Lennox G24M2-45, G24M3-75, G24M2-60, G24M4-75, G24M3/4-100 Installation Instructions Manual

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

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.

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G24M Unit Dimensions - inches (mm)

G24M3/4120

GAS PIPING

INLET

2 (51)

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 191/2 inches (495 mm) or 19 inches (483 mm).

41/4 (105)

2 (51)

AIR FLOW

F Left Side G Right Side

ELECTRICAL INLETS

(Top & Bottom)

(25)

*191/2

(495)

*19

(483) SUPPLY

AIR

OPENING

TOP VIEW

295/8

(752)

GAS PIPING

INLET

(Both Sides)

(25)

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

G24M245 G24M260 G24M360 G24M375 G24M475

G24M3/4100 G24M3/4120 G24M4/5100 G24M4/5120

G24M4/5140

in. 17 361/4 15 63/4 27/16 111/2 61/2

mm 432 921 381 171 62 293 165

in. 201/2 39 181/2 83/8 41/4 13 8

mm 521 991 470 213 108 331 203

in. 231/4 39 211/4 9-3/4 41/4 12-31/32 73/32

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

connection. The dimensions shown were

(25)

taken after the flange was bent.

(381)

**191/2

(495)

191/2

(495)

RETURN AIR KNOCKOUT (Either Side)

3/4 (19)

Return Air

Opening

(25)

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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 (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

In Canada, installation must conform with current National Standard of Canada CAN/CGAB149.1 Installation Code for Natural Gas Burning Appliances and Equipment" and CAN/CGAB149.2 Installation Code for Propane Gas Burning Appliances and Equipment," local plumbing or waste water codes and other applicable local codes.

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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/CGAB149 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.

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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 (ANSIZ223.1). 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.

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 gasfired 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 fuelburning 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.

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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.

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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

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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

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Setting Equipment

The Lennox G24M multiposition gas furnace can be installed as shipped in upflow or horizontal position with righthand or lefthand 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.

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

BOTTOM ON

UNIT TOP

Page 9

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 noncombustible flooring, on combustible floor using an additive base, or on a reverseflow 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

Page 10

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 reverseflow 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

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

Page 11

3 - Using heavy gauge perforated steel straps

(plumber's straps") Install as shown in figure 12.

Note - Straps 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

Using Heavy Gauge Perforated Steel Straps

Level unit - side to side and end to end.

PLUMBER'S

STRAPS

Horizontal Application

(Plumber's Straps")

Inches (mm)

Use existing blower deck screws to secure

straps. Also use washers, if required.

11/2 (38)

213/16 (72)

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.

Duct System

101/4 (260)

At the unit's top corners, secure each strap to the furnace, positioned

as shown, using at least two sheetmetal screws: maximum screw length - 3/4 in. and minimum screw size - # 10.

TOP OF UNIT

RETURN AIR

OPENING

END VIEW

11/2 (38)

1/2 (13)

TOP OF UNIT

SUPPLY AIR

OPENING

END VIEW

11/2 (38)

SUPPLY

AIR

11/2 (38)

1/2 (13)

FIGURE 12

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.

Supply Air Plenum

Furnaces installed without a cooling coil require the installa tion of a removable access panel in the supply air duct. The access panel should be large enough to permit inspection (ei ther by smoke or reflected light) of the heat exchanger for leaks after installation . The furnace access panel must al ways be in place when the furnace is operating and it must not allow leaks into the supply air duct system.

Return Air Plenum 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.

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. Use fiberglass sealing strips between the plenum and the furnace cabinet to en sure a tight seal. If a filter is installed, size the return air duct to fit the filter frame.

In downflow applications, use the following steps when instal ling return air plenum:

1 - Flange bottom edge of plenum with a hemmed edge.

See figure 13.

2 - Use fiberglass sealing strips between plenum and the

unit cabinet to ensure a tight seal.

Page 11

Page 12

3 - In all cases, secure the plenum to the top flanges of the

furnace using sheet metal screws. See figure 13.

