COMFORT-AIRE Century GDD92C Service Manual
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COMFORT-AIRE Century GDD92C Service Manual

COMFORT-AIRE Century GDD92C Service Manual

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SERVICE MANUAL
GDD92C
This is a safety alert symbol and should never be ignored. When you see this symbol on labels or in manuals, be alert to
the potential for personal injury or death.
WARNING
Improper installation, adjustment, alteration, service
or maintenance can cause property damage, personal
injury or loss of life. Installation and service must be
performed by a licensed professional HVAC installer (or
equivalent), service agency or the gas supplier.
CAUTION
As with any mechanical equipment, contact with sharp
sheet metal edges can result in personal injury. Take
care while handling this equipment and wear gloves
and protective clothing.
508134-01

Table of Contents

Technical Specifications - GDD92C. ...........................2
Parts Arrangement.......................................................5
Electrical ......................................................................6
Placement & Installation ............................................20
Joint Cementing Procedure .......................................21
Venting Practices .......................................................22
Vent Piping Guidelines ..............................................23
Condensate Piping ....................................................36
Start-Up .....................................................................40
Heating System Service Checks ...............................41
Typical Operating Characteristics ..............................45
Maintenance ..............................................................46
Wiring Diagram ..........................................................49
(Continued) ................................................................51
Sequence of Operation..............................................53
Electric shock hazard.
Can cause injury or death. Before attempting
to perform any service or maintenance,
turn the electrical power to unit OFF at
disconnect switch(es). Unit may have
multiple power supplies.
*P508134-01*
Issue 2045
WARNING
(P) 508134-01
Page 1 of 53

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Summary of Contents for COMFORT-AIRE Century GDD92C

  • Page 1: Table Of Contents

    SERVICE MANUAL GDD92C This is a safety alert symbol and should never be ignored. When you see this symbol on labels or in manuals, be alert to the potential for personal injury or death. Table of Contents Technical Specifications - GDD92C......2 Parts Arrangement............5 Electrical ..............6 Placement &...

  • Page 2: Technical Specifications - Gdd92C

    Technical Specifications - GDD92C MODEL NUMBER GUIDE 0 0 4 4 5 5 3 3 M M REV CODE G = GAS FURNACE REVISION CONFIGURATION NOM. CFM X 100 DD = DOWNFLOW 2 TON ADD ON COOLING 3 TON ADD ON COOLING AFUE 4 TON ADD ON COOLING 80 = 80% EFFICENCY...
  • Page 3 BLOWER PERFORMANCE DATA Heating CFM @ .10" - .80" w.c. Motor Heating Size Blower Temp Rise Blower Model (hp) Size (F°) Speed 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 High 1395 1365 1330 1305 1275 1245 Med/High 1270 1245 1215 1180 1140...
  • Page 4 ACCESSORY LIST CATALOG NUMBER DESCRIPTION External Filter Rack Kits 1.841018 1 pack (16 x 25) 1.841039 10 pack (16 x 25) Natural to LP Kits 11K50 1-Stage - 90% 11K45 High Altitude 2-Stage >7500’ 17H62 1-Stage - 90% - For 030 Capacity Only 17H90 High Altitude (>7500’) - For 030 Capacity Only Return Air Base...

  • Page 5: Parts Arrangement

    Parts Arrangement Bag Assemblies Blower Assembly Control Box (includes integrated control, transformer and door switch) Cabinet Blower Deck Blower Access Panel Heat Exchanger Cold End Header Box Heating Combustion Compartment Air Inducer Access Panel Gas Valve Burner Box Assembly Figure 1. Page 5 of 53 Issue 2045 508134-01...

