Lennox G50UH Series User manual

Page 1
05/09
*2P0509*
505,254M
*P505254M*
E2006 Lennox Industries Inc.
Dallas, Texas, USA
RETAIN THESE INSTRUCTIONS
FOR FUTURE REFERENCE
INSTALLATION
INSTRUCTIONS
G50UH(X) Series
GAS FURNACE
505,254M
05/2009
Supersedes 08/2006
Table of Contents
Unit Dimensions 2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
G50UH(X) Parts Arrangement 3. . . . . . . . . . . . . . . . . . . .
G50UH(X) Gas Furnace 4. . . . . . . . . . . . . . . . . . . . . . . . . .
Shipping and Packing List 4. . . . . . . . . . . . . . . . . . . . . . . .
Safety Information 4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Use of Furnace as a Construction Heater 5. . . . . . . . . . .
General 5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Combustion, Dilution & Ventilation Air 6. . . . . . . . . . . . . .
Setting Equipment 9. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Filters 13. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Duct System 13. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Venting 13. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Gas Piping 21. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Electrical 22. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Unit Start−Up 26. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Gas Pressure Adjustment 27. . . . . . . . . . . . . . . . . . . . . . . .
High Altitude Information 28. . . . . . . . . . . . . . . . . . . . . . . . .
Other Unit Adjustments 28. . . . . . . . . . . . . . . . . . . . . . . . . .
Blower Performance Data 29. . . . . . . . . . . . . . . . . . . . . . . .
Service 33. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Planned Service 34. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Repair Parts List 35. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Ignition Control Board Diagnostic Codes 35. . . . . . . . . . .
Troubleshooting 36. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Start−Up & Performance Check List 40. . . . . . . . . . . . . . . .
WHAT TO DO IF YOU SMELL GAS:
Do not store or use gasoline or other
flammable vapors and liquids in the
vicinity of this or any other ap-
pliance.
Installation and service must be
performed by a qualified installer,
service agency or the gas supplier.
DDo not try to light any appliance.
DDo not touch any electrical switch; do not
use any phone in your building.
DImmediately call your gas supplier from a
neighbor’s phone. Follow the gas supplier’s
instructions.
DIf you cannot reach your gas supplier, call
the fire department.
FIRE OR EXPLOSION HAZARD.
Failure to follow safety warnings exact-
ly could result in serious injury, death,
or property damage.
WARNING
DLeave the building immediately.
Litho U.S.A.

Page 2
505254M 05/2009
G50UH(X) Unit Dimensions − inches (mm)
1Bottom Return
Air Opening
GAS PIPING INLET
(Either Side)
1Bottom Return
Air Opening
FLUE OUTLET
(Top)
ELECTRICAL INLET
(Either Side)
ELECTRICAL INLET
(Either Side)
SUPPLY AIR
OPENING
AIR FLOW
FRONT VIEW SIDE VIEW
TOP VIEW
A
B9/16 (14)
C
D
3/4 (19)
3/4 (19)
28−1/2
(724)
19−7/16
(494)
23−1/2
(597)
4−1/4
(108)
14 (356) Right
13−1/4 (337) Left
4−7/8 (124) Right
2−1/4 (57) Left
40
(1016)
3−3/4 (95)
4
(102)
1−15/16 (49)
23
(584)
14
(356)
9/16
(14)
3−3/4
(95)
3−1/4 (83) Right
8−1/8 (206) Left
2FLUE OUTLET
(Either Side)
TOP VIEW
1OPTIONAL
EXTERNAL
SIDE RETURN
AIR FILTER KIT
(Either Side)
16
(406)
14−3/4
(375)
5/8 (16)
3OPTIONAL
EXTERNAL
SIDE RETURN
AIR FILTER KIT
(Either Side)
23-3/4 (603)
25 (635)
2Flue outlet may be horizontal but furnace must be
vented vertically
3Optional External Side Return Air Filter Kit is not for use
with the optional RAB Return Air Base.
1NOTE − 60C and 60D size units that require air volumes
over 1800 cfm (850 L/s) must have one of the following:
1. Single side return air with transition, to accommodate
20 x 25 x 1 in. (508 x 635 x 25 mm) air filter. Required to
maintain proper air velocity across the filter.
2. Single side return air with optional RAB Return Air
Base
3. Bottom return air.
4. Return air from both sides.
5. Bottom and one side return air.
See Blower Performance Tables for additional informa-
tion.
1OPTIONAL
RETURN CUTOUT
(Either Side)
Model No
A B C D
Model No. in. mm in. mm in. mm in. mm
G50UH−24A−045,
G50UH−24A−070,
G50UH−36A−070
14−1/2 368 13−3/8 340 13 330 4−1/2 114
G50UH−36B−090,
G50UH−48B−090 17−1/2 446 16−3/8 416 16 406 6 152
G50UH−36C−110,
G50UH−48C−110,
G50UH−48C−135,
G50UH−60C−110
21 533 19−7/8 504 19−1/2 495 7−3/4 197
G50UH−60D−135,
G50UH−60D−155 24−1/2 622 23−3/8 546 23 584 9−1/2 241

Page 3 G50UH Series
G50UH(X) Parts Arrangement
FIGURE 1
Flue Transition
Combustion Air Inducer
Combustion Air
Orifice
Combustion Air
Pressure Switch
Flue Collector Box
Heat Exchanger
Flame Sensor
Gas Valve
Burners
Ignitor
NOxInsert
Primary Limit
Blower Assembly
Capacitor
Door Interlock Switch
SureLight®Control Board
Control Transformer
Gasket
Flue Box Gasket
Flame Rollout Switches*
Flame Rollout Bracket
Gas Orifices
Ignitor Bracket
Burner Bottom Shield
Limit Shield
Secondary Limit
(NOxUnits Only)
Air Deflector
G50UH−48C−135,
G50UH−60C−110 &
G50UH−60D−155
Units Only
*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.

