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American Standard *UD Series Operation Manual

40" residential gas furnace.
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4 0 " R e s i d e n t i a l G a s
4 0 " R e s i d e n t i a l G a s
F u r n a c e O p e r a t i o n
F u r n a c e O p e r a t i o n
© American Standard Inc. 1999
© American Standard Inc. 1999
• Model Evolution/Nomenclature
• Model Evolution/Nomenclature
• Heating Sequence of Operation
• Heating Sequence of Operation
• Schematics
• Schematics
• Ignition Systems
• Ignition Systems
• Service/Troubleshooting
• Service/Troubleshooting
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Table of Contents

   Related Manuals for American Standard *UD Series

   Summary of Contents for American Standard *UD Series

  • Page 1 • Model Evolution/Nomenclature • Model Evolution/Nomenclature • Heating Sequence of Operation • Heating Sequence of Operation • Schematics • Schematics • Ignition Systems • Ignition Systems • Service/Troubleshooting • Service/Troubleshooting © American Standard Inc. 1999 © American Standard Inc. 1999...
  • Page 2: Table Of Contents

    Preface Air Conditioning and heating service technicians based on White-Rogers controls and provides the must have a working knowledge of basic electrical and narrative and schematic drawingsnecessary to refrigeration service procedures. In order to service provide this understanding for thesefurnaces. Also gas furnaces, a thorough understanding of the units included is a description of operating principles of sequence of operation is essential.
  • Page 3 Contents – continued Manifold Pressure Settings ............................Direct Vent Manifold Pressure Check ......................... Determining Natural Gas Furnace Input ........................Single Stage Twinning Kit ............................Field Wiring Diagrams – Single Stage and Two Stage Thermostats ............... Two Stage Twinning Kit .............................. Fields Wiring Diagram –...
  • Page 4: Model Evolution

    40" Residential Gas Furnace Evolution Third Quarter 1991 – UD-R and UD-C 40" induced draft upflow models introduced to replace the TUD-B linear burner upflow models. Second Quarter 1992 – DD-R and DD-C 40" induced draft downflow/horizontal models introduced to replace the TDD-B linear burner downflow models and the THP, THS and THD series horizontal models.
  • Page 5: Model Nomenclature

    Model Nomenclature U C 0 4 0 C 9 2 4 A Furnace Configuration U = Upflow U = Upflow/Horizontal D = Downflow/Horizontal Type C = Condensing – 90% AFUE D = Induced Draft – 80% AFUE E = 78%/80% AFUE X = Direct Vent Condensing Y = Direct Vent Condensing Variable-Speed 78%/80% AFUE Cumberland...
  • Page 6: Component Identification - Ud/ Dd-r Models

    Component Identification – UD/ DD-R Models 1ST STAGE INDUCED DRAFT PRESSURE SWITCH BLOWER (2 SPEED) 2ND STAGE HIGH TEMPERATURE PRESSURE SWITCH LIMIT (TCO) GAS VALVE HIGH VOLTAGE (2 STAGE) AND ACCESSORY FLAME ROLL-OUT HOOK-UP MAY BE A FUSE LINK FLAME ROLL-OUT OR A BIMETAL SWITCH MAY BE A FUSE LINK OR A BIMETAL SWITCH...
  • Page 7: Component Identification - Uy/ Dy-r Models

    Component Identification – UY/ DY-R Models HIGH TEMPERATURE LIMIT SWITCH BURNER SIGHT GLASS ELECTRICAL FLAME ROLL-OUT JUNCTION BOX SWITCH (MANUAL RESET) 2 STAGE GAS VALVE 2ND STAGE PRESSURE SWITCH INDUCED DRAFT BLOWER (2 SPEED) 1ST STAGE PRESSURE SWITCH TCO (LIMIT) LINE CHOKE (NOT ON ALL MODELS) DOOR SWITCH...
  • Page 8: Integrated Furnace Controls (i.f.c.)