  • Page 6: Electrical

    Circuit Breaker (CB8) Electrical A 24V circuit breaker is also located in the control box. The switch provides overcurrent protection to the transformer (T1). The breaker is rated at 3A at 32V. If the current ELECTROSTATIC DISCHARGE (ESD) exceeds this limit the breaker will trip and all unit operation Precautions and Procedures will shutdown.
  • Page 7 1/4” Quick Connect Terminals 120HUM Humidifier 120VAC LINE 120VAC XFMR Transformer 120VAC CIRC Indoor Blower 120VAC Indoor Air Quality Accessory 120VAC NEUTRALS Common 120VAC HUM24 Humidifier 24VAC 3/16” Quick Connect Terminals COOL Cooling Tap 24VAC HEAT Heating Tap 24VAC Continuous Blower 24VAC PARK (no power) Park terminal for unused speed taps Flame Sense...
  • Page 8 Red LED Flash Code Diagnostic Codes / Status of Furnace No power to control or board fault detected Heartbeat Normal Operation - Idle, Continuous Fan, Cool Continuous Rapid Flash Call for Heat / Burner Operation Reverse Line Voltage Polarity Improper Earth Ground Burner failed to light, or lost flame during heat demand Low Flame Signal - check flame sensor Watchguard - burner failed to light, exceeded maximum number of retries or recycles...
  • Page 9 Heating Fan Off Time Fan off time (time that the blower operates after the heat demand has been satisfied) can be adjusted by moving the jumper to a different setting. The unit is shipped with a factory fan off setting of 90 seconds. For customized comfort, monitor the supply air temperature once the heat demand is satisfied.
  • Page 10 IGNITOR BURNERS ROLLOUT SWITCHES FRONT BURNER BOX PLATE SENSOR GAS VALVE Figure 5. Burner Box Assembly Flame Rollout Switches (Figure 5) A microamp DC meter is needed to check the flame signal on the integrated control. Flame rollout switches S47 are SPST N.C. high temperature limits located on the left and right of the front buner box Flame (microamp) signal is an electrical current which plate.
  • Page 11 Primary Limit Control (Figure 6) MANIFOLD PRESSURE Primary limit (S10) used on GDD92C units is located ADJUSTMENT SCREW in the heating vestibule panel. When excess heat is (under barbed fitting) MANIFOLD sensed in the heat exchanger, the limit will open. Once PRESSURE the limit opens, the furnace control energizes the OUTLET...
  • Page 12 Flame Signal In Microamps Normal Drop Out 0.5 - 1.4 Flame Sensor Terminal Remove Sensor Wire from Intergrated Control and Intergrated Connect Alligator Clip (−) Control to Frame Sensor Lead Remove Sensor Wire from Intergrated Control and Connect Alligator Clip (+) to Terminal on Control Multi−Meter Flame Sensor...
  • Page 13 Test 1 Check ignitor circuit for correct resistance. Remove 4-pin plug from control. Check ohms reading across terminals 2 and 4. Reading should be between 39 and 70 ohms. If value is correct, this is the only test needed. If the reading on the meter is not correct, (0 or infinity) then a second test is needed.
  • Page 14 Combustion Air Inducer (B6) & Cold End Header Box On start-up, the switch monitors whether the combustion air inducer is operating. It closes a circuit to the integrated All GDD92C units use a combustion air inducer to move air control when the difference in pressure across the through the burners and heat exchanger during heating combustion air inducer orifice exceeds a non-adjustable operation.
  • Page 15 Black Tubing (positive +) Red and Black Tubing or Red Tubing (negative -) To Cold End Header Box To Cold End Header Box Field Provided Tubing To Pressure Switch “+” High “-” 1 - Remove thermostat demand and allow unit to 4 - Operate unit and observe manometer reading.
  • Page 16 Problem Corrective Action Check that the pressure switch is open without the combustion air inducer Pressure switch stuck closed operating. Replace if defective. Check for restricted vent. Remove all blockage. Pressure switch does not close due to obstruction in vent pipe Check for proper vent sizing.
  • Page 17 Blower Compartment Center Blower Wheel in Blower Housing IMPORTANT Each blower is statically and dynamically balanced as an assembly before installation in the unit. GDD92C units are equipped with a constant torque ECM motor. It has a DC motor coupled to an electronic control module both contained in the same motor housing.
  • Page 18 Multi−Meter (set to VAC) Multi−Meter (set to VAC) Test 1 Test 3 (if necessary) Turn on power to unit. Check for 120 volts across terminals Check for 120 volts across terminals “CIRC” and “Neutrals” “L” and “N” on input plug P48. If voltage is present continue on the integrated control.
  • Page 19 Testing the Motor (Figure 17) Motor Module Installation If any motor fails the below tests, do not install the new All replacement motor control modules look similar; control module. The motor is defective and it also must be however, each module is designed for a specific motor replaced.

