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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.
Unit Dimensions ..........................................................2
Parts Arrangement.......................................................3
Gas Furnace ................................................................4
Shipping and Packing List ...........................................4
Safety Information .......................................................4
General ........................................................................6
Combustion, Dilution & Ventilation Air .........................6
Installation ...................................................................9
Filters .........................................................................12
Duct System ..............................................................12
Venting Practices .......................................................14
Condensate Piping ....................................................29
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 installer (or
equivalent), service agency or the gas supplier.
Manufactured By
Comfort-Aire / Century
1900 Wellworth Ave.
Jackson, MI 49203
507714-01
INSTALLATION INSTRUCTIONS
GDD95A & GDD92A
Warm Air Gas Furnace
Downflow Air Discharge
This manual must be left with the homeowner for future reference.
Table of Contents
WARNING
Save these instructions for future reference
Gas Piping .................................................................32
Electrical ....................................................................34
Unit Start-Up ..............................................................38
Air for Non-Direct Vent Applications ..........................42
Other Unit Adjustments..............................................43
Blower Performance GDD92A ...................................44
Blower Performance GDD95A ...................................45
Service.......................................................................47
Planned Service ........................................................49
Repair Parts List ........................................................49
Start-Up & Performance Checklist.............................50
As with any mechanical equipment, personal injury can
result from contact with sharp sheet metal edges. Be
careful when you handle this equipment.
Issue 1716
CAUTION
*P507714-01*
(P) 507714-01
Page 1 of 52
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Summary of Contents for COMFORT-AIRE GDD95A
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Page 1: Table Of Contents
Air for Non-Direct Vent Applications ......42 General ................6 Other Unit Adjustments..........43 Combustion, Dilution & Ventilation Air ......6 Blower Performance GDD92A ........44 Installation ..............9 Blower Performance GDD95A ........45 Filters .................12 Service...............47 Duct System ..............12 Planned Service ............49 Venting Practices ............14 Repair Parts List ............49 Condensate Piping ............29... -
Page 2: Unit Dimensions
Unit Dimensions Model GDD95A / GDD92A 045-3 17-1/2 16-3/8 070-3 090-4 090-5 19-7/8 19-1/2 110-5 Page 2 of 52 Issue 1716 507714-01... -
Page 3: Parts Arrangement
Parts Arrangement BAG ASSEMBLY CONTROL BOX (Includes integrated control, transformer and door switch) BLOWER MOTOR (hidden) BLOWER COMPARTMENT ACCESS PANEL COMBUSTION AIR INDUCER BLOWER DECK HEAT EXCHANGER PRIMARY HEATING LIMIT COMPARTMENT COLD END ACCESS PANEL HEADER BOX GAS VALVE BURNER BOX ASSEMBLY (includes flame sensor, rollout switches and ignitor) -
Page 4: Gas Furnace
Gas Furnace Shipping and Packing List This Category IV gas furnace is shipped ready for Package 1 of 1 contains: installation in the downflow position. 1 - Assembled Gas Unit The furnace is equipped for installation in natural gas 1 - Bag assembly containing the following: applications. - Page 5 In order to ensure proper unit operation in non-direct vent applications, combustion and ventilation air supply must be provided according to the current National Fuel Gas Code or CSA-B149 standard. Locations and Clearances This furnace is CSA International certified for installation clearances to combustible material as listed on the unit nameplate and in the table in Figure 14.
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Page 6: General
NOTE: The Commonwealth of Massachusetts stipulates • A room thermostat must control the furnace. The use of fixed jumpers that will provide continuous heating is these additional requirements: not allowed. • Gas furnaces shall be installed by a licensed plumber •... - Page 7 Unconfined Space An unconfined space is an area such as a basement WARNING or large equipment room with a volume greater than 50 cubic feet (1.42 m³) per 1,000 Btu (.29 kW) per hour of Insufficient combustion air can cause headaches, the combined input rating of all appliances installed in that nausea, dizziness or asphyxiation.
- Page 8 a minimum free area of 1 square inch per 4,000 Btu they connect. The minimum dimension of rectangular (645 mm² per 1.17kW) per hour of total input rating of all air ducts shall be no less than 3 inches (75 mm). In equipment in the enclosure (see Figure 6 and Figure 9).
