Emerson 50A55 Furnace User Manual
Contents
1. NO Is gas valve manual knob in ON position NO 4G YES Turn manual knob to OFF position Connect manometer to outlet pressure tap Turn knob to ON position Energize system Is outlet pressure detected after ignitor warm up time YES NO 4K Is gas at source NO YES Connect voltmeter system 4M Is 24V detected across gas valve leads after ignitor warm up time NO YES Replace gas valve Energize system Check operation Refer to service facts or installers guide for proper pressure settings Replace broken or present at to gas valve defective wiring control terminals leads Energize Restore gas Check operation IGN amp IGN j supply at source 4N Is 24V present across control MV terminals after ignitor warm up time NO YES Repair or replace broken leads to gas valve Check operation Turn manual knob to ON position Check operation Purge system of air Energize system Check operation 4J YES Is manifold pressure adjusted to required setting NO Adjust manifold to required pressure setting Check operation Check operation Replace control module Check operation A WARNIN a l Wu lt q 9 4 p S W If diagnostic indicator LED shows continuous flashing turn off gas supply at source before disconnec2. YES Replace pressure switch Energize system Check operation shows A WARNING If diagnostic indicator LED off gas supply at source before disconnecting electrical power continuous flashing turn 192 www white rodgers com YES Is diagnostic LED flashing 3 times NO YES Jumper pressure switch Does ignitor glow NO 3I YES Place incline manometer in series with pressure switch tubing Is pressure Replace pressure greater than switch Check dee oe operation Remove vent connector from furnace flue collar Is Correct blocked pressure r greater than or incorrectly pressure switch installed vent specs Check operation Repair leaks in inducer assembly or replace induced draft motor Check operation INTEGRATED FURNACE CONTROL MODULE TROUBLESHOOTING GUIDE White y 4A Main Burner Ignition Check Inducer ON Does ignitor warm up and glow YES Turn power OFF to furnace Unplug ignitor from wire harness Connect voltmeter across ignitor wiring harness leads from control Energize system Is 120V present at ignitor leads Replace ignitor Check operation NO Is 120V NEUTRAL NO Replace control Check operation Rodgers CHART 4 4E Does burner ignite YES
3. INTEGRATED FURNACE CONTROL MODULE TROUBLESHOOTING GUIDE White y Rodgers WARNING Failure to read and follow all instructions carefully before in stalling or operating this control could cause personal injury and or property damage 50A55 INTEGRATED FURNACE CONTROL MODULE Qualified Serviceman s Troubleshooting Guide TROUBLESHOOTING PROCEDURE If the light on the module is on continuously the fault is likely to be internal to the module To make sure interrupt line or 24 volt thermostat power for a few seconds and then restore If internal fault is indicated again and flame sensor is not shorted to ground replace control A flashing light indicates the problem is most likely in the external components or wiring Proceed as follows A WARNING Turn power off before any troubleshooting or servicing begins Line voltage 120 VAC could be present on the surface of the ignitor if the sys tem is not correctly wired Such voltage can cause serious injury or death The following steps must be performed first before any troubleshooting begins 1 Disconnect electric power to system at main fuse or circuit breaker 2 Visually inspect equipment for apparent damage Check wiring for loose connections 3 Check for proper grounding and reversed polarity A Check continuity for C terminal on module to electrical service ground and connection at the furnace junction box If ground connection is open check module g
4. ansformer Check transformer Check operation operation a l W lt q 9 zZ p S Wu A WARNING If diagnostic indicator LED shows continuous flashing turn off gas supply at source before disconnecting electrical power 190 www white rodgers com INTEGRATED FURNACE CONTROL MODULE White y Rodgers TROUBLESHOOTING GUIDE CHART 2 Place thermostat 2A system switch in i cooling mode and fan Does indoor Cooling switch in AUTO blower energize YES Cycle position Lower Check temperature selection lever to call for a cooling cycle R amp Y contacts close at cooling fan speed NO 2C 2D With door Does indoor blower energize at heating fan speed Is thermostat terminal Y connected to furnace terminal Y switch closed jumper control terminals R amp Y YES YES NO NO Correct wiring from thermostat terminal Y to Y on furnace Check operation 2G Is 24V present across control terminals Y amp C YES NO 2l 2J 2K Is 24V Is 24V present at present at ee control terminals control terminals i p i y 3 G amp C ransformer Is 120V present at control terminals LINE amp LINE NEUTRAL Repair low voltage wiring from transformer to control Check operation Correct 120V power supply to control Check op
