White Rodgers 37-6753B Thermostat User Manual
Contents
1. 25 VAC 50 60 Hz 0 6 pf Ignitor Relay 6 0 amp 120 VAC 50 60 Hz resistive Flame Current Requirements Minimum current to insure flame detection 1 ua DC Maximum current for non detection 0 1 ja DC Maximum allowable leakage resistance 100 M ohms Measured with a DC microammeter in 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 and LP Gas Air Mixtures are all approved for use TIMING SPECIFICATIONS All times are in seconds unless noted otherwise 50A55 474 50A55 571 PRE PURGE TRIAL FOR IGNITION 4 PERIOD IGNITION ACTIVATION 1 PERIOD RETRIES VALVE SEQUENCE PERIOD INTERPURGE Far osre s howourmwe 9e Ea m 4 1 12 5 300 DELAY TO HEAT ON 45 60 100 DELAY TO HEAT OFF 140 180 2 DELAY TO COOL OFF 0 80 0 80 MINIMUM IGNITOR 11 11 WARM UP WARM UP INITIAL IGNITOR 17 17 attempts ES These times will vary depending on option switch position The control is factory set at O sec delay OPERATION section for further information This time will vary depending on the condition of cool off is set at O seconds2. that will result from the various jumper conditions OPTION JUMPER CONDITION COOL delay to fan off Jumper Condition Installed Clipped open 0 sec 80 sec HEAT MODE In atypical system a call for heat is initiated by closing the thermostat contacts This starts the 50A55 control s heat ing sequence The inducer blower and optional humidifier are energized and the ignitor is powered within one second These controls have an adaptive algorithm that adjusts the duration of the ignitor warm up for the purpose of extending ignitor life Upon initial application of power the warm up time is 17 seconds The ignitor on time will then be increased or decreased depending on whether or not flame is achieved The warm up time is limited to a maximum of 21 seconds During the first 64 warm up periods following power up the warm up time may not be less than 17 seconds Upon a call for heat if the warm up time has not been locked it will be decreased by one second This reduction of the ignitor on time will continue until flame fails to be achieved resulting in a retry In the event of a retry the warm up time will be increased by two seconds and locked at that duration Once the warm up time is locked it remains fixed until another call for heat results in a retry in which case the warm up time is again increased by two seconds and remains locked In the event of two successive retry attempts the warm up time w
3. LED will also flash once at power up
4. To obtain an 80 second delay to cool off clip the jumper wire and DELAY TO COOL ON EE WARM UP 1st 64 ELECTRONIC AIR to cool off and 100 sec delay to heat off See the jumper With the jumper installed the delay to separate the jumper legs MOUNTING AND WIRING Do not use on circuits exceeding specified volt age Higher voltage will damage control and could cause shock or fire hazard To prevent electrical shock and or equipment damage disconnect electric power to system at main fuse or circuit breaker box until installation is complete Failure to earth ground the appli ance or reversing the neutral and hot wire con nection to the line can cause shock hazard Shut off main gas to heating system until instal lation is complete Route and secure all wiring as far from flame as practical to prevent fire and or equipment damage INSTALLATION All wiring should be installed according to local and national electrical codes and ordinances The control must be secured to an area that will experi ence a minimum of vibration and remain below the maxi mum ambient temperature rating of 175 F The control is approved for minimum ambient temperatures of 40 F Any orientation is acceptable Refer to the wiring diagram and wiring table when con necting the 50A55 control to other components of the system UL approved 105 C rated 18 gauge stranded 4 thick insulation wire is recommended for all low voltage sa
5. WHITE RODGERS 50A55 474 amp 50A55 571 Integrated Furnace Controls 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 50A55 474 and 50A55 571 are automatic gas inter rupted ignition controls that employ a microprocessor to continually monitor analyze and control the proper op eration 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 J Y GENERAL PRECAUTION Application of this type of control may cause flame rollout on initial start up and could cause personal injury and or property damage Replace only with exact model number includ ing dash number Failure to use exact replace ment control could cause personal injury and or property damage If in 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 el
