White Rodgers 50A66-743 Thermostat User Manual
Contents
1. BLOWER INDUCER COMPRESSOR CONTACTOR THERMOSTAT PRESSURE SWITCH N O LIMIT N C O ROLLOUT IGN N 4 Pin Connector 12 Pin Connector W G R Y C HLO Pin 1 Not Used Pin 2 TH Pin 3 Not Used Pin 4 RO1 Pin 5 TR Pin 6 HLI Pin 7 GND Pin 8 MV COM Pin 9 PSI Pin 10 RO2 Pin 11 MV Pin 12 WIRING TYPICAL SYSTEM WIRING TABLE 50A66 TERMINAL SYSTEM COMPONENT TERMINAL TYPE CONNECTION Terminal block with captive screws low voltage thermostat W terminal or equivalent low voltage thermostat G terminal or equivalent low voltage thermostat R terminal or equivalent low voltage thermostat Y terminal or equivalent 2nd wire from Y terminal goes to 24 VAC HOT side of compressor contactor coil 24 VAC COMMON side of compressor contactor coil high limit OUTPUT 24 VAC transformer low voltage HIGH side rollout switch OUTPUT 24 VAC transformer low voltage COMMON side high limit INPUT MUST BE RELIABLY GROUNDED TO CHASSIS gas valve COMMON pressure switch INPUT rollout switch INPUT gas valve inducer HOT side ignitor HOT side inducer NEUTRAL side ignitor NEUTRAL side input voltage 120 VAC HOT side FMR 1 4 spade terminal 24 VAC transformer line voltage HOT side EAC optional 1 4 spade terminal electronic air cleaner HOT side 120 VOLT NEUTRAL 1 4 spade terminal Terminals for 1202. installed according to local and na tional electrical codes and ordinances The control must be secured to an area that will experience a minimum of vibration and remain below the maximum ambient temperature rating of 175 F The control is ap proved for minimum ambient temperatures of 40 F Any orientation is acceptable Refer to the wiring diagram and wiring table when connect ing the 50A66 control to other components of the system UL approved 105 C rated 18 gauge stranded c4 thick insulation wire is recommended for all low voltage safety circuit connections Refer to 50A66 specification sheet for recommended terminals to mate with those on the control UL approved 105 C rated 16 gauge min stranded 4 64 thick insulation wire is recommended for all line voltage connections Refer to 50A66 specification sheet for rec ommended terminals to mate with those on the control After installation or replacement follow appliance manu facturer s recommended installation or service instructions to ensure proper operation WIRING HOT LINE ELECTRONIC AIR CLEANER 24V HUMIDIFIER FLAME TYPICAL SYSTEM WIRING DIAGRAM 120 VAC NEUTRAL LINE H 24 VAC CLASS Il le TRANSFORMER 120 VOLT NEUTRAL SENSOR gt r L 1_FP__ 38 I I PROBE LEGEND Low Voltage 24 VAC Line Voltage 120 VAC N C Normally closed switch N O Normally open switch N C CIRCULATOR
3. Volt NEUTRAL for line transformer 5 terminals circulator electronic air cleaner and humidifier FP E33 3 16 spade terminal flame sensor probe 1 4 spade terminal Circulator blower fan speed terminal HUM optional 1 4 spade terminal humidifier HOT side 24 V HUM E2 1 4 receptacle 24 VAC humidifier maximum recommended flame probe wire length is 36 inches OPERATION OPTION SWITCHES The option switches on the 50A66 743 control are used to determine the length of the heat delay to fan off period The following table shows the time periods that will result from the various switch positions OPTION SWITCH POSITIONS HEAT delay Set switch to fan off 1 2 60 sec 90 sec 120 sec 180 sec COOL delay to fan off 2 sec 45 sec Factory Setting HEAT MODE In a typical system a call for heat is initiated by closing the thermostat contacts This starts the 50A66 control s heating sequence The inducer blower and humidifier are energized After a 15 second prepurge period the 768A Silicon Nitride ignitor is powered This controller has an adaptive algorithm that reduces the ignitor temperature to slightly greater than the minimum temperature required to ignite gas in each particular application The control measures the line voltage and determines an initial ignitor temperature setting based on the measurement After each successful ignition the control lowers the i
