COMFORT-AIRE Century GUH95C Service Manual
  1. Manuals
  2. Brands
  3. COMFORT-AIRE Manuals
  4. Furnace
  5. GUH95C
  6. Service manual

COMFORT-AIRE Century GUH95C Service Manual

Hide thumbs Also See for Century GUH95C:
Table of Contents

Advertisement

Quick Links

SERVICE MANUAL
GUH95C
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.
508093-01

Table of Contents

Technical Specifications - GUH95C.. ...........................2
Parts Arrangement.......................................................5
Electrical ......................................................................6
Placement & Installation ............................................20
Joint Cementing Procedure .......................................21
Venting Practices .......................................................22
Vent Piping Guidelines ..............................................23
Condensate Piping ....................................................38
Start-Up .....................................................................43
Heating System Service Checks ...............................44
Typical Operating Characteristics ..............................48
Maintenance ..............................................................49
Wiring Diagram ..........................................................52
(Continued) ................................................................54
Sequence of Operation..............................................56
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.
*P508093-01*
Issue 2033
WARNING
(P) 508093-01
Page 1 of 56

Advertisement

Table of Contents
loading
Need help?

Need help?

Do you have a question about the Century GUH95C and is the answer not in the manual?

Questions and answers

Subscribe to Our Youtube Channel

Related Manuals for COMFORT-AIRE Century GUH95C

Summary of Contents for COMFORT-AIRE Century GUH95C

  • Page 1: Table Of Contents

    SERVICE MANUAL GUH95C 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 - GUH95C......2 Parts Arrangement............5 Electrical ..............6 Placement &...

  • Page 2: Technical Specifications - Guh95C

    Technical Speci ications - GUH95C MODEL NUMBER GUIDE UH 95 UH 95 0 0 4 4 5 5 B B 3 M REV CODE G = GAS FURNACE REVISION CONFIGURATION NOM. CFM X 100 2 TON ADD ON COOLING UH = UPFLOW/HORIZONTAL 3 TON ADD ON COOLING 4 TON ADD ON COOLING AFUE...
  • Page 3 BLOWER PERFORMANCE DATA CFM @ external static pressure - " w.c. Motor Blower Temp Blower Model Size (hp) Size Rise (F°) Speed High 1290 1275 1220 1215 1190 Med/High 1190 1150 1120 1090 1060 1015 1000 GUH95C045B3M 10 x 8 35 - 65 1080 1045...
  • Page 4 ACCESSORY LIST PART 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 1-Stage 13X57 30k BTUH Return Air Base 68W62 17.5"...

  • Page 5: Parts Arrangement

    Parts Arrangement TOP CAP BURNER BOX ASSEMBLY HEAT EXCHANGER ASSEMBLY GAS VALVE FLUE COLLAR COMBUSTION AIR INDUCER CABINET BLOWER ASSEMBLY COMBUSTION AIR PRESSURE PROVE SWITCH CONTROL BOX COLD END HEADER BOX Figure 1. Page 5 of 56 Issue 2033 508093-01...

  • 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 Burner Assembly Rollout Switch(s) Flame Sensor Ignitor Gas Valve Burner Box Front 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 GUH95C units is located in ADJUSTMENT SCREW 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 Wire Remove sensor from integrated control and connect alligator clip (−) to flame sensor lead. Multi−Meter Intergrated Control Set Dial to DC MicroAmps Flame Sensor Terminal (−) T o Flame Terminal (+) To Control Sensor Terminal...
  • 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 GUH95C 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. GUH95C 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 Exhaust Flush Mount 1-1/2" 2" Concentric 3" Concentric VENT Accelerator Accelerator Concentric Kit Capacity PIPE DIA. (Dia. X Length) (Dia. X Length) (in.) 71M80 69M29 60L46 1-1/2" x12" 2" x12" 51W11** +44W92++ +44W92++ 44W93+ 1-1/2 2-1/2"...

