Lennox G23 Series User manual

INSTALLATION INSTRUCTIONS
2000 Lennox Industries Inc.
Dallas, Texas, USA
INSTALLATION
INSTRUCTIONS
G23(X) SERIES UNITS
GAS UNITS
503,884M
1/2000
Supersedes 5/99
Table of Contents
Unit Dimensions 2. . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Parts Arrangement 3. . . . . . . . . . . . . . . . . . . . . . . . . . .
Requirements 4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
General 5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Combustion, Dilution, & Ventilation Air 5. . . . . . . . . .
Installation - Setting Equipment 7. . . . . . . . . . . . . . . .
Return Air Opening Guidelines 7. . . . . . . . . . . . . . . . .
Filters & Optional Filter Assembly 8. . . . . . . . . . . . . .
Duct System 9. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Venting 9. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Gas Piping 16. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Electrical 17. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Unit Start-Up 21. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Gas Pressure Adjustment 22. . . . . . . . . . . . . . . . . . . .
High Altitude Information 23. . . . . . . . . . . . . . . . . . . . .
Other Unit Adjustments 23. . . . . . . . . . . . . . . . . . . . . .
Service 24. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Repair Parts List 26. . . . . . . . . . . . . . . . . . . . . . . . . . . .
SureLight Troubleshooting 27. . . . . . . . . . . . . . . . . . . .
Start-Up & Performance Check List 31. . . . . . . . . . . .
RETAIN THESE INSTRUCTIONS
FOR FUTURE REFERENCE
WHAT TO DO IF YOU SMELL GAS:
Do not store or use gasoline or other
flammable vapors and liquids in the vi
cinity of this or any other appliance.
Installation and service must be per
formed by a qualified installer, ser
vice agency or the gas supplier.
Do not try to light any appliance.
Do not touch any electrical switch; do not use
any phone in your building.
Immediately call your gas supplier from a
neighbor's phone. Follow the gas supplier's
instructions.
If you cannot reach your gas supplier, call the
fire department.
Extinguish any open flames.
If the information in this manual is not
followed exactly, a fire or explosion
may result causing property damage,
personal injury, or death.
WARNING
Litho USA

Page 2
G23(X) Unit Dimensions - inches (mm)
AIR FLOW
SUPPLY
AIR
OPENING
FLUE
OUTLET
4 (102)
11/16
(41)
B
C
F
GAS PIPING INLET
(Both Sides)
ELECTRICAL INLETS
(Both Sides)
RETURN AIR
KNOCKOUT
(Either Side)
281/2
(724)
A
23 (584)
115/16 (49)
G
45/8
(117)
TOP VIEW
FRONT VIEW
SIDE VIEW
11/16
(41)
4 (102)
233/4 (603)
25 (635)
5/8
(16)
J
H
5/8 (16)
EXTERNAL
SIDE RETURN
AIR FILTER KIT
(Either Side)
(Optional)
133/16 (335) Left
1315/16 (354) Right
2-3/8 (60) Left
5 (127) Right
Return Air
Knockout (Bottom)
Bottom Return
Air Knockout
187/8
(479)
23 (584)
D
E
Model No. A B C D E F G H J
G23Q2(X)-50
G23Q3(X) 50
in. 40 161/4 141/8 12 12 21/8 5 14 123/4
G23Q3(X)50
G23Q2/3(X)75 mm 1016 413 359 305 305 54 127 356 324
G23Q3(X) 100
in. 40 211/4 191/8 14 14 35/8 71/2 16 143/4
G23Q3(X)100 mm 1016 540 486 356 356 92 191 406 375
G23Q4/5(X)75
G23Q3/4
(
X
)
-100 in. 46 211/4 191/8 18 18 15/8 71/2 20 183/4
G23Q3/4(X) 100
G23Q4/5(X)-100
G23Q3/4(X)-125 mm 1168 540 486 457 457 41 191 508 476
G23Q5/6
(
X
)
125 in. 46 261/4 241/8 18 18 41/8 10 20 183/4
G23Q5/6(X)125
G23Q5/6(X)-150 mm 1168 667 613 457 457 105 254 508 476

Page 3
G23(X) Parts Arrangement
FIGURE 1
G23(X) UNIT WITH PANELS REMOVED
IGNITOR ASSEMBLY
MANIFOLD AND
GAS VALVE
GAS ORIFICE
DURALOKTM
HEAT EXCHANGER
(Assembly)
FLUE
COLLECTOR BOX
TOP CAP GLASS FIBER
GASKET
ORIFICE PLATE
(FLUE TRANSITION
ASSEMBLY)
FLUE OUTLET
GLASS FIBER
GASKET
UPPER VEST
PANEL
FLAME
BAFFLES
(NOxunits only)
RIGHT MANIFOLD BRACKET
ROLL-OUT BRACKET
MID VEST PANEL
PRIMARY LIMIT
MANIFOLD END
PLUG
ROLL-OUT SWITCH
LEFT MANIFOLD BRACKET
COMBUSTION
AIR BLOWER
PRIMARY LIMIT
ALTERNATE STYLE
BURNER ASSEMBLY
CONTROL BOX
SUPPLY AIR
OPENING
TOP CAP
BLOWER
ASSEMBLY
CAPACITOR
AND BRACKET
COMBUSTION
BLOWER
GASKET
FLUE BOX GLASS FIBER
GASKET
COMBUSTION
AIR PROVING
(PRESSURE) SWITCH
DOOR INTERLOCK SWITCH
SURELIGHT CONTROL BOARD
CONTROL
TRANSFORMER
CONTROL VOLTAGE
CIRCUIT BREAKER

