Lennox G24M2-45, G24M3-75, G24M2-60, G24M4-75, G24M3/4-100 Installation Instructions Manual
...
INSTALLATION
2000 Lennox Industries Inc.
Dallas, Texas
RETAIN THESE INSTRUCTIONS
FOR FUTURE REFERENCE
INSTRUCTIONS
G24M Series
GAS FURNACE
SureLight Ignition System
504,197M
02/2000
Supersedes 503,981M
Table of Contents
G24M Unit Dimensions 2. . . . . . . . . . . . . . . . . . . . . .
G24M Parts Arrangement 3. . . . . . . . . . . . . . . . . . . .
G24M Gas Furnace 3. . . . . . . . . . . . . . . . . . . . . . . . .
Shipping and Packing List 3. . . . . . . . . . . . . . . . . . . .
Requirements 3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
General 4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Combustion, Dilution & Ventilation Air 5. . . . . . . . . .
Setting Equipment 8. . . . . . . . . . . . . . . . . . . . . . . . . .
Duct System 11. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Venting 12. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Gas Piping 19. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Electrical 21. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Unit Start-up 24. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Gas Pressure Adjustment 25. . . . . . . . . . . . . . . . . . .
High Altitude Information 25. . . . . . . . . . . . . . . . . . . .
Other Unit Adjustments 25. . . . . . . . . . . . . . . . . . . . .
Service 27. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Repair Parts List 28. . . . . . . . . . . . . . . . . . . . . . . . . . .
Ignition Control Board Diagnostic Codes 28. . . . . .
Troubleshooting 29. . . . . . . . . . . . . . . . . . . . . . . . . . .
G24M Start-up & Performance Check List 32. . . . .
Litho USA
Do not store or use gasoline or oth
er 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.
WARNING
If the information in this manual is not
followed exactly, a fire or explosion
may result causing property damage,
personal injury or death.
WHAT TO DO IF YOU SMELL GAS:
Do not try to light any appliance.
Extinguish any open flames.
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 suppli
er's instructions.
If you cannot reach your gas supplier, call
the fire department.
Page 1
G24M Unit Dimensions - inches (mm)
G24M3/4120
GAS PIPING
INLET
2 (51)
E
D
FLUE
OUTLET
*NOTE - The supply air opening is equipped with a 3/4 inch (19 mm)
scored flange that may be bent 90 for plenum connection. The dimen
sions shown were taken after the flange was bent.
The double scored flange at the front of the supply air open
ing may be bent for a total opening dimension (front to rear)
of either 191/2 inches (495 mm) or 19 inches (483 mm).
41/4
(105)
A
2 (51)
AIR FLOW
F Left Side
G Right Side
ELECTRICAL INLETS
(Top & Bottom)
*C
1
(25)
1
(25)
*191/2
(495)
*19
(483)
SUPPLY
AIR
OPENING
TOP VIEW
295/8
(752)
GAS PIPING
INLET
(Both Sides)
1
(25)
1
(25)
1
(25)
B
ELECTRICAL
INLETS
(Either Side)
**NOTE The return air opening is
Return Air
**C
Opening
FRONT VIEW SIDE VIEW
Model No. A B C D E F G
G24M245
G24M260
G24M360
G24M375
G24M475
G24M3/4100
G24M3/4120
G24M4/5100
G24M4/5120
G24M4/5140
in. 17 361/4 15 63/4 27/16 111/2 61/2
mm 432 921 381 171 62 293 165
in. 201/2 39 181/2 83/8 41/4 13 8
mm 521 991 470 213 108 331 203
in. 231/4 39 211/4 9-3/4 41/4 12-31/32 73/32
mm 591 991 540 248 108 329 180
equipped with a 3/4 inch (19 mm) scored
flange that may be bent 90 for plenum
1
connection. The dimensions shown were
(25)
taken after the flange was bent.