PLENUM

FIBERGLASS

SEALING STRIP

SECURE

HEMMED EDGE

CABINET

SIDE PANEL

FIGURE 13

4 - In closet installations, it may be necessary to install

sheet metal screws from the inside. If this is the case, make plenum with a removable front to install screws as shown in figure 14.

SECURE FROM

INSIDE

FIBERGLASS

SEALING STRIP

PLENUM

HEMMED EDGE

CABINET

SIDE PANEL

FIGURE 14

Venting

Venting Using a Masonry Chimney

The following additional requirements apply when a lined masonry chimney is used to vent an G24M 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 15 and 16 for com mon venting.

A Category I appliance must never be connected to a chim ney 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 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 according

to the provided venting tables for the USA, and the ap propriate venting tables in the standards of CAN/CGA B149.1 and B149.2 of the Natural Gas and Propane Installation Code in Canada.

A vent adapter is factoryinstalled on the combustion air blower outlet of all models, except the G24M-140. On the G24M-140, the flue adapter is supplied with the furnace, and must be fieldinstalled, between the combustion air blower flue outlet and the vent connector, using one or two corrosionresistant screws. Modification of or failure to

install the adapter will cause unsafe unit operation and will void AGA and CGA unit certification. The vent con

nector does not require insulation.

The G24M series units are classified as fan-assisted Cate gory I furnaces when vertically vented according to the latest edition of ANSI Z21.47 Central Furnace Standard in the USA and the current standards of CAN/CGA B149.1 and B149.2 of the Natural Gas and Propane Installation Code in Canada. A fan-assisted Category I furnace is an appliance equipped with an integral mechanical means to either draw or force products of combustion through the combustion chamber and/or heat exchanger.

NOTE - Use these instructions as a guide. They do not su persede local codes.

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. Proper application, 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.

Install the first vent connector elbow a minimum of 6 inches (152 mm) from the furnace vent outlet.

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, sized according to the provided venting tables.

A type B1 vent or masonry chimney liner shall terminate above the roof surface with a listed cap or a listed roof assembly ac cording to the terms of their respective listings and the vent manufacturer's instructions.

Do not install a manual damper, barometric draft regulator, or flue restrictor between the furnace and the chimney.

If type B1 doublewall vent is used inside a chimney, no oth er appliance can be vented into the chimney. Outer wall of type B1 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 15.

The space between the liner and the chimney wall should NOT be insulated with puffed mica or any other loose granular insulating material.

If B1 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 method 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 na tionally recognized standards, lined or relined with suitable materials or replaced with a gas vent or chimney suitable for venting G24M series units. The chimney passageway must be checked periodically to ensure that it is clear and free of obstructions.

Page 12

Page 13

Common Venting Using Metal-lined Masonry Chimney

SEALED

MAX. LENGTH

-- SEE NOTE 1

5 ft. (1.5 m)

minimum

4 in. (102 mm)

minimum

APPLIANCE

VENT CONNECTOR

SEE NOTE 2

OTHER

BELOW.

MIN. LENGTH -- AS

SHORT AS PRACTICAL

G24M

EXTERIOR

CHIMNEY WITH

B1 VENT OR

INSULATED

VENT PIPE.

PERMANENTLY

SEALED FIREPLACE

OPENING

FLEXIBLE

NOTE 1 - Refer to the provided venting tables for installations in the USA and the venting tables in CAN/CGA-B149.1 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 CAN/CGA-B149.1 for installations in Canada.

FIGURE 15

Common Venting Using Tile-lined Interior Masonry

Chimney and Combined Vent Connector

NOTE- Refer to provided venting tables for installations in the USA and the venting tables in current CAN/CGAB149.1 for installations in Canada.

MINIMUM LENGTH = AS SHORT AS PRACTICAL. FOR MAXIMUM LENGTH SEE NOTE TO LEFT

INTERIOR TILE-LINED MASONRY CHIMNEY

NOTE - chimney must be properly sized per provided venting tables or lined with listed metal lining system.