Page 4
Requirements
All G23(X) units are Canadian Standards Association
(CSA) certified.
In the USA, installation of Lennox gas central furnaces
must conform with local building codes. In the absence of
local codes, units must be installed according to the cur
rent National Fuel Gas Code (ANSIZ223.1) in the United
States. The National Fuel Gas Code is available from the
following address:
American National Standards Institute, Inc.
11 West 42nd Street
New York, NY 10036
Air supply for combustion and ventilation must conform to
the methods outlined in the current National Fuel Gas Code.
WARNING
Product contains fiberglass wool.
Disturbing the insulation in this product during
installation, maintenance, or repair will expose you
to fiberglass wool dust. 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
This furnace is CSA certified for installation clearances to
combustible material as listed on the unit rating plate and
in table 1. Accessibility and service clearances must take
precedence over fire protection clearances.
TABLE 1
Clearances Location Inches (mm)
Service access Front 24 (610)
Side and rear 0 (0)
To combustible Top 1 (25)
To
combustible
materials Flue 6 (152)*
Floor 0 (0)**
Around com
bustion cham
Front
B1Vent
3 (76)
b
us
ti
on c
h
am
ber air opening
Front
Single Wall Vent
4 (102)
NOTE-Service access clearance must be maintained.
* 1 inch (25mm) for type B1" Vent Pipe.
**For installation on combustible floors, appliance shall not be installed
directly on carpeting, tile, or other combustible material other than wood
flooring.
Vent installations must be in accordance with the pro
vided venting tables and applicable provisions of local
building codes.
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 ac
cording to recommended good practice requirements
and current National Fuel Gas Code.
Unit must be adjusted to obtain a temperature rise within
the range specified on appliance rating plate.
G23(X) units must be installed so that electrical compo
nents are protected from water.
When the furnace is used with cooling units, it shall be
installed in parallel with, or on the upstream side of, cool
ing units to avoid condensation in the heating compart
ment. 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 damp
er 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, the 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 Nation
al Electric Code (ANSI/NFPA No. 70) is available from
the following address:
National Fire Protection Association
1 Battery March Park
Quincy, MA 02269
Field wiring connection with unit must meet or exceed
specifications of type T wire and withstand a 63F (17C)
temperature rise.
This furnace is designed for a minimum continuous return
air temperature of 60° dry bulb for cases in which a ther
mostat night setback is used. Return air temperature
must not exceed a maximum of 85F db.
NOTE - G23(X) series units must not be used as a
construction heater during any phase of construction.
Very low return air temperatures, harmful vapors and
misplacement of the filters will damage the unit and low
er its efficiency.

Page 5
General
These instructions are intended as a general guide and
do not supersede local codes in any way. Consult authori
ties having jurisdiction before installation.
A-Shipping and Packing List
1 - Assembled G23(X) furnace
1 - Bag assembly containing
1-Electrical makeup box
3-Wire nuts
1-Green ground wire
1-Brown accessory wire
1-Wiring harness
1-Snap bushing
2-Filter clips
B-Shipping Damage
Check equipment for shipping damage. If you find any
damage, immediately contact the last carrier.
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, ap
pliance 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 combus
tion, negative pressure (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 poten
tially dangerous situation.
In the absence of local codes concerning air for combus
tion and ventilation, use the guidelines and procedures in
this section to install G23(X) furnaces to ensure efficient
and safe operation. You must consider combustion air
needs and requirements for exhaust vents and gas pip
ing. 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 com
plete and official position of the ANSI on the referenced
subject, which is represented only by the standard in its
entirety.
All gasfired appliances require air for the combustion
process. If sufficient combustion air is not available, the
furnace or other appliance will operate inefficiently and
unsafely. 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 required to en
sure proper combustion and to prevent a downdraft. In
sufficient air causes incomplete combustion which can re
sult in carbon monoxide.
Combustion Air Requirements
WARNING
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. Exces
sive exposure to contaminated combustion air will
result in safety and performance related problems.
Avoid exposure to the follow-ing 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
In addition to providing combustion air, fresh outdoor air
dilutes contaminants in the indoor air. These contami
nants may include bleaches, adhesives, detergents, sol
vents 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 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 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 proce
dures 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.