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505254M 05/2009
G50UH(X) Gas Furnace
The G50UH(X) gas furnace is shipped ready for installation
in the upflow or horizontal position (left or right). The fur-
nace is shipped with the bottom panel in place. The bottom
panel must be removed if the unit is to be installed in a hori-
zontal application. The panel may also be removed in up-
flow applications.
Shipping and Packing List
Package 1 of 1 contains
1 − Assembled G50UH(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 be ordered separately:
1 − Thermostat
1 − Hanging bracket (for horizontal installations)
1 − Propane/LP changeover kit
1 − High altitude kit
1 − Return air base
1 − Side filter kit
Check equipment for shipping damage. If you find any
damage, immediately contact the last carrier.
DANGER
Danger of explosion.
There are circumstances in which odorant used with
LP/propane gas can lose its scent. In case of a leak,
LP/propane gas will settle close to the floor and may
be difficult to smell. An LP/propane leak detector
should be installed in all LP applications.
Safety Information
WARNING
Improper installation, adjustment, alteration, service
or maintenance can cause property damage, person-
al injury or loss of life. Installation and service must
be performed by a licensed proffessional installer (or
equivalent), 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.
G50UH(X) units are CSA International certified to ANSI
Z21.47 and CSA 2.3 standard.
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/NFPA 54). 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 National
Standard of Canada 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 open-
ings 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. Accessibil-
ity 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 at-
mosphere, the furnace must be installed according to rec-
ommended good practice requirements and current Na-
tional 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. Fail-
ure to do so may cause erratic limit operation.
This G50UH(X) furnace must be installed so that its electri-
cal components are protected from water.

Page 5 G50UH Series
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 manu-
ally 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 ad-
dress:
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.
NOTE − This furnace is designed for a minimum continuous
return air temperature of 60°F (16°C) or an intermittent op-
eration 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.
The G50UH(X) furnace may be installed in alcoves, clos-
ets, attics, basements, garages, and utility rooms in the up-
flow or horizontal position.
This furnace design has not been CSA International certi-
fied for installation in mobile homes, recreational vehicles,
or outdoors.
Use of Furnace as a Construction Heater
Lennox does not recommend the use of G50UH 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.
G50UH units may be used for heating of buildings or struc-
tures under construction, if the following conditions are
met:
DThe vent system must be permanently installed per
these installation instructions.
DA room thermostat must control the furnace. The use of
fixed jumpers that will provide continuous heating is not
allowed.
DThe return air duct must be provided and sealed to the
furnace.
DReturn air temperature range between 60°F (16°C) and
80°F (27°C) must be maintained.
DAir filters must be installed in the system and must be
maintained during construction.
DAir filters must be replaced upon construction comple-
tion.
DThe input rate and temperature rise must be set per the
furnace rating plate.
DOne hundred percent (100%) outdoor air must be pro-
vided for combustion air requirements during construc-
tion. 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.
DThe furnace heat exchanger, components, duct sys-
tem, air filters and evaporator coils must be thoroughly
cleaned following final construction clean−up.
DAll 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 stipu-
lates these additional requirements:
DGas furnaces shall be installed by a licensed plumb-
er or gas fitter only.
DThe gas cock must be T handle" type.
DWhen 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 fol-
lowing general recommendations must be considered
when installing a G50UH(X) furnace:
DPlace the furnace as close to the center of the air dis-
tribution system as possible. The furnace should also be
located close to the chimney or vent termination point.
DDo not install the furnace where drafts might blow direct-
ly into it. This could cause improper combustion and un-
safe operation.
DDo not block the furnace combustion air openings with
clothing, boxes, doors, etc. Air is needed for proper
combustion and safe unit operation.
DWhen the furnace is installed in an attic or other insu-
lated space, keep insulation away from the furnace.

Page 6
505254M 05/2009
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 Cal-
ifornia 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 prac-
tices make it necessary to bring in air from outside for com-
bustion. 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 out-
side air is brought into the house for combustion, negative
pressure (outside pressure is greater than inside pressure)
will build to the point that a downdraft can occur in the fur-
nace vent pipe or chimney. As a result, combustion gases
enter the living space creating a potentially dangerous situ-
ation.
In the absence of local codes concerning air for combus-
tion and ventilation, use the guidelines and procedures in
this section to install G50UH(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 per-
mission from the National Fuel Gas Code (ANSI-Z223.1).
This reprinted material is not the complete and official posi-
tion of the ANSI on the referenced subject, which is repre-
sented only by the standard in its entirety.
In Canada, refer to the standard CSA B149 installation
codes.
CAUTION
Do not install the furnace in a corrosive or contami-
nated atmosphere. Meet all combustion and ventila-
tion 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 rust-
ing 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 com-
bustion 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 pro-
cess. If sufficient combustion air is not available, the fur-
nace or other appliances will operate inefficiently and un-
safely. Enough air must be provided to meet the needs of
all fuel-burning appliances and appliances such as ex-
haust fans which force air out of the house. When fire-
places, 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. In-
sufficient air causes incomplete combustion which can re-
sult in carbon monoxide.
In addition to providing combustion air, fresh outdoor air di-
lutes contaminants in the indoor air. These contaminants
may include bleaches, adhesives, detergents, solvents
and other contaminants which can corrode furnace compo-
nents.
The requirements for providing air for combustion and ven-
tilation 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 com-
bined 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 un-
confined, it might be necessary to bring in outdoor air for
combustion if the structure does not provide enough air by