    White-Rodgers Integrated Furnace Controls – 50A50 & 50A51 Series Fan On The White-Rodgers Integrated Furnace Control (I.F.C.) is an automatic ignition control module that uses When the thermostat fan switch is in the ON position, microcomputer based circuitry to continuously monitor, 24V AC is applied from the thermostat “G”...
  • Page 9: Heating Blower On And Off Delay

    White-Rodgers Integrated Furnace Controls – 50A50 & 50A51 Series Heating Blower On and Off Delay 50A51-405 Control These controls provide a fixed 45 second indoor “blower on” delay after the flame is sensed during heating cycles. After this time delay, the indoor blower motor will be energized to run on heating speed.
  • Page 10: Self Diagnostic Features 50a50 And 50a51

    White-Rodgers Self Diagnostic Features – 50A50/50A51 Series LED Flash Rate The integrated furnace control incorporates system fault analysis for quick gas flow shutoff, coupled with Normal Operation automatic ignition retry upon sensing a fault correction. • The LED will flash for 1 second at power-up The integrated furnace control tests for internal and external faults before allowing a heating •...
  • Page 11: Integrated Furnace Control Timing

    White-Rodgers Integrated Furnace Control Timing...
  • Page 12: Abnormal Furnace Operation - 50a50 And 50a51

    White-Rodgers 50A50/50A51 Fault Diagnostics System Lockout (Loss Of Flame) When the Control has gone into system lockout due to loss of flame, the Control must reset before When the Control fails to detect a flame current the system will restart the heating operation. The signal during the trial for ignition period,1 the gas Control may be manually reset by setting the valve and ignitor will be de-energized and the retry...
  • Page 13 White-Rodgers 50A50/50A51 Fault Diagnostics 50A50-405/406 Prior To Revision E4 If the 1st stage pressure switch closes and then opens during the ignitor warm-up period, the Control will If the condensate drain is blocked on condensing begin flashing the diagnostic LED 3 times to indicate (90%) furnace models, either by debris, improper a pressure switch problem and wait 10 seconds for draining, or by freezing condensate, the pressure...
  • Page 14 White-Rodgers 50A50/50A51 Fault Diagnostics Pressure Switch Problem Thermal Protection Devices At any time during a call for heat, if the Control senses 50A51-495/-506/-507 Two Stage Variable-Speed Systems the high temperature limit (and/or aux. limit) or flame The induced draft motor will always be energized to roll out switch(es) are open, the gas valve is de-energized, high speed.
  • Page 15: Single Stage 50a50 Sequence Of Operation

    Single Stage 50A50 and 50A55 Sequence of Operation White-Rodgers Integrated Furnace nals #1 a. The redundant and main solenoids are Controls 50A50-405/-406/-471/-472/ energized allowing gas flow and main burner ignition. -473/-474/-571 and 50A55-571/-474 When flame current is detected by the control through Models its terminal “FP”...
  • Page 16: Wiring Schematic - Single Stage 50a50 Integrated Furnace Control

    Wiring Schematic Single Stage (White-Rodger’s 50A50 and 50A55 Series Integrated Furnace Controls) 120 VOLT, 60 HZ., 1 PH. POWER SUPPLY PER LOCAL CODES 50A50-ALL INTEGRATED FURNACE CONTROL COOL I.D. “A” HEAT DOOR BLOWER SWITCH “B” PARK MTR. “C” PARK HOT 120VAC BK/1 LINE BK/4...
  • Page 17: Two Stage 50a51-405 Sequence Of Operation

    Two Stage 50A51 Sequence of Operation White-Rodgers Integrated Furnace the main valve low and redundant gas valve Control 50A51-405/-495 Models solenoids g, a are de-energized. The control will begin a interpurge cycle and adds additional seconds When the service disconnect 1 is in the “ON” position, to the hot surface ignitor warm-up timing (see note).
  • Page 18: Wiring Schematic - Two Stage Heat 50a51-405 Integrated Furnace Control

    Wiring Schematic Two Stage Heat (White-Rodgers 50A51 Series Integrated Furnace Control) 120 VOLT, 60 HZ., 1 PH. POWER SUPPLY PER LOCAL CODES 50A51-405 INTEGRATED FURNACE CONTROL COOL I.D. “A” PARK DOOR BLOWER SWITCH “B” HEAT LO MTR. “C” HEAT HI BK/1 LINE HOT 120VAC...
  • Page 19: Two Stage Variable Speed Sequence Of Operation