6. ectrical codes and ordinances This control is a precision instrument and should be handled carefully Rough handling or distorting compo nents could cause the control to malfunction CONTENTS Description Precautions Specifications Installation Mounting amp Wiring Operation ENS WHITE RODGERS DIVISION EMERSON ELECTRIC CO Rt 9797 REAVIS ROAD emerson ST LOUIS MISSOURI 63123 5398 Printed in U S A DESCRIPTION To prevent electrical shock and or equipment damage disconnect electric power to system at main fuse or circuit breaker box until installation is complete Label all wires prior to disconnection when ser vicing controls Wiring errors can cause im proper and dangerous operation This control is not intended for use in locations where it may come in contact with water Suit able protection must be provided to shield the control from exposure to water dripping spray ing rain etc Do not use on circuits exceeding specified volt age Higher voltage will damage control and could cause shock or fire hazard Do not short out terminals on gas valve or pri mary control to test Short or incorrect wiring will damage thermostat and could cause personal injury and or property damage PART NO 37 5800C Replaces 37 5800B 9751 SPECIFICATIONS ELECTRICAL RATINGS O 77 F 25 C Input Voltage 25 VAC 50 60 Hz Max Input Current 25 VAC 0 45 amp Relay Load Ratings Valve Relay 1 5 amp
7. es to 24 VAC HOT side of compressor contactor coil 24 VAC COMMON side of compressor contactor coil MV 2 terminals gas valve both gas solenoids are connected in parallel TR 24 VAC transformer low voltage COMMON side TH 24 VAC transformer low voltage HIGH side FP 12 pin flame sensor probe PS connector pressure switch INPUT HLI amp harness high limit INPUT HLO high limit OUTPUT GND MUST BE RELIABLY GROUNDED TO CHASSIS 3 unused terminals inducer HOT side 4 pin ignitor HOT side connector inducer NEUTRAL side amp harness BR ignitor NEUTRAL side input voltage 120 VAC HOT side EAC optional spade terminal circulator blower NEUTRAL terminal input voltage 120 VAC NEUTRAL side XFMRN spade terminal electronic air cleaner NEUTRAL side maximum recommended flame probe wire length is 36 inches OPERATION OPTION SWITCHES 50A55 474 only The option switches on the 50A55 474 control are used to determine the length of the cool delay to fan off and heat delay to fan off periods The following tables show the time periods that will result from the various switch posi tions OPTION SWITCH POSITIONS COOL delay to fan off 0 sec On 80 sec Off Set switch to fan off 2 3 60 sec 100 sec 140 sec 180 sec OPTION JUMPER 50A55 571 only The option jumper on the 50A55 571 control is used to determine the length of the cool delay to fan off period The following table shows the time periods
8. fety circuit connections Refer to 50A55 specification sheet for recommended terminals to mate with those on the control UL approved 105 C rated 16 gauge min stranded 4 thick insulation wire is recommended for all line voltage connections Refer to 50A55 specification sheet for rec ommended terminals to mate with those on the control The 50A55 has only one serviceable part an automotive type fuse which protects the low voltage transformer from damage if its output is short circuited If the fuse has opened up remove whatever caused the short circuit and replace the fuse with only a 3 Amp automotive type fuse If the fuse is not the cause of the control s problem replace the entire 50A55 control There are no other user serviceable parts TYPICAL SYSTEM WIRING DIAGRAM HOT NEUTRAL LINE LINE 120 VAC 24 VAC CLASS Il TRANSFORMER TH INDUCER HUMIDIFIER IGNITOR 474 only ELECTRONIC AIR CLEANER 474 only COMPRESSOR CONTACTOR OD HIGH LIMIT AUX HIGH N C LIMIT N C Low Voltage 24 VAC Line Voltage 120 VAC N C Normally closed switch N O Normally open switch TYPICAL SYSTEM WIRING TABLE TERMINAL TYPE CONNECTION low voltage thermostat W terminal or equivalent Terminal low voltage thermostat G terminal or equivalent block with low voltage thermostat R terminal or equivalent captive low voltage thermostat Y terminal or equivalent screws 2nd wire from Y terminal go