VENT

CONNECTOR

OTHER

APPLIANCE

G24M

SEE NOTE 1 BELOW

PERMANENTLY SEALED FIREPLACE OPENING

Note 1 - 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 CAN/CGA-B149.1 for installations in Canada.

FIGURE 16

General Venting Requirements

All G24M furnaces must be vented according to these instructions. 1 - Vent diameter recommendations and maximum al

lowable piping runs are found in the provided venting tables for the USA, and the appropriate venting tables

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 vent ing tables in the standards of CAN/CGA B149.1 and B149.2 of the Natural Gas and Propane Installation Code for Canada.

in the standards of CAN/CGA B149.1 and B149.2 of the Natural Gas and Propane Installation Code for Canada.

Page 13

Page 14

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 maximum vent capacity. The flow area of the vertical vent, how

ever, shall not exceed 7 times the flow area of the listed appliance categorized vent area, drafthood out let area or flue collar area unless designed according to approved engineering methods.

4 - For multiple appliance vents: The flow area of the larg

est 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.

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, see tables 4 and 5, are assumed to have no elbows in the vent system. For all other vent config urations, 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) be yond two, the maximum capacity listed in the venting table should be reduced by 10 percent (0.90 x maxi mum listed capacity).

7 - The common venting tables 6, 7, 8, and 9 were gener

ated 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 3

Connector

Diameter

inches (mm)

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)

Maximum Horizontal

Connector Length

feet (m)

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 ex ceed 11/2 feet (.46 m) for each inch (25 mm) of com mon vent diameter.

9 - The vent pipe should be as short as possible with

the least number of elbows and angles required to complete 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. See local and national installation codes for support intervals and methods. National installation code in the USA is current edition of Na tional fuel Gas Code (ANSI-Z223.1). National installa tion codes in Canada are current editions of CAN/ CGA-B149 codes.

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 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 maximum 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 dedicated

or common venting system, the venting system 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 for the USA, and the appropriate venting tables in the standards of CAN/CGA B149.1 and B149.2 of the Natural Gas and Propane Installation Code for Canada. If the existing system is in conflict with these requirements, the venting system must be re sized.

Page 14

Page 15

TABLE 4

(

)L(

)

(feet)

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

feet

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).

Lateral

feet

0 0 78 0 152 0 251 0 375

2 13 51 18 97 27 157 32 232

4 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

2 12 57 16 109 25 178 28 263

5 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

2 12 61 17 118 23 194 26 289

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

5 22 65 30 130 39 219 49 330

10 29 59 40 121 51 206 64 315

15 35 53 48 11 2 61 195 76 301

0 0 97 0 202 0 349 0 540

2 10 75 14 149 18 250 20 377

5 21 71 29 143 38 242 47 367

10 28 64 38 133 50 229 62 351

15 34 58 46 124 59 217 73 337

20 48 52 55 11 6 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

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

3 Inch 4 Inch 5 Inch 6 Inch

Appliance Input Rating in Thousands of Btu Per Hour

MIN MAX MIN MAX MIN MAX MIN MAX

Page 15

Page 16

TABLE 5

(

)L(

)

(feet)

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

feet

Lateral

feet

0 38 77 59 151 85 249 126 373

2 39 51 60 96 85 156 123 231

4 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

2 39 56 59 108 83 176 121 261

5 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

2 39 61 59 117 82 193 11 9 287

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 11 6 499

2 38 69 57 136 80 225 11 5 337

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 11 4 537

2 37 74 56 148 78 248 11 3 375

5 50 68 73 140 100 239 141 363

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

10 NR NR 91 144 122 255 171 397

15 NR NR 11 5 131 151 239 208 377

20 NR NR NR NR 181 223 246 357

30 NR NR NR NR NR NR NR NR

3 Inch 4 Inch 5 Inch 6 Inch

Appliance Input Rating in Thousands of Btu Per Hour

MIN MAX MIN MAX MIN MAX MIN MAX

Page 16

Page 17

ent

Height

Rise

Height

(feet) (feet)

onnector

Rise

TABLE 6

VENT CONNECTOR CAPACITY

TYPE B DOUBLE-WALL VENTS WITH TYPE B DOUBLE-WALL CONNECTORS

SERVING TWO OR MORE CATEGORY I APPLIANCES

Vent and Connector Diameter - D (inches)