    Two Stage Variable Speed Sequence of Operation White-Rodgers Integrated Furnace seconds (see note) to the hot surface ignitor warm-up Controls 50A51-505/-506/-507 and timing. The control energizes the gas valve for the 50A61-605 Models second attempt to establish main burner ignition. If again flame current is not sensed by the control When the service disconnect 1 is in the “ON”...
  • Page 20: Wiring Schematic - Two Stage Variable Speed 50a51-505/50a51-506 Integrated Furnace Control

    Wiring Schematic Two Stage Variable Speed (White-Rodgers 50A51 and 50A61 Series Integrated Furnace Controls) 120 VOLT, 60 HZ., 1 PH. POWER SUPPLY PER LOCAL CODES BK/8 WH/7 DOOR BLOWER GR/BK SWITCH 50A51-505/-506 MOTOR INTEGRATED FURNACE CONTROL BK/2 OPTIONAL BK/3 JUMPER BK/1 LINE YL/BK...
  • Page 21: Integrated Control Quick Reference

    Integrated Control Quick Reference Service Tips 8. If a lockout occurs, the control automatically resets the trial for ignition sequence every one or two hours To the qualified service man, these controls are provided a call for heat continues to exist. See Timing very simple and easy to work on.
  • Page 22: Furnace Ecm Tm 2 Motor Operation

    Furnace ECM 2 Motor Operation A Call on “Y” and “G” together. The indoor blower Cooling Cycle – Blower Time Delay to off is will run at 100% and the red “Y” LED will be on, controlled by the ECM 2 Motor and Dip Switch “YLO”...
  • Page 23: Ecm Tm 2 Variable Speed Furnace Motor Quick Check

    2 Variable Speed Furnace Motor Quick Check Blower Motor Will Not Run 3. Unplug 16 wire low voltage harness from the motor. Jumper 24 Volts A.C. to motor low voltage plug 1. Jumper 24 Volt A.C. “R” terminal to “G” terminal on pins number 12 and number 15 and pins number 1 the Motor Control Board.
  • Page 24 2 Variable Speed Furnace Motor Quick Check 5. Plug the 16 wire low voltage harness from the motor back into the motor control board. Jumper “G IN” pin to “G OUT” pin of the White-Rodgers Integrated Control which plugs into the low voltage motor control board.
  • Page 25: Schematic - Motor Control Board

    Furnace Motor Control Board Schematic – CNT1537 DIP SWITCHES L2 FAN DIAGRAM "B" PI 5 PI 7 PI 4 PI 11 PI 1 PI 12 PI 3 PI 2 TERMINAL DIAGRAM PI 9 BLOCK "A" PI 15 PI 6 PI 14 PI 10 PI 13 PI 8...
  • Page 26: Flame Rectification Principle - Measurement

    Flame Rectification Principle – Measurement The White-Rodgers 50A50 and 50A51 integrated The flame current microamp signal can be measured with many of the new digital volt OHM meters. controls use the flame rectification principle to prove that flame is present after the gas valve has been However, there are many digital meters which do not have microamp scales but can read DC volts.
  • Page 27: Flame Current Tester/simulator

    White-Rodgers Flame Current Tester/Simulator To Be Used With The Following White-Rodgers Control Models: Did light on tester come on? Yes/No W.R. Module is OK, check: 50E47-060, 50A50 and 50A51 series 1. Flame sensor May be used on other ignition modules that have 2.
  • Page 28: Combustion Air Pressure Switch Check - Measurement

    Combustion Air Pressure Switch Check – Measurement The combustion air pressure switch proves operation If the measured static pressure reading does not meet of the induced draft motor and that adequate air is the switch specifications, the following items should provided to ensure complete combustion of the fuel be checked: being supplied to the burner.
  • Page 29: Furnace Pressure Switch Settings

