Lennox G40UH−36A−045, G40UH−36A−070, G40UH−36B−090, G40UH−48B−070, G40UH−48B−090 Installation Instructions Manual
...
INSTALLATION
©2006 Lennox Industries Inc.
Dallas, Texas, USA
RETAIN THESE INSTRUCTIONS
FOR FUTURE REFERENCE
INSTRUCTIONS
G40UH(X) Series
GAS FURNACE
505,181M
03/2006
Supersedes 505,011M
Table of Contents
Unit Dimensions 2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
G40UH(X) Parts Arrangement 3. . . . . . . . . . . . . . . . . . . . .
G40UH(X) Gas Furnace 4. . . . . . . . . . . . . . . . . . . . . . . . . .
Shipping and Packing List 4. . . . . . . . . . . . . . . . . . . . . . . .
Safety Information 4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
General 5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Combustion, Dilution & Ventilation Air 5. . . . . . . . . . . . . .
Setting Equipment 8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Filters 12. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Duct System 12. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Venting 12. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Gas Piping 20. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Electrical 21. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Unit Start−Up 25. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Gas Pressure Adjustment 26. . . . . . . . . . . . . . . . . . . . . . .
High Altitude Information 27. . . . . . . . . . . . . . . . . . . . . . . .
Other Unit Adjustments 27. . . . . . . . . . . . . . . . . . . . . . . . . .
Service 28. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Repair Parts List 30. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Ignition Control Board Diagnostic Codes 31. . . . . . . . . . .
Troubleshooting 32. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Start−Up & Performance Check List 35. . . . . . . . . . . . . . .
Litho U.S.A.
Failure to follow safety warnings exactly could result in serious injury, death,
or property damage.
Do not store or use gasoline or other
flammable vapors and liquids in the
vicinity of this or any other appliance.
Installation and service must be
performed by a qualified installer,
service agency or the gas supplier.
03/06
*2P0306*
WARNING
FIRE OR EXPLOSION HAZARD.
WHAT TO DO IF YOU SMELL GAS:
D Do not try to light any appliance.
D Do not touch any electrical switch; do not
use any phone in your building.
D Leave the building immediately.
D Immediately call your gas supplier from a
neighbor’s phone. Follow the gas supplier’s
instructions.
D If you cannot reach your gas supplier, call
the fire department.
Page 1
505,181M
*P505181M*
G40UH(X) Unit Dimensions − inches (mm)
*NOTE − 60C and 60D units that require air volumes
over 1800 cfm (850 L/s) must have one of the following:
1. Return air from single side with transition which will
accommodate 20 x 25 x 1 in. (508 x 635 x 25 mm)
cleanable air filter. (Required to maintain proper air
velocity.)
2. Return air from single side with optional RAB Return
Air Base.
3. Return air from bottom.
4. Return air from both sides.
5. Return air from bottom and
Refer to Engineering Handbook for additional information.
**Flue outlet may be horizontal but furnace must be
vented vertically
Optional external side return air filter kit cannot be used
with the optional RAB Return Air Base.
A
B 9/16 (14)
one side.
OPTIONAL
EXTERNAL
SIDE RETURN
AIR FILTER KIT
(Either Side)
40
(1016)
3−3/4 (95)
D
FLUE OUTLET
(Top)
OPTIONAL
EXTERNAL
SIDE RETURN
AIR FILTER KIT
(Either Side)
3−1/4 (83) Right
8−1/8 (206) Left
14 (356) Right
13−1/4 (337) Left
4−7/8 (124) Right
2−1/4 (57) Left
TOP VIEW
3−3/4
(95)
SUPPLY AIR
OPENING
23-3/4 (603)
25 (635)
TOP VIEW
28−1/2
(724)
19−7/16
(494)
**FLUE OUTLET
(Either Side)
ELECTRICAL INLET
(Either Side)
GAS PIPING INLET
(Either Side)
ELECTRICAL INLET
(Either Side)
9/16
(14)
3/4 (19)
Model No.