3 Inch 4 Inch 5 Inch 6 Inch

MIN MAX MIN MAX MIN MAX MIN MAX

1 22 37 35 66 46 106 58 164

2 23 41 37 75 48 121 60 183

3 24 44 38 81 49 132 62 199

1 22 40 35 72 49 114 64 176

2 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

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

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

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

2 21 64 33 118 47 190 62 299

3 22 66 34 123 48 198 64 309

Appliance Input Rating in Thousands of Btu Per Hour

TABLE 7

COMMON VENT CAPACITY

TYPE B DOUBLE-WALL VENTS WITH TYPE B DOUBLE-WALL CONNECTORS

SERVING TWO OR MORE CATEGORY I APPLIANCES

ent

Height

(feet)

6 92 81 140 11 6 204 161 309 248

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

FAN + FAN FAN + NAT FAN + FAN FAN + NAT FAN + FAN FAN + NAT FAN + FAN FAN + NAT

4 Inch 5 Inch 6 Inch 7 Inch

Appliance Input Rating in Thousands of Btu Per Hour

Common Vent Diameter - D (inches)

Page 17

Page 18

TABLE 8

Height

Rise

Height

VENT CONNECTOR CAPACITY

TYPE B DOUBLE-WALL VENTS WITH SINGLE-WALL METAL CONNECTORS

SERVING TWO OR MORE CATEGORY I APPLIANCES

ent

Height

(feet) (feet)

onnector

Rise

1 NR NR NR NR NR NR NR NR

2 NR NR NR NR NR NR 168 182

3 NR NR NR NR 121 131 174 198

1 NR NR 79 87 116 138 177 214

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

2 50 62 81 115 117 185 177 290

3 54 64 85 119 122 193 185 300

3 Inch 4 Inch 5 Inch 6 Inch

MIN MAX MIN MAX MIN MAX MIN MAX

Vent and Connector Diameter - D (inches)

Appliance Input Rating in Thousands of Btu Per Hour

TABLE 9

COMMON VENT CAPACITY

TYPE B DOUBLE-WALL VENTS WITH SINGLE-WALL METAL CONNECTORS

SERVING TWO OR MORE CATEGORY I APPLIANCES

ent

Height

(feet)

6 89 78 136 11 3 200 158 304 244

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

FAN + FAN FAN + NAT FAN + FAN FAN + NAT FAN + FAN FAN + NAT FAN + FAN FAN + NAT

4 Inch 5 Inch 6 Inch 7 Inch

Appliance Input Rating in Thousands of Btu Per Hour

Common Vent Diameter - D (inches)

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 properly vent the remaining attached appliances. The fol lowing test should be conducted while each appliance in operation and the other appliances not in operation re main connected to the common venting system. If the venting system has been installed improperly, the system must be corrected as indicated in the general venting re quirements section.

1 - Seal any unused openings in the common venting

system.

2 - Visually inspect the venting system for proper size and

horizontal pitch. Determine there is no blockage or re striction, leakage, corrosion, or other deficiencies 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 ap pliances not connected to the common venting sys tem. Turn on any exhaust fans, such as range hoods and bathroom exhausts, so they will operate at maxi mum speed. Do not operate a summer exhaust fan. Close fireplace dampers.

4 - Follow the lighting instructions. Place the appliance

being inspected in operation. Adjust thermostat so ap pliance 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 ciga rette, cigar or pipe.

Page 18

Page 19

6 - After determining that each appliance remaining con

nected to the common venting system properly vents when tested as indicated in step 3, return doors, win dows, exhaust fans, fireplace dampers and any other gasburning appliance to their previous condition of use.