    Furnace Pressure Switch Settings Closing Opening High Closing Opening Pressure Pressure Factory Replacement Altitude Pressure Pressure Factory Replacement Models In W.C. In W.C. Number Number In W.C. In W.C. Number Part –0.5 ± .05 –0.41 ± 04 UD-C-A, B, C, D/ DD-C, A, B –0.65 C340071P01 SWT 1255...
  • Page 30: Gas Valves

    Gas Valves Recommended Replacement Production Furnace Model Gas Valve Natural Propane/LP FUA/FCA-A-A FUA/FCA-A-B,C UC-C-A,B/ DC-C-A,B,C A,B1 UD-C-A,B,H/ DD-C-A,B,C,D,J,K A,B1 UD/ DD-R-A C,G,K,L2 D,G,K,L2 UE/ DE-A-A,B UJ-A-A UX/ DX-C-A UY/ DY-R-A FUA-A-E/FCA-A-E TUE-A-K/TDE-A-K UX/ DX-C-C UC-C/ DC-C-C UD-C-H/ DD-C-C3 UD-R-K/ DD-R-F UX-R-V, W/ DX-R-V, W UY-R-V, W/ DY-R-V, W UE-A-L/ DE-A-M...
  • Page 31 Gas Valves – continued Replacement Part No. Opening Factory Outlet Propane Natural Valve Models Supplier Characteristics Pressure Settings Convertible Valve Spring Spring 36E01-221 White-Rodgers Fast 3.3 in W.C. VAL-2905 KIT-1401 KIT-1402 36E98-205 White-Rodgers Slow 3.3 in W.C. VAL-4335 KIT-1401 KIT-1402 36E96-211 White-Rodgers 2-Stage...
  • Page 32: Manifold Pressure Settings

    Manifold Pressure Settings The 40" gas furnaces are shipped from the factory valve and does not require a regulator spring change for use with natural gas. Conversion to propane for LP conversion. requires a change in the main burner orifices. The Note: It is necessary to adjust the “Hi”...
  • Page 33: Direct Vent Manifold Pressure Check

    Direct Vent Manifold Pressure Check The 40" Direct Vent furnaces (single and two stage) Example: 3.50" W.C. gas valve outlet pressure tap reference the burner box inlet static to provide proper reading, gas valve regulation. The burner box static pressure –.15"...
  • Page 34: Determining Natural Gas Furnace Input

    Determining Natural Gas Furnace Input CUBIC FEET • Measure the time taken for two revolutions of the two cubic foot dial. • Call gas supplier for BTU/Cu.Ft. Heating value of gas – or – • Use 1000 BTU/Cu.Ft. as value (If specific value not available) * Heating value of gas based on sea level pressure.
  • Page 35: Single Stage Twinning Kit

    Single Stage Twinning Kit Typical Installations with a Coil BAYTWIN400A – For use with all 40" furnaces with White-Rodgers 50A50 integrated furnace controls. The BAYTWIN400A Twinning Kit is used when twinning upflow furnaces with identical model numbers. These identical furnaces must have the same gas input and airflow.
  • Page 36: Field Wiring Diagrams - Single Stage And Two Stage Thermostats

    Field Wiring Diagram for Single Stage Thermostat and Single Stage Furnace, Outdoor Unit Without Transformer LEGEND NOTES: RFS. REVERSE FLOW SWITCH 1. REVERSE FLOW SWITCHES MUST BE INSTALLED ON EACH FURNACE BLOWER HOUSING. INTEGRATED FURNACE CONTROL 2. THERMOSTAT MUST ENERGIZE “G” WITH A CALL FOR HEAT. RELAY A PILOT DUTY RELAY (PROVIDED) AS IN ELECTRIC HEAT MODELS.
  • Page 37: Two Stage Twinning Kit

    Two Stage Twinning Kit Typical Installations with a Coil BAYTWIN300A – For use with all two stage 40” furnaces with White-Rodgers 50A51-405 ignition controls. The BAYTWIN300A Kit includes a twinning harness that connects to each of the furnace controls to provide synchronization of heating and cooling operation.
  • Page 38: Fields Wiring Diagram - Twinning Ud-r Furnaces

    Field Wiring Diagram for Twinning UD-R Furnaces with Two Stage Heat and Single Stage Cooling Thermostat NOTES: LEGEND 1. REVERSE FLOW SWITCHES MUST BE INSTALLED ON EACH FURNACE BLOWER HOUSING. RFS. REVERSE FLOW SWITCH (PROVIDED) 2.. IF OUTDOOR UNIT HAS A 24 VOLT TRANSFORMER, ISOLATING INTEGRATED FURNACE CONTROL RELAY MUST BE INSTALLED (FIELD SUPPLIED).
  • Page 39: Single Wire Twinning - For Models With Twin Terminals

    Single Wire Twinning – For Models with Twin Terminals Twinning Connection Diagram for Twinning 1 Stage Furnaces with Single Wire Twinning Feature 1 Stage Heating Only Thermostat NOTES: 1. BOTH FURNACES MUST BE POWERED FROM THE SAME 115V. LEG OF CIRCUIT PANEL. FURNACE NO.
  • Page 40: Radiant Sense Ignition Controls

    White-Rodgers Radiant Sense Ignition Controls There were four versions, of the 50A52-100 Radiant Sense engineering code applied to the back of the control board Controls and three versions of the 50A52-101 control and one in black ink. The number of relays and the type of radiant sensor version of the 50A52-102.
  • Page 41: Identifying Radiant Sense Controls

    Identifying Radiant Sense Controls 50A52-100 Version 1 (E90) 50A52-100 Versions 2 and 3 (E91, E92) E90 – Cooling fan runs when limit opens E91 – Heating fan runs when limit opens in heating only. E92 – SPDT Radiant Sensor 50A52-100 Version 4 (E93) 50A52-101 Version 4 (E93, E1, E2, E3) 50A52-102 (E90, E4) E93, E1 –...
  • Page 42: Radiant Energy Sensor

    Radiant Energy Sensor S.P.D.T. ASSEMBLY VIEW TERMINAL RIVET MAGNET WASHER TERMINAL EPOXY CONTACTS STATIONARY CONTACT ARMATURE CALIBRATION SCREW BIMETAL STATIONARY GLASS TERMINAL SWITCHCASE RIVET BRACKET S.P.D.T. PICTORIAL VIEW Caution! Do Not alter the position of the ignitor or the gas may not light. The ignitor must be located within the burner face as shown at right.
  • Page 43: 50a52-100 Sequence Of Operation

    White-Rodgers 50A52-100 Sequence of Operation Version 1 (E90) 7 Relays, 2 Wire Flame open contacts K 4B h open, but the redundant valve Switch Radiant Sensor is held open due to the EQSO resistor in series with the RV coil. Normally closed contact K 4A j closes, allow- This control allows a constant re-try for ignition after ing the main valve to open (thus gas flows and ignition a flame failure.
  • Page 44: Wiring Schematic - Version 1 Radiant Sense Control

    Wiring Schematic Version 1 Radiant Sense Control 115 VOLT 60 HZ. 1PH. POWER SUPPLY PER LOCAL CODES DOOR FURNACE CONTROL SWITCH “C” I.D. “B” “A” HEAT MTR. COOL BK/1 LINE BK/4 XFMR BK/6 BK/5 VENT MTR. WH/1 LINE CIRC WH/6 WH/5 IMPORTANT: FURNACE CONTROL WH/4...
  • Page 45: 50a52-100 Sequence Of Operation

    White-Rodgers 50A52-100 Sequence of Operation Version 2 (E91) 6 Relays, 2 Wire Flame ignition takes place) and the K 3 fan time delay circuit h starts the time delay to start the indoor blower Switch Radiant Sensor (normally a 45 second delay), then warm air circulation This control allows a constant re-try for ignition after begins.
  • Page 46: Wiring Schematic - Version 2 Radiant Sense Control

    Wiring Schematic Version 2 Radiant Sense Control 115 VOLT 60 HZ. 1PH. POWER SUPPLY PER LOCAL CODES DOOR FURNACE CONTROL SWITCH “C” I.D. “B” “A” HEAT MTR. COOL BK/1 LINE BK/4 XMFR BK/6 BK/5 VENT MTR. WH/1 LINE CIRC WH/6 WH/5 IMPORTANT: FURNACE CONTROL WH/4...
  • Page 47: 50a52-100 Sequence Of Operation

    White-Rodgers 50A52-100 Sequence of Operation Version 3 (E92) 6 Relays, 3 Wire Flame Thus gas flows and ignition takes place. The fan time Switch Radiant Sensor delay circuit starts the time delay to start the indoor blower (normally a 45 second delay), then warm air This control allows a constant re-try for ignition after circulation begins.
  • Page 48: Wiring Schematic - Version 3 Radiant Sense Control

    Wiring Schematic Version 3 Radiant Sense Control 115 VOLT 60 HZ. 1PH. POWER SUPPLY PER LOCAL CODES DOOR FURNACE CONTROL SWITCH “C” I.D. “B” “A” HEAT MTR. COOL BK/1 LINE BK/4 XFMR BK/6 BK/5 VENT MTR. WH/1 LINE CIRC WH/6 WH/5 IMPORTANT: FURNACE CONTROL WH/4...
  • Page 49: 50a52-100/101/102 Sequence Of Operation

    White-Rodgers 50A52-100/101/102 Sequence of Operation Version 4 (E93, E1, E2, E3) 5 Relays, is present, within the 90 second flame proving time, one re-try will be initiated after a 60 second purge by the com- 3 Wire Flame Switch Radiant Sensor bustion blower.
  • Page 50: Wiring Schematic - Version 4 Radiant Sense Control

    Wiring Schematic Version 4 Radiant Sense Control 115 VOLT 60 HZ. 1PH. POWER SUPPLY PER LOCAL CODES DOOR FURNACE CONTROL SWITCH “C” I.D. “B” “A” HEAT MTR. COOL BK/1 LINE BK/4 XFMR BK/6 BK/5 VENT MTR. WH/1 LINE CIRC WH/6 WH/5 IMPORTANT: FURNACE CONTROL WH/4...
  • Page 51: Troubleshooting Procedures

    White-Rodgers Troubleshooting Procedures Furnace Models 50A50 and 50A51 6. Inspect vent pipe for signs of corrosion or condensation. 7. Re-connect power to system. f the light on the module is on continuously, the fault is 8. Check system operation. likely to be internal to the module. To make sure, interrupt If problem is found, refer to the fault index chart for that line or 24 volt thermostat power for a few seconds and particular problem or proceed directly to the trouble-...
  • Page 52: 50a50 Flow Chart 1

    50A50 Flow Chart 1 Does Return Place Thermostat Indoor Blower indoor blower fan switch to in the on position. Check run at HEAT AUTO position. speed? Is 120V Is LED Is 24V Is 24V Indoor blower present at light on control present at present at fault.
  • Page 53: 50a50 Flow Chart 2

    50A50 Flow Chart 2 Place Thermostat system switch in cooling Does Return mode and fan switch in indoor blower Cooling Cycle thermostat energize at AUTO position. Lower Check to desired cooling fan temperature selection setting. speed? lever to call for a cooling cycle.
  • Page 54: 50a50 Flow Chart 3

    50A50 Flow Chart 3 Call for heat. Is induced Is diagnostic Inducer Draft Motor Thermostat draft motor LED flashing and Pressure contacts energized? 3 times? Switch Check R & W close. Is 24V Repair low Jumper present at Is Diagnostic voltage wiring pressure control terminals...
  • Page 55: 50a50 Flow Chart 4

    50A50 Flow Chart 4 Diagnostic Does ignitor Main burner Does burner LED flashing warm up and ignition check ignite? fast (2 times per glow? Inducer ON. sec.) continously. Turn power OFF to furnace. Unplug ignitor Is gas Repair low from wire harness. valve manual voltage wiring Connect voltemeter across...
  • Page 56: 50a50 Flow Chart 5

    50A50 Flow Chart 5 Blower Does ignitor at heat speed System is Does main Flame Sensor remain energized within one minute of functioning burner remain Check with flame burner ignition? properly. lit? present? De-energize system. Blower Disconnect 12 pin Repair wiring and/or at heat speed connector.
  • Page 57: 50a51 Flow Chart 1

    50A51 Flow Chart 1 Place Does indoor Return fan Inducer Blower thermostat fan blower run at switch to AUTO Check switch in the HEAT speed? position. ON position. Is LED Is 120V Is 24V Is 24V Indoor blower present at light on control present at present at...
  • Page 58: 50a51 Flow Chart 2

    50A51 Flow Chart 2 Place thermostat in Place thermostat in Does cooling mode and fan heating mode. Fan Is induced switch in auto position. indoor blower switch in auto position. draft motor Lower temperature Raise temperature set energize at low heat energized? set-point to call for point to call for heat.
  • Page 59: 50a51 Flow Chart 3

    50A51 Flow Chart 3 Diagnostic Is diagnostic Does ignitor LED flashing fast Does burner LED flashing 3 warm up and (2 times per second) ignite? times? glow? continuously. Turn power OFF to furnace. Unplug ignitor Is gas Jumper Turn manual knob from wire harness.
  • Page 60: 50a51 Flow Chart 4

    50A51 Flow Chart 4 Blower Does ignitor at heat speed System is Does main Flame Sensor remain energized within one minute of functioning burner remain Check with flame burner ignition? properly. lit? present? De-energize system. Disconnect 12 pin Is 120V Repair wiring and/or connector.
  • Page 61: 50a51 Flow Chart 5

    50A51 Flow Chart 5 Does Does blower Does gas induced motor Heat thermostat System functioning motor switch to valve switch to shift to high speed contacts W2 & R close. properly. high heat speed high heat? after 30 sec. (1st stage operation) after 30 sec.
  • Page 62: 50a52 Flow Chart 1

    50A52 Flow Chart 1 Indoor Blower Check Place Thermostat in Fan On (G) Return Fan Does Indoor Chart 4 Switch to Auto Blower Run Position Cool Speed? Is 120 VAC Present Is 24 VAC Present Is 24 VAC Present Replace Control Terminals at TH and TR R&C Terminals?
  • Page 63: 50a52 Flow Chart 2

    50A52 Flow Chart 2 Inducer Draft Motor and Pressure Switch Check Call for Heat Thermostat Contact R and W Close Is Induced Draft Pressure Switch Chart 3 Normally Open Motor Energized? Contacts Close? Jumper PCOM Check T-Stat, Check 24 Volt to PO After Call Low Voltage B/C to W...
  • Page 64: 50a52 Flow Chart 3

    50A52 Flow Chart 3 Main Burner Ignition Check, Inducer On Does Does Chart 4 Burner Ignitor Glow? Ignite? Check Ignitor Position Sensor Open, Is Gas Is 24 VAC Present and Gas Pressure. Check Wiring, Present at at “GC” and “FSI” Note: Air in Gas Replace Switch Burner?
  • Page 65: 50a52 Flow Chart 4

    50A52 Flow Chart 4 Radiant Sensor Check Blower at Does Ignitor Remain System Does Main Heat Speed Energized with Flame Operation Burner Remain Lit? within 45 sec of Present for More Than Proper Gas Valve On? 1 second? Check Gas Pressure Does Burner Is 120 VAC Present at or Clean Orifices.
  • Page 66: Legends - System Wiring

    Legend – System Wiring 50A50 and 50A51 Models 24 V. Factory Wiring LINE V. Terminal 24 V. Factory Wiring LINE V. Number Type System Component Connection Earth Ground low voltage thermostat W terminal 1st stage heat Chassis Ground low voltage thermostat W terminal 2nd stage heat captive low voltage thermostat G terminal indoor fan Junction...
  • Page 67 Legend – System Wiring 50A52 Model Terminal Number Type System Component Connection low voltage thermostat W terminal (or equivalent) low voltage thermostat G terminal (or equivalent) captive screw low voltage thermostat R terminal (or equivalent) low voltage thermostat Y terminal (or equivalent) or 3/16"...
  • Page 68 Notes...
  • Page 69 Notes...
  • Page 70 Pub. No. 34-4054-06 P.I. (L)

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