15
(381)
**191/2
(495)
191/2
(495)
RETURN AIR
KNOCKOUT
(Either Side)
3/4 (19)
Return Air
Opening
1
(25)
1
(25)
Page 2
G24M Parts Arrangement
G24M
PARTS IDENTIFICATION
COMBUSTION AIR
BLOWER
FRONT LOUVERED
PANEL
TRANSFORMER
CONTROL
BOARD
HEAT EXCHANGER
ASSEMBLY
FLUE BOX
PRESSURE
SWITCH
PRIMARY
LIMIT
LOW PRESSURE SWITCH
(Propane Only)
BURNER
ASSEMBLY
DOOR INTERLOCK SWITCH
VENT ADAPTER
NOx
TURBULATOR
SECONDARY
LIMITS
BLOWER ASSEMBLY
CABINET TOP
G24M
CABINET
CABINET
BOTTOM
G24M Gas Furnace
The G24M gas furnace is shipped ready for installation
in the upflow position. The unit can easily be converted
for installation in either downflow or horizontal ap
plications. The furnace is shipped with a bottom seal
panel in place for side return air in upflow applications.
Shipping and Packing List
Package 1 of 1 contains:
1 - Assembled G24M unit (includes vent adapter except
for 140 kBtuh units)
1 - Vent adapter (140 kBtuh units only)
The following additional items may be ordered separately,
if required:
1 - Thermostat
1 - External filter rack kit
1 - Hanging bracket kit
1 - Propane/LP changeover kit
Check equipment for shipping damage. If you find any
damage, immediately contact the last carrier.
Requirements
Lennox G24M units are American Gas Association (AGA)
and Canadian Gas Association (CGA) 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 current Na
tional Fuel Gas Code (ANSIZ223.1) 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
In Canada, installation must conform with current National
Standard of Canada CAN/CGAB149.1 Installation Code
for Natural Gas Burning Appliances and Equipment" and
CAN/CGAB149.2 Installation Code for Propane Gas
Burning Appliances and Equipment," local plumbing or
waste water codes and other applicable local codes.
Page 3
Adequate clearance must be made around the air open
ings into the vestibule area. Provisions must be made for
proper operation and for combustion air and ventilation air
supply according to the current National Fuel Gas Code or
CAN/CGAB149 standards.
Vent installations must be according to the provided vent
ing tables and applicable provisions of local building codes.
This furnace is AGA and CGA certified for installation clear
ances to combustible material as listed on the unit rating plate
and in the tables in figures 5, 7 and 9. Accessibility and ser
vice 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 lo
cated no less than 18 inches (457 mm) above the floor. The
furnace must be located or protected to avoid physical dam
age by vehicles. When a furnace is installed in a public garage,
hangar, or other building that has a hazardous atmosphere,
the furnace must be installed according to recommended
good practice requirements and current National Fuel Gas
Code or CAN/CGA B149.1 and B149.2 standards.
The furnace must be adjusted to obtain a temperature rise
within the range specified on the unit rating plate.
The G24M furnace must be installed so that electrical com
ponents are protected from water.
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.
Field wiring connections must meet or exceed specifica
tions of type T wire and withstand a maximum temperature
rise of 180°F (82°C) .
When the furnace is installed so that supply ducts carry air
circulated by the furnace to areas outside of the space con
taining the furnace, return air shall be handled by a duct(s)
sealed to the furnace casing and terminating outside space
containing furnace.
NOTE - G24M series units must not be used as a construc
tion heater during any phase of construction. Very low re
turn air temperatures, harmful vapors and misplacement of
the filters will damage the unit and lower its efficiency.
The Lennox G24M furnace may be installed in alcoves,
closets, attics, basements, garages and utility rooms in the
upflow, downflow, or horizontal position.
This furnace design has not been AGA or CGA certified for
installation in mobile homes, recreational vehicles, or out
doors.
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.
When the furnace is used with cooling units, it shall be
installed in parallel with, or on the upstream side of, cooling
units to avoid condensation in the heating compartment.
With a parallel flow arrangement, a damper (or other means
to control the flow of air) must adequately prevent chilled air
from entering the furnace. If the damper is manually oper
ated, 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 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
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 should be considered
when installing the Lennox G24M furnace.
The furnace should be placed as close to the center of the
air distribution system as possible. The furnace should also
be located close to the chimney or vent termination point.
Do not install the furnace where drafts might blow directly
into it. This could cause improper combustion and unsafe
operation.
Do not block furnace combustion air openings with cloth
ing, boxes, doors, etc. Combustion air is needed for proper
combustion and safe unit operation.