9. ill be unlocked and set to 21 seconds If flame is then achieved the warm up time will begin adapting again with the next call for heat If however this third attempt fails to achieve flame the control will go into system lockout 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 circulatorfan is energized at heat speed If there is an optional electronic air cleaner on the system the electronic air cleaner is also energized When the thermo stat is satisfied the gas valve is de energized After proof of flame loss the delay to fan off period begins and the inducer blower remains energized to purge the system for 5 seconds 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 50A55 control goes into the retry sequence The retry sequence provides a 60 second wait following an unsuccessful ignition attempt flame not detected After this wait the ignition sequence is restarted with 2 seconds of ignitor warm up time If this ignition attempt is unsuccessful one more retry will be made before the control goes into system lock
10. o need to reset the flame rollout sensor switch 3 Afteronehourinlockout the control will automatically reset itself DIAGNOSTIC FEATURES The 50A55 control continuously monitors its own opera tion and the operation of the system The LED light on the control will flash slowly one flash per second if there are no failures and no call for heat If there is a call for heat the LED will flash quickly one flash per half second If a failure occurs the LED will indicate a failure code as shown below If the failure is internal to the control the light will stay on continuously In this case the entire control should be replaced as the control is not field repairable Ifthe LED is continuously off there may be no power to the control the fuse on the control may be open or there may be a failure in the control If the sensed failure is in the system external to the control the LED will flash in the following flash pause sequences to indicate failure status each flash will last approximately 0 25 seconds and each pause will last approximately 2 seconds 2 flashes then pause System lockout noflame check line polarity Pressure switch problem Thermal protection device open Flame sensed with gas valve off 115 Volt AC power reversed Gas valve circuit error Low flame sense signal 3 flashes then pause 4 flashes then pause 5 flashes then pause 6 flashes then pause 7 flashes then pause 8 flashes then pause The
11. out If flame is detected then lost the 50A55 control will repeat the initial ignition sequence for a total of ten recycles After ten unsuccessful recycle attempts the control will go into system lockout If flame is established for more than 10 seconds after ignition the 50A55 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 11 times before system lockout During burner operation amomentary loss of power of 50 milliseconds or longer will de energize the main gas valve When power is restored the gas valve will remain de energized and a restart of the ignition sequence will begin immediately A momentary loss of gas supply flame blowout or a shorted or open condition in the flame probe circuit will be sensed within 2 0 seconds The gas valve will de ener gize and the control will restart the ignition sequence A recycle will begin and the burner will operate normally if the gas supply returns or the fault condition is corrected before the last ignition attempt Otherwise the control will go into system lockout If the control has gone into system lockout it may be possible to reset the control by a momentary power interruption of one second or longer Refer to SYSTEM LOCKOUT FEATURES COOL MODE In atypical system a call for cool is initiated by closing the thermostat contacts This energizes
12. the 50A55 control The compressor and optional electronic air cleaner are energized and the circulator fan is energized at cool speed After the thermostat is satisfied the compressor is de energized and the optional cool mode delay to fan off period begins After the optional delay to fan off period ends the circulator fan and electronic air cleaner op tional 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 When system lockout occurs the gas valve is de ener gized the circulator blower is energized at heat speed and if flame is sensed the inducer blower is energized The diagnostic indicator light will flash or glow continu ously to indicate system status System lockout will never override any precautionary features Toresetthe control after system lockout do one of the following 1 Interrupt the call for heat or cool at the thermostat for atleast one second but less than 20 seconds if flame is sensed with the gas valve de energized interrupt ing the call for heat at the thermostat will not reset the control 2 Interrupt the 24 VAC power at the control for at least one second You may als
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