Page 6
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 either from inside the
building or from outside.
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).
EQUIPMENT IN CONFINED SPACE
ALL AIR FROM INSIDE
CHIMNEY OR
GAS VENT
WATER
HEATER
OPENINGS
(To Adjacent
Room)
FIGURE 2
NOTE-Each opening shall have a free area of at least one square
inch per 1,000 Btu per hour of the total input rating of all equipment in
the enclosure, but not less than 100 square inches.
G23
FURNACE
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 communi
cate 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 calculat
ing 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
ALL AIR FROM OUTSIDE
(Inlet Air from Crawl Space 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 per 4,000 Btu 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
VENTILATION
LOUVERS
(For unheated crawl
space)
FIGURE 3
G23
FURNACE
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 per 4,000 Btu per hour of the total input
rating of all equipment in the enclosure.
CHIMNEY
OR GAS
VENT
WATER
HEATER
OUTLET
AIR
VENTILATION LOUVERS
(Each end of attic)
INLET AIR
(Ends 12 in. above
bottom)
FIGURE 4
G23
FURNACE

Page 7
EQUIPMENT IN CONFINED SPACE
ALL AIR FROM OUTSIDE
OUTLET AIR
INLET AIR
WATER
HEATER
CHIMNEY
OR GAS
VENT
FIGURE 5
NOTE-Each air duct opening shall have a free area of at least one
square inch per 2,000 Btu 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 per 4,000 Btu per hour of the total input rating of all
other equipment in the enclosure.
G23
FURNACE
Installation - Setting Equipment
Select a location that allows for required clearances listed
on the unit rating plate. Also consider gas supply connec
tions, electrical supply, vent connection and installation
and service clearances [24 inches (610 mm) at unit front].
The furnace must be level.
NOTE - 1/3 and 1/2 hp blower motors are equipped with
either four flexible mounting legs or 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).
This shipping bolt and flat washer must be removed be-
fore the furnace is put into operation. Once the shipping
bolt and washer are removed, the rigid leg will not touch
the blower housing.
Return Air Opening Guidelines
WARNING
Blower door must be securely in place when blower
and burners are operating. Gas fumes, which could
contain carbon monoxide, can be drawn into living
space resulting in personal injury or death.
WARNING
Improper installation of unit can result in personal
injury or death. Combustion and flue products
must never be allowed to enter the return air system
or air in the living space. Use sheet metal screws
and joint tape to seal return air system to furnace.
In platform installations with furnace return, the fur
nace 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.
Allow absolutely no sagging, cracks, gaps, etc.
For no reason should return and supply air duct
systems ever be connected to or from other heating
devices such as a fireplace or stove, etc. Fire, ex
plosion, carbon monoxide poisoning, personal in
jury and/or property damage could result.
Return air can be brought in either side or at the bottom of
the unit. Scribe lines show the outline of each side and the
bottom return air opening.
Bottom Return Air Applications
If cold air return is to terminate through the floor under the
furnace, a direct, airtight and sealed connection must be
made to the bottom of the furnace.
1 - Cut opening in floor or platform. Using knockouts
provided, cut bottom of base panel. See figure 6.
FIGURE 6
KNOCKOUT PATTERN FOR BOTTOM RETURN
AIR APPLICATION
2 - Bend a flange on return air plenum and lower into
floor or platform opening. See figure 7.
3 - Position unit over return air opening. Seal unit air
tight with return air plenum.

Page 8
FIGURE 7
G23 UNIT
RETURN AIR
PLENUM
PROPERLY
SIZED FLOOR
OPENING
BOTTOM RETURN AIR APPLICATION
Side Return Air Applications
For installations where the return air is taken from a return
air drop, unit may be installed using either the left or right
side of furnace.
For side return air applications, cut furnace cabinet at
maximum dimensions given on page 2. Embossed cor
ners are provided on both cabinet sides for return air
opening location.
Filters & Optional Filter Assembly
This unit is not equipped with a filter. Filter racks and reus
able foam filters are available from Lennox in single kits
(44J20 for 14 x 25 filters; 44J22 for 16 x 25 filters; 44J21
for 20 x 25 filters) or 10pack kits (66K61 for 14 x 25 filters;
66K63 for 16 x 25 filters; 66K62 for 20 x 25 filters). A filter
must be in place any time the unit is in operation.
Bottom Return Air Applications
1 - Remove blower access panel.
2 - Install filter clips, provided with unit, by slipping
folded section of clip on edge of bottom opening. See
figure 8.
3 - Place filter in bottom of blower compartment beneath
rear filter clip. Press down on filter sides. Filter clips
flex allowing filter to snap into place.
4 - To remove filter, press clip and pull filter up and out.
Side Return Air Applications
An external filter rack, ordered separately, is available
from Lennox.
FIGURE 8
BOTTOM RETURN FILTER INSTALLATION
FURNACE
BASE BOTTOM
REAR FILTER
CLIP
RETURN AIR OPENING
SIDE FILTER
CLIPS (2)
FURNACE
FRONT
FURNACE
BACK
1 - Align filter rack opening with the inside edge of the
side return opening. Bottom of rack should be
approximately 1 inch (25.4mm) from the bottom and
3 inches (76mm) from the front of the unit.
2 - Screw filter rack into place with the six self drill, self
tap screws provided in the kit. See figure 9.
3 - Push filter door pins through the two holes in filter
door from the inside of the uchannel. See figure 10.
4 - Position filter door on end of filter so that the thumb
tab side of the filter door is away from the furnace.
Squeeze thumb tabs to secure filter to door.
FIGURE 9
SIDE RETURN FILTER INSTALLATION
(Inches-mm)
RETURN
AIR OPENING
1-15/16 in.
(49)
BLOWER DECK
15/16 in.
(24)
CABINET BASE BOTTOM
RETURN AIR PLENUM SIZE
12-3/4 in. X 23-1/2 in. (324 X 597)
for 14 in. Filter
14-3/4 in. x 23-1/2 in. (375 x 597)
for 16 in. filter
18-3/4 in. x 23-1/2 in. (476 x 597)
for 20 in. Filter
12 in. (305) for
14 in. Filter
14 in. (356) for
16 in. filter
18 in. (457) for
20 in. Filter