5. dgers CONTROL MODULE NOS FURNACE EQUIPPED WITH COMBUSTION AIR BLOWER CONTINUOUS FLASHING DIAGNOSTIC CHART A INDICATOR WARNS OF A PROBLEM THAT COULD CAUSE PERSONAL INJURY OR FIRE TURN OFF GAS SUPPLY BEFORE TURNING OFF ELECTRICAL POWER 1A Place thermostat Does indoor blower run at HEAT speed YES Return fan Indoor Blower switch to fan switch in Check the ON position AUTO position NO Does LED Is 24V Is 24V iste Indoor blower flash 1 time present at present at present at YES fault Repair or when disconnect control control control terminals replace Check is turned terminals terminals COOL amp CIR operation ON R amp C G amp C NEUTRAL Replace control Replace control Check operation Check operation Repair wiring from control to thermostat Check operation 1G Is 120V Is 24V present Is 120V Is 120V Is 24V present across present at present across present across across 12 pi control terminals control terminals i ins primary of control secondary of connector pins TH LINE amp LINE XFMR amp XFMR transformer transformer amp TR on the YES NEUTRAL NEUTRAL control NO NO NO NO Repair wiring and or plug connection Check operation Correct 120V power supply Check operation Repair wiring to Replace tr
6. eration Repair low voltage wiring to thermostat Check operation www white rodgers com Return thermostat to desired setting 2F Does indoor blower energize at cooling fan speed Repair low voltage wiring to thermostat Check operation YES NO 2H Is 120V present at control terminals COOL amp CIR NEUTRAL Indoor blower fault Repair or replace motor Check operation YES NO Replace control Check operation Replace transformer Check operation Repair wiring between control and transformer primary Check operation a l Wu lt a 9 z lt S Lu A WARNING If diagnostic indicator LED shows continuous flashing turn off gas supply at source before disconnecting electrical power 191 a l W lt l q 9 z p S Wu TROUBLESHOOTING GUIDE White y Rodgers INTEGRATED FURNACE CONTROL MODULE Inducer Draft Motor and Pressure Switch Check CHART 3 3A Call for heat Thermostat contacts R amp W close Is induced draft motor energized NO Is diagnostic LED flashing 2 times NO Disconnect electric power at fuse or circuit breaker Test for continuity across pressure switch Check inducer wiring If OK i Is pressure repair or replace switch welded inducer motor closed Check operation
7. round connection and the electrical service ground connection Repair and retest Re connect electric power to system Check for voltage between the line neutral terminal and furnace ground If voltage exists the main power supply lines are improperly connected to the furnace REVERSED POLARITY Again disconnect electric power to system then reverse incoming supply leads to furnace Repeat step D Recheck system for proper operation If neither apparent damage loose connection nor reversed polarity is the problem proceed to troubleshooting chart or fault index chart that is suggested by the actual condition NOTE This troubleshooting guide is not for 50A55 4XX modules found on Trane equipment or 50A55 1XX modules found on Lennox equipment FAULT INDEX CHART No manual fan Power supply and voltage No fan at cooling speed No induced draft motor LED flashing 2X without inducev LED flashing 3X with inducet 006 Ignitor does not glow Burner does not stay lit Gas supply problem No outlet pressure Gas valve does not energize Flame sensor fault Burner ground Polarity check Ignitor stays on after burner ignition e_WSISKS NON INON 0272 TAY TECHNICAL HELP COOL H x E18 2 e pF www white rodgers com 189 TROUBLESHOOTING INTEGRATED FURNACE White y GUIDE Ro
8. ting electrical power www white rodgers com 193 a l Wu lt q S z p S Lu TROUBLESHOOTING GUIDE White y Rodgers INTEGRATED FURNACE CONTROL MODULE 5A Does main lit burner remain CHART 5 5B Does ignitor remain energized with flame present De energize system Disconnect 12 pin connector Connect ohmmeter from flame sensor pin FP to burner GROUND 5F Is resistance less than 50 megohms 50 000 000 Ohms Disconnect lead from flame sensor Connect ohmmeter from sensor to burner ground Is sensor lead good NO Repair or replace wire Is resistance less than 50 megohms Replace sensor Energize system Check operation Replace flame operation 194 Disconnect flame sensor from wire Measure continuity from wire end to FP pin on 12 pin connector Energize system Check operation sensor lead Check Disconnect AC power to system at main fuse or circuit breaker Connect voltmeter from control terminal LINE NEUTRAL to BURNER GROUND Energize module YES 5K Is control ground wire connected to burner ground YES NO Connect ground wire from burner to 12 pin connector terminal GROUND Check operation 5C Is blower at heat speed System is within 1 minute functioning of burner igni
9. tion properly Is 120V present at control terminals HEAT amp CIR NEUTRAL Repair wiring and or replace indoor blower motor Check operation Replace control module Check operation Reverse 120V LINE amp NEUTRAL Is 120V present at burner ground YES a wires Energize system Check operation Connect a microammeter Clean surface of flame sensor with fine steel wool Reinstall Check operation in series with flame sensor and sensor lead Energize system Measure current when burner ignites YES 50 5P Remove sensor Does sensor have carbon or dust buildup Is 1 microamp or more present Replace control Check operation A WARNING If diagnostic indicator LED shows continuous flashing turn off gas supply at source before disconnecting electrical power www white rodgers com
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