When the furnace is installed in an attic or other insulated
space, keep insulation away from the furnace.
Page 4
WARNING
Product contains fiberglass wool.
Disturbing the insulation in this product during
installation, maintenance, or repair will expose you
to fiberglass wool. Breathing this may cause lung
cancer. (Fiberglass wool is known to the State of
California to cause cancer.)
Fiberglass wool may also cause respiratory, skin,
and eye irritation.
To reduce exposure to this substance or for further
information, consult material safety data sheets
available from address shown below, or contact your
supervisor.
Lennox Industries Inc.
P.O. Box 799900
Dallas, TX 75379-9900 USA
Combustion, Dilution & Ventilation Air
In the past, there was no problem in bringing in sufficient out
door air for combustion. Infiltration provided all the air that was
needed. In today's homes, tight construction practices make it
necessary to bring in air from outside for combustion. Take into
account that exhaust fans, appliance vents, chimneys, and
fireplaces force additional air that could be used for combus
tion out of the house. Unless outside air is brought into the
house for combustion, negative pressure (outside pressure is
greater than inside pressure) will build to the point that a down
draft can occur in the furnace vent pipe or chimney. As a result,
combustion gases enter the living space creating a potentially
dangerous situation.
In the absence of local codes concerning air for combustion
and ventilation, use the guidelines and procedures in this
section to install G24M furnaces to ensure efficient and safe
operation. You must consider combustion air needs and re
quirements for exhaust vents and gas piping. A portion of this
information has been reprinted with permission from the Na
tional Fuel Gas Code (ANSIZ223.1). This reprinted material
is not the complete and official position of the ANSI on the ref
erenced subject, which is represented only by the standard in
its entirety.
In Canada, refer to the standard CAN/CGA B149.1 and
B149.2 installation codes.
CAUTION
Do not install furnace in a corrosive or contaminated
atmosphere. Meet all combustion and ventilation air
requirements, as well as all local codes.
WARNING
Product contains fiberglass wool.
Disturbing the insulation in this product during
installation, maintenance, or repair will expose you
to fiberglass wool. Breathing this may cause lung
cancer. (Fiberglass wool is known to the State of
California to cause cancer.)
Fiberglass wool may also cause respiratory, skin,
and eye irritation.
To reduce exposure to this substance or for further
information, consult material safety data sheets
available from address shown below, or contact your
supervisor.
Lennox Industries Inc.
P.O. Box 799900
Dallas, TX 75379-9900 USA
All gasfired appliances require air for the combustion pro
cess. If sufficient combustion air is not available, the fur
nace or other appliance will operate inefficiently and un
safely. Enough air must be provided to meet the needs of all
fuelburning appliances and appliances such as exhaust
fans which force air out of the house. When fireplaces, ex
haust fans, or clothes dryers are used at the same time as
the furnace, much more air is required to ensure proper
combustion and to prevent a downdraft. Insufficient air
causes incomplete combustion which can result in carbon
monoxide.
In addition to providing combustion air, fresh outdoor air 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
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.
Page 5
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 com
bined 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 cir
culated by the furnace to areas outside the space containing
the furnace, the return air must be handled by ducts which are
sealed to the furnace casing and which terminate outside the
space containing the furnace. This is especially important
when the furnace is mounted on a platform in a confined space
such as a closet or small equipment room. Even a small leak
around the base of the unit at the platform or at the return air
duct connection can cause a potentially dangerous negative
pressure condition. Air for combustion and ventilation can be
brought into the confined space either from inside the building
or from outside.
EQUIPMENT IN CONFINED SPACE
CHIMNEY
OR GAS
VENT
G24M
FURNACE
NOTE-Each opening shall have a free area of at least one square
inch (645 mm2) per 1,000 Btu (.29 kW) per hour of the total input rat
ing of all equipment in the enclosure, but not less than 100 square
inches (64516 mm2).
ALL AIR FROM INSIDE
WATER
HEATER
OPENINGS
(To Adjacent
Room)
FIGURE 1
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 rat
ing 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 1.