G40UH−24A−045,
G40UH−24A−070,
G40UH−36A−045,
G40UH−36A−070
G40UH−36B−090,
G40UH−48B−070,
G40UH−48B−090
G40UH−36B−110,
G40UH−48C−110,
G40UH−48C−135,
G40UH−60C−110
G40UH−60D−135
G40UH−60D−155
23
(584)
*Side Return
Air Opening
(Either Side)
23−1/2
(597)
*Bottom Return
Air Opening
AIR FLOW
C
*Bottom Return
Air Opening
14−3/4
(375)
3/4 (19)
4
(102)
16
(406)
5/8 (16)
4−1/4
(108)
FRONT VIEW SIDE VIEW
A B C D
in. mm in. mm in. mm in. mm
14−1/2 368 13−3/8 340 13 330 4−1/2 11 4
17−1/2 446 16−3/8 416 16 406 6 152
21 533 19−7/8 454 19−1/2 495 7−3/4 197
24−1/2 622 23−3/8 546 23 584 9−1/2 241
14
(356)
1−15/16 (49)
Page 2
G40UH(X) Parts Arrangement
Gasket
Flue Box Gasket
Flue Collector Box
Air Deflector
G40UH−48C−135,
G40UH−60C−110, &
G40UH−60D−155
Units Only
Heat Exchanger
Flue Transition
Flame Sensor
Flame Rollout Switches*
Flame Rollout Bracket
Gas Valve
Burners
Gas Orifices
Igniter Bracket
Combustion Air
Combustion Air
Pressure Switch
Combustion Air Inducer
Primary Limit
(NOx Units Only)
Igniter
Orifice
Limit Shield
NOx Insert
Secondary Limit
Burner Bottom Shield
Door Interlock Switch
*135 and 155 kBtuh units only −−
Flame rollout switches are located
on brackets on the inner sides (one
on the left and one on the right) of
the burner box.
Integrated Ignition
Control Board
Blower Assembly
Capacitor
Control Transformer
FIGURE 1
Page 3
G40UH(X) Gas Furnace
The G40UH(X) gas furnace is shipped ready for installation in the upflow and horizontal position (left or right)
fueled by natural gas. A conversion kit (ordered separately) is required for use in propane/LP gas applications. The
furnace is shipped with the bottom panel in place. The bottom panel must be removed if the unit is to be installed in a
horizontal application. The panel may also be removed in
upflow applications.
Shipping and Packing List
Package 1 of 1 contains
1 − Assembled G40UH(X) unit
1 − Bag assembly containing the following:
2 − Screws
3 − Wire nuts
1 − Snap bushing
1 − Snap plug
1 − Wire tie
1 − Vent warning label
1 − Owner’s manual and warranty card
The following items may also be ordered separately:
1 − Thermostat
1 − Hanging bracket (for horizontal installations)
1 − Propane/LP changeover kit
Check equipment for shipping damage. If you find any
damage, immediately contact the last carrier.
Safety Information
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 qualified installer, service agency
or the gas supplier.
CAUTION
As with any mechanical equipment, personal injury
can result from contact with sharp sheet metal
edges. Be careful when you handle this equipment.
G40UH(X) units are CSA International certified to ANSI
Z21.47 and CSA 2.3 standards.
In the USA, installation of gas furnaces must conform with local building codes. In the absence of local codes, units must
be installed according to the current National Fuel Gas Code
(ANSI-Z223.1). The National Fuel Gas Code is available
from the following address:
American National Standards Institute, Inc.
11 West 42nd Street
New York, NY 10036
In Canada, installation must conform with current CSA
B149 Natural Gas and Propane Installation Codes, local
plumbing or waste water codes and other applicable local
codes.
Adequate clearance must be made around the air openings into the vestibule area. In order to ensure proper unit
operation, combustion and ventilation air supply must be
provided according to the current National Fuel Gas Code
or CSA B149 standards.