7 - If improper venting is observed during any of the

above tests, the common venting system must be cor rected. The common venting system should be re sized to approach the minimum size as determined by using the appropriate tables in appendix G in the cur rent standards of the National Fuel Gas Code ANSI Z223.1 in the USA, and the appropriate Category 1 Natural Gas and Propane appliances venting sizing tables in the current standards of the CAN/CGA B149.1 and B149.2 in the Natural Gas and Propane Installation Code in Canada.

Horizontal Venting

Side Wall Venting Kit Wiring

CK-43 CONTROL BOX

THERMOSTAT CONNECTIONS

TERMINAL IN FURNACE

JUNCTION BOX

WR Y G

SWG POWER VENTER

MOTOR

FACTORY-INSTALLED WIRING FIELD-INSTALLED WIRING

THERMOSTAT

24 VAC

PRESSURE

SWITCH

120VAC

L1 MN

354

RELAY

T1 T2 T3

FIGURE 17

When horizontally vented, the minimum clearance for termination from electric meters, gas meters, regulators and relief equipment is 4 feet (1.2 m) for US installations. Refer to the current CAN/CGA B149.1 and B149.2 for installations in Canada or with authorities having local ju risdiction.

At vent termination, care must be taken to maintain pro tective coatings over building materials (prolonged expo sure to exhaust condensate can destroy protective coat ings). It is recommended that the exhaust outlet not be located within 6 feet (1.8 m) of a condensing unit because the condensate can damage the painted coating.

Gas Piping

GAS SUPPLY

1 - This unit is shipped standard for left or right side instal

lation of gas piping (or top entry in horizontal applica tions). Connect the gas supply to the piping assembly.

2 - When connecting the gas supply, factors such as

length of run, number of fittings and furnace rating must be considered to avoid excessive pressure drop. Table 10 lists recommended pipe sizes for typical ap plications.

3 - The gas piping must not run in or through air ducts,

clothes chutes, gas vents or chimneys, dumb waiters or elevator shafts.

4 - The piping should be sloped 1/4 inch (6.4 mm) per 15 feet

(4.57 m) upward toward the meter from the furnace. The piping must be supported at proper intervals [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.

5 - In some localities, codes may require installation of a

manual main shutoff valve and union (furnished by the installer) external to the unit. Union must be of the ground joint type.

This furnace design is certified by the American Gas Association and the Canadian Gas Association for hori zontal venting through an outside wall only with the use of a Field Controls Company Model SWG4L side wall venting kit available as Lennox part number 79J15. 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 17 for field wiring of side wall horizontal venting kit.

IMPORTANT

Compounds used on threaded joints of gas piping must be resistant to the actions of liquified petro leum gases.

NOTE - Install a 1/8 inch NPT plugged tap in the field piping upstream of the gas supply connection to the unit. The tap must be accessible for test gauge connection. See figure 18.

NOTE - In case emergency shutoff is required, shut off main manual gas valve and disconnect main power to unit. These devices should be properly labeled by the installer.

Page 19

Page 20

TABLE 10

Nominal

Internal

GAS PIPE CAPACITY - FT3/HR (M3/HR)

Nominal Internal

Iron Pipe Size

inches (mm)

1/4

(6.35)

3/8

(9.53)

1/2

(12.7)

3/4

(19.05)

(25.4)

1-1/4

(31.75)

1-1/2

(38.1)

(50.8)

2-1/2

(63.5)

(76.2)

(101.6)

Diameter

inches (mm)

.364

(9.246)

.493

(12.522)

.622

(17.799)

.824

(20.930)

1.049

(26.645)

1.380

(35.052)

1.610

(40.894)

2.067

(52.502)

2.469

(67.713)

3.068

(77.927)

4.026

(102.260)

(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)

(1.13)

(2.69)

175

(4.96)

360

(10.19)

680

(919.25)

1400

(39.64)

2100

(59.46)

3950

(111.85)

6300

(178.39)

11000

(311.48)

23000

(651.27)

(.82)

(1.84)

120

(3.40)

250

(7.08)

465

(13.17)

950

(26.90)

460

(41.34)

2750

(77.87)

4350

(123.17)

7700

(218.03)

15800

(447.39)

(.68)

(1.47)

(2.75)

200

(5.66)

375

(10.62)

770

(21.80)

1180

(33.41)

2200

(62.30)

3520

(99.67)

6250

(176.98)

12800

(362.44)

NOTE-Capacity given in cubic feet (m3 ) of gas per hour and based on 0.60 specific gravity gas.