Air from Outside
If air from outside is brought in for combustion and ventilation,
the confined space must have two permanent openings. One
opening shall be within 12 inches (305 mm) of the top of the
enclosure and one opening within 12 inches (305 mm) of the
bottom. These openings must communicate directly or by
ducts with the outdoors or spaces (crawl or attic) that freely
communicate with the outdoors or indirectly through vertical
ducts. Each opening shall have a minimum free area of 1
square inch (645 mm2) per 4,000 Btu (1.17 kW) per hour of
total input rating of all equipment in the enclosure. See figures
2 and 3. When communicating with the outdoors through hori
zontal 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 4.
When ducts are used, they shall be of the same cross-sec
tional area as the free area of the openings to which they con
nect. The minimum dimension of rectangular air ducts shall
be no less than 3 inches (75 mm). In calculating free area,
the blocking effect of louvers, grilles, or screens must be
considered. If the design and free area of protective covering
is not known for calculating the size opening required, it may
be assumed that wood louvers will have 20 to 25 percent free
area and metal louvers and grilles will have 60 to 75 percent
free area. Louvers and grilles must be fixed in the open posi
tion or interlocked with the equipment so that they are opened
automatically during equipment operation.
Page 6
CHIMNEY OR
GAS VENT
EQUIPMENT IN CONFINED SPACE
ALL AIR FROM OUTSIDE
(Inlet Air from Crawlspace and Outlet Air to Ventilated
Attic)
VENTILATION LOUVERS
(Each end of attic)
CHIMNEY
OR GAS
VENT
G24M
FURNACE
VENTILATION
LOUVERS
(For unheated crawl space)
OUTLET
AIR
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.
FIGURE 2
EQUIPMENT IN CONFINED SPACE
ALL AIR FROM OUTSIDE
(All Air Through Ventilated Attic)
VENTILATION LOUVERS
(Each end of attic)
OUTLET
AIR
WATER
HEATER
INLET
AIR
EQUIPMENT IN CONFINED SPACE
ALL AIR FROM OUTSIDE
CHIMNEY
OR GAS
VENT
WATER
HEATER
G24M
FURNACE
NOTE-The inlet and outlet air openings shall each have a
free area of at least one square inch (645 mm2) per 4,000
Btu (1.17 kW) per hour of the total input rating of all equip
ment in the enclosure.
FIGURE 3
INLET AIR
(Ends 12" above
bottom)
WATER
HEATER
Page 7
OUTLET AIR
G24M
FURNACE
INLET AIR
NOTE-Each air duct opening shall have a free area of at least
one square inch (645 mm2) per 2,000 Btu (.59 kW) per hour of
the total input rating of all equipment in the enclosure. If the
equipment room is located against an outside wall and the air
openings communicate directly with the outdoors, each 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.
FIGURE 4
Setting Equipment
The Lennox G24M multiposition gas furnace can be
installed as shipped in upflow or horizontal position with
righthand or lefthand discharge. The furnace can easi
ly be converted for downflow applications.
Select a location that allows for required clearances
listed on the unit rating plate. Also consider gas supply
connections, electrical supply, vent connection and
installation and service clearances [24 inches (610 mm)
at unit front].
NOTE - 1/3 and 1/2 hp blower motors are equipped with ei
ther 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 before the
furnace is put into operation. Once the shipping bolt and
washer are removed, the rigid leg will not touch the fan
housing.
Upflow Applications
The Lennox G24M furnace is shipped in a standard upflow
position. Level the furnace using shims or leveling bolts. Four
knockouts in the furnace base panel are factory-provided for
the installation of leveling bolts (field-provided). Allow for
clearances to combustible materials as indicated on the unit
rating plate. Minimum clearances for closet or alcove installa
tions are shown in figure 5.
In upflow applications, 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 airtight
seal between the bottom of the furnace and the platform to
ensure proper and safe operation.
Knockouts are provided on both sides of the furnace cabi
net for installations with side return air. When side return air
is used, seal the bottom of the furnace using the panel pro
vided.
An upflow filter rack is available and must be ordered sepa
rately. The adjustable rack can be installed beneath the fur
nace (flush with cabinet edges) for bottom return air ap
plications or on the side of the furnace for side return air.
Upflow Application
Installation Clearances
TOP
LEFT
SIDE
BOTTOM
Vent
Connector
Type
TOP 1 in. (25 mm)
*FRONT 2 in. (51 mm)
BACK 0
SIDES 0
VENT 1 in. (25 mm)
*Front clearance in alcove installation must be 24 in. (610
mm). Maintain a minimum of 24 in. (610 mm) for front service
access.