Page 7 G50UH Series
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 cu-
bic 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 con-
taining 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
dangerous negative pressure condition. Air for combustion
and ventilation can be brought into the confined space ei-
ther from inside the building or from outside.
EQUIPMENT IN CONFINED
SPACE ALL AIR FROM INSIDE
CHIMNEY
OR GAS
VENT
FURNACE
WATER
HEATER
OPENINGS
(To Adjacent
Room)
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 rat-
ing of all equipment in the enclosure, but not less than 100 square
inches (64516 mm2).
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 ventila-
tion, the confined space must have two permanent open-
ings. 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 di-
rectly or by ducts with the outdoors or spaces (crawl or at-
tic) 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 en-
closure. 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−sec-
tional 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 cov-
ering is not known for calculating the size opening required,
it may be assumed that wood louvers will have 20 to 25 per-
cent 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 opera-
tion.

Page 8
505254M 05/2009
EQUIPMENT IN CONFINED SPACE
ALL AIR FROM OUTSIDE
(Inlet Air from Crawlspace and Outlet Air
to Ventilated Attic)
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.
VENTILATION LOUVERS
(Each end of attic)
OUTLET
AIR WATER
HEATER
INLET
AIR
CHIMNEY OR
GAS VENT
FURNACE
VENTILATION
LOUVERS
(For unheated crawl space)
FIGURE 3
EQUIPMENT IN CONFINED SPACE
ALL AIR FROM OUTSIDE
(All Air Through Ventilated Attic)
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 equip-
ment in the enclosure.
CHIMNEY
OR GAS
VENT
WATER
HEATER
OUTLET
AIR
VENTILATION LOUVERS
(Each end of attic)
INLET AIR
(Ends 12 in.
above bottom)
FURNACE
FIGURE 4
EQUIPMENT IN
CONFINED SPACE
ALL AIR FROM
OUTSIDE
OUTLET AIR
INLET AIR
WATER
HEATER
CHIMNEY
OR GAS
VENT
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 open-
ing 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.
FURNACE
FIGURE 5

Page 9 G50UH Series
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 fur-
nace. Doing so will adversely affect the operation of
the safety control devices, which could result in per-
sonal injury or death.
The G50UH(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.
NOTE − 1/3 hp blower motors are equipped with four flex-
ible mounting legs. 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 wash-
er (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. Af-
ter 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 al-
cove installations are shown in figure 6.
Upflow Application Installation Clearances
Top
Bottom
Left Side Right Side
Type of Vent
Connector Type C Type B1
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 installation 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.
FIGURE 6

Page 10
505254M 05/2009
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 applica-
tion, 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) clean-
able 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)
FIGURE 7
Return Air
Plenum
Transition
20" X 25" X 1"
(508mm X635mm X 25mm)
Cleanable Filter
Optional Return Air Base
(Upflow Applications Only −− For use with B, C and D cabinets only)
NOTE− Optional Side Return Air Filter Kits are not for use with RAB Return Air Base.
1Both 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..
2To 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.
1Unit side return
air
Opening
FRONT VIEW SIDE VIEW
27−5/8 (702)
4
(102)
123 (584)
Overall
(Maximum)
OPTIONAL RAB
RETURN AIR BASE
23 (584)
7−1/4 (184)
7/8
(22)
3/4
(19)
122−7−16
(570)
Overall
(Maximum)
SIDE RETURN
AIR OPENINGS
(Either Side)
FURNACE
FRONT
14
(356)
AIR FLOW
5−5/8
(143)
1Minimum
11 (279)
2Maximum
14 (356)
21 (533) RAB−C (98M58)
24−1/2 (622) RAB−D (98M59)
17−1/2 (446) RAB−B (98M60)
FIGURE 8

Page 11 G50UH Series
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
FIGURE 9
Screw
Bottom Panel
Bottom Cap
Leveling an Upflow Unit
When the side return air inlets are used in an upflow ap-
plication, it may be necessary to install leveling bolts on the
bottom of the furnace. Use field−supplied corrosion−resist-
ant 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 fig-
ure 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 bot-
tom 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.
FIGURE 10
1−3/4
(44)
1−3/4
(44)
3/8
(10)
1−3/4 (44)
3/8
(10)
3/8
(10)
3/8
(10)
1−3/4
(44)
Leveling Bolt Installation
Leveling Bolt
Locations
Leveling Bolt
Locations
Inches (mm)
Furnace Front
Furnace
Bottom
Horizontal Applications
The G50UH(X) furnace can be installed in horizontal ap-
plications.
Allow for clearances to combustible materials as indicated
on the unit nameplate. Minimum clearances for closet or al-
cove installations are shown in figure 11.
Horizontal Application
Installation Clearances
Top
Bottom
Left End Right End
Vent Connector
Type Type C Type B1
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 fur-
nace directly on carpeting, tile or other combustible materials oth-
er than wood flooring.
FIGURE 11

Page 12
505254M 05/2009
This furnace may be installed in either an attic or a crawl-
space. Either suspend the furnace from roof rafters or floor
joists, as shown in figure 12, or install the furnace on a plat-
form, as shown in figure 13. The unit must be supported at
both ends and beneath the blower deck to prevent sagging.
Typical Horizontal Application
Unit Suspended in Attic or Crawlspace
Leave sufficient clearance between rod and unit to
remove access panel.
FIGURE 12
1/4 in. ROD
ANGLE
IRON U−CHANNELS
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 sus-
pend the unit in this way, support must be providedfor 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 instal-
lation. See figure 9.
Horizontal Application
Unit Installed on Platform
WORKING
PLATFORM
GAS
ENTRY
VENT
PIPE
NOTE − Line contact is permis-
sible. See the unit nameplate for
clearances.
FIGURE 13
WARNING
Improper installation of the furnace can result in per-
sonal 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 ple-
num. 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. Al-
low 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 proper-
ty 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 inju-
ry or death.

Page 13 G50UH Series
Filters
This unit is not equipped with a filter or rack. A field−pro-
vided high−velocity filter is required for the unit to operate
properly. Table 1 lists recommended filter sizes.
A filter must be in place any time the unit is operating.
TABLE 1
Furnace Filter Size
Furnace
Cabinet Size Side Return Bottom Return
14−1/2" 16 X 25 X 1 (1) 14 X 25 X 1 (1)
17−1/2" 16 X 25 X 1 (1) 16 X 25 X 1 (1)
21" 16 X 25 X 1 (1) 20 X 25 X 1 (1)
24−1/2" 16 X 25 X 1 (2) 24 X 25 X 1 (1)
Duct System
Use industry-approved standards to size and install the
supply and return air duct system. This will result in a quiet
and low-static system that has uniform air distribution.
NOTE − Do not operate the furnace with an external static
pressure that exceeds 0.5 inches w.c. Higher external stat-
ic pressures may cause erratic limit operation.
Supply Air Plenum
If the furnace is installed without a cooling coil, a removable
access panel must be installed in the supply air duct. The
access panel should be large enough to permit inspection
(either by smoke or reflected light) of the heat exchanger
for leaks after the furnace is installed. The furnace access
panel must always be in place when the furnace is operat-
ing and it must not allow leaks into the supply air duct sys-
tem.
Return Air Plenum
NOTE − Return air must not be drawn from a room
where this furnace, or any other gas−fueled appliance
(i.e., water heater), or carbon monoxide−producing de-
vice (i.e., wood fireplace) is installed.
When return air is drawn from a room, a negative pressure
is created in the room. If a gas appliance is operating in a
room with negative pressure, the flue products can be
pulled back down the vent pipe and into the room. This re-
verse flow of the flue gas may result in incomplete combus-
tion and the formation of carbon monoxide gas. This toxic
gas might then be distributed throughout the house by the
furnace duct system.
In upflow applications, the return air can be brought in
through the bottom or either side of the furnace. If a furnace
with bottom return air is installed on a platform, make an air-
tight seal between the bottom of the furnace and the plat-
form to ensure that the unit operates properly and safely.
Use fiberglass sealing strips, caulking, or equivalent seal-
ing method between the plenum and the furnace cabinet to
ensure a tight seal. If a filter is installed, size the return air
duct to fit the filter frame.
Venting
A 4−inch diameter flue transition is factory-installed on the
combustion air inducer outlet of all models. Modifying or
removing the flue transition will cause the unit to oper-
ate unsafely and will void the unit certification. The
vent connector does not require insulation.
The combustion air inducer may be rotated clockwise or
counterclockwise by 90° to allow for top or side vent dis-
charge in all applications. When the unit is installed, the flue
transition must be in the 9 o’clock, 12 o’clock or 3 o’clock
position. The unit will not vent properly with the flue
transition pointed down in the 6 o’clock position. Re-
move the four mounting screws, rotate the assembly (in-
cluding the gasket), then reinstall the mounting screws.
See figure 14. Use the provided wire tie to bundle the pres-
sure switch wires with the inducer motor power leads.
Route the wires away from moving parts and the heat
of the inducer motor to prevent damage to the wires.
FIGURE 14
Combustion Air Inducer
Mounting Screws
MOUNTING SCREWS
90° 90°
(Remove)
(Remove)
Power Leads
Flue Transition
(Do not remove)
Flue Outlet
Hole
(Reattach
Cutout Here)
Supply Air
Opening
Top View of Furnace
Top Cap
Cut
out Optional
Flue Outlet
Optional Flue Outlet
(Horizontal Installation)
FIGURE 15

Page 14
505254M 05/2009
Use sheet metal shears to remove the cut out from the side
of the cabinet. Use the two provided sheet metal screws to
install the cut out on the top cap to cover the original flue
outlet opening. See figure 15.
The G50UH(X) series units are classified as fan−assisted
Category I furnaces when vertically vented according to
the latest edition of National Fuel Gas Code (NFPA 54 /
ANSI Z223.1) in the USA and the current standards of CSA
B149 Natural Gas and Propane Installation Codes in Can-
ada. A fan−assisted Category I furnace is an appliance
equipped with an integral mechanical means to either draw
or force combustion products through the combustion
chamber and/or heat exchanger.
NOTE − Use these instructions as a guide. They do not su-
persede local codes. This furnace must be vented accord-
ing to all local codes these installation instructions, and the
provided venting tables in these instructions
The venting tables in this manual were extracted from the
National Fuel Gas Code (NFPA 54 / ANSI Z223.1) and are
provided as a guide for proper vent installation. Proper ap-
plication, termination, construction and location of vents
must conform to local codes having jurisdiction. In the ab-
sence of local codes, the NFGC serves as the defining doc-
ument.
Refer to the tables and the venting information contained in
these instructions to properly size and install the venting
system.
IMPORTANT
Once the venting system is installed, attach the Dis-
connected Vent" warning sticker to a visible area of
the plenum near the vent pipe. The warning sticker
is provided in the bag assembly.
WARNING
Asphyxiation hazard. The exhaust vent for this fur-
nace must be securely connected to the furnace flue
transition at all times.
FLUE TRANSITION
COLLAR
VENT CONNECTION
VENT
PIPE
FURNACE
FIGURE 16
Use self−drilling sheet metal screws or a mechanical fas-
tener to firmly secure the vent pipe to the round collar of the
flue transition. If self−drilling screws are used to attach the
vent pipe, it is recommended that three be used. Drive one
self−drilling screw through the front and one through each
side of the vent pipe and collar. See figure 16.
Install the first vent connector elbow at a minimum of six
inches (152 mm) from the furnace vent outlet.
Venting Using a Masonry Chimney
The following additional requirements apply when a lined
masonry chimney is used to vent this furnace.
Masonry chimneys used to vent Category I central fur-
naces must be either tile-lined or lined with a listed metal
lining system or dedicated gas vent. Unlined masonry
chimneys are prohibited. See figures 17 and 18 for com-
mon venting.
A chimney with one or more sides exposed to the outside of
the structure is considered to be an exterior chimney.
An exterior masonry chimney that is not tile−lined must be
lined with B1 vent or a listed insulated flexible metal vent.
An exterior tile−lined chimney that is sealed and capped
may be lined with a listed uninsulated flexible metal vent.
If the existing chimney will not accommodate a B1 vent or
an insulated flexible vent pipe liner, either the chimney
must be rebuilt to accommodate one of these liners or an
alternate approved venting method must be found.
Insulation for the flexible vent pipe must be an encapsu-
lated fiberglass sleeve recommended by the flexible vent
pipe manufacturer. See figure 17.
G50UH units installed in upflow applications may be
vented into a tile−lined masonry chimney without using a
listed metal liner, provided that the optional masonry chim-
ney vent adapter kit (18M79) is used. Instructions provided
with the kit must be followed exactly.
DO NOT insulate the space between the liner and the
chimney wall with puffed mica or any other loose gran-
ular insulating material
Common Venting Using Metal−Lined Masonry Chimney
4 in. (102 mm)
minimum
MIN. LENGTH −− AS
SHORT AS PRACTICAL
MAX. LENGTH
−− SEE NOTE 1
BELOW.
SEALED
PERMANENTLY
SEALED FIREPLACE
OPENING
EXTERIOR
CHIMNEY WITH
METAL
LINER
VENT CONNECTOR
SEE NOTE 2
NOTE 1 − Refer to the provided venting tables for installations in the USA
and the venting tables in CSA B149 for installations Canada.
NOTE 2 − Either single-walled or double-walled vent connector may be
used. Refer to the capacity requirements shown in the provided venting
tables for installations in USA and the venting tables in current CSA
B149 for installations in Canada.
OTHER
APPLIANCE
FURNACE
FIGURE 17
5 ft. (1.5 m)
minimum