Length of Pipe - feet (m)

(.57)

(1.27)

(2.32)

170

(4.81)

320

(9.06)

660

(18.69)

990

(28.03)

1900

(53.80)

3000

(84.95

5300

(150.07)

10900

(308.64)

(.51)

(1.13)

(2.07)

151

(4.28)

285

(8.07)

580

(16.42)

900

(25.48)

1680

(47.57)

2650

(75.04)

4750

(134.50)

9700

(274.67)

(.45)

(1.02)

(1.87)

138

(3.91)

260

(7.36)

530

(15.01)

810

(22.94)

1520

(43.04)

2400

(67.96)

4300

(121.76)

8800

(249.18)

(.42)

(.73)

(1.73)

125

(3.54)

240

(6.80)

490

(13.87)

750

(21.24)

1400

(39.64)

2250

(63.71)

3900

(110.43)

8100

(229.36)

(.40)

(.88)

(1.61)

118

(3.34)

220

(6.23)

460

(13.03)

690

(19.54)

1300

(36.81)

2050

(58.05)

3700

(104.77)

7500

(212.37)

(.37)

(.82)

(1.50)

110

(3.11)

205

(5.80)

430

(12.18)

650

(18.41)

1220

(34.55)

1950

(55.22)

3450

(97.69)

7200

(203.88)

100

(30.480)

(.34)

(.76)

(1.42)

103

(2.92)

195

(5.52)

400

(11.33)

620

(17.56)

1150

(32.56)

1850

(52.38)

3250

(92.03)

6700

(189.72)

Left Side Piping

(Standard)

MANUAL

MAIN SHUT-OFF

VALV E

(With 1/8 in. NPT

Plugged Tap Shown)

GROUND

JOINT

UNION

DRIP LEG

AUTOMATIC

GAS VALVE

(with manual

shut-off valve)

PROVIDED

AND INSTALLED

FIGURE 18

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 af ter leak test has been completed. Do not use matches, candles, flame or other sources of ignition to check for gas leaks.

NOTE - In case emergency shutoff is required, shut off the main manual gas valve and disconnect the main power to the furnace. These devices should be properly labeled by the installer.

The furnace must be isolated from the gas supply system by closing its individual manual shutoff valve during any

FIELD

AUTOMATIC

GAS VALVE

(with manual

shut-off valve)

MANUAL

MAIN SHUT-OFF

VALV E

(With 1/8 in. NPT

Plugged Tap

Shown)

GROUND

JOINT

UNION

DRIP LEG

Right Side Piping

(Alternate)

pressure testing of the gas supply system at pressures equal to or less than 1/2 psig (3.48 kPa).

IMPORTANT

When testing pressure of gas lines, gas valve must be disconnected and isolated. See figure 19. Gas valves can be damaged if subjected to more than 1/2 psig (3.48 kPa).

MANUAL MAIN

SHUT-OFF VALVE

WILL NOT HOLD

NORMAL TEST

PRESSURE

CAP

FIGURE 19

ISOLATE

GAS VALVE

FURNACE

Page 20

Page 21

Electrical

CAUTION

Electrostatic discharge can affect electronic com ponents. Take precautions during furnace installa tion and service to protect the furnace's electronic controls. Precautions will help to avoid control ex posure to electrostatic discharge by putting the fur nace, the control and the technician at the same electrostatic potential. Neutralize electrostatic charge by touching hand and all tools on an un painted unit surface, such as the gas valve or blow er deck, before performing any service procedure.

These units operate on 120 volt, single phase, 60 hz electrical power. Refer to figure 20 for field wiring and figure 22 for schematic wiring diagram and trouble shooting.

1 - Select circuit protection and wire size according to the

unit rating plate.

2 - Knockouts are provided on both sides of the furnace

cabinet to facilitate wiring.