Page 9
5 - Guide filter and filter door into the filter rack which is
installed on the side of the furnace. Push door into fil
ter rack until secure.
6 - To remove filter, pull filter door pins until door is re
leased from filter rack.
FIGURE 10
FILTER DOOR ASSEMBLY
FILTER DOOR
PINS
FILTER
DOOR FILTER
FILTER DOOR
PIN
TAB
TAB
Duct System
Size and install supply and return air duct system using
industryapproved standards that result in a quiet and
low-static system with a uniform air distribution. Refer
to ACCA (Air Conditioning Contractors of America)
Manual N.
Supply Air Plenum
Furnaces installed without a cooling coil require the
installation of a removable access panel 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 installation. The furnace ac
cess panel must always be in place when the furnace is
operating and it must not allow leaks into the supply air
duct system.
Return Air Plenum
NOTE - For bottom return air, return air duct should be se
cured to the unit using rivets or Slocks. For side return air,
secure return air duct to filter rack using screws. When us
ing screws, take care to avoid interference with the filter
which may cause improper filtration.
Return air must not be drawn from a room where this
furnace, or any other gas appliance (ie., a water heat
er), is installed. When return air is drawn from a room,
a negative pressure is created in the room. If a gas ap
pliance is operating in a room with negative pressure, the
flue products can be pulled back down the vent pipe and
into the room. This reverse flow of the flue gas may result
in incomplete combustion and the formation of carbon
monoxide gas. This toxic gas might then be distributed
throughout the house by the furnace duct system.
Venting
G23(X) series furnaces must be vented in compliance
with all local codes, the venting tables provided in this
manual, and these instructions.
The G23(X) series units are classified as fan assisted
Category I type furnaces when vertically vented accord
ing to the latest edition of ANSI Z21.47 Central Furnace
Standard in the USA. The definition of a fan assisted
Category I type furnace is an appliance equipped with an
integral mechanical means to either draw or force prod
ucts of combustion through the combustion chamber and/
or heat exchanger.
The vent sizing 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. Prop
er application, termination, construction and location of
vents must conform to local codes having jurisdiction. In
the absence of local codes, the NFGC serves as the de
fining document.
Refer to the tables and the venting information contained
in these instructions to properly size and install the vent
ing system.
The G23(X) series units have the following flue collar
sizes: -50 unit, 3 inch diameter; -75 and -100 units, 4 inch
diameter; and -125 & -150 units, 5 inch diameter. Use this
information in conjunction with the provided venting
tables to properly size the vent or vent connector that at
taches to the furnace flue collar.
Venting Using a Masonry Chimney
The following additional requirements apply when a lined
masonry chimney is used to vent an G23X furnace.
A Category I appliance must never be connected to a
chimney that is servicing a solid-fuel appliance. If a fire
place chimney flue is used to vent this appliance, the fire
place opening must be permanently sealed.
A chimney with one or more sides exposed to the outside
of the structure is considered to be an exterior chimney. A
Type B or listed chimney lining system passing through an
unused masonry chimney flue is not considered to be ex
posed to the outdoors.
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.

Page 10
FIGURE 11
COMMON VENTING USING TILE-LINED INTERIOR MASONRY
CHIMNEY AND COMBINED VENT CONNECTOR
G23
OTHER APPLIANCE
VENT
CONNECTOR
(Double-walled,
single-walled, or in
sulated single-
walled pipe)
MINI. LENGTH = AS SHORT
AS PRACTICAL.
FOR MAX. LENGTH SEE ITEM 4, ON
THE FOLLOWING PAGE.
INTERIOR TILE-
LINED MASONRY
CHIMNEY
NOTE - CHIMNEY MUST BE
PROPERLY SIZED PER THE
PROVIDED VENTING TABLES
OR LINED WITH LISTED METAL
LINING SYSTEM.
NOTE - If vent connector length exceeds 15
ft. (4.5 m), entire length of single-walled
vent connector must be insulated.
PERMANENTLY SEALED
FIREPLACE OPENING
A fan-assisted furnace may be commonly vented into an
existing lined masonry chimney if the following conditions
are met:
1 - The chimney is currently serving at least one draft
hood equipped appliance.
2 - The vent connectors and chimney are sized in accor
dance with the provided venting tables.
IMPORTANT
SINGLE appliance venting of a fanassisted fur
nace 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 insu
lated single wall flexible vent lining system, sized
according to the provided venting tables.
See figures 11 and 12 for common venting.
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.
Do not install a manual damper, barometric draft regula
tor, or flue restrictor between the furnace and the chim
ney.
If type B doublewall vent is used inside a chimney, no oth
er appliance can be vented into the chimney. Outer wall of
type B vent pipe must not be exposed to flue products.
Insulation for the flexible vent pipe must be an encapsu
lated fiberglass sleeve recommended by the flexible vent
pipe manufacturer. See figure 12.
The space between the liner and the chimney wall
should NOT be insulated with puffed mica or any oth
er loose granular insulating material.
FIGURE 12
COMMON VENTING USING
METAL-LINED MASONRY CHIMNEY
4 IN. MIN.
(102mm)
5 FT. (1.5 m)
MINIMUM MIN. LENGTH -- AS
SHORT AS PRACTICAL
MAX. LENGTH -- SEE
ITEM 10, PAGE 11
SEALED
PERMANENTLY
SEALED FIREPLACE
OPENING
EXTERIOR
CHIMNEY WITH B
VENT OR
INSULATED
FLEXIBLE VENT
PIPE.