Vent installations must be consistent with the venting
tables (in this instruction) and applicable provisions of local
building codes.
This furnace is CSA International certified for installation
clearances to combustible material as listed on the unit
nameplate and in the tables in figures 6 and 11. Accessibility
and service clearances must take precedence over fire
protection clearances.
NOTE − For installation on combustible floors, the furnace
shall not be installed directly on carpeting, tile, or other
combustible material other than wood flooring.
For installation in a residential garage, the furnace must
be installed so that the burner(s) and the ignition source
are located no less than 18 inches (457 mm) above the
floor. The furnace must be located or protected to avoid
physical damage by vehicles. When a furnace is installed
in a public garage, hangar, or other building that has a hazardous atmosphere, the furnace must be installed according to recommended good practice requirements and current National Fuel Gas Code or CSA B149 standards.
NOTE − Furnace must be adjusted to obtain a temperature
rise within the range specified on the unit nameplate. Failure
to do so may cause erratic limit operation and premature heat
exchanger failure.
This G40UH(X) furnace must be installed so that its electrical components are protected from water.
When this furnace is used with cooling units, it shall be
installed in parallel with, or on the upstream side of, cooling
units to avoid condensation in the heating compartment.
With a parallel flow arrangement, a damper (or other means
to control the flow of air) must adequately prevent chilled air
from entering the furnace. If the damper is manually operated, it must be equipped to prevent operation of either the
heating or the cooling unit, unless it is in the full HEAT or
COOL setting.
When installed, this furnace must be electrically grounded
according to local codes. In addition, in the United States,
installation must conform with the current National Electric
Code, ANSI/NFPA No. 70. The National Electric Code
(ANSI/NFPA No. 70) is available from the following address:
National Fire Protection Association
1 Battery March Park
Quincy, MA 02269
In Canada, all electrical wiring and grounding for the unit
must be installed according to the current regulations of the
Canadian Electrical Code Part I (CSA Standard C22.1)
and/or local codes.
Page 4
NOTE − This furnace is designed for a minimum continuous return air temperature of 60°F (16°C) or an intermittent operation down to 55°F (13°C) dry bulb for cases
where a night setback thermostat is used. Return air temperature must not exceed 85°F (29°C) dry bulb.
NOTE − G40UH(X) series units should not be installed as
a unit heater.
The G40UH(X) furnace may be installed in alcoves, closets, attics, basements, garages, and utility rooms in the upflow or horizontal position.
This furnace design has not been CSA International certified for installation in mobile homes, recreational vehicles,
or outdoors.
Lennox does not recommend the use of G40UH(X) units as
a construction heater during any phase of construction.
Very low return air temperatures, harmful vapors and operation of the unit with clogged or misplaced filters will damage the unit.
G40UH(X) units may be used for heating of buildings or
structures under construction, if the following conditions
are met:
D The vent system must be permanently installed per
these installation instructions.
D A room thermostat must control the furnace. The use of
fixed jumpers that will provide continuous heating is not
allowed.
D The return air duct must be provided and sealed to the
furnace.
D Return air temperature range between 60°F (16°C) and
80°F (27°C) must be maintained.
D Air filters must be installed in the system and must be
maintained during construction.
D Air filters must be replaced upon construction comple-
tion.
D The input rate and temperature rise must be set per the
furnace rating plate.
D One hundred percent (100%) outdoor air must be pro-
vided for combustion air requirements during construction. Temporary ducting may supply outdoor air to the
furnace. Do not connect duct directly to the furnace.
Size the temporary duct following these instructions in
section for Combustion, Dilution and Ventilation Air in a
confined space with air from outside.
D The furnace heat exchanger, components, duct system,
air filters and evaporator coils must be thoroughly
cleaned following final construction clean−up.
D All furnace operating conditions (including ignition, in-
put rate, temperature rise and venting) must be verified
according to these installation instructions.
NOTE − The Commonwealth of Massachusetts stipulates these additional requirements:
D Gas furnaces shall be installed by a licensed plumb-
er or gas fittter only.
D The gas cock must be T handle" type.
D When a furnace is installed in an attic, the passage-
way to and service area surrounding the equipment
shall be floored.
General
These instructions are intended as a general guide and do
not supersede local codes in any way. Consult authorities
having jurisdiction before installation.
In addition to the requirements outlined previously, the following general recommendations must be considered
when installing a G40UH(X) furnace:
• Place the furnace as close to the center of the air distribution system as possible. The furnace should also be
located close to the chimney or vent termination point.
• Do not install the furnace where drafts might blow directly into it. This could cause improper combustion and unsafe operation.
• Do not block the furnace combustion air openings with
clothing, boxes, doors, etc. Air is needed for proper
combustion and safe unit operation.
• When the furnace is installed in an attic or other insulated space, keep insulation away from the furnace.
WARNING
Product contains fiberglass wool.
Disturbing the insulation in this product during
installation, maintenance, or repair will expose you
to fiberglass wool. Breathing this may cause lung
cancer. (Fiberglass wool is known to the State of California to cause cancer.)
Fiberglass wool may also cause respiratory, skin,
and eye irritation.
To reduce exposure to this substance or for further
information, consult material safety data sheets
available from address shown below, or contact your
supervisor.
Lennox Industries Inc.
P.O. Box 799900
Dallas, TX 75379−9900
Combustion, Dilution & Ventilation Air
In the past, there was no problem in bringing in sufficient outdoor air for combustion. Infiltration provided all the air that
was needed. In today’s homes, tight construction practices
make it necessary to bring in air from outside for combustion. Take into account that exhaust fans, appliance vents,
chimneys, and fireplaces force additional air that could be
used for combustion out of the house. Unless outside air is
brought into the house for combustion, negative pressure
Page 5
(outside pressure is greater than inside pressure) will build
to the point that a downdraft can occur in the furnace vent
pipe or chimney. As a result, combustion gases enter the living space creating a potentially dangerous situation.
In the absence of local codes concerning air for combustion and ventilation, use the guidelines and procedures in
this section to install G40UH(X) furnaces to ensure efficient
and safe operation. You must consider combustion air
needs and requirements for exhaust vents and gas piping.
A portion of this information has been reprinted with permission from the National Fuel Gas Code (ANSI-Z223.1).
This reprinted material is not the complete and official position of the ANSI on the referenced subject, which is represented only by the standard in its entirety.
In Canada, refer to the CSA B149 installation codes.
CAUTION
Do not install the furnace in a corrosive or contaminated atmosphere. Meet all combustion and ventilation air requirements, as well as all local codes.
CAUTION
Insufficient combustion air can cause headaches,
nausea, dizziness or asphyxiation. It will also cause
excess water in the heat exchanger resulting in rusting and premature heat exchanger failure. Excessive
exposure to contaminated combustion air will result
in safety and performance related problems. Avoid
exposure to the following substances in the combustion air supply:
Permanent wave solutions
Chlorinated waxes and cleaners
Chlorine base swimming pool chemicals
Water softening chemicals
De-icing salts or chemicals
Carbon tetrachloride
Halogen type refrigerants
Cleaning solvents (such as perchloroethylene)
Printing inks, paint removers, varnishes, etc.
Hydrochloric acid
Cements and glues
Antistatic fabric softeners for clothes dryers
Masonry acid washing materials
All gas-fired appliances require air for the combustion process. If sufficient combustion air is not available, the furnace or other appliances will operate inefficiently and unsafely. Enough air must be provided to meet the needs of all
fuel-burning appliances and appliances such as exhaust
fans which force air out of the house. When fireplaces, exhaust fans, or clothes dryers are used at the same time as
the furnace, much more air is necessary to ensure proper
combustion and to prevent a downdraft. Insufficient air
causes incomplete combustion which can result in carbon
monoxide.