Page 15 G50UH Series
Common Venting Using Tile−Lined Interior Masonry Chimney and Combined Vent Connector
MINIMUM LENGTH = AS SHORT AS PRACTICAL.
FOR MAXIMUM LENGTH SEE NOTE TO LEFT
INTERIOR TILE−LINED
MASONRY CHIMNEY
NOTE − the chimney must be properly
sized per provided venting tables or
lined with listed metal lining system.
PERMANENTLY
SEALED FIREPLACE
OPENING
VENT
CONNECTOR
SEE NOTE 1 BELOW
NOTE − Either single-walled or double-walled vent connector may be used. Refer to the capacity requirements as shown in the pro-
vided venting tables for installations in USA and the venting tables in current CSA B149 for installations in Canada.
NOTE− Refer to provided venting tables
for installations in the USA and the
venting tables in current CSA B149 for
installations in Canada.
FURNACE
OTHER
APPLIANCE
FIGURE 18
IMPORTANT
SINGLE appliance venting of a fan-assisted furnace
into a tile-lined masonry chimney (interior or outside
wall) is PROHIBITED. The chimney must first be lined
with either type B1 vent or an insulated single wall
flexible vent lining system which has been sized ac-
cording to the provided venting tables and the vent
pipe manufacturer’s instructions.
A fan−assisted furnace may be commonly vented into an
existing lined masonry chimney if the following conditions
are met:
SThe chimney is currently serving at least one drafthood
equipped appliance
SThe vent connectors and chimney are sized according
to the provided venting tables for the USA, and the ap-
propriate venting tables in the standards of CSA B149
Natural Gas and Propane Installation Codes in Cana-
da.
If type B1 double-wall vent is used inside a chimney, no oth-
er appliance can be vented into the chimney. The outer wall
of type B1 vent pipe must not be exposed to flue products.
A type B1 vent or masonry chimney liner shall terminate
above the roof surface with a listed cap or a listed roof as-
sembly according to the terms of their respective listings
and the vent manufacturer’s instructions.
When inspection reveals that an existing chimney is not
safe for the intended purpose, it shall be rebuilt to conform
to nationally recognized standards, lined or relined with
suitable materials, or replaced with a gas vent or chimney
suitable for venting G50UH(X) series units. The chimney
passageway must be checked periodically to ensure that it
is clear and free of obstructions.
Do not install a manual damper, barometric draft regulator,
or flue restrictor between the furnace and the chimney.
Never connect a Category I appliance to a chimney that is
servicing a solid−fuel appliance. If a fireplace chimney flue
is used to vent this appliance, the fireplace opening must
be permanently sealed.
A type B or listed chimney lining system that passes
through an unused masonry chimney flue is not considered
to be exposed to the outdoors.
General Venting Requirements
Vent all G50UH(X) furnaces according to these instruc-
tions:
1 − Vent diameter recommendations and maximum allow-
able piping runs are found in the provided venting
tables for the USA, and the appropriate venting tables
in the standards of CSA B149 Natural Gas and Pro-
pane Installation Codes for Canada.
2 − In no case should the vent or vent connector diameter
be less than the diameter specified in the provided
venting tables for the USA, and the appropriate venting
tables in the standards of CSA B149 Natural Gas and
Propane Installation Codes for Canada.
3 − Single appliance vents − If the vertical vent or tile-lined
chimney has a larger diameter or flow area than the
vent connector, use the vertical vent diameter to de-
termine the minimum vent capacity and the vent
connector diameter to determine the maximum vent
capacity. The flow area of the vertical vent, however,
shall not exceed 7 times the flow area of the listed ap-
pliance categorized vent area, drafthood outlet area or
flue collar area unless designed according to approved
engineering methods.
4 − Multiple appliance vents − The flow area of the largest
section of vertical vent or chimney shall not exceed 7
times the smallest listed appliance categorized vent
area, drafthood outlet area or flue collar area unless
designed according to approved engineering meth-
ods.

Page 16
505254M 05/2009
5 − The entire length of single wall metal vent connector
shall be readily accessible for inspection, cleaning,
and replacement.
6 − Single appliance venting configurations with zero lat-
eral lengths (tables 3 and 4) are assumed to have no
elbows in the vent system. For all other vent configura-
tions, the vent system is assumed to have two 90° el-
bows. For each additional 90° elbow or equivalent (for
example two 45° elbows equal one 90° elbow) beyond
two, the maximum capacity listed in the venting table
should be reduced by 10% (0.90 x maximum listed ca-
pacity).
7 − The common venting tables (5, 6, 7, and 8) were gen-
erated using a maximum horizontal vent connector
length of 1−1/2 feet (.46 m) for each inch (25 mm) of
connector diameter as follows:
TABLE 2
Connector Diameter
inches (mm)
Maximum Horizontal
Connector Length feet (m)
3 (76) 4−1/2 (1.37)
4 (102) 6 (1.83)
5 (127) 7−1/2 (2.29)
6 (152) 9 (2.74)
7 (178) 10−1/2 (3.20)
8 − If the common vertical vent is offset, the maximum
common vent capacity listed in the common venting
tables should be reduced by 20%, the equivalent of two
90° elbows (0.80 x maximum common vent capacity).
The horizontal length of the offset shall not exceed
1-1/2 feet (.46 m) for each inch (25 mm) of common
vent diameter.
9 − The vent pipe should be as short as possible with the
least number of elbows and angles required to com-
plete the job. Route the vent connector to the vent us-
ing the shortest possible route.
10 − A vent connector shall be supported without any dips
or sags and shall slope a minimum of 1/4 inch (6.4 mm)
per linear foot (305 mm) of connector, back toward the
appliance.
11 − Vent connectors shall be firmly attached to the furnace
flue collar by self−drilling screws or other approved
means, except vent connectors of listed type B vent
material which shall be assembled according to the
manufacturer’s instructions. Joints between sections
of single wall connector piping shall be fastened by
screws or other approved means.
12 − When the vent connector used for Category I ap-
pliances must be located in or pass through a crawl-
space or other areas which may be cold, that portion of
the vent connector shall be constructed of listed
double-wall type B vent material or material having
equivalent insulation qualities.
13 − All venting pipe passing through floors, walls, and ceil-
ings must be installed with the listed clearance to com-
bustible materials and be fire stopped according to lo-
cal codes. In absence of local codes, refer to NFGC
(Z223.1).
14 − No portion of the venting system can extend into, or
pass through any circulation air duct or plenum.
15 − Vent connectors serving Category I appliances shall
not be connected to any portion of mechanical draft
systems operating under positive pressure such as
Category III or IV venting systems.
16 − If vent connectors are combined prior to entering the
common vent, the maximum common vent capacity
listed in the common venting tables must be reduced
by 10%, the equivalent of one 90° elbow (0.90 x maxi-
mum common vent capacity).
17 − The common vent diameter must always be at least as
large as the largest vent connector diameter.
18 − In no case, shall the vent connector be sized more than
two consecutive table size diameters over the size of
the draft hood outlet or flue collar outlet.
19 − Do not install a manual damper, barometric draft regu-
lator or flue restrictor between the furnace and the
chimney.
20 − When connecting this appliance to an existing dedi-
cated or common venting system, you must inspect the
venting system’s general condition and look for signs
of corrosion. The existing vent pipe size must conform
to these instructions and the provided venting tables
for the USA, and the appropriate venting tables in the
standards of CSA B149 Natural Gas and Propane
Installation Codes for Canada. If the existing venting
system does not meet these requirements, it must be
resized.