3 - Install the room thermostat according to instructions

provided with the thermostat.

4 - Install a separate disconnect switch (protected by ei

ther fuse or circuit breaker) near the unit so power can be turned off for servicing.

5 - Before connecting the thermostat or the power wiring,

check to make sure the wires will be long enough to facilitate servicing at a later date. Remove the blower access panel and open the panel to check wire length for access.

6 - Complete wiring connections to the equipment using

wiring diagram provided with unit and wiring diagrams

shown in figures 20 and 22. Use 18 gauge wire or larg er for thermostat connections.

7 - Electrically ground the unit according to local codes or,

in the absence of local codes, according to the current National Electric Code (ANSI/NFPA No. 70) for the USA and current Canadian Electric Code part 1 (CSA standard C22.1) for Canada.

NOTE - The G24M furnace contains electronic com ponents that are polarity sensitive. Make sure that the furnace is wired correctly and is properly grounded.

8 - One line voltage accessory ACC" terminal is provided

on the furnace control board with a protective plastic cap. Any accessory rated up to 4 amps can be con nected to this terminal (after removing the protective cap) with the neutral leg of the circuit being connected to the line voltage neutral wire. See figure 21 for con trol board configuration. This terminal is energized whenever the blower is in operation.

9 - One line voltage heating accessory HTG ACC" termi

nal is provided on the furnace control board with a pro tective plastic cap. Any accessory rated up to 4 amps can be connected to this terminal (after removing the protective cap) with the neutral leg of the circuit being connected to the line voltage neutral wire. See figure 21 for control board configuration. This terminal is en ergized in the heating mode whenever the blower is in operation.

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 the G24M is running in the heating mode, the in

door blower will run on the heating speed.

3 - When there is a cooling demand, the indoor blower will

run on the cooling speed.

Page 21

Page 22

FIELD INSTALLED CLASS II 24V FIELD INSTALLED LINE VOLTAGE

TYPICAL G24M FIELD WIRING DIAGRAM

(120V, 1PH, 60HZ)

COMBUSTION

PRESSURE SWITCH

PRIMARY LIMIT

AIR BLOWER

120V, 1PH, 60 HZ

L1 N

FUSED OR CIRCUIT BREAKER

(FURNISHED BY INSTALLER)

DISCONNECT

GND

THERMOSTAT

TO COMPRESSOR

CONTACTOR

GAS

GWRY

FLAME ROLLOUT SWITCHES

TRANSFORMER

GWYCR

SURELIGHT CONTROL

VALV E

SECONDARY

LIMITS

DOOR

INTERLOCK

SWITCH

BLACK

WHITE

FIGURE 20

50A62 SureLight INTEGRATED CONTROL BOARD

(Silicon Nitride Ignition System)

ACB COOL ACB HEAT PARK ACB LOW ACC TX HOT HTG ACC NEUTRALS 24VAC HOT 24VAC RTN FLAME SENSE

TERMINAL DESIGNATIONS

Blower - Cooling Speed (Line Volt) Blower - Heating Speed (Line Volt) Alternate Blower Speeds (Dead) Continuous Low Speed Blower Accessory Terminal (Line Volt) 120VAC Hot to Transformer 120VAC Hot Input Heat Only Accessory (Line Volt) 120VAC Neutrals 24VAC Hot from Transformer 24VAC Return from Transformer Flame Sense Terminal

FIGURE 21

Page 22

Page 23

G24M Schematic Wiring Diagram

(120V, 1PH, 60HZ)

FIGURE 22

Page 23

Page 24

Unit Start-Up

WARNING

Do not use this furnace if any part has been underwa ter. Immediately call a qualified service technician to inspect the furnace and to replace any part of the control system and any gas control which has been under water.

WARNING

If overheating occurs or if gas supply fails to shut off, shut off the manual gas valve to the appliance before shutting off electrical supply.

CAUTION

Before attempting to perform any service or mainte nance, turn the electrical power to unit OFF at dis connect switch.

FOR YOUR SAFETY READ BEFORE LIGHTