband Minimum Position Damper Open Damper Close Figure 12 Pressure Dependent with Actuator Feedback Control Logic pligem 1 50 VAV Terminal Control Applications Application Note Fan Operation Small fans are used in some VAV boxes typically in conjunction with a heating coil The fan serves two purposes e It produces a flow of plenum air through the heating coil even if the box damper is fully closed to the primary air source when heating is required e It improves occupant comfort by providing better mixing of the delivered air and room air by maintaining a constant airflow through the diffuser regardless of the position of the box damper That is as the box damper closes the fan pu
117. tood There are margins for error in the measurement equipment used by the controller as well as that used by the balancer Therefore it is important that both contractors controls and balancing understand the equipment techniques and expectations of each other Factors Affecting Controller Flow Reading Following is a list of some factors that may contribute to controller flow reading inaccuracy e Incorrect values entered into the controller for box area flow multiplier airflow pickup gain or differential pressure input range e Auto Zero ran when the supply air fan was running and the VAV box damper was not tightly closed off Failure to tightly close the box damper may be caused by damaged damper seal bent damper blades poorly designed dampers or an actuator collar or other linkage which is not tightly locked to the damper shaft The linkage may be set allowing the actuator to come to an internal travel stop before the damper fully closes Any of these cause the incorrectly indicated differential pressure The most reliable method to zero the differential pressure is to disconnect the high and low side tubing from the box pickup pressure taps and command Auto Zero via the Commissioning mode of HVAC PRO e Error caused by differential pressure transducer drift since the most recent Auto Zero This may be particularly noticeable during project startup when power is shut off in the evening and ambient temperatures are not mai
118. tpoint The linked dampers are proportionally modulated when the zone temperature is between the heating and cooling setpoints Baseboard heat can be added to the control strategy The baseboard loop has its own tuning parameters and operates to satisfy the zone heating setpoint The volume damper flow loop maintains a constant volume setpoint utilizing proportional plus integral control As the difference between actual flow and the volume setpoint becomes greater than the deadband the actuator is commanded to operate in the proper direction The actuator stops driving when the flow loop error is within the deadband The volume damper flow loop can be tuned through the adjustment of separate proportional band and integration time Use the Pattern Recognition Adaptive Control PRAC automated tuning process within HVAC PRO to determine the proper tuning parameters for the control loop Hot Deck Cold Deck 100 Cold Deck l Open ncreasing peno 0 B Zone La Temperature Comfort Zone Actual Actual Heating Cooling Setpoint Setpoint c vgph 1 Figure 21 Hot Cold Deck Control Zone Damper VAV Terminal Controller Applications Application Note 67 Dual to Single Duct Conversion The conversion box has the same control sequence of operation as a standard pressure independent single duct sequence The additional control loop process that is added is a binary output command that triggers at the heating setpoint The BO energi
119. ts Volts Span Volts Al Sensor Type Voltage Voltage Voltage Voltage Voltage Voltage Al Units In WG fpm cfm VDC VDC VDC Al Filter Value 8 8 8 8 8 8 Al Input Low 1 0 a ai 0 7 0 0 1 0 Al Input High 5 0 A Kg 6 0 5 0 5 0 Al Output Low 0 0 a Kn 0 0 0 0 0 0 Al Output High 1 5 SE SER 5 3 5 0 4 0 i Do not round the ranging coefficients for non linear sensors because significant errors will result i Define per box or airflow pickup manufacturer specifications ees Define per sensor specifications User Defined Flow Parameters for Other Non Linear Sensors The procedure included in the Detailed Procedures section can be used to linearize most other sensors A regression analysis of the sensor is required which can be done using commercial spreadsheet or specific curve fitting programs to fit the sensor to a 6th or lower order polynomial The 6th order equation is Y L6 x L5 xX L4 x1 L3 xX L2 x L1 xX Lo See the Detailed Procedures section for additional information 30 VAV Terminal Control Applications Application Note Supply Multiplier English IP Calculation for Delta P Sensor During balancing calculate the supply multiplier from the area the flow hood cfm reading and the controller Delta P indication as shown below The displayed Delta P must be reduced by 0 005 introduced by Auto Zero If Supply Delta P gt 0 005 Supply Delta P Supply Delta P 0 005 or else Supply Delta P 0 0 2 Supply Multiplier
120. ts of the zone under control or the mechanical system To control the damper position the flow loop uses a proportional and integral algorithm The proportional integral control can be tuned to control any actuator that provides an end to end damper travel time of one minute or greater The controller internally multiplies the programmed stroke time of incremental actuators by 1 5 to provide overdrive to ensure end of travel is reached Incremental Output Damper Heat The controller uses two binary outputs to position the control device The timing of these outputs is based on an operator specified stroke time The controller uses the command to determine the required position of the device Then the controller causes the appropriate output triac to energize for a percent of full stroke to achieve the required device position As the new command rises above the current command the controller energizes the appropriate output to open the control device As the new command decreases below the current command the controller energizes the other output to close the control device When the difference is within the step size of the incremental actuator neither output energizes leaving the device in its current position That is the change in the output command must be significant enough to cause the device to open or close to get some corrective action to take place VAV Terminal Controller Applications Application Note 35 The controller