** For installations on a combustible floor, do not install the
furnace directly on carpeting, tile or other combustible mate
rials other than wood flooring.
Type C Type B1
1 in. (25 mm)
2 in. (51 mm)
0
0
6 in. (152 mm)
0**FLOOR 0**
RIGHT
SIDE
FIGURE 5
UNIT CONVERSION FOR DOWNFLOW APPLICATION
REMOVE
TOP CAP
REMOVE
FOUR
SCREWS
REMOVE
BOTTOM
UPFLOW CONFIGURATION DOWNFLOW CONFIGURATION
SINGLE-WALLED VENT
PIPE FROM COMBUSTION
AIR BLOWER FLUE
ADAPTER TO FURNACE
FLUE OUTLET
(Furnished by installer)
WIRE HARNESS JACK
PLUGS AND SENSOR
LEAD AT CONTROL
DISCONNECT WIRE
HARNESS JACKPLUGS
AND SENSOR LEAD
FROM CONTROL
BOARD
FIGURE 6
Page 8
RECONNECT
BOARD
REINSTALL
TOP CAP ON
UNIT BOTTOM
ROTATE HEAT
EXCHANGER &
REINSTALL
REINSTALL
BOTTOM ON
UNIT TOP
Downflow Applications
The Lennox G24M furnace is shipped in the upflow config
uration and must be converted for downflow installation.
Refer to figure 6 and the following steps to convert the unit
for downflow installation:
1 - Place unit on its back and remove access panel.
2 - Disconnect wire harness jackplugs from control
board.
3 - Disconnect sensor lead from control board.
4 - Remove four screws securing cabinet top cap to cabi
net.
5 - Remove four screws holding heat exchanger assem
bly in place. Slide heat exchanger out through top of
cabinet.
6 - Rotate heat exchanger 180o and slide back into cabi
net through top. Resecure using four screws.
7 - Remove four screws securing cabinet bottom piece
to cabinet. Replace with cabinet top cap.
8 - Use four screws to install cabinet bottom piece where
cabinet top was.
9 - Reconnect sensor lead to control board.
10- Reconnect wire harness jackplugs to control board.
11- Replace unit access panel.
12- Use cord clip located on right side of furnace to
hold wiring away from hot surfaces in heating
compartment. Install two #10 sheet metal screws in
cabinet top to provide a better air seal.
In downflow applications, the unit can be installed in three dif
ferent ways: on noncombustible flooring, on combustible
floor using an additive base, or on a reverseflow cooling cab
inet. Do not drag unit across floor.
Allow clearances to combustible materials as indicated on
unit rating plate. Minimum clearances for closet or alcove
installations are shown in figure 7.
DOWNFLOW INSTALLATION CLEARANCES
TOP
(60 Hz. only)
A separate downflow filter kit is available for use in down
flow applications.
A-Installation on Non-Combustible Flooring
1 - Cut floor opening keeping in mind the clearances
listed on the unit rating plate. Also, keep in mind gas
supply and electrical supply, vent connections and
sufficient installation and service clearances. See
table 1 for correct floor opening size.
TABLE 1
NONCOMBUSTIBLE FLOOR OPENING
UNIT
G24M-45/60/75 19-3/4 502 15-1/4 388
G24M-100/120 19-3/4 502 18-3/4 477
G24M-140 19-3/4 502 21-1/2 546
NOTE - Floor opening dimensions listed are 1/4" (6mm) larger than unit
openings.
Front to Rear Side to Side
in mm in mm
2 - Flange warm air plenum and lower into opening.
3 - Set unit over plenum.
4 - Check to see that an adequate seal is made.
B-Installation on Combustible Flooring
1 - When unit is installed on a combustible floor, an addi
tive base (ordered separately) must be installed be
tween the furnace and the floor. See table 2 for open
ing size to cut in the floor.
TABLE 2
ADDITIVE BASE FLOOR OPENING
UNIT
G24M-45/60/75 21-7/8 556 17-5/16 440
G24M-100/120 21-7/8 556 20-3/4 528
G24M-140 21-7/8 556 23-1/2 597
NOTE - Floor opening dimensions listed are 1/4" (6mm) larger than addi
tive base openings.
