Honeywell T921A User's Manual
Contents
1. fall heating application When opposite motor action is required reverse the B and W connections Refer to the appropriate instructions when wiring the 2 position actua tor Figs 9 and 10 INSTALLATION Fig 5 Terminals on back of thermostats TOP TOP T921A B T921E H HEATER A TOP TOP AUXILIARY SWITCH T921F TERMINALS T921G M9038 Fig 6 Typical wiring diagram for T921A SERIES 90 MODULATING MOTOR T921A TRANSFORMER POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED A INTERCHANGE B AND W CONNECTIONS TO REVERSE DIRECTION OF MOTOR TRAVEL Ms9g0 60 2242 2 T921A B E G INSTALLATION SETTING AND ADJUSTING Fig 7 Typical wiring diagram for T921B SERIES 90 MODULATING MOTOR T921B A POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED A INTERCHANGE B AND W CONNECTIONS TO REVERSE DIRECTION OF MOTOR TRAVEL Migo Fig 8 Typical wiring diagram for T921E TIMER SWITCH OPTIONAL TRANSFORMER SERIES 90 MODULATING MOTOR A POWER SUPPLY PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED A H TERMINAL IS A BLACK LEADWIRE M5988A Fig 9 Typical wiring diagram for T921F SERIES 90 MODULATING MOTOR T921F 2 POSITION ACTUATOR AUXILIARY SWITCH A CLASS 2 POWER SUPPLY INTERCHANGE B AND W CONNECTIONS TO REVERSE DIRECTION OF MOTOR TRAVEL USE FOR CLASS 2 CIRCUITS MAKES R TO B O2. to 49 C temperature setting scale when the outdoor bulb is at 60 F 16 C DIMENSIONS Refer to Fig 2 ACCESSORIES Compression fittings immersion wells Refer to the appropriate specification or the TRADELINE Cata log 314439 Mounting Clips For mounting a capillary tub ing averaging element in a duct T921A B E G SPECIFICATIONS 7640HX Averaging Element Mounting Kit For mount ing in existing installations where access to the duct is impractical Q615A Enclosure To protect the device when mounted outside splash proof 801534 Calibration Wrench 107324A Bulb Holder For mounting the bulb in a duct 34886A Outdoor Bulb Shield To protect the outdoor bulb mounting Fig 2 T991B approximate installation dimensions in in mm KNOCKOUT FOR 1 2 INCH CONDUIT BOTH ENDS 1 4 7 108 lt 2 57 a 24 57 8 143 7 ap 6 DIAMETER 3 3 110 8 Vi Oe A OUTDOOR BULB SIZE VARIES INVERSELY WITH THE RESET RATIO A INDOOR BULB LENGTH AND DIAMETER IS 4 1 2 114 INCH BY 1 2 13 INCH EXCEPT FOR THE AVERAGING ELEMENT WHICH IS 1 8 3 INCH DIAMETER BY 12 FT 3 M LONG A CLEARANCE NECESSARY TO REMOVE COVER M9108 60 2242 2 T921A B E G INSTALLATION Installation CAUTION Disconnect power supply before installation to prevent electrical shock and equipment damage WHEN INSTALLING THIS PRODUCT 1 Installer must be a trained experienced se
3. models except as noted below TRADELINE MODEL AVAILABLE T921A Thermostat for vertical or horizontal mounting TEMPERATURE RANGE AND SCALE 56 to 84 F 13 to 29 ADDITIONAL FEATURES e TRADELINE packed with cross reference label and special TRADELINE instructions e T6051A may be used in electric heat systems e They all include slotted sides and an add on faceplate to allow the thermostat to be mounted horizontally They also include the 127246A Adapter Plate As sembly for vertical mounting on a horizontal conduit box or for horizontal mounting on a vertical conduit box STANDARD MODEL MODELS T921A Heating or cooling applications T921B Is the same as the T921A but includes a cool heat changeover switch T921E Includes a switch and heater that provide a night setback of approximately 10 F 5 5 C T921F Includes an spdt low voltage Class 2 auxiliary switch that operates at the low end of the throttling range T921G Includes an spdt low voltage Class 2 auxiliary switch that operates at the high end of the throttling range SETTING ADJUSTMENT RANGE T921A B E G 56 to 84 F 13 to 29 C T921A B E G 13 to 29 C 56 to 84 F T921A 42 to 75 F 5 to 24 C T921A B 66 to 95 F 19 to 35 C THERMOMETER Bimetal Scale ranges T921A only 45 to 75 F 7 to 24 C All other models 60 to 90 F 16 to 32 C 15 to 35 C 59 to 95 F T921A is also avail
4. 991 CHECKOUT After the thermostat is wired and mounted check to be sure the thermostat and controlled equipment are function ing properly Before proceeding allow from one to three hours for the system to stabilize T921A 1 Set the temperature setting indicator to room tem perature by using the setting adjustment knob or an Allen wrench see Fig 11 The valve or damper motor should be at midpoint 2 Move the setpoint 5 F 3 C below room tempera ture In a heating application the valve or damper should close in a cooling application the valve or damper should open If the valve or damper is driven in the opposite direction interchange the wires at the B and W terminals NOTE If a proportional action limit control is used the motor may not move the damper or valve all the way closed or open Check the limit action after interchang ing the wiring 3 Move the setpoint 5 F 3 C above room tempera ture In a heating application the valve or damper should open in a cooling application the valve or damper should close 4 If the valve or damper responds properly to the thermostat move the setpoint to the desired temperature Home and Building Control Honeywell Inc 1985 Douglas Drive North 740 Ellesmere Road Golden Valley MN 55422 Scarborough Ontario MIP 2V9 Printed in U S A Home and Building Control Honeywell Limited Honeywell Limit e T921B 1 Place the changeover switch see Fig 11 in
5. Honeywell T921A B E G Proportional Control Thermostats T921 Thermostats provide 3 wire low voltage proportional control for Series 90 135 ohm valve motors damper motors and balancing relays in heating or cooling system applications T921A T921B T921E 60 70 80 90 HONEYWELL Ll T921G E Accessory faceplates available for horizontal mount ing of T921A B E models E COOL HEAT changeover switch in the T921B E Night setback mechanism and switch in the T921E E A spdt single pole double throw Class 2 auxiliary switch in the T921F G which operates at the low T921F and high T921G end of the throttling range E A bellows element adjusts the potentiometer slider to regulate motor operation E Various temperature ranges are available E All models are available with a thermometer and a locking cover CONTENTS RY 7 161 61011 0 Ee 2 Ordering Information cccccccsccccccssceceesseseeees 2 INSTA GHON oas aena TTAN sks 4 Setting ANd Adjusting eccccccccccccssssssssstecesseees 7 OP OV ALON sessenta is nE rE 7 O J D Rev 1 94 e Honeywell Inc 1994 e Form Number 60 2242 2 T921A B E G SPECIFICATIONS ORDERING INFORMATION Specifications TRADELINE MODELS TRADELINE models are selected and packaged to provide ease of stocking ease of handling and maximum replacement value TRADELINE model specifications are the same as those of the standard
6. N TEMPERATURE FALL BELOW THROTTLING RANGE 2 F 1 C DIFFERENTIAL SEE FIG 10 M5993 Fig 10 Typical wiring diagram for T921G SERIES 90 MODULATING MOTOR T921G 2 POSITION ACTUATOR A CLASS 2 POWER SUPPLY A INTERCHANGE B AND W CONNECTIONS TO REVERSE DIRECTION OF MOTOR TRAVEL A USE FOR CLASS 2 CIRCUITS MAKES R TO B ON TEMPERATURE RISE ABOVE THROTTLING RANGE 1 F 0 5 C DIFFERENTIAL SEE FIG 11 M5996 Setting and Adjusting TEMPERATURE SETTING Adjust all T921 models at the top of the thermostat for vertically mounted models and on the left side for horizon tally mounted models using the setting adjustment knob or an Allen wrench see Fig 11 The device is shipped with the temperature setting indicator at the center of the tem perature range Without removing the cover turn the set ting adjustment knob or use an Allen wrench so the indica tor is at the desired average room temperature 60 2242 2 ADDITIONAL FEATURES T921B SUMMER WINTER CHANGEOVER The T921B includes a summer winter changeover switch It is labeled COOL HEAT For horizontally mounted models this switch is located on the left side of the thermostat For vertically mounted models it is lo cated on the top of the thermostat see Fig 11 T921E NIGHT SETBACK The T921E includes a manual night setback switch located on the top of the thermostat see Fig 11 This switch energizes a heater that offsets the ther mostat ap
7. able with a blank cover and no thermometer AUXILIARY SWITCH DIFFERENTIAL T921F 2 F 1 C T921G 1 F 0 5 C THROTTLING RANGE Fixed T921A 2 5 F 1 C midscale T921B E 4 F 2 C T921F 6 F 3 C T921G 5 F 2 5 C Variable T921A model available with potentiometer for 5 to 6 F 2 5 to 3 C throttling range ELECTRICAL RATINGS Voltage 24 to 30 Vac Auxiliary Switch Contact Rating When Used For Pilot Duty 100 VA at 30 Vac DIMENSIONS Refer to Fig 1 ACCESSORIES ORDER SEPARATELY 127246A Adapter Plate Assembly for mounting all mod els vertically on a horizontal conduit box T921 models are shipped with a faceplate for vertical mount ing When mounting the T921A B E horizontally see Table 1 to order the faceplate with the appropriate scale NOTE Do not mount the T921F G horizon tally 34297B Thermostat Guard Assembly and 138541A Mounting Plate 133722A Thermostat Guard clear plastic cover 133723A Thermostat Guard beige plastic cover Ordering Information When purchasing replacement and modernization products from your TRADELINE wholesaler or your distributor refer to the TRADELINE Catalog or price sheets for complete ordering number or specify 1 Model number 2 Scale range 3 Accessories if desired If you have additional questions need further information or want to comment on our products or services please write or phone 1 You local Hon
8. eywell Home and Building Control Sales Office check the white pages of the phone directory 2 Home And Building Control Customer Satisfaction Honeywell Inc 1885 Douglas Drive North Minneapolis Minnesota 55422 1 800 468 1502 In Canada Honeywell Limited Honeywell Limitee 740 Ellesmere Road Scarborough Ontario M1P 2V9 International Sales and Service Offices in all Principal Cities of the world Manufacturing in Australia Canada Finland France Germany Japan Mexico Netherlands Spain Taiwan United Kingdom U S A 60 2242 2 Fig 1 T921 approximate installation dimen sions in in mm ACCESSORY ADAPTER PLATE 127246A FOR SETTING MOUNTING ON HORIZONTAL CONDUIT BOX ADJUSTMENT KNOB HORIZONTAL CONDUIT BOX FOR VERTICAL CONDUIT BOX 2 rt 3 5 Lote Sea 53 73 137 194 yl A T 21 57 la A 2 11 16 69 INCHES FOR ag T921F G MODELS M9107 TABLE 1 ACCESSORY FACEPLATE 56 to 84 F 13 to 29 C 135135A 13 to 29 C 56 to 84 F 135135B 42 to 75 F 5 to 24 C 135135C 66 to 95 F 19 to 35 C 135135D 56 to 84 F 13 to 29 C 135135C Blank faceplate REPLACEMENT PART 130224 Locking Cover Knob OPTIONAL SPECIFICATION USING THE T991B Alternate proportional control similar to the T921A but uses an outdoor temperature automatic control point reset T991B with 3 1 2 1 reset and 50 to 120 F 10
9. proximately 10 F 6 C lowering the temperature for night operation Leave this switch in the OFF position for normal operation turn it to the ON position for lower night time temperature CALIBRATION IMPORTANT Do not recalibrate unless the thermostat continues to be out of adjustment after several hours of operation T921 Thermostats are calibrated at the factory so when the room temperature matches the setpoint temperature the wiper is at the center of the active potentiometer winding If the thermostat is out of calibration proceed as follows see Fig 11 1 Remove the thermostat cover 2 Turn the thermostat setting adjustment knob or an Allen wrench until the valve or damper motor is at mid point 3 Loosen the indicator lock screw and move the indica tor to room temperature Tighten the lock screw 4 Replace the thermostat cover Recheck the calibra tion and repeat the procedure if necessary In the T921 a vapor filled bellows moves the potenti ometer wiper by expanding or contracting in proportion to temperature changes As the wiper moves the appropriate motor winding is energized opening or closing the valve or damper to compensate for the temperature change in the controlled area Operation of the auxiliary switch in the T921F G is shown in Figs 12 and 13 See Table 3 for the throttling range of each thermostat The T921F Auxiliary Switch makes R W at the low end of the throttling range on temperature
10. r plate 6 Make all electrical connections to the terminals on the back of the thermostat before mounting the instrument on the backplate Refer to the Wiring section 7 Mount the thermostat on the backplate with the mount ing screws 8 After performing the checkout tests replace the ther mostat cover and tighten the locking screw 60 2242 2 ADD FACEPLATES FOR HORIZONTAL MOUNTING T921A B E ONLY T921 models are shipped with a faceplate for vertical mounting When mounting the T921A B E horizontally see Table 2 to order the faceplate with the appropriate scale NOTE Do not mount the T921F G horizontally TABLE 2 ACCESSORY FACEPLATE 56 to 84 F 13 to 29 C 135135A 13 to 29 C 56 to 84 F 135135B 42 to 75 F 5 to 24 C 135135C 66 to 95 F 19 to 35 C 135135D 56 to 84 F 13 to 29 C 135135C4 Blank faceplate Affix the accessory faceplate when mounting the T921A B E models horizontally with contemporary cov ers Peel the backing strip from the faceplate and place it lightly over the vertical faceplate Align the edges and corners and make sure the scales align with the markings Press firmly over the entire surface Do not attempt to reapply once the faceplate has been mounted Fig 3 Vertical mounting of T921A B E G Thermostats on vertical conduit box T921A B E Thermostats can also be mounted horizontally on horizontal conduit box using add on faceplate Do not mo
11. rise and makes R B at 2 F 1 C below the low end of the throttling range on temperature fall The T921G Auxiliary Switch makes R W at the high end of the throttling range on temperature fall and R B at F 0 5 C above the high end of the throttling range on temperature rise TABLE 3 THERMOSTAT THROTTLING RANGES Throttling Range T921A 2 5 F T921B 2 5 F 1 5 C midscale 1 5 C midscale T921F 6 F 77 C T921G 5 F 3 C T921A B E G SETTING AND ADJUSTING OPERATION Fig 11 Internal view of vertically mounted T921 horizontally mounted model is similar POTENTIOMETER WIPER SETTING A m smao KNOB TEMPERATURE SETTING INDICATOR INDICATOR LOCK SCREW BELLOWS A SUMMER WINTER COOL HEAT CHANGEOVER SWITCH ON T921B ONLY NIGHT SETBACK SWITCH ON T921E ONLY M9039 Operation Fig 12 T921F auxiliary switch operation TEMPERATURE AEE NER E OEE ea E EEE THROTTING 1 5 C RANGE 6 F 4 C SETPOINT TEMPER eet Seeee Sok ATURE TEMPERATURE FALL 3 F 15 C R W MAKES 2 F 1 C TEMPERATURE DIFFERENTIAL RISE i R B MAKES M5990 60 2242 2 T921A B E G OPERATION Fig 13 T921G auxiliary switch operation TEMPERATURE TEMPERATURE FALL R B MAKES 42 5 F 1 F 0 5 C 1 5 CI LL RW Makes DIFFERENTIAL TEMPERATURE RISE SETPOINT TEMPER ba daanan ATURE Ie THROTTING 2 hts ites SE f RANGE 5 F 3 C 2 5 F 1 5 C M5
12. rvice tech nician 2 All wiring must comply with applicable electrical codes ordinances and regulations 3 Do not exceed the ratings listed on the device name plate 4 After the installation is complete conduct a thorough checkout of the product operation LOCATION Locate the thermostat about 5 feet 1 5m above the floor in an area with good air circulation at average room temperature Do not mount the thermostat where it can be affected by drafts or dead spots behind doors and in corners hot or cold air from ducts radiant heat from the sun or appliances concealed pipes and chimneys unheated uncooled areas such as an outside wall behind the thermostat MOUNTING 1 Disconnect power supply before installation to pre vent electrical shock and equipment damage 2 Loosen the locking screw at the bottom of the case with an Allen wrench 3 Lift off the thermostat cover 4 Remove the mounting screws that secure the thermo stat to the backplate and remove the backplate 5 Fasten the backplate to the conduit box see Fig 3 Use the 127246A Adapter Plate Assembly ordered sepa rately to mount the thermostat vertically on the horizontal conduit box or to mount the thermostat horizontally on the vertical conduit box see Fig 4 NOTE When an accessory adapter plate is used fasten the adapter plate to the conduit box with the two screws provided Then fasten the backplate to the adapte
13. the HEAT position and follow steps 1 through 3 of the T921A procedure 2 Move the switch to the COOL position and repeat steps 1 through 3 of the T921A procedure 3 If the valve or damper responds properly to the thermostat move the setpoint to the desired temperature T921E 1 Place the night setback switch see Fig 11 in the OFF position and follow steps 1 through 3 of the T921A procedure 2 Move the setpoint 5 F 3 C above room tempera ture the valve or damper should open 3 Move the night setback switch to the ON position as the heater in the thermostat warms up the valve or damper should be driven toward the closed position Allow 30 minutes for the heater and bellows to warm up 4 If the valve or damper responds properly to the thermostat move the setpoint to the desired temperature T921F 1 Follow steps 1 through 3 of the T921A procedure 2 Move the setpoint at least 10 F 6 C above room temperature The auxiliary switch should be make R B and the valve or damper should be open for heating applica tion Lower the setpoint gradually the auxiliary switch should make R W before the setting indicator reaches room temperature As the setting indicator moves below room temperature the valve or damper should be driven closed 3 If the valve or damper responds properly to the thermostat move the setpoint to the desired temperature T921G 1 Follow steps 1 through 3 of the T921A procedure 2 Move
14. the setpoint at least 6 F 4 C below room temperature The auxiliary switch should be made R B and the valve or damper should be closed for heating applica tion Raise the setpoint gradually the auxiliary switch should make R W before the setting indicator reaches room temperature As the setting indicator moves above room temperature the valve or damper should open 4 If the valve or damper responds properly to the thermostat move the setpoint to the desired temperature Honeywell Helping You Control Your World QUALITY IS KEY
15. unt T921F G horizontally NOTE ACCESSORY FACEPLATE FOR USE WHEN THE THERMOSTAT IS MOUNTED HORIZONTALLY A PEEL OFF BACKING AND APPLY OVER VERTICAL FACEPLATE AFTER MOUNTING IS COMPLETE CONDUIT MOUNTING BOX SCREWS LOCKING SCREW M9037 Fig 4 Vertical mounting of T921A B E G Thermostats on horizontal conduit box T921A B E Thermostats can also be mounted horizontally on vertical conduit box using add on faceplate Do not mount T921F G horizontally NOTE ACCESSORY FACEPLATE FOR USE WHEN THE THERMOSTAT IS MOUNTED HORIZONTALLY PEEL OFF BACKING AND APPLY OVER VERTICAL FACEPLATE AFTER MOUNTING IS COMPLETE MOUNTING SCREWS 127246A LOCKING ACCESSORY ADAPTER SCREW PLATE COVER M9036 WIRING Be sure all wiring must complies with applicable electri cal codes ordinances and regulations Do not exceed the following electrical ratings Voltage 24 to 30 Vac Auxiliary Switch Contact Ratings 100 VA at 30 Vac Make all electrical connections to the terminals on the back of the thermostat before mounting the instrument onto the conduit box Terminal locations for all models are shown in Fig 5 Note the difference in terminal designa tions for the auxiliary switch on the T921F and G The H Heater terminal on the T921E is a black leadwire Typical wiring diagrams are shown in Figs 6 through 10 Wire the T921 color to color when the modulating motor must drive the valve or damper open on temperature
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