Page 11
If B vent or an insulated flexible vent pipe cannot be used
as liners, the chimney must be rebuilt to accommodate
one of these methods or some alternate approved meth
od must be found to vent the appliance.
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 G23(X) series units. The chimney
passageway must be checked periodically to ensure that
it is clear and free of obstructions.
General Venting Requirements
All G23(X) furnaces must be vented in accordance with
the methods outlined in these instructions.
1 - Vent diameter recommendations and maximum runs
allowed are found in the provided venting tables.
2 - In no case should the vent or vent connector diame
ter be less than the diameter specified in the pro
vided venting tables.
3 - For 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 determine the minimum vent capacity and the
vent connector diameter to determine the maxi
mum vent capacity. The flow area of the vertical
vent, however, shall not exceed 7 arial the flow area
of the listed appliance categorized vent area, draft
hood outlet area or flue collar area unless designed
in accordance with approved engineering methods.
4 - For multiple appliance vents: The flow area of the
largest section of vertical vent or chimney shall not
exceed 7 arial the smallest listed appliance catego
rized vent area, flue collar area or drafthood outlet
area unless designed according to with approved en
gineering methods.
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 are assumed to have no elbows in the
vent system. See tables 3 and 4. 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 maximum listed capacity).
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 mm) for each inch (25 mm) of
connector diameter as follows in table 2:
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 ca
pacity). The horizontal length of the offset shall not
exceed 1 1/2 feet (.46 mm) 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. The vent connector should be routed to
the vent using 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 to
ward the appliance.
11- Vent connectors shall be firmly attached to furnace
flue collars by screws or other approved means, ex
cept vent connectors of listed type B vent material
which shall be assembled according to the manufac
turer'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
ceilings must be installed with the listed clearance to
combustible materials and be fire stopped according
to local 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 operation under positive pressure such as
Category III or IV venting systems.

Page 12
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 max
imum 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 reg
ulator or flue restrictor between the furnace and the
chimney.
20- When connecting this appliance to an existing dedi
cated or common venting system, the venting sys
tem, must be inspected for signs of corrosion, and
general condition. The sizing of the vent system must
be reviewed and must conform to these instructions
and the provided venting tables. If the existing sys
tem is in conflict with these requirements, the venting
system must be resized.
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)
Hei
g
ht Lateral 3 Inch 4 Inch 5 Inch 6 Inch
Height
H (feet)
Lateral
L (feet) Appliance Input Rating in Thousands of Btu Per Hour
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
211 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 maximum listed capacity).

Page 13
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)
Hei
g
ht Lateral 3 Inch 4 Inch 5 Inch 6 Inch
Height
H (feet)
Lateral
L (feet) Appliance Input Rating in Thousands of Btu Per Hour
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 maximum listed capacity).

Page 14
TABLE 5
CAPACITY OF TYPE B DOUBLE-WALL VENTS WITH TYPE B DOUBLE-WALL CONNECTORS
SERVING TWO OR MORE CATEGORY I APPLIANCES VENT CONNECTOR CAPACITY
Vent and Connector Diameter - D (inches)
Vent
Height
Connector
Rise
3 Inch 4 Inch 5 Inch 6 Inch
Height
H
(
feet
)
Rise
R
(
feet
)
Appliance Input Rating in Thousands of Btu Per Hour
H
(feet)
R
(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
CAPACITY OF TYPE B DOUBLE-WALL VENTS WITH TYPE B DOUBLE-WALL CONNECTORS
SERVING TWO OR MORE CATEGORY I APPLIANCES COMMON VENT CAPACITY
Common Vent Diameter - D (inches)
Vent
Height
4 Inch 5 Inch 6 Inch 7 Inch
Height
H
(
feet
)
Appliance Input Rating in Thousands of Btu Per Hour
H
(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
TABLE 7
CAPACITY OF TYPE B DOUBLE-WALL VENT WITH SINGLE-WALL METAL CONNECTORS
SERVING TWO OR MORE CATEGORY I APPLIANCES VENT CONNECTOR CAPACITY
Connector
Vent and Connector Diameter - D (inches)
Vent
Height
C
onnector
Rise 3 Inch 4 Inch 5 Inch 6 Inch
Height
H
(
feet
)
Rise
R
(feet)
Appliance Input Rating in Thousands of Btu Per Hour
H
(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