121. tware Release 8 0 2 VAV Terminal Control Applications Application Note Using VAV Applications Introduction The Variable Air Volume VAV Controller is an electronic device for digital control of single duct dual duct for this release fan powered and supply exhaust VAV terminal configurations This bulletin provides an overview of the VAV Controller and includes procedures for creating single and dual duct applications Refer to the Variable Air Volume Modular Assembly VMA 1400 Series Application Note LIT 6375125 for information on applications specific to the VAV Modular Assembly VMA1400 This bulletin describes how to e calculate user defined flow parameters for other non linear sensors e create a VAV single duct application e create a VAV dual duct application VAV Terminal Controller Applications Application Note 3 Key Concepts Variable Air Volume VAV Controller The Variable Air Volume VAV controller is an electronic device for digital control of single duct dual duct fan powered and supply exhaust VAV terminal configurations Along with the control capability of the VAV box the controller can also integrate the control of the room or zone baseboard heat and lighting logic You may use the VAV as a standalone controller or connected to the Metasys Network through a Network Control Module NCM Metasys Companion Facilitator or N30 Supervisory Controller When connected to the Metasys Network the
122. ulate flow Setting the flow coefficient to 0 zero disables square root extraction VAV Terminal Controller Applications Application Note 55 CFM Hot Deck Cold Deck Cold Deck Heating Hot Deck Cooling Cooling Maximum Heating Minimum Maximum Minimum y Hot Deck Cold Deck Hot Deck r Cooling Minimum 4 Cold Deck Heating Minimum Fone 0 A Temperature a gt a gt a gt a gt Box Baseboard Comfort Zone Cooling Heating Prop Prop Prop Band Band Band Actual Heating Actual Cooling Setpoint Setpoint a vgph 1 Figure 15 Control Sequence for Pressure Independent Hot and Cold Decks 56 VAV Terminal Control Applications Application Note Mode of Operation Generator Occupied Temporary Occupied Standby Boost Unoccupied Power Fail Restart Shutdown Warmup Cooldown Auto Zero Al Setpoint Selector Zone Cooling Setpoint Zone Heating Setpoint Integration Time Constant PI Sequencer Control Logic AA Cooling Prop Band Baseboard Heat Prop Band Box Heating Prop Band Baseboard Box Heating Cooling Cold Deck command DA Command Hot Deck Delta P GK o 0 to d 00 0 to i 00 Delta P Separate CFM Reset Schedules for Hot and Cold Decks Flow Calculation Hot Deck Area Hot Deck Multiplier Cold Deck Flow Cold ESCH Setpoint Hot ae Setpoint Hot Deck Flow Cold Deck Flow Control Loop Hot Deck Flow Control Loop Flow Calculation Cold Deck Ar
123. xer The unused points however can be user defined and used with a single sideloop For more detailed information on the operation of sideloops see Appendix A Sideloop Applications LIT 6375 160 4 VAV Terminal Control Applications Application Note VAV System Operation Theory VAV System A VAV system maintains the air supply at a constant temperature while individual zone thermostats vary the flow of air to each space maintaining the desired zone temperature This is unlike a constant volume system that maintains a constant volume of airflow to the space but varies the temperature of the air stream in response to space temperature changes VAV systems are predominantly single duct but about 15 are dual duct designs In either case the supply air temperature and static pressure of the air handling unit are controlled by a Metasys Air Handling Unit AHU or DX 91x0 controller while each zone has its own Metasys digital VAV controller Note The DX 91x0 does not support HVAC PRO applications Refer to the System 9100 Technical Manual FAN 636 4 for more information on the DX 91x0 The air handling system typically maintains about 1 inch W C static pressure inside the longest run of duct work away from the supply fan This ensures that each VAV terminal unit has enough pressure at its inlet to deliver the maximum required flow of air into the space As each VAV box opens and closes in response to the temperature changes in the sp
124. zed by using a larger bias during unoccupied periods for example The controller defines the deadband to be the zone setpoint bias For stable control and expected component life a bias of at least 0 1 should be used Internally the control offset is set to 50 so the control can function above and below setpoint Zone control loop tuning parameters for proportional band and integration time are available The proportional band uses a positive value for direct action The output from the zone control loop or Zone Command is a value of 0 to 100 which is used by the discharge temperature reset schedule When baseboard control is included and heating is required the radiation valve is sequenced prior to resetting the discharge flow from heating minimum to heating maximum as shown in Figure 22 Tuning is facilitated by a proportional band Basebd Prop Band which must have a negative value to produce the reverse acting heating ramp Also the radiation control loop uses the zone integration time Discharge Temperature Reset Zone command values from 0 to 100 reset the discharge The lower limit of the discharge temperature setpoint is set by the value of the Low Disch Setpt parameter the upper limit is equal to the sum of the low limit plus the Disch Reset Band Figure 20 64 VAV Terminal Control Applications Application Note Temperature Discharge Reset Band Disharge EES Low Limit Setpoint Ki gt a
125. zes a V11 3 Way Air Valve If the controller is calling for heating the V11 switches air to the existing pneumatic actuators on the dual duct box so that the hot deck is open and the cold deck is closed Once the zone temperature is above the heating setpoint the V11 reverses its action to open the cold deck and close the hot deck i i Cooling Maximum I CFM Heating Minimum i I i Cooling Minimum I I Increasing Zone La gt Temperature 0 a la Ja Box Baseboard Cooling Heating Prop Band Prop Band Prop Band Actual Heating Setpoint Actual Cooling Setpoint VAVG15 1 Figure 22 Control Sequence for Dual to Single Duct Conversion 68 VAV Terminal Control Applications Application Note Pressure Independent Cold Deck with Pressure Dependent Hot Deck The pressure independent cold deck with pressure dependent hot deck control strategy accomplishes flow control of the cold deck and room control of the hot deck Both are independent control loops controlled from a common zone temperature setpoint The cold deck operates between user defined minimum and maximum flow setpoints As the zone temperature increases above the zone cooling setpoint the cold deck resets between the minimum to the maximum flow setpoint Zone temperature directly controls the hot deck As the zone temperature decreases below the zone setpoint and through the heating proportiona

VAV Terminal Control Applications Application Note

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