In addition to providing combustion air, fresh outdoor air
dilutes contaminants in the indoor air. These contaminants may include bleaches, adhesives, detergents, solvents and other contaminants which can corrode furnace
components.
The requirements for providing air for combustion and ventilation depend largely on whether the furnace is installed in
an unconfined or a confined space.
Unconfined Space
An unconfined space is an area such as a basement or
large equipment room with a volume greater than 50 cubic
feet (1.42 m3) per 1,000 Btu (.29 kW) per hour of the combined input rating of all appliances installed in that space.
This space also includes adjacent rooms which are not
separated by a door. Though an area may appear to be unconfined, it might be necessary to bring in outdoor air for
combustion if the structure does not provide enough air by
infiltration. If the furnace is located in a building of tight
construction with weather stripping and caulking around
the windows and doors, follow the procedures in the air
from outside section.
Confined Space
A confined space is an area with a volume less than 50 cubic feet (1.42 m3) per 1,000 Btu (.29 kW) per hour of the
combined input rating of all appliances installed in that
space. This definition includes furnace closets or small
equipment rooms.
When the furnace is installed so that supply ducts carry air
circulated by the furnace to areas outside the space containing the furnace, the return air must be handled by ducts
which are sealed to the furnace casing and which terminate
outside the space containing the furnace. This is especially
important when the furnace is mounted on a platform in a
confined space such as a closet or small equipment room.
Even a small leak around the base of the unit at the platform
or at the return air duct connection can cause a potentially
negative pressure condition. Air for combustion and dangerous ventilation can be brought into the confined space
either from inside the building or from outside.
Page 6
EQUIPMENT IN CONFINED
CHIMNEY
OR GAS
VENT
FURNACE
NOTE−Each opening shall have a free area of at least one square
inch (645 mm2) per 1,000 Btu (.29 kW) per hour of the total input rating of all equipment in the enclosure, but not less than 100 square
inches (64516 mm2).
SPACE ALL AIR FROM INSIDE
WATER
HEATER
OPENINGS
(To Adjacent
Room)
FIGURE 2
Air from Inside
If the confined space that houses the furnace adjoins a
space categorized as unconfined, air can be brought in by
providing two permanent openings between the two
spaces. Each opening must have a minimum free area of 1
square inch (645 mm2) per 1,000 Btu (.29 kW) per hour of
total input rating of all gas−fired equipment in the confined
space. Each opening must be at least 100 square inches
(64516 mm2). One opening shall be within 12 inches (305
mm) of the top of the enclosure and one opening within 12
inches (305 mm) of the bottom. See figure 2.
Air from Outside
If air from outside is brought in for combustion and ventilation, the confined space must have two permanent openings. One opening shall be within 12 inches (305 mm) of the
top of the enclosure and one opening within 12 inches (305
mm) of the bottom. These openings must communicate directly or by ducts with the outdoors or spaces (crawl or attic) that freely communicate with the outdoors or indirectly
through vertical ducts. Each opening shall have a minimum
free area of 1 square inch (645 mm2) per 4,000 Btu (1.17
kW) per hour of total input rating of all equipment in the enclosure. See figures 3 and 4. When communicating with
the outdoors through horizontal ducts, each opening shall
have a minimum free area of 1 square inch (645 mm2) per
2,000 Btu (.56 kW) per total input rating of all equipment in
the enclosure. See figure 5.
When ducts are used, they shall be of the same cross−sectional area as the free area of the openings to which they
connect. The minimum dimension of rectangular air ducts
shall be no less than 3 inches (75 mm). In calculating free
area, the blocking effect of louvers, grilles, or screens must
be considered. If the design and free area of protective covering is not known for calculating the size opening required,
it may be assumed that wood louvers will have 20 to 25 percent free area and metal louvers and grilles will have 60 to
75 percent free area. Louvers and grilles must be fixed in the
open position or interlocked with the equipment so that they
are opened automatically during equipment operation.