Page 15
TABLE 8
CAPACITY OF TYPE B DOUBLE-WALL VENTS WITH SINGLE-WALL METAL CONNECTORS
SERVING TWO OR MORE CATEGORY I APPLIANCES COMMON VENT CAPACITY
Common Vent Diameter - D (inches)
Vent
Height
4 Inch 5 Inch 6 Inch 7 Inch
Height
H
(
feet
)
Appliance Input Rating in Thousands of Btu Per Hour
H
(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 the 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
properly vent the remaining attached appliances. The
following test should be conducted while each appliance
is in operation and the other appliances not in operation
remain connected to the common venting system. If the
venting system has been installed improperly, the sys
tem must be corrected as indicated in the general vent
ing requirements section.
1 - Seal any unused openings in the common venting
system.
2 - Visually inspect the venting system for proper size
and horizontal pitch and determine there is no block
age or restriction, leakage, corrosion and other defi
ciencies which could cause an unsafe condition.
3 - To the extent that it is practical, close all building
doors and windows and all doors between the space
in which the appliances remaining connected to the
common venting system are located and other
spaces of the building. Turn on clothes dryers and
any appliances not connected to the common vent
ing system. Turn on any exhaust fans, such as range
hoods and bathroom exhausts, so they will operate
at maximum speed. Do not operate a summer ex
haust fan. Close fireplace dampers.
4 - Following the lighting instruction, place the appliance
being inspected in operation. Adjust thermostat so
appliance will operate continuously.
5 - Test for spillage of flue gases at the draft hood relief
opening after 5 minutes of main burner operation.
Use the flame of a match or candle, or smoke from a
cigarette, cigar or pipe.
6 - After determining that each appliance remaining
connected to the common venting system properly
vents when tested as indicated in step 3, return
doors, windows, exhaust fans, fireplace dampers
and any other gasburning appliance to their pre
vious condition of use.
7 - If improper venting is observed during any of the
above tests, the common venting system must be
corrected. The common venting system should be
resized to approach the minimum size as deter
mined by using the appropriate tables in appendix G
in the current standards of the National Fuel Gas
Code ANSI Z223.1.
Horizontal Venting
SIDE WALL VENTING KIT WIRING
C
L1
L2 120VAC
M
L1 MN T1 T2 T3
WR Y G
W
G
R
Y
24 VAC
THERMOSTAT
THERMOSTAT CONNECTIONS
TERMINAL IN FURNACE
JUNCTION BOX
RELAY
CK-43 CONTROL BOX
PRESSURE
SWITCH
SWG
POWER
VENTER
MOTOR
FIGURE 13
T
FIELD INSTALLED WIRING
FACTORY INSTALLED WIRING
NO
2
1
3
5
4
This furnace is design certified by the American Gas As
sociation for horizontal venting through an outside wall
only with the use of a Field Controls Company Model
SWG-4L side wall venting kit available from Lennox Deal
er Service Center. No other Field brand venting kit or any
other manufacturer's venting kit is acceptable. Horizontal
venting of this furnace without the use of the above stated
kit is prohibited. See figure 13 for field wiring of side wall
horizontal venting kit.
When horizontally vented, the minimum clearance for ter
mination from electric meters, gas meters, regulators,
and relief equipment is 4 feet (1.2m).

Page 16
Gas Piping
CAUTION
If a flexible gas connector is required or allowed by
the authority that has jurisdiction, black iron pipe
shall be installed at the gas valve and extend out
side the furnace cabinet.
1 - This unit is shipped standard for left or right side
installation of gas piping (or top entry in horizontal
applications). Connect the gas supply to the piping
assembly.
2 - A piping hole is also fabricated in the right side of the
unit for alternate piping arrangements.
3 - When connecting gas supply, factors such as length
of run, number of fittings and furnace rating must be
considered to avoid excessive pressure drop. Table
9 recommends pipe sizes for typical applications.
4 - The gas piping must not run in or through air ducts,
clothes chutes, gas vents or chimneys, dumb wait
ers, or elevator shafts.
5 - The piping should be sloped 1/4 inch (6.4 mm) per 15
feet (4.57 m) upward toward the meter from the fur
nace. The piping must be supported at proper inter
vals [every 8 to 10 feet (2.44 to 3.01 m) using suitable
hangers or straps. A drip leg should be installed in
vertical pipe runs to the unit.
6 - In some localities, codes may require installation of a
manual main shutoff valve and union (furnished by
installer) that are external to the unit. Union must be
of the ground joint type.
IMPORTANT
Compounds used on threaded joints of gas piping
must be resistant to the actions of liquified petro
leum gases.
NOTE - If an emergency shutoff is required, shut off the
main manual gas valve and disconnect the main power
from the unit. Properly label these devices.
NOTE - Install an 1/8 inch NPT plugged tap into the field
piping. Install the tap so that it is upstream of where the
unit connects to the gas supply. The tap must be accessi
ble for test gauge connection. See figure 14.
FIGURE 14
GROUND
JOINT
UNION
LEFT SIDE PIPING
(STANDARD)
RIGHT SIDE PIP
ING
AUTOMATIC
GAS VALVE
MANUAL
MAIN SHUT-OFF
VALVE
1/8 in. NPT
PLUGGED TAP
GROUND
JOINT
UNION
MANUAL
MAIN SHUT-
OFF VALVE
1/8 in. NPT
PLUGGED TAP
AUTOMATIC
GAS VALVE
Leak Check
After gas piping is completed, carefully check all piping
connections (factory- and field-installed) for gas leaks.
Use a leak detecting solution or other preferred means.
CAUTION
Some soaps used for leak detection are corrosive
to certain metals. Carefully rinse piping thoroughly
after leak test has been completed. Do not use
matches, candles, flame or other sources of igni
tion to check for gas leaks.
IMPORTANT
When testing pressure of gas lines, gas valve must
be disconnected and isolated. See figure 15. Gas
valves can be damaged if subjected to more than
1/2 psig (3.48 kPa).