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Page 9: Installation
Shipping Bolt Removal Units with a 1/2 hp blower motors are equipped with three WARNING flexible legs and one rigid leg. The rigid leg is equipped with a shipping bolt and a flat white plastic washer (rather If this unit is being installed in an application with than the rubber mounting grommet used with a flexible combustion air coming in from a space serviced by an mounting leg). - Page 10 Figure 13. NOTE: These units may be equipped with a shipping pad under the blower housing. Remove the shipping pad prior to operation. * Front Back Allow for clearances to combustible materials as indicated Sides 0† on the unit nameplate. Minimum clearances for closet or alcove installations are shown in Figure 14.
- Page 11 After opening is cut, set the combustible flooring base into opening. FURNACE Check fiberglass strips on the combustible flooring base to make sure they are properly glued and positioned. PROPERLY Lower supply air plenum into the combustible flooring SIZED FLOOR SUPPLY AIR base until plenum flanges seal against fiberglass OPENING...
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Page 12: Filters
In all cases, plenum should be secured to top of (by reflected light) of the heat exchanger for leaks after the furnace using sheet metal screws. furnace is installed. The furnace access panel must always be in place when the furnace is operating and it must not Make certain that an adequate seal is made. - Page 13 When return air is drawn from a room, a negative pressure is created in the room. If a gas appliance is operating in CAUTION a room with negative pressure, the flue products can be pulled back down the vent pipe and into the room. This Solvent cements for plastic pipe are flammable liquids reverse flow of the flue gas may result in incomplete and should be kept away from all sources of ignition.
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Page 14: Venting Practices
Low temperature solvent cement is recommended during Immediately after applying last coat of cement to pipe, cooler weather. Metal or plastic strapping may be used as and while both inside socket surface and end of pipe vent pipe hangers. Uniformly apply a liberal coat of PVC are wet with cement, forcefully insert end of pipe into primer for PVC or use a clean dry cloth for ABS to clean socket until it bottoms out. - Page 15 DANGER CARBON MONOXIDE POISONING HAZARD Failure to follow the steps outlined below for each appliance connected to the venting system being placed into operation could result in carbon monoxide poisoning or death. The following steps shall be followed for each appliance connected to the venting system being placed into operation, while all other appliances connected to the venting system are not in operation.
- Page 16 Exhaust? In some applications which permit the use of several different sizes of vent pipe, a combination vent pipe may be used. Contact Comfort-Aire / Century for assistance in sizing vent pipe in these applications. Capacity Min. Vent Length* How many? 15 ft.
- Page 17 GDD95A / GDD92A Maximum Allowable Intake or Exhaust Vent Length in Feet Standard Termination at Elevation 0 - 10,000 ft 2" Pipe 2-1/2" Pipe 3" Pipe Number of 90° Model Model Model Elbows Used Concentric Termination Elevation 0 - 10,000 ft 2"...
- Page 18 GDD95A / GDD92A 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 - 4,500 ft 2" Pipe 2-1/2" Pipe 3" Pipe Number of 90°...
- Page 19 Figure 24. Typical Intake Pipe Connections (Direct Vent Applications) Intake Piping This furnace may be installed in either direct vent or non- direct vent applications. In non-direct vent applications, when intake air will be drawn into the furnace from the surrounding space, the indoor air quality must be considered.
- Page 20 Follow the next two steps when installing the unit in Non- Direct Vent applications where combustion air is taken Roof Terminated from indoors and flue gases are discharged outdoors. Exhaust Pipe Use field-provided materials and the factory-provided air intake screen to route the intake piping as shown in Figure 29.
- Page 21 exhaust pipe should be insulated with 1/2” (13 mm) Armaflex or equivalent. In extremely cold climate areas, 3/4” (19 mm) Armaflex or equivalent may be necessary. Insulation on outside runs of exhaust pipe must be painted or wrapped to protect insulation from deterioration. Exhaust pipe insulation may not be necessary in some specific applications.
- Page 22 ‡ 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 29. Vent Termination Clearances for Non-Direct Vent Installations...
- Page 23 ‡ 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 Vent Installations...
- Page 24 Details of Intake and Exhaust Piping NOTE: Care must be taken to avoid recirculation of exhaust back into intake pipe. Terminations for Direct Vent Installations NOTE: In Direct Vent installations, combustion air is taken On field supplied terminations, a minimum distance from outdoors and flue gases are discharged to outdoors.
- Page 25 FIELD-PROVIDED 2” EXTENSION FOR 2” PVC PIPE REDUCER MAY BE REQUIRED 1-1/2” (38mm) accelerator 1” EXTENSION FOR 3” PVC PIPE TO ADAPT LARGER VENT provided on 71M80 & 44W92 PIPE SIZE TO TERMINATION kits for -45 and -70 units OUTSIDE INTAKE WALL FURNACE...
- Page 26 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 27 Details of Exhaust Piping Terminations for Non- Direct Vent Applications Exhaust pipe may be routed either horizontally through an outside wall or vertically through the roof. In attic or SIZE TERMINATION closet installations, vertical termination through the roof PER EXHAUST PIPE is preferred.
- Page 28 Exhaust through Crawl Space Vent Option All 33” condensing gas furnaces (92%+) are now approved Exhaust from to be vented down through a crawl space. The following Furnace diagrams show the approved methods. Ensure a sanitary To Termination tee is used as directed for condensate control. Consult the vent tables for vent lengths and approved materials.
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Page 29: Condensate Piping
Figure 49 shows the furnace and evaporator coil Condensate Piping using a separate drain. If necessary, the condensate line from the furnace and evaporator coil can drain This unit is designed for either right or left side exit of together. See Figure 50. The field provided vent must condensate piping in downflow applications. - Page 30 Figure 49. Evaporator Coil Using a Separate Drain Figure 51. Condensate Trap with Optional Overflow Switch Figure 50. Evaporator Coil Using a Common Drain Page 30 of 52 Issue 1716 507714-01...
- Page 31 Figure 52. Trap Drain Assembly Using 1/2” PVC or 3/4” PVC 507714-01 Issue 1716 Page 31 of 52...
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Page 32: Gas Piping
Gas Piping IMPORTANT Compounds used on threaded joints of gas piping must be resistant to the actions of liquified petroleum gases. CAUTION If a flexible gas connector is required or allowed by the authority that has jurisdiction, black iron pipe shall Leak Check be installed at the gas valve and extend outside the After gas piping is completed, carefully check all piping... - Page 33 Figure 54. Gas Pipe Capacity - FT³/HR (kL/HR) Nominal Length of Pipe - feet (m) Internal Iron Pipe Diameter Size - - inches inches (3.048) (6.096) (9.144) (12.192) (15.240) (18.288) (21.336) (24.384) (27.432) (30.480) (mm) (mm) .622 (12.7) (17.799) (4.96) (3.40) (2.75) (2.32)
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Page 34: Electrical
The unit is equipped with a field makeup box on the left Electrical hand side of the cabinet. A field-provided make-up box can be installed on the exterior of the right side of the furnace to facilitate installation. Seal unused openings on left side ELECTROSTATIC DISCHARGE (ESD) with plugs removed from right side. - Page 35 Indoor Blower Speeds one amp is connected to this terminal, it is necessary to use an external relay. See Figure 61 for control board When the thermostat is set to “FAN ON”, the indoor configuration. This terminal is energized in the heating blower will run continuously on the heating speed mode when the combustion air inducer is operating.
- Page 36 045-3 070-3 090-4 110-5 Figure 59. Typical Wiring Diagram For GDD92A Page 36 of 52 Issue 1716 507714-01...
- Page 37 045-3 070-3 090-5 110-5 Figure 60. Typical Wiring Diagram For GDD95A 507714-01 Issue 1716 Page 37 of 52...
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Page 38: Unit Start-Up
Figure 61. Integrated Control (Automatic Hot Surface Ignition System) Unit Start-Up CAUTION FOR YOUR SAFETY READ BEFORE OPERATING Before attempting perform service maintenance, turn the electrical power to unit OFF at disconnect switch. WARNING BEFORE LIGHTING the unit, smell all around the furnace Do not use this furnace if any part has been underwater. - Page 39 Follow the lighting instructions to place the unit into Replace the heating compartment access panel. operation. 10. Turn on all electrical power to the unit. Set the thermostat to initiate a heating demand. 11. Set the thermostat to desired setting. Allow the burners to fire for approximately 3 minutes.
- Page 40 Gas Pressure Adjustment While waiting for the unit to stabilize, observe the flame. Flame should be stable and should not lift from Gas Flow (Approximate) burner. Natural gas should burn blue. Seconds for One Revolution After allowing unit to stabilize for 5 minutes, record Natural Capacity manifold pressure and compare to value given in...