EQUIPMENT IN CONFINED SPACE
CHIMNEY OR
GAS VENT
VENTILATION LOUVERS
(Each end of attic)
FURNACE
VENTILATION
LOUVERS
(For unheated crawl space)
NOTE−The inlet and outlet air openings shall each have a free area of at least one square inch (645 mm2)
per 4,000 Btu (1.17 kW) per hour of the total input rating of all equipment in the enclosure.
(Inlet Air from Crawlspace and Outlet Air to Ventilated Attic)
OUTLET
AIR
ALL AIR FROM OUTSIDE
WATER
HEATER
INLET
AIR
FIGURE 3
Page 7
CHIMNEY
OR GAS
VENT
EQUIPMENT IN CONFINED SPACE
ALL AIR FROM OUTSIDE
(All Air Through Ventilated Attic)
VENTILATION LOUVERS
(Each end of attic)
OUTLET
AIR
The G40UH(X) gas furnace can be installed as shipped
in either the upflow position or the horizontal position,
with right-hand or left-hand air discharge.
Select a location that allows for the required clearances
that are listed on the unit nameplate. Also consider gas
supply connections, electrical supply, vent connection,
and installation and service clearances [24 inches (610
mm) at unit front]. The unit must be level.
FURNACE
NOTE−The inlet and outlet air openings shall each have a
free area of at least one square inch (645 mm2) per 4,000
Btu (1.17 kW) per hour of the total input rating of all equipment in the enclosure.
INLET AIR
(Ends 12 in.
above bottom)
WATER
HEATER
FIGURE 4
EQUIPMENT IN
CONFINED SPACE
ALL AIR FROM
OUTSIDE
OUTLET AIR
FURNACE
CHIMNEY
OR GAS
VENT
WATER
HEATER
NOTE − 1/3 hp blower motors are equipped with four flexible mounting legs, and 1/2 hp blower motors are equipped
with three flexible legs and one rigid leg. The rigid leg is
equipped with a shipping bolt and a flat white plastic washer (rather than the rubber mounting grommet used with a
flexible mounting leg). The bolt and washer must be re-
moved before the furnace is placed into operation. After the bolt and washer have been removed, the rigid leg
will not touch the blower housing.
Upflow Applications
Allow for clearances to combustible materials as indicated
on the unit nameplate. Minimum clearances for closet or alcove installations are shown in figure 6.
Upflow Application Installation Clearances
Top
Left Side
Right Side
INLET AIR
NOTE − Each air duct opening shall have a free area of at least
one square inch (645 mm2) per 2,000 Btu (.59 kW) per hour of
the total input rating of all equipment in the enclosure. If the
equipment room is located against an outside wall and the air
openings communicate directly with the outdoors, each opening shall have a free area of at least one square inch (645 mm2)
per 4,000 Btu (1.17 kW) per hour of the total input rating of all
other equipment in the enclosure.
FIGURE 5
Setting Equipment
WARNING
Do not install the furnace on its front or its back. Do
not connect the return air ducts to the back of the furnace. Doing so will adversely affect the operation of
the safety control devices, which could result in personal injury or death.
Page 8
Bottom
Type of Vent
Connector
Top 1 in. (25 mm) 1 in. (25 mm)
*Front 3 in. (76 mm) 3 in. (76 mm)
Back 0 0
Sides 0† 0
Vent 6 in. (152 mm) 1 in. (25 mm)
Floor 0‡ 0‡
*Front clearance in alcove installation must be 24 in. (610 mm).
Maintain a minimum of 24 in. (610 mm) for front service access.
‡For installations on a combustible floor, do not install the furnace
directly on carpeting, tile or other combustible materials other
than wood flooring.
†Left side requires 3 inches if a single wall vent is used on 14−1/2
inch cabinets, or 2 inches if a single wall vent is used on 17−1/2
inch cabinets.