Page 17 G50UH Series
TABLE 3
Capacity of Type B Double−Wall Vents with Type B Double−Wall Connectors
Serving a Single Category I Appliance
Vent and Connector Diameter − D (inches)
Height
H
Lateral
L
3 Inch 4 Inch 5 Inch 6 Inch
H
(
feet
)
L
(
feet
)
Appliance Input Rating in Thousands of Btu Per Hour
(feet)
(feet)
MIN MAX MIN MAX MIN MAX MIN MAX
0 0 78 0 152 0 251 0 375
6
2 13 51 18 97 27 157 32 232
64 21 49 30 94 39 153 50 227
6 25 46 36 91 47 149 59 223
0 0 84 0 165 0 276 0 415
8
2 12 57 16 109 25 178 28 263
85 23 53 32 103 42 171 53 255
8 28 49 39 98 51 164 64 247
0 0 88 0 175 0 295 0 447
10
2 12 61 17 118 23 194 26 289
10 5 23 57 32 113 41 187 52 280
10 30 51 41 104 54 176 67 267
0 0 94 0 191 0 327 0 502
2 11 69 15 136 20 226 22 339
15 5 22 65 30 130 39 219 49 330
10 29 59 40 121 51 206 64 315
15 35 53 48 112 61 195 76 301
0 0 97 0 202 0 349 0 540
2 10 75 14 149 18 250 20 377
20
5 21 71 29 143 38 242 47 367
20 10 28 64 38 133 50 229 62 351
15 34 58 46 124 59 217 73 337
20 48 52 55 116 69 206 84 322
0 0 100 0 213 0 374 0 587
2 9 81 13 166 14 283 18 432
5 21 77 28 160 36 275 45 421
30 10 27 70 37 150 48 262 59 405
15 33 64 44 141 57 249 70 389
20 56 58 53 132 66 237 80 374
30 NR NR 73 113 88 214 104 346
NOTE − Single appliance venting configurations with zero lateral lengths are assumed to have no elbows in the vent system. For all other
vent configurations, the vent system is assumed to have two 90° elbows. For each additional 90° elbow or equivalent (for example two 45°
elbows equal one 90° elbow) beyond two, the maximum capacity listed in the venting table should be reduced by 10 percent (0.90 x maxi-
mum listed capacity).

Page 18
505254M 05/2009
TABLE 4
Capacity of Type B Double−Wall Vents with Single−Wall Metal Connectors
Serving a Single Category I Appliance
Vent and Connector Diameter − D (inches)
Height
H
Lateral
L
3 Inch 4 Inch 5 Inch 6 Inch
H
(
feet
)
L
(
feet
)
Appliance Input Rating in Thousands of Btu Per Hour
(feet)
(feet)
MIN MAX MIN MAX MIN MAX MIN MAX
0 38 77 59 151 85 249 126 373
6
2 39 51 60 96 85 156 123 231
64 NR NR 74 92 102 152 146 225
6 NR NR 83 89 114 147 163 220
0 37 83 58 164 83 273 123 412
8
2 39 56 59 108 83 176 121 261
85 NR NR 77 102 107 168 151 252
8 NR NR 90 95 122 161 175 243
0 37 87 57 174 82 293 120 444
10
2 39 61 59 117 82 193 119 287
10 5 52 56 76 111 105 185 148 277
10 NR NR 97 100 132 171 188 261
0 36 93 56 190 80 325 116 499
2 38 69 57 136 80 225 115 337
15 5 51 63 75 128 102 216 144 326
10 NR NR 95 116 128 201 182 308
15 NR NR NR NR 158 186 220 290
0 35 96 54 200 78 346 114 537
2 37 74 56 148 78 248 113 375
20
5 50 68 73 140 100 239 141 363
20 10 NR NR 93 129 125 223 177 344
15 NR NR NR NR 155 208 216 325
20 NR NR NR NR 186 192 254 306
0 34 99 53 211 76 372 110 584
2 37 80 55 164 76 281 109 429
5 49 74 72 157 98 271 136 417
30 10 NR NR 91 144 122 255 171 397
15 NR NR 115 131 151 239 208 377
20 NR NR NR NR 181 223 246 357
30 NR NR NR NR NR NR NR NR
NOTE − Single appliance venting configurations with zero lateral lengths are assumed to have no elbows in the vent system. For all other
vent configurations, the vent system is assumed to have two 90° elbows. For each additional 90° elbow or equivalent (for example two 45°
elbows equal one 90° elbow) beyond two, the maximum capacity listed in the venting table should be reduced by 10 percent (0.90 x maxi-
mum listed capacity).