  • Page 20: Placement & Installation

    Placement & Installation Piping and Fittings Specifications Schedule 40 PVC (Pipe) D1785 Pipe & Fittings Specifications Schedule 40 PVC (Cellular Core Pipe) F891 All pipe, fittings, primer and solvent cement must conform with American National Standard Institute and the American Schedule 40 PVC (Fittings) D2466 Society for Testing and Materials (ANSI/ASTM) standards.

  • Page 21: Joint Cementing Procedure

    STANDARD CONCENTRIC Outdoor Outdoor Exhaust 1-1/2” 2” 3” Exhaust Flush Accelerator Concentric Concentric Concentric VENT Accelerator Mount Kit Capacity PIPE DIA. (Dia. X Length) (Dia. X Length) (in.) 71M80 69M29 60L46 1-1/2” X 12” 2” X 12” 51W11 ** or 44W93+ +44W92++ +44W92++ 1-1/2...

  • Page 22: Venting Practices

    seconds after last application of cement. Hammer REPLACING FURNACE THAT blows should not be used when inserting pipe. CHIMNEY WAS PART OF A COMMON OR GAS VENT VENT SYSTEM After assembly, wipe excess cement from pipe at end (Check sizing for water of fitting socket.

  • Page 23: Vent Piping Guidelines

    Vent Piping Guidelines Capacity Min. Vent Length* 15 ft or 5 ft plus 2 elbows or 045, 070, 090 NOTE: Comfort-Aire/Century has approved use of 10 ft plus 1 elbow DuraVent® Centrotherm manufactured vent pipe and *Any approved termination may be added to the minimum...
  • Page 24 Maximum Allowable Intake or Exhaust Vent Length in Feet Standard Termination at Elevation 0 - 10,000 ft 1-1/2" Pipe 2" Pipe 2-1/2" Pipe 3" Pipe Number of 90° Model Model Model Model Elbows Used Concentric Termination Elevation 0 - 10,000 ft 1-1/2"...
  • Page 25 Maximum Allowable Exhaust Vent Length with Furnace Installed in a Closet or Basement Using Ventilated Attic or Crawl Space for Intake in Feet Standard Termination at Elevation 0 - 10,000 ft 1-1/2" Pipe 2" Pipe 2-1/2" Pipe 3" Pipe Number of 90° Capacity Capacity Capacity...
  • Page 26 TYPICAL EXHAUST PIPE CONNECTIONS NOTE: 1-1/2” Vent Pipe Pipe size determined in Table 11A and Table 11B. Diameter Allowed Only on 045/070 Units 2” 2” 2” 2” 3” 1-1/2” 2” TRANSITION TRANSITION *2” **2” EXHAUST EXHAUST EXHAUST INTAKE EXHAUST EXHAUST TOP VIEW DO NOT transition DO NOT transition...
  • Page 27 Intake Piping The GDD92C furnace may be installed in either INTAKE direct vent or non-direct vent applications. In non- SCREEN (Provided) direct vent applications, when intake air will be drawn into the furnace from the surrounding space, the indoor air quality must be considered and guidelines listed in Combustion, Dilution and Ventilation Air section must be followed.
  • Page 28 In Direct Vent applications, combustion air is taken from outdoors and the flue gases are discharged to the outdoors. The GDD92C is then classified as a direct vent, Roof Terminated Exhaust Pipe Category IV gas furnace. In both Non-Direct Vent and Direct Vent applications, the vent termination is limited by local building codes.
  • Page 29 Maximum Allowable Exhaust Vent Pipe Length (in ft.) without Insulation in Unconditioned Space for Winter Design Temperatures Single - Stage High Efficiency Furnace Unit Input Size Vent Pipe Winter Design Temperatures ºF (ºC) Diameter 1-1/2 in. 32° to 21° 2 in. (0 to -6) 2-1/2 in.
  • Page 30 ‡ Permitted only if veranda, porch, deck or balcony is fully open on a minimum of two sides beneath the floor. Comfort-Aire/Century recommends avoiding this location if possible. Figure 28. Vent Termination Clearances for Direct Installations 508134-01...
  • Page 31 Details of Intake and Exhaust Piping 3” (76MM) MIN. SIZE PER EXHAUST PIPE Inches (MM) Terminations for Direct Vent Installations TERMINATION SIZE NOTE: In Direct Vent installations, combustion air is taken REDUCTION TABLE from outdoors and flue gases are discharged to outdoors. UNCONDITIONED ATTIC SPACE 8”...
  • Page 32 If intake and exhaust piping must be run up a side 1 1/2” (38mm) accelerator wall to position above snow accumulation or other provided on 71M80 & 44W92 EXHAUST kits for -045 and -070 models obstructions, piping must be supported. At least one VENT bracket must be used within 6”...
  • Page 33 ‡ Permitted only if veranda, porch, deck or balcony is fully open on a minimum of two sides beneath the floor. Comfort-Aire/Century recommends avoiding this location if possible. Figure 37. Vent Termination Clearances for Non-Direct Installations...
  • Page 34 Details of Exhaust Piping Terminations for Non- STRAIGHT-CUT OR * SIZE TERMINATION PIPE PER EXHAUST Direct Vent Applications ANGLE-CUT IN DIRECTION PIPE TERMINATION SIZE REDUCTION TABLE OF ROOF SLOPE * Exhaust pipes may be routed either horizontally through an outside wall or vertically through the roof. In attic or closet installations, vertical termination through the roof EXHAUST VENT Minimum 12”...
  • Page 35 FIELD FABRICATED WALL TERMINATION NOTE − FIELD−PROVIDED REDUCER MAY BE 2” (51mm) 3” (76mm) REQUIRED TO ADAPT LARGER VENT PIPE SIZE Vent Pipe Vent Pipe TO TERMINATION A− Minimum clearance above grade or average 12” (305 mm) 12” (305 mm) snow accumulation B−...