4. White y Rodgers 50A66 743 Integrated Furnace Control INSTALLATION INSTRUCTIONS Operator Save these instructions for future use FAILURE TO READ AND FOLLOW ALL INSTRUCTIONS CAREFULLY BEFORE INSTALLING OR OPERATING THIS CONTROL COULD CAUSE PERSONAL INJURY AND OR PROPERTY DAMAGE The 50A66 743 is an automatic gas interrupted ignition control that employs a microprocessor to continually monitor analyze and control the proper operation of the gas burner inducer and fan Signals interpreted during continual surveillance of the thermostat and flame sensing element initiate automatic ignition of the burner sensing of the flame and system shut off during normal operation These controls incorporate system fault analysis for quick gas flow shut off coupled with automatic ignition retry upon sensing a fault correction Installation should be done by a qualified heating and air conditioning contractor or licensed electrician Ifin doubt about whether your wiring is millivolt line or low voltage have it inspected by a qualified heating and air conditioning contractor or licensed electrician Do not exceed the specification ratings All wiring must conform to local and national electrical codes and ordinances This control is a precision instrument and should be handled carefully Rough handling or distorting components could cause the control to malfunction Following installation or replacement follow manufactu
5. an off period begins When the purge is complete the inducer blower and humidifier are de energized After the delay to fan off period ends the circulator fan and electronic air cleaner are de energized If flame is not detected both valves are de energized the ignitor is turned off and the 50A66 control goes into the retry sequence The retry sequence provides a 15 second wait following an unsuccessful ignition attempt flame not detected After this wait the ignition sequence is restarted If this ignition attempt is unsuccessful three more retries will be made before the control goes into system lockout If flame is detected then lost the 50A66 control will repeat the initial ignition sequence for a total of three recycles After three unsuccessful recycle attempts the control will go into system lockout If flame is established for more than 10 seconds after ignition the 50A66 controller will clear the ignition attempt or retry counter If flame is lost after 10 seconds it will restart the ignition sequence This can occur a maximum of four times before system lockout A momentary loss of gas supply flame blowout or a shorted or open condition in the flame probe circuit will be sensed within 2 seconds The gas valve will de energize and the control will restart the ignition sequence Recycles will begin and the burner will operate normally if the gas supply returns or the fault condition is corre
6. cted before the last ignition attempt Otherwise the control will go into system lockout If the control has gone into system lockout it may be possi ble to reset the control by a momentary power interruption of ten seconds or longer Refer to PRECAUTIONARY SYSTEM LOCKOUT AND DIAGNOSTIC FEATURES COOL MODE In a typical system a call for cool is initiated by closing the thermostat contacts This starts the 50A66 control s cooling sequence The compressor is energized and the delay to fan on period begins After the delay to fan on period ends the circulator fan is energized at cool speed The electronic air cleaner optional is also energized After the thermostat is satisfied the compressor is de energized and the delay to fan off period begins After the delay to fan off period ends the circulator fan and electronic air cleaner are de energized MANUAL FAN ON MODE If the thermostat fan switch is moved to the ON position the circulator fan heat speed and optional electronic air cleaner are energized When the fan switch is returned to the AUTO position the circulator fan and electronic air cleaner optional are de energized SYSTEM LOCKOUT AND DIAGNOSTIC FEATURES SYSTEM LOCKOUT FEATURES 2 Interrupt the 24 VAC power at the control for at least ten seconds You may also need to reset the flame When system lockout occurs the gas valve is de energized f rollout sensor switch The circulator blower may be energiz
7. ed at heat speed for some faults and if flame is sensed the inducer bloweris 3 After one hour in lockout the control will automatically energized The diagnostic indicator light will flash or glow reset itself continuously to indicate system status System lockout i i ti feat will never override the precautionary features DIAGNOSTIC FEATURES To reset the control after system lockout do one of the following The 50A66 743 control continuously monitors its own operation and the operation of the system If a failure oc curs the DS 1 red and DS 2 green LEDs will indicate a failure code as shown below 1 Interrupt the call for heat at the thermostat for at least one second but for less than 20 seconds if flame is sensed with the gas valve de energized interrupting the call for heat at the thermostat will not reset the control TROUBLESHOOTING DIAGNOSTIC TABLE DS 1 Red DS 2 Green Error Condition Comments Troubleshooting Simultaneous Simultaneous Normal operation No fault slow flash slow flash Simultaneous Simultaneous Normal operation with Normal operation fast flash fast flash call for heat Slow flash On Open limit switch Verify continuity through rollout switch circuit Off Slow flash Pressure switch stuck Pressure switch stuck closed Check switch function verify closed open inducer is turning off Pressure switch stuck open Check pressure switch function and tubing Verif
8. gnitor temperature slightly for the next ignition attempt The control continues to lower the ignitor temperature until ignition does not occur and the control goes into retry mode For the second attempt to ignite gas within the same call for heat the control increases the ignitor temperature to the value it was on the third previous successful ignition After ignition is successful the control sets the ignition temperature at this value for the next 255 calls for heat after which the control repeats the adaptive algorithm The control is constantly making adjustments to the ignitor temperature to compensate for changes in the line voltage The 80 VAC Silicon Nitride ignitor manufactured by White Rodgers must be used These ignitors are special ly designed to operate with the 50A66 s adaptive ignition routine to ensure the most efficient ignitor temperature At the end of the ignitor warm up time both valves in the 36E manifold gas valve are opened Flame must be detected within 4 seconds If flame is detected the delay to fan on period begins After the delay to fan on period ends the circulator fan is energized at heat speed If there is an optional electronic air cleaner on the system the electronic air cleaner and the humidifier are energized When the thermostat is 6 satisfied the gas valve is de energized After proof of flame loss the inducer blower remains energized to purge the system for 5 seconds and the delay to f
9. ignition Trial for Ignition The period of time between initiation of gas flow and the action to 4 Period IAP deactivation of the ignition means prior to the end of TFI Retries The additional attempts within the same thermostat cycle for ignition 4 times when the supervised main burner flame is not proven within the first trial for ignition period Valve Sequence Valve sequence period equals 4 seconds trial for ignition period x 20 Period 1 initial try 2 retries 12 seconds Interpurge The period of time intended to allow for the dissipation of any unburned 15 gas or residual products of combustion between the failed trial for ignition and the retry period Post Purge The period of time intended to allow for the dissipation of any unburned 5 gas or residual products of combustion at the end of a furnace burner operating cycle Post purge begins at the loss of flame sense Lockout Time ANSI standard rated module timing 250 Heat Delay To Fan On_ The period of time between proof of the supervised main burner flame 45 and the activation of the blower motor at Heat speed Heat Delay To Fan Off The period of time between the loss of a call for heat and the 60 90 120 180 deactivation of the blower motor at Heat speed Cool Delay To Fan On The period of time after a thermostat demand for cool before energizing 2 the circulator blower motor at Cool speed Cool Delay To Fan Off The per
10. iod of time between the loss of a call for cool and the 2 45 deactivation of the blower motor at Cool speed Ignitor Warm up The length of time allowed for the igniter to heat up prior to the initiation 20 of gas flow Auto Reset After one 1 hour of internal or external lockout the control will auto 60 minutes matically reset itself and go into an auto restart purge for 60 seconds Humidifier Yes Electronic Air Cleaner Yes This time will vary depending on option switch position The control is factory set at 90 seconds HEAT delay to fan off and 45 seconds COOL delay to fan off See OPERATION section for further information A WARNING FIRE HAZARD e Do not exceed the specified voltage Replace existing control with exact model and dash number Protect the control from direct contact with water dripping spraying rain etc Labelall wires before disconnection when servicing controls Wiring errors can cause improper and dangerous operation Route and secure wiring away from flame SHOCK HAZARD e Disconnect electric power before servicing e Ensure proper earth grounding of appliance e Ensure proper connection of line neutral and line hot wires EXPLOSION HAZARD e Shut off main gas to appliance until installation is complete INSTALLATION CAUTION Do not short out terminals on gas valve or primary control Short or incorrect wiring may damage the thermostat MOUNTING AND WIRING All wiring should be
11. nput Current 25 VAC 0 45 amp Relay Load Ratings Valve Relay 1 5 amp 25 VAC 50 60 Hz 0 6 pf Ignitor Relay 2 0 amp 120 VAC 50 60 Hz resistive Inducer Relay 2 2 FLA 3 5 LRA 120 VAC Circulator Relay 14 5 FLA 25 0 LRA 120 VAC Flame Current Requirements Minimum currentto insure flame detection 0 25 pa DC Maximum current for non detection 0 1 pa DC Maximum allowable leakage resistance 100 M ohms Measured witha DC microammeterin the flame probe lead OPERATING TEMPERATURE RANGE 40 to 175 F 40 to 80 C HUMIDITY RANGE 5 to 93 relative humidity non condensing MOUNTING Surface mount multipoise Timing Specs 60 Hz maximum Flame Establishing Time 0 8 sec Flame Failure Response Time 2 0 sec At 50 Hz all timing specifications should be increased by 20 Gases Approved Natural Manufactured Mixed Liquified Petroleum andLP Gas Air Mixtures are all approved for use TIMING SPECIFICATIONS All times are in seconds unless noted otherwise Period TFI Ignition Activation shut off the gas flow in the event of failure to establish proof of the supervised ignition source or the supervised main burner flame The period of time between energizing the main gas valve and 4 Event Definition 50A66 743 Pre Purge The period of time intended to allow for the dissipation of any unburned 15 gas or residual products of combustion at the beginning of a furnace operating cycle prior to initiating
12. rer s recommended installation service instructions to ensure proper CAUTION Do not short out terminals on gas valve or primary control Short or incorrect wiring may damage the thermostat CONTENTS Description Precautions Specifications Installation Mounting amp Wiring Operation System Lockout and Diagnostic Features Troubleshooting EMERSON DESCRIPTION 50A66 743 Cross Reference Information zwee sowas o zwaai emos J PRECAUTIONS A WARNING Lh Failure to comply with the following warnings could result in personal injury or property damage FIRE HAZARD e Do not exceed the specified voltage e Replace existing control with exact model and dash number e Protect the control from direct contact with water dripping spraying rain etc If the control has been in direct contact with water replace the control Labelall wires before disconnection when servicing controls Wiring errors can cause improper and dangerous operation e Route and secure wiring away from flame SHOCK HAZARD e Disconnect electric power before servicing e Ensure proper earth grounding of appliance e Ensure proper connection of line neutral and line hot wires EXPLOSION HAZARD e Shut off main gas to appliance until installation is complete PART NO 37 7473A www white rodgers com www emersonclimate com 1313 SPECIFICATIONS ELECTRICAL RATINGS 77 F 25 C Input Voltage 25 VAC 50 60 Hz Max I
13. the appliance manufacturer Fast flash Slow flash Grounding or Verify the control and furnace are properly grounded Check reversed polarity and reverse polarity primary if incorrect Alternate fast flash Alternate fast flash Module ignitor contact failure Fault code indicates the module ignitor contacts are not functioning properly Replace module HOMEOWNER HELP LINE 1 800 284 2925 White Rodgers is a business of Emerson Electric Co The Emerson logo is a trademark and service mark of Emerson Electric Co White y Rodgers amp www white rodgers com www emersonclimate com EMERSON
14. y inducer is turning on and pulling sufficient vacuum to engage switch Alternate Alternate slow External lockout Failure to sense flame is often caused by carbon deposits on slow flash flash retries the flame sensor a disconnected or shorted flame sensor lead or a poorly grounded furnace Carbon deposits can be cleaned with emery cloth Verify sensor is not contacting the burner and is located in a good position to sense flame Ignitor must be positioned to light the gas immediately when the valve opens If the ignitor has been replaced verify hot spot position has not changed Check sensor lead for shorting and verify furnace is grounded properly Slow flash Off Flame sensed with gas Verify the gas is operating and shutting down properly Flame valve de energized in burner assembly should extinguish promptly at the end of the cycle Check orifices and gas pressure On Slow flash Open rollout switch Verify continuity through rollout switch circuit On On Module internal fault Module contacts for gas valve not operating or processor condition fault Reset control if condition persists replace module Slow flash Fast flash Low flame sense Low flame sense current is often caused by carbon deposits current on the flame sensor a poorly grounded furnace or a mis aligned flame sense probe Carbon deposits can be cleaned with emery cloth Check or improve furnace and module ground Verify sensor is located in or very near flame as specified by
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