Page 19 G50UH Series
TABLE 5
Vent Connector Capacity
Type B Double−Wall Vents with Type B Double−Wall Connectors
Serving Two or More Category I Appliances
Vent
Connector
Vent and Connector Diameter − D (inches)
V
en
t
Hei
g
ht
C
onnec
t
or
Rise 3 Inch 4 Inch 5 Inch 6 Inch
Height
H
(feet)
Rise
R
(feet)
Appliance Input Rating in Thousands of Btu Per Hour
(feet) (feet) MIN MAX MIN MAX MIN MAX MIN MAX
1 22 37 35 66 46 106 58 164
62 23 41 37 75 48 121 60 183
6
3 24 44 38 81 49 132 62 199
1 22 40 35 72 49 114 64 176
82 23 44 36 80 51 128 66 195
3 24 47 37 87 53 139 67 210
1 22 43 34 78 49 123 65 189
10 2 23 47 36 86 51 136 67 206
3 24 50 37 92 52 146 69 220
1 21 50 33 89 47 142 64 220
15 2 22 53 35 96 49 153 66 235
3 24 55 36 102 51 163 68 248
1 21 54 33 99 46 157 62 246
20 2 22 57 34 105 48 167 64 259
3 23 60 35 110 50 176 66 271
1 20 62 31 113 45 181 60 288
30 2 21 64 33 118 47 190 62 299
3 22 66 34 123 48 198 64 309
TABLE 6
Common Vent Capacity
Type B Double−Wall Vents with Type B Double−Wall Connectors
Serving Two or More Category I Appliances
Vent
Common Vent Diameter − D (inches)
V
en
t
Hei
g
ht 4 Inch 5 Inch 6 Inch 7 Inch
Height
H
(feet)
Appliance Input Rating in Thousands of Btu Per Hour
(feet) FAN + FAN FAN + NAT FAN + FAN FAN + NAT FAN + FAN FAN + NAT FAN + FAN FAN + NAT
6 92 81 140 116 204 161 309 248
8 101 90 155 129 224 178 339 275
10 110 97 169 141 243 194 367 299
15 125 112 195 164 283 228 427 352
20 136 123 215 183 314 255 475 394
30 152 138 244 210 361 297 547 459

Page 20
505254M 05/2009
TABLE 7
Vent Connector Capacity
Type B Double−Wall Vents with Single−Wall Metal Connectors
Serving Two or More Category I Appliances
Vent
Connector
Vent and Connector Diameter − D (inches)
V
en
t
Hei
g
ht
C
onnec
t
or
Rise 3 Inch 4 Inch 5 Inch 6 Inch
Height
H
(feet)
Rise
R
(feet)
Appliance Input Rating in Thousands of Btu Per Hour
(feet) (feet) MIN MAX MIN MAX MIN MAX MIN MAX
1 NR NR NR NR NR NR NR NR
62 NR NR NR NR NR NR 168 182
6
3 NR NR NR NR 121 131 174 198
1 NR NR 79 87 116 138 177 214
15 2 NR NR 83 94 121 150 185 230
3 NR NR 87 100 127 160 193 243
1 47 60 77 110 113 175 169 278
30 2 50 62 81 115 117 185 177 290
3 54 64 85 119 122 193 185 300
TABLE 8
Common Vent Capacity
Type B Double−Wall Vents with Single−Wall Metal Connectors
Serving Two or More Category I Appliances
Vent
Common Vent Diameter − D (inches)
V
en
t
Hei
g
ht 4 Inch 5 Inch 6 Inch 7 Inch
Height
H
(feet)
Appliance Input Rating in Thousands of Btu Per Hour
(feet) FAN + FAN FAN + NAT FAN + FAN FAN + NAT FAN + FAN FAN + NAT FAN + FAN FAN + NAT
6 89 78 136 113 200 158 304 244
8 98 87 151 126 218 173 331 269
10 106 94 163 137 237 189 357 292
15 121 108 189 159 275 221 416 343
20 131 118 208 177 305 247 463 383
30 145 132 236 202 350 286 533 446
Removal of the Furnace from Common Vent
In the event that an existing furnace is removed from a
venting system commonly run with separate gas ap-
pliances, the venting system is likely to be too large to prop-
erly vent the remaining attached appliances.
Conduct the following test while each appliance is operat-
ing and the other appliances (which are not operating) re-
main connected to the common venting system. If the vent-
ing system has been installed improperly, you must
correct the system as indicated in the general venting re-
quirements section.
1 − Seal any unused openings in the common venting sys-
tem.
2 − Inspect the venting system for proper size and horizon-
tal pitch. Determine that there is no blockage, restric-
tion, leakage, corrosion, or other deficiencies which
could cause an unsafe condition.
3 − Close all building doors and windows and all doors be-
tween the space in which the appliances remaining
connected to the common venting system are located
and other spaces of the building. Turn on clothes dry-
ers and any appliances not connected to the common
venting system. Turn on any exhaust fans, such as
range hoods and bathroom exhausts, so they will oper-
ate at maximum speed. Do not operate a summer ex-
haust fan. Close fireplace dampers.
4 − Follow the lighting instructions. Turn on the appliance
that is being inspected. Adjust the thermostat so that
the appliance operates continuously.
5 − After the main burner has operated for 5 minutes, test
for leaks of flue gases at the draft hood relief opening.
Use the flame of a match or candle, or smoke from a
cigarette, cigar, or pipe.
6 − After determining that each appliance connected to the
common venting system is venting properly, (step 3)
return all doors, widows, exhaust fans, fireplace damp-
ers, and any other gas−burning appliances to their pre-
vious mode of operation.
7 − If a venting problem is found during any of the preced-
ing tests, the common venting system must be modi-
fied to correct the problem.