  • Page 22: Venting Practices

    Promptly apply solvent cement to end of pipe and REPLACING FURNACE THAT inside socket surface of fitting. Cement should be CHIMNEY WAS PART OF A COMMON OR GAS applied lightly but uniformly to inside of socket. Take VENT VENT SYSTEM (Check sizing care to keep excess cement out of socket.

  • Page 23: Vent Piping Guidelines

    Vent Piping Guidelines NOTE: Comfort-Aire/Century has approved the use of DuraVent and Centrotherm manufactured vent pipe and ® terminations as an option to PVC. When using the PolyPro by DuraVent or InnoFlue by Centrotherm ® ® venting system the vent pipe requirements stated in the unit installation instruction –...
  • Page 24 Use the following steps to correctly size vent pipe diameter. 030, 045, Furnace capacity? 070, 090, 110, 135 Standard or Which termination? Concentric? See Table 3 Which needs most Intake or elbows? Exhaust? How many? 1-1/2”, 2”, Desired pipe size? 2-1/2”...
  • Page 25 GUH95C Maximum Allowable Intake or Exhaust Vent Length in Feet Standard Termination at Elevation 0 - 4,500 ft 1-1/2” Pipe 2” Pipe 2-1/2" Pipe 3" Pipe Number Capacity Capacity Capacity Capacity of 90° Elbows Used Standard Termination at Elevation 4,501 - 10,000 ft 1-1/2”...
  • Page 26 GUH95C Maximum Allowable Intake or Exhaust Vent Length in Feet Concentric Termination at Elevation 0 - 4,500 ft 1-1/2” Pipe 2” Pipe 2-1/2" Pipe 3" Pipe Number Capacity Capacity Capacity Capacity of 90° Elbows Used Concentric Termination Elevation 4501 - 10,000 ft 1-1/2”...
  • Page 27 Maximum Allowable Exhaust Vent Lengths with Furnace Installed in a Closet or Basement Using Ventilated Attic or Crawl Space for Intake Air in Feet Standard Termination at Elevation 0 - 4,500 ft 1-1/2” Pipe 2” Pipe 2-1/2" Pipe 3" Pipe Number Capacity Capacity...
  • Page 28 TYPICAL EXHAUST PIPE CONNECTIONS IN UPFLOW DIRECT OR NON-DIRECT VENT APPLICATIONS Pipe size determined in Table 11 through Table 13 2” 2” 2” 2” 3” 2” TRANSITION EXHAUST *2” 030/045/070 Only 1-1/2” DO NOT transition from smaller to larger pipe in horizontal runs TRANSITION of exhaust pipe.
  • Page 29 Intake Piping TYPICAL AIR INTAKE PIPE CONNECTIONS The GUH95C furnace may be installed in either UPFLOW NON-DIRECT VENT APPLICATIONS direct vent or non-direct vent applications. In non- direct vent applications, when intake air will be drawn into Intake the furnace from the surrounding space, the indoor air Debris Screen quality must be considered and guidelines listed in...
  • Page 30 In Direct Vent applications, combustion air is taken Ventilation Louvers from outdoors and the flue gases are discharged to the Inlet Air outdoors. The GUH95C is then classified as a direct vent, Roof Terminated (Minimum 12 in. Exhaust Pipe Category IV gas furnace. (305mm) above Attic Floor) In both Non-Direct Vent and Direct Vent applications, the...
  • Page 31 Maximum Allowable Exhaust Vent Pipe Length (in ft.) without Insulation in Unconditioned Space For Winter Design Temperatures Single - Stage High Efficiency Furnace Table 14. Conditioned Space Exhaust Pipe Pipe Insulation Intake Conditioned Pipe Unconditioned Space Space Figure 29. Insulating Exhaust Pipe in an Unconditioned Space Page 31 of 56 Issue 2033 508093-01...
  • Page 32 ‡ 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 30. Vent Termination Clearances for Direct Installations 508093-01...
  • Page 33 Details of Intake and Exhaust Piping PVC beyond the outside wall. Intake piping should be as short as possible. See Figure 42. Terminations for Direct Vent Installations NOTE: In Direct Vent installations, combustion air is taken 3” (76MM) MIN. from outdoors and flue gases are discharged to outdoors. SIZE PER EXHAUST PIPE Inches (MM) TERMINATION SIZE...
  • Page 34 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 35 ‡ 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 39. Vent Termination Clearances for Non-Direct Installations...
  • Page 36 Details of Exhaust Piping Terminations for Non- STRAIGHT-CUT OR Direct Vent Applications ANGLE-CUT IN DIRECTION 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 Minimum 12”...
  • Page 37 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 38: Condensate Piping