  • Page 36: Condensate Piping

    If this is not possible, a heat cable kit may be used on the condensate trap and line. Heating cable kit is available from Comfort-Aire/Century various lengths; 6 ft. (1.8m) - kit no. 26K68 and 24 ft. (7.3m) - kit no. 26K69.
  • Page 37 Field Provided Vent 1” min. 2” max. above Trap can be installed a maximum condensate drain. of 5ft. from furnace (*PVC only) Condensate Drain Field Provided Vent Connection 1” min. 2” max. above condensate drain. 1” min. 2” max . 5’...
  • Page 38 Optional Condensate Drain Connection Adapter 3/4 inch slip X 3/4 inch mpt (not furnished) 90° Street Elbow 3/4 inch PVC (not furnished) Adapter 3/4 inch slip X 3/4 inch mpt (not furnished) Condensate Drain Connection In Unit 1 (25 mm) Min. Vent 2 (50 mm) Max.
  • Page 39 Optional Condensate Drain Connection Adapter 1/2 inch slip X 1/2 inch mpt (Not Furnished) 90° Street Elbow 1/2 inch PVC (Not Furnished) Adapter 1/2 inch slip X 1/2 inch mpt (Not Furnished) Condensate Drain Connection In Unit 1 (25 mm) Min. Vent 2 (50 mm) Max.

  • Page 40: Start-Up

    Start-Up WARNING If you do not follow these instructions exactly, a fire Preliminary and Seasonal Checks or explosion may result causing property damage, Inspect electrical wiring, both field and factory installed personal injury or death. for loose connections. Tighten as required. Check voltage at disconnect switch.

  • Page 41: Heating System Service Checks

    Testing Gas Piping Move gas valve switch to OFF. Replace the access panel. IMPORTANT Failure To Operate In case emergency shutdown is required, turn off the If the unit fails to operate, check the following: main shut-off valve and disconnect the main power to 1.
  • Page 42 Supply Pressure Measurement Tee into the gas valve regulator vent hose and connect to test gauge negative “-”. When testing supply gas pressure, use the 1/8” N.P.T. plugged tap located on the gas valve to facilitate test gauge Start unit and let run for 5 minutes to allow for steady connection.
  • Page 43 Proper Combustion Some units installed at altitude of 4501 - 10,000 feet (1373 to 3048 m) may require a pressure switch change which Furnace should operate minimum 15 minutes with correct can be ordered separately and a manifold de-rate. See manifold pressure and gas flow rate before checking Table 16 or Table 17 for manifold pressures at all altitudes.
  • Page 44 Proper Ground and Voltage Compare the readings to Table 20. If the readings exceed the maximum shown in Table 20, make repairs before operating the furnace. CAUTION In addition, measure the AC voltage from Line Hot to Line Neutral (spade terminals) on the integrated Electric Shock Hazard.