Page 17
FIGURE 15
MANUAL MAIN SHUT-OFF
VALVE WILL NOT
HOLD NORMAL
TEST PRESSURE
CAP
FURNACE
ISOLATE
GAS
VALVE
CAP
The furnace must be isolated from the gas supply system
by closing its individual manual shutoff valve during any
pressure testing of the gas supply system at pressures
equal to or greater than 1/2 psig (3.48 kPa).
TABLE 9
GAS PIPE CAPACITY - FT3/HR (kL/HR)
Nominal Internal Length of Pipe-Feet(m)
Nominal
Iron Pipe Size
-Inches(mm)
Internal
Diameter
-Inches(mm) 10
(3.048)
20
(6.096)
30
(9.144)
40
(12.192)
50
(15.240)
60
(18.288)
70
(21.336)
80
(24.384)
90
(27.432)
100
(30.480)
1/4
(6.35)
.364
(9.246)
43
(1.13)
29
(.82)
24
(.68)
20
(.57)
18
(.51)
16
(.45)
15
(.42)
14
(.40)
13
(.37)
12
(.34)
3/8
(9.53)
.493
(12.522)
95
(2.69)
65
(1.84)
52
(1.47)
45
(1.27)
40
(1.13)
36
(1.02)
33
(.73)
31
(.88)
29
(.82)
27
(.76)
1/2
(12.7)
.622
(17.799)
175
(4.96)
120
(3.40)
97
(2.75)
82
(2.32)
73
(2.07)
66
(1.87)
61
(1.73)
57
(1.61)
53
(1.50)
50
(1.42)
3/4
(19.05)
.824
(20.930)
360
(10.19)
250
(7.08)
200
(5.66)
170
(4.81)
151
(4.28)
138
(3.91)
125
(3.54)
118
(3.34)
110
(3.11)
103
(2.92)
1
(25.4)
1.049
(26.645)
680
919.25)
465
(13.17)
375
(10.62)
320
(9.06)
285
(8.07)
260
(7.36)
240
(6.80)
220
(6.23)
205
(5.80)
195
(5.52)
1-1/4
(31.75)
1.380
(35.052)
1400
(39.64)
950
(26.90)
770
(21.80)
660
(18.69)
580
(16.42)
530
(15.01)
490
(13.87)
460
(13.03)
430
(12.18)
400
(11.33)
1-1/2
(38.1)
1.610
(40.894)
2100
(59.46)
460
(41.34)
1180
(33.41)
990
(28.03)
900
(25.48)
810
(22.94)
750
(21.24)
690
(19.54)
650
(18.41)
620
(17.56)
2
(50.8)
2.067
(52.502)
3950
(111.85)
2750
(77.87)
2200
(62.30)
1900
(53.80)
1680
(47.57)
1520
(43.04)
1400
(39.64)
1300
(36.81)
1220
(34.55)
1150
(32.56)
2-1/2
(63.5)
2.469
(67.713)
6300
(178.39)
4350
(123.17)
3520
(99.67)
3000
(84.95
2650
(75.04)
2400
(67.96)
2250
(63.71)
2050
(58.05)
1950
(55.22)
1850
(52.38)
3
(76.2)
3.068
(77.927)
11000
(311.48)
7700
(218.03)
6250
(176.98)
5300
(150.07)
4750
(134.50)
4300
(121.76)
3900
(110.43)
3700
(104.77)
3450
(97.69)
3250
(92.03)
4
(101.6)
4.026
(102.260)
23000
(651.27)
15800
(447.39)
12800
(362.44)
10900
(308.64)
9700
(274.67)
8800
(249.18)
8100
(229.36)
7500
(212.37)
7200
(203.88)
6700
(189.72)
NOTE-Capacity given in cubic feet of gas per hour (kilo liters of gas per hour) and based on 0.60 specific gravity gas.
Electrical
A field makeup box is provided for line voltage wiring.
Line voltage wiring to unit is done through the J69 jack
from the field makeup box to plug P69 from the control
box. See figures 17 and 18 for makeup box installation.
Figure 19 shows thermostat designations for identifica
tion purposes. Refer to figure 20 for control box arrange
ment, 21 for a detail of the SureLight integrated control
board (SureLight control), figure 22 for schematic wiring
diagram and troubleshooting, and figure 23 for point to
point field wiring.
1 - Install field makeup box on either side, inside or out
of the cabinet. Wiring knockouts are provided in box
and cabinet. See figures 17 and 18.
2 - Remove cap from knockout in blower deck on the
same side as the installed makeup box.
3 - Electrically ground unit in accordance with local
codes or, in the absence of local codes, in accor
dance with the current National Electric Code (ANSI/
NFPA No. 70). The green ground wire is provided in
the field make-up box.
To ensure proper grounding of the furnace, two star
washers are included in the electrical makeup box
bag assembly. Place the star washer on securing
screw before installing the makeup box. Make sure
the star washer breaks the paint on the cabinet so
that the washer is touching metal. Unit is not properly
grounded if paint has not been removed by star
washer.

Page 18
4 - An optional 120 volt accessory wire is provided with
G23(X) units. Install brown accessory wire into J69
jack plug by inserting the pin of the brown wire into the
open socket of the jack. See figure 16. Any accessory
rated up to 4 amps can be
connected to this wire. Con
nect the neutral leg of the ac
cessory to the neutral white
wire in the makeup box.
Connect the brown wire to the
ACC terminal; the terminal is
energized whenever the
blower is energized. You can
also connect the brown wire
to the HTG ACC terminal; the
terminal is energized when
the thermostat calls for heat.
The accessory terminal is energized whenever the
blower is in operation. A troubleshooting flowchart
for the SureLight control is located on pages 28-31.
5 - Insert the three pin (P69) plug from control box into
knockout provided in blower deck.
6 - Connect jack (J69) from makeup box to jack plug in
blower deck.
FIGURE 17
INTERIOR MAKE-UP BOX
INSTALLATION
P69 from
Control Box
J69
MAKE-UP
BOX
BUSHING
FIGURE 18
EXTERIOR MAKE-UP BOX
INSTALLATION
P69 from
Control Box
J69
(Shown with accessory
wire connected)
MAKE-UP
BOX
BUSHING
RING
7 - Select wire size according to the blower motor amps.
8 - Snaphole bushing is provided for the wiring entry
hole in the cabinet. A snaphole plug is provided to
seal the unused wire entry hole.
9 - Install room thermostat according to instructions pro
vided with thermostat. See figure 19 for thermostat
designations. If furnace is being used with heat pump
refer to FM21 installation instruction.
Thermostat
FIGURE 19
COMPRESSOR
COMMON
HS UNIT
COMMON
HS UNIT
COMPRESSOR
G23(X)
Furnace
Condensing
Unit
G23(X) and CONDENSING UNIT
THERMOSTAT DESIGNATIONS
(Refer to specific thermostat and outdoor unit.)
COMMON
POWER
HEAT
INDOOR BLOWER
Y
C
R
W1
G
C
R
W1
G
Y
C
R
G
C
R
W
G
COOLING
10 - Install a separate fused disconnect switch near the
unit so power can be turned off for servicing.
11 - To complete the wiring connections to the equip
ment, refer to the wiring diagrams provided with the
unit. (Figures 22 and 23) Use 18 gauge wire or larger
for thermostat connections.
Indoor Blower Speeds (Refer to Figure 22)
1 - When the thermostat is set to "FAN ON", the indoor
blower will run continuously on low speed when there
is no cooling or heating demand.
2 - When there is a cooling demand, the indoor blower
will run on the cooling speed.
3 - When there is a heating demand, the indoor blower
will run on the heating speed.
G23(X) CONTROL BOX
TRANSFORMER
SureLight
LOW VOLTAGE
TERMINAL STRIP
CIRCUIT
BREAKER
DOOR INTERLOCK SWITCH
FIGURE 20
BLACK
WHITE
NEUTRAL
BROWN
J69
INSTALLING BROWN
ACCESSORY WIRE TO
J69
FIGURE 16

Page 19
ACB COOL Blower - Cooling Speed (Line Volt)
ACB HEAT Blower - Heating Speed (Line Volt)
PARK Unused Blower (Dead)
ACB LOW Continuous Low Speed Blower
ACC Accessory Terminal (Line Volt)
TX 120VAC Hot to Transformer
HOT 120VAC Hot Input
HTG ACCHeat Only Accessory (Line Volt)
NEUTRALS 120VAC Neutrals
24VAC HOT24VAC Hot from Transformer
24VAC RTN24VAC Return from Transformer
FLAME SENSE Flame Sense Terminal
SURELIGHT INTEGRATED CONTROL BOARD
FIGURE 21
TERMINAL DESIGNATIONS
Cat No. 24L85
2

Page 20
G23(X) SCHEMATIC WIRING DIAGRAM
FIGURE 22