    above 5” may result in a flooded heat exchanger if the Condensate Piping combined primary drain line were to become restricted. NOTE: In horizontal applications it is recommended to This unit is designed for either right- or left-side exit of install a secondary drain pan underneath the unit and condensate piping in upflow applications.
  • Page 39 If unit will be started immediately upon completion of installation, prime trap per procedure outlined in Unit Start-Up section. Condensate line must slope downward away from the trap to drain. If drain level is above condensate trap, condensate pump must be used. Condensate drain line should be routed within the conditioned space to avoid freezing of condensate and blockage of drain line.
  • Page 40 Figure 49. Evaporator Coil Using a Common Drain Figure 48. Condensate Trap with Optional Overflow Switch IMPORTANT When combining the furnace and evaporator coil drains together, the A/C condensate drain outlet must be vented to relieve pressure in order for the furnace pressure switch to operate properly.
  • Page 41 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 42 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 43: 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 44: 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 45 Furnace should operate at least 5 minutes before checking Manifold Pressure Measurement gas flow. Determine time in seconds for two revolutions of Follow the steps below and use Figure 55 as a reference. gas through the meter. (Two revolutions assures a more Gas manifold Kit 10L34 provides additional components if accurate time.) Divide by two and compare to time in Table needed.
  • Page 46 Proper Combustion Some units installed at altitude of 4501 - 10,000 feet (1373 to 3048 m) may require a pressure switch change Furnace should operate minimum 15 minutes with correct which can be ordered separately and a manifold de-rate. manifold pressure and gas flow rate before checking See Table 18 or Table 19 for manifold pressures at all combustion.
  • Page 47 Proper Ground and Voltage as a function of load indicates a poor or partial ground. Compare the readings to Table 21. If the readings exceed the maximum shown in Table 21, make repairs CAUTION before operating the furnace. In addition, measure the AC voltage from Line Hot If a flexible gas connector is required or allowed by to Line Neutral (spade terminals) on the integrated the authority that has jurisdiction, black iron pipe shall...

  • Page 48: Typical Operating Characteristics

    External Static Pressure Typical Operating Characteristics 1. Tap locations shown in Figure 58. 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 49: Maintenance

    Filter Size Maintenance Cabinet Width Side Return Bottom Return 17-1/2” 16 x 25 x 1 (1) 16 x 25 x 1 (1) 21” 20 x 25 x 1 (1) WARNING 24-1/2” 16 x 25 x 1 (2) 24 x 25 x 1 (1) ELECTRICAL SHOCK, FIRE, Table 22.
  • Page 50 Winterizing and Condensate Trap Care 10. Disconnect condensate drain line from the cold end header box. 1. Turn off power to the furnace. 11. Disconnect condensate drain tubing from flue collar. Have a shallow pan ready to empty condensate water. Remove screws that secures the flue collar into place.
  • Page 51 Cleaning the Burner Assembly (if needed) 30. Reinstall the cold end header box. 1. Turn off electrical and gas power supplies to furnace. 31. Reinstall the combustion air inducer. Reconnect the Remove upper and lower furnace access panels. plug to the wire harness. Disconnect the wires from the gas valve.

  • Page 52: Wiring Diagram

    Wiring Diagram 508093-01 Issue 2033 Page 52 of 56...

  • Page 53: 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 54: 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 IS VOLTAGE ABOVE 70 VOLTS? IGNITOR WARM UP -- 20 SECONDS. 75 VOLTS, HEATING SEQUENCE RESTARTS.

  • Page 55: 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 56: 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).

Table of Contents