  • Page 45: Typical Operating Characteristics

    External Static Pressure Typical Operating Characteristics 1. Tap locations shown in Figure 54. Punch a 1/4” diameter hole in supply and return air Blower Operation and Adjustment plenums. Insert manometer hose flush with inside edge of hole or insulation. Seal around the hose with NOTE: The following is a generalized procedure and does permagum.

  • Page 46: Maintenance

    Furnace Cabinet Width Filter Size Maintenance B (17-1/2”) 16 x 25 x 1 (1) C (21”) Table 21. WARNING ELECTRICAL SHOCK, FIRE, Exhaust and Air Intake Pipes OR EXPLOSION HAZARD. Check the exhaust and air intake pipes and all connections Failure to follow safety warnings exactly could result in for tightness and to make sure there is no blockage.
  • Page 47 Winterizing and Condensate Trap Care 10. Mark and disconnect all combustion air pressure tubing from cold end header collector box. 1. Turn off power to the furnace. 11. Mark and remove wires from pressure switch Have a shallow pan ready to empty condensate water. assembly.
  • Page 48 Cleaning the Burner Assembly (if needed) 29. Reinstall the cold end header box. 1. Turn off electrical and gas power supplies to furnace. 30. Reinstall the combustion air inducer. Reconnect the Remove upper and lower furnace access panels. combustion air inducer to the wire harness. Disconnect the 2-pin plug from the gas valve.

  • Page 49: Wiring Diagram

    Wiring Diagram Page 49 of 53 Issue 2045 508134-01...

  • Page 50: Troubleshooting: Heating Sequence Of Operation

    Troubleshooting: Heating Sequence of Operation HEATING SEQUENCE OF OPERATION ABNORMAL HEATING MODE NORMAL HEATING MODE POWER ON GAS VALVE OFF. COMBUSTION AIR INDUCER OFF. INDOOR BLOWER DELAY OFF. CONTROL SELF-CHECK OKAY? LED SLOW FLASH (RESET CONTROL BY TURNING MAIN POWER OFF.) LED FLASHES CODE 1 - POLARITY IS POLARITY CORRECT? REVERSED.

  • Page 51: Troubleshooting: Heating Sequence Of Operation (Continued)

    Troubleshooting: Heating Sequence of Operation (Continued) HEATING SEQUENCE CONTINUED 15 SECOND COMBUSTION AIR INDUCER PREPURGE INITIATED BY CLOSED PRESSURE SWITCH. LED FLASHES CODE 13 - LOW LINE VOLTAGE. ONCE VOLTAGE IS ABOVE IGNITOR WARM UP -- 20 SECONDS. IS VOLTAGE ABOVE 70 VOLTS? 75 VOLTS, HEATING SEQUENCE RESTARTS.

  • Page 52: Troubleshooting: Cooling Sequence Of Operation

    Troubleshooting: Cooling Sequence of Operation COOLING SEQUENCE OF OPERATION POWER ON IGNITION CONTROL MAIN POWER ON. LED FLASHES STEADY - CIRCUIT BOARD FAILURE CONTROL SELF DIAGNOSTIC CHECK. GAS VALVE OFF. COMBUSTION AIR INDUCER OFF. IS CONTROL OPERATING NORMALLY? INDOOR BLOWER OFF WITH NORMAL DELAY. INTERRUPT MAIN POWER TO RESET CONTROL.

  • Page 53: Troubleshooting: Continuous Fan / Accessories Sequence Of Operation

    Troubleshooting: Continuous Fan / Accessories Sequence of Operation CONTINUOUS FAN / ACCESSORIES SEQUENCE OF OPERATION LED: SLOW FLASH RATE REMAINS UNCHANGED THROUGHOUT SEQUENCE. MANUAL FAN SELECTION MADE AT THERMOSTAT. CONTROL (G) ENERGIZES SYSTEM FAN AT FAN SPEED. EAC TERMINAL IS ENERGIZED. THERMOSTAT CALLS FOR HEAT (W).

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