Type C Type B1
FIGURE 6
Return Air −− Upflow Applications
Return air can be brought in through the bottom or either
side of the furnace installed in an upflow application. If the
furnace is installed on a platform with bottom return, make
an airtight seal between the bottom of the furnace and the
platform to ensure that the furnace operates properly and
safely. The furnace is equipped with a removable bottom
panel to facilitate installation.
Markings are provided on both sides of the furnace cabinet
for installations that require side return air. Cut the furnace
cabinet at the maximum dimensions shown on page 2.
NOTE − When air volumes over 1800 cfm (850 L/s) are
required with 60C or 60D models in an upflow application, the following return air options are available:
1 − Return air from single side with transition which will
accommodate 20 x 25 x 1 in. (508 x 635 x 25 mm) cleanable air filter. (Required to maintain proper air velocity.)
See figure 7.
2 − Return air from single side with optional RAB Return
Air Base. See figure 8.
3 − Return air from bottom.
4 − Return air from both sides.
5 − Return air from bottom and
one side.
Refer to Engineering Handbook for additional information.
Side Return Air
(with transition and filter)
20" X 25" X 1"
(508mm X635mm X 25mm)
Cleanable Filter
Return Air
Plenum
Transition
FIGURE 7
Optional Return Air Base
(Upflow Applications Only −− For use with B, C and D cabinets only)
1
23 (584)
Overall
(Maximum)
1
Unit side return air
Opening
5−5/8
(143)
SIDE RETURN
AIR OPENINGS
(Either Side)
23 (584)
27−5/8 (702)
SIDE VIEW
1
Minimum
11 (279)
2
Maximum
14 (356)
1
22−7−16
(570)
Overall
(Maximum)
AIR FLOW
17−1/2 (446) RAB−B (98M60)
21 (533) RAB−C (98M58)
24−1/2 (622) RAB−D (98M59)
FURNACE
FRONT
7−1/4 (184)
OPTIONAL RAB
RETURN AIR BASE
4
(102)
14
(356)
7/8
(22)
FRONT VIEW
NOTE− Optional Side Return Air Filter Kits are not for use with RAB Return Air Base.
1
Both the unit return air opening and the base return air opening must be covered by a single plenum or IAQ cabinet.
Minimum unit side return air opening dimensions for units requiring 1800 cfm or more of air (W x H): 23 x 11 in.
(584 x 279 mm).
The opening can be cut as needed to accommodate plenum or IAQ cabinet while maintaining dimensions shown.
Side return air openings must be cut in the field. There are cutting guides stenciled on the cabinet for the side return
air opening. The size of the opening must not extend beyond the markings on the furnace cabinet..
2
To minimize pressure drop, the largest opening height possible (up to 14 inches) is preferred.
NOTE− Optional Side Return Air Filter Kits are not for use with RAB Return Air Base.
3/4
(19)
FIGURE 8
Page 9
Removing the Bottom Panel
Remove the two screws that secure the bottom cap to the
furnace. Pivot the bottom cap down to release the bottom
panel. Once the bottom panel has been removed, reinstall
the bottom cap. See figure 9.
Removing the Bottom Panel
Leveling Bolt Installation
Furnace Front
3/8
(10)
3/8
(10)
Inches (mm)
1−3/4
(44)
Screw
Bottom Cap
Bottom Panel
FIGURE 9
Leveling an Upflow Unit
When the side return air inlets are used in an upflow application, it may be necessary to install leveling bolts on the
bottom of the furnace. Use field−supplied corrosion−resistant 5/16 inch machine bolts (4) and nuts (8). See figure 10.
NOTE − The maximum length of the bolt is 1−1/2 inches.
1 − Lie the furnace on its back and drill a 5/16 inch diame-
ter hole in each corner of the furnace’s bottom. See figure 10 for the correct location of the holes. Drill through
the bottom panel and the bottom flange of the cabinet.
2 − Install one bolt and two nuts into each hole. Screw the
first nut onto a bolt and then insert the bolt into a hole. A
flat washer may be added between the nut and the bottom of the unit.