COMBUSTIBLE FLOORING INSTALLATION
Front to Rear Side to Side
in mm in mm
LEFT
SIDE
BOTTOM
VENT
CONNECTOR
TOP 1" (25mm) 1" (25mm)
*FRONT 2" (51mm) 2" (51mm)
BACK 00
SIDES 00
VENT 6" (152mm) 1" (25mm)
FLOOR NC** NC**
NC - Non-combustible floor
*Front clearance in alcove installation must be a min. of 24" (610mm)
for front service access.
**With additive base on combustible floor.
TYPE C TYPE B1
FIGURE 7
RIGHT
SIDE
Page 9
G24M UNIT
ADDITIVE
BASE
1. Cut correct size floor opening
2. Set additive base into opening.
3. Set supply air plenum into additive base.
4. Set unit.
FIGURE 8
SUPPLY AIR
PLENUM
PROPERLY
SIZED FLOOR
OPENING
2 - After opening is cut, set the additive base into opening.
3 - Check fiberglass strips on additive base to make sure
they are properly glued and positioned.
4 - Lower supply air plenum into additive base until ple
num flanges seal against fiberglass strips.
5 - Set unit on additive base so unit flanges drop into ple
num. Refer to figure 8.
NOTE – Be careful not to damage fiberglass strips.
Check for tight seal.
C-Installation on Cooling Cabinet
1 - Refer to reverseflow coil installation instructions for
correctly sized opening in floor and installation of cabi
net.
2 - When cooling cabinet is in place, install furnace so
flanges drop inside cabinet opening.
3 - Seal cabinet and check for air leakage.
Horizontal Applications
The Lennox G24M furnace can be installed in horizontal
applications in either upflow or downflow configuration
(See figure 6). It is preferable to install the unit in the stan
dard upflow configuration, if possible, because the vent
pipe will not interfere with service access for blower. Install
two #10 screws in the cabinet bottom (upflow configura
tion) or cabinet top (downflow configuration) to provide a
better air seal. The unit cannot be installed on its back.
Horizontal Application
Installation Clearances
LEFT
SIDE
Vent
Connector
Type
TOP 00
*FRONT 2 in. (51 mm) 2 in. (51 mm)
BACK 00
SIDES 2 in. (51 mm) 2 in. (51 mm)
VENT
FLOOR 0** 0**
TOP
BOTTOM
Type C
6 in. (152 mm)
RIGHT
SIDE
Type B1
1 in. (25 mm)
See figure 10 for furnace installations on a platform.
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 air conditioning coil to drain.
Horizontal Application
NOTE - Line contact is permissible. See the unit rating plate for clearances.
Unit Installed on Platform
GAS
ENTRY
VENT
PIPE
WORKING
PLATFORM
FIGURE 10
Anyone of the following methods may be used to suspend the
furnace from roof rafters or floor joists:
1 - Using Lennox hanging bracket kit catalog num
ber 46J66 Install as indicated in the installation instructions
provided with the hanging bracket kit.
2 - Using angle iron with at least 1/4 in. diameter
rods Install as shown in figure 11.
Note - Rods must not interfere with plenum or ex
haust piping; cooling coils and supply and return
air plenums must be supported separately.
Unit Suspended in Attic or Crawlspace
Level unit - side to side and end to end.
Leave sufficient clearance between rod and unit to
remove access panels.
Horizontal Application
Using Angle Iron and Rods
*Front clearance in alcove installation must be 24 in.
(610 mm). Maintain a minimum of 24 in. (610 mm) for
front service access.
** For installations on a combustible floor, do not install
the furnace directly on carpeting, tile or other combus
tible materials other than wood flooring.
FIGURE 9
Allow for clearances to combustible materials as indicated
on the unit rating plate. Minimum clearances for closet or
alcove installations are shown in figure 9.
Furnaces may be installed in either an attic or a crawlspace.
Page 10
1/4 in. ROD
ANGLE
SUPPORT TIES -
INSTALL TO PREVENT
SPREADING
Secure the angle iron to the unit with sheetmetal screws:
maximum screw length - 3/4 in. and minimum screw size - # 10.
IRON
FIGURE 11
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