White Rodgers 50A55-3797 Installation Instructions
Contents
1. after loss of the supervised ignition source or the supervised main burner flame Retries The additional attempts within the same thermostat cycle for ignition when the supervised main burner flame is not proven within the first trial for ignition period Trial for Ignition Period TFI The period of time between initiation of gas flow and the action to shut off the gas flow in the event of failure to establish proof of the supervised ignition source or the supervised main burner flame Red LED Flash Error Condition Slow Flash Normal operation Fast Flash Normal operation External lockout exceeded retries 3 Pressure switch problem vent on Inducer problem 4 Open high temperature limit switch 5 Flame sensed with gas valve de energized 6 Reversed polarity 8 Low flame sense current oe Control failure Control failure TROUBLESHOOTING Commenis Troubleshooting Normal no Call for Heat Normal Call for Heat Failure to sense flame is often caused by carbon deposits on 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 Check sensor lead for shorting and verify furnace is grounded properly Verify gas supply to valve gas valve in On position and appliance lighting properly Verify flame reaches flame sensor durin2. 50A55 3797 Integrated Furnace Control INSTALLATION INSTRUCTIONS White Rodgers FAILURE TO READ AND FOLLOW ALL INSTRUCTIONS CAREFULLY BEFORE INSTALLING OR OPERATING THIS CONTROL COULD CAUSE PERSONAL INJURY AND OR PROPERTY DAMAGE DESCRIPTION The 50A55 3797 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 It is designed as a replacement for the following controls Trane White Rodgers CNT02891 50A55 474 CNT03799 50A55 476 CNT02789 50A55 571 50A55 3797 PRECAUTIONS A WARNING Failure to comply with the following warnings could result in personal injury or property damage FIRE HAZARD 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 If the control has been in direct contact with water replace the control Installation should be done by a qualified heating and air condit
3. COMMON side of compressor contactor coil high limit OUTPUT flame sensor probe 24 VAC transformer low voltage HIGH side not used not used 24 VAC transformer low voltage COMMON side high limit INPUT MUST BE RELIABLY GROUNDED TO CHASSIS MV COM Pin 9 gas valve COMMON PS Pin 10 pressure switch INPUT Pin 11 not used MV Pin 12 gas valve IND Pin 1 inducer HOT side IGN Pin 2 ignitor HOT side IND N Pin 3 inducer NEUTRAL side IGN N Pin 4 ignitor NEUTRAL side input voltage 120 VAC HOT side HUM optional CIR N circulator blower NEUTRAL terminal input voltage 120 VAC NEUTRAL side humidifier NEUTRAL side captive screws OPTION SWITCHES The option switches on the 50A55 3797 control are used to determine the length of the heat delay to fan off periods and cool delay to fan off period The following tables shows the time periods that will result from the various switch positions COOL OFF DELAY HEAT OFF DELAY HEAT MODE In atypical system a call for heat is initiated by closing the thermostat contacts This starts the 50A55 control s heating sequence The inducer blower and optional humidifier are energized and the ignitor is powered This controller has an adaptive algorithm that adjusts the duration of the ignitor warm up to extend 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 o
4. VAC 50 60 Hz 0 6 pf Ignitor Relay 6 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 current to insure flame detection 1 ya DC Maximum current for non detection 0 1 pa DC Maximum allowable leakage resistance 100 M ohms Measured with a DC microammeter inthe 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 INSTALLATION MOUNTING AND WIRING Allwiring should be installed according to local and national 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 approved for minimum ambient temperatures of 40 F Any orientation is acceptable Refer to the wiring diagram and wiring table when connecting the 50A55 control to other components of the system UL approved 105 C rated 18 gauge stranded 2 64 thick insulation wire is recommended for all low voltage safety circ
5. e possible to reset the control by a momentary power interruption of one second or longer Refer to SYSTEM LOCKOUT FEATURES COOL MODE In a typical system a call for cool is initiated by closing the thermostat contacts This energizes the 50A55 control and the compressor The cool delay to fan on period begins After the delay period ends the optional electronic air cleaner is energized and the circulator fan is energized at cool speed After the thermostat is satisfied the compressor is de energized and the cool mode delay to fan off period begins After the delay to fan off period ends the circulator fan and electronic air cleaner optional 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 OPERATION SYSTEM LOCKOUT AND DIAGNOSTIC FEATURES SYSTEM LOCKOUT FEATURES When system lockout occurs the gas valve is de energized 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 continuously to indicate system status System lockout will never override the precautionary features To reset the control after system lockout do one of the following 1 Interrupt the ca
6. ergizing the circulator blower motor at Cool speed Flame Failure Response Time FFRT The period of time between loss of the supervised main burner flame and the action to shut off the gas supply Heat Delay To Fan Off The period of time between the loss of a call for heat and the deactivation of the blower motor at Heat speed Heat Delay To Fan On The period of time between proof of the supervised main burner flame and the activation of the blower motor at Heat speed Igniter Warm up Time The length of time allowed for the igniter to heat up prior to the initiation of gas flow Ignition Activation Period IAP The period of time between energizing the main gas valve and deactivation of the ignition means prior to the end of TFI Inter purge The period of time intended to allow for the dissipation of any unburned gas or residual products of combustion between the failed trial for ignition and the retry period Post purge Time The period of time intended to allow for the dissipation of any unburned gas or residual products of combustion at the end of a furnace burner operating cycle Post purge begins at the loss of flame sense Pre purge Time The period of time intended to allow for the dissipation of any unburned gas or residual products of combustion at the beginning of a furnace operating cycle prior to initiating ignition Recycles The additional attempts within the same thermostat cycle for ignition