- Page 41 93W88 Pressure switch is factory set. No adjustment necessary. All models use the factory-installed pressure switch from 0-4500 feet (0-1371 m). GDD95A Pressure Switch Requirements at Varying Altitudes 0 - 4500 ft 4501 - 7500 ft 7501 - 10000 ft...
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Page 42: Testing For Proper Venting And Sufficient Combustion Air For Non-Direct Vent Applications
Testing for Proper Venting and Sufficient Combustion Air for Non-Direct Vent Applications Seal any unused openings in the venting system. Visually inspect the venting system for proper size WARNING and horizontal pitch. Determine there is no blockage CARBON MONOXIDE POISONING HAZARD or restriction, leakage, corrosion, or other deficiencies which could cause an unsafe condition. -
Page 43: Other Unit Adjustments
Thermostat Heat Anticipation Other Unit Adjustments Set the heat anticipator setting (if adjustable) according to the amp draw listed on the wiring diagram that is attached to the unit. Primary Limit The primary limit is located on the heating compartment Electrical vestibule panel. -
Page 44: Blower Performance Gdd92A
Blower Performance GDD92A GDD92A 045*B3 Performance (Less Filter) External Air Volume / Watts at Various Blower Speeds Static High Medium - High Medium - Low Pressure in. Watts Watts Watts Watts w.g. 0.00 1615 1385 1205 1045 0.10 1605 1375 1195 1035 0.20... -
Page 45: Blower Performance Gdd95A
1155 1510 1400 1315 0.90 1455 1110 1390 1350 1210 Blower Performance GDD95A GDD95A 045*B3 Performance (Less Filter) External Air Volume / Watts at Various Blower Speeds Static High Medium - High Medium - Low Pressure in. Watts Watts Watts Watts w.g. - Page 46 GDD95A 070*B3 Performance (Less Filter) External Air Volume / Watts at Various Blower Speeds Static High Medium - High Medium - Low Pressure in. Watts Watts Watts Watts w.g. 0.00 1515 1315 1095 0.10 1490 1300 1075 0.20 1445 1275 1065 0.30...
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Page 47: Service
Check amp-draw on the blower motor with the blower Service compartment access panel in place. Motor Nameplate____________ Actual____________ WARNING Winterizing and Condensate Trap Care 1. Turn off power to the furnace. ELECTRICAL SHOCK, FIRE, OR EXPLOSION HAZARD. Have a shallow pan ready to empty condensate water. Failure to follow safety warnings exactly could result in Remove the clean out cap from the condensate trap and empty water. - Page 48 Cleaning the Burner Assembly 16. Remove screws along vestibule sides and bottom which secure vestibule panel and heat exchanger 1. Turn off electrical and gas power supplies to furnace. assembly to cabinet. Remove two screws from blower Remove upper and lower furnace access panels. rail which secure bottom heat exchanger flange.
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Page 49: Planned Service
Table 15. Diagnostic Codes Repair Parts List The following repair parts are available through Comfort-Aire / Century dealers. When ordering parts, include the complete furnace model number listed on the CSA nameplate. All service must be performed by a licensed professional installer (or equivalent), service agency, or gas supplier. -
Page 50: Start-Up & Performance Checklist
Start-Up & Performance Checklist Page 50 of 52 Issue 1716 507714-01... - Page 51 UNIT OPERATION HEATING MODE COOLING MODE GAS MANIFOLD PRESSURE “W.C.” ______ INDOOR BLOWER AMPS ______ COMBUSTION SAMPLE CO CO _____ PPM TEMPERATURE DROP ______ ______ Return Duct Temperature INDOOR BLOWER AMPS ______ ______ Supply Duct Temperature ______ Temperature Drop TEMPERATURE RISE TOTAL EXTERNAL STATIC (dry coil) Supply Duct Temperature ______...
- Page 52 Requirements for Commonwealth of Massachusetts Modifications to NFPA-54, Chapter 10 INSPECTION. The state or local gas inspector of the side wall, horizontally vented, gas-fueled equipment Revise NFPA-54 section 10.8.3 to add the following shall not approve the installation unless, upon requirements: inspection, the inspector observes carbon monoxide For all side wall, horizontally vented, gas-fueled equipment...
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