3 − Screw another nut onto the bolt on the inside of the fur-
nace base. A flat washer may be added between the
nut and the bottom of the unit.
4 − Adjust the outside nut to the appropriate height and
tighten the inside nut to secure the arrangement.
NOTE − The unit may be tilted back−to−front a maximum of
1". This will ensure proper draining of the heat exchanger.
1−3/4
(44)
Leveling Bolts
Furnace
Bottom
Leveling Bolts
3/8
(10)
1−3/4
(44)
1−3/4 (44)
3/8
(10)
FIGURE 10
Horizontal Applications
The G40UH(X) furnace can be installed in horizontal applications.
Allow for clearances to combustible materials as indicated
on the unit nameplate. Minimum clearances for closet or alcove installations are shown in figure 11.
Horizontal Application
Installation Clearances
Top
Left End
Bottom
Vent Connector
Type
Top 0 0
*Front 3 in. (76 mm) 3 in. (76 mm)
Back 0 0
Ends 2 in. (51 mm) 2 in. (51 mm)
Vent 6 in. (152 mm) 1 in. (25 mm)
Floor 0‡ 0‡
*Front clearance in alcove installation must be 24 in. (610 mm).
Maintain a minimum of 24 in. (610 mm) for front service access.
‡For installations on a combustible floor, do not install the furnace
directly on carpeting, tile or other combustible materials other
than wood flooring.
Type C Type B1
Right End
FIGURE 11
Page 10
This furnace may be installed in either an attic or a crawlspace. Either suspend the furnace from roof rafters or
floor joists, as shown in figure 12, or install the furnace on
a platform, as shown in figure 13. The unit must be supported at both ends and beneath the blower deck to prevent sagging.
NOTE − In horizontal applications, the unit must be level side to side. The unit may be tilted back to front a maxi-
mum of 1". This will ensure proper draining of the heat exchanger.
Typical Horizontal Application
Unit Suspended in Attic or Crawlspace
Leave sufficient clearance between rod and unit to
remove access panel.
Horizontal Application
Unit Installed on Platform
NOTE − Line contact is permissible. See the unit nameplate for
clearances.
GAS
ENTRY
VENT
PIPE
WORKING
PLATFORM
FIGURE 13
1/4 in. ROD
ANGLE
IRON
U−CHANNELS
FIGURE 12
NOTE − Heavy gauge perforated sheet metal straps
(plumbers’ straps) may be used to suspend the unit from
roof rafters or ceiling joists. When straps are used to suspend the unit in this way, support must be provided for both
the ends and the middle of the furnace to prevent sagging.
The straps must not interfere with the plenum or exhaust
piping installation. Securing screws should be 1/2 inch
from the top edge and 1−1/2 inch from the side edge in all
cases. Cooling coils and supply and return air plenums
must be supported separately.
NOTE − When the furnace is installed on a platform in a
crawlspace, it must be elevated enough to avoid water
damage and to allow the evaporator coil to drain.
Return Air −− Horizontal Applications
Return air can be brought in through the end of a furnace
installed in a horizontal application. The furnace is
equipped with a removable bottom panel to facilitate
installation. See figure 9.
WARNING
Improper installation of the furnace can result in personal injury or death. Combustion and flue products
must never be allowed to enter the return air system
or the living space. Use screws and joint tape to seal
the return air system to the furnace.
In platform installations with bottom return air, the
furnace should be sealed airtight to the return air plenum. A door must never be used as a portion of the
return air duct system. The base must provide a
stable support and an airtight seal to the furnace. Allow absolutely no sagging, cracks, gaps, etc.
The return and supply air duct systems must never
be connected to or from other heating devices such
as a fireplace or stove, etc. Fire, explosion, carbon
monoxide poisoning, personal injury and/or property damage could result.
WARNING
The blower access panel must be securely in place
when the blower and burners are operating. Gas
fumes, which could contain carbon monoxide, can
be drawn into living space resulting in personal injury or death.
Page 11
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