7. g ignition attempts and gas pressures are correct Check switch function verify inducer is working correctly Refer to wiring diagram terminals PS Verify continuity through limit switch circuit Refer to wiring diagram terminals HLO Verify the gas valve is operating and shutting down properly Flame in burner assembly should extinguish promptly at the end of the cycle Check orifices and gas pressure Verify the control and furnace are properly grounded Check and reverse polarity primary or secondary if incorrect Indicates the gas valve relay contacts on the ignition module is not functioning properly Replace the ignition module Low flame sense current is often caused by carbon deposits 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 the appliance manufacturer Refer to wiring diagram FS terminal and GND Replace IFC Verify power to the control TECHNICAL SUPPORT 1 888 725 9797 White Rodgers is a business of Emerson Electric Co White Rodgers es The Emerson logo is a EM ERSON trademark and service mark www white rodgers com N of Emerson Electric Co www emersonclimate com
8. 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 an additional 1 second of ignitor warm up time 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 During burner operation a momentary 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 energize andthe control will restartthe ignition sequence Recycles will begin and the burner will operate normally if the gas supply returns or the fault condition is corrected If the control has gone into system lockout it may b
9. ioning contractor or licensed electrician 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 electrical 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 Label all wires before disconnection when servicing controls Wiring errors can cause improper and dangerous operation proper operation Route and secure wiring away from flame Following installation or replacement follow manufacturer s recommended installation service instructions to ensure SHOCK HAZARD Disconnect electric power before servicing yi CAUTION Donotshortoutterminals on gas valveor primary control Short or incorrect wiring may damage the thermostat EMERSON www white rodgers com www emersonclimate com Ensure proper earth grounding of appliance Ensure proper connection of line neutral and line hot wires EXPLOSION HAZARD Shut off main gas to appliance until installation is complete PART NO 37 7515B Replaces 37 7515A 1422 SPECIFICATIONS ELECTRICAL RATINGS 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 25
10. ll 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 interrupting 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 also need to reset the flame rollout sensor switch 3 After one hour in lockout the control will automatically reset itself DIAGNOSTIC FEATURES The 50A55 3797 control continuously monitors its own operation and the operation of the system If a failure occurs the LED will indicate a failure code as shown in Troubleshooting section If the failure is internal to the control the light will stay off In this case the entire control should be replaced as the control is not field repairable 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 DEFINITION OF TERMS Auto Restart After one 1 hour of internal or external lockout the control will automatically reset itself and go into an auto restart purge for 60 seconds Cool Delay To Fan Off The period of time between the loss of a call for cool and the deactivation of the blower motor at Cool speed Cool Delay To Fan On The period of time after a thermostat demand for cool before en
11. n 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 11 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 one second and locked in 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 one second and remains locked Inthe event of two successive retry attempts the warm up time will be unlocked and setto 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 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 optional electronic air cleaner is energized and the circulator fan is energized at heat speed When the thermostatis satisfied the gas valve is de energized After proof of flame loss the heat delay OPERATION to fan off period begins and the
12. ping 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 Route and secure wiring away from flame SHOCK HAZARD Disconnect electric power before servicing Ensure proper earth grounding of appliance Ensure proper connection of line neutral and line hot wires EXPLOSION HAZARD Shut off main gas to appliance until installation is complete HOT LINE TYPICAL SYSTEM WIRING DIAGRAM ELECTRONIC AIR CLEANER FLAME SENSOR LEGEND Low Voltage 24 VAC Line Voltage 120 VAC N C Normally closed switch N O Normally open switch 120 VAC D 24 VAC CLASS II e TRANSFORMER CIRCULATOR BLOWER EAC HUM INDUCER 4 Pin Connector f COMPRESSOR CONTACTOR THERMOSTAT HIGH LIMIT AUX HIGH LIMIT N C PRESSURE SWITCH 4 Pin Connector 12 Pin Connector WIRING NEUTRAL LINE WIRING TYPICAL SYSTEM WIRING TABLE 50A55 3797 TERMINAL SYSTEM COMPONENT TERMINAL TYPE CONNECTION W low voltage thermostat W terminal or equivalent Terminal low voltage thermostat G terminal or equivalent block with 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
13. uit 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 64 thick insulation wire is recommended for all line voltage connections Refer to 50A55 specification sheet for recommendedterminals to mate with those on the control After installation or replacement follow appliance manufacturers recommended installation or service instructions to ensure proper operation The 50A55 has only one serviceable part an automotive type fuse which protects the low voltage transformer from damage ifits outputis short circuited Ifthe fuse has opened up remove whatever caused the short circuit and replace the fuse with only a 5 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 2 TIMING SPECIFICATIONS All times are in seconds unless noted otherwise 50A55 3797 PePuge 0 e 13 64 attempts Interpurge These times will vary depending on option switch position See OPERATION section for further information A CAUTION Donotshort out terminals on gas valve or primary control Short or incorrect wiring may damage the thermostat A WARNING FIRE HAZARD Do not exceed the specified voltage Replace existing control with exact model and dash number Protect the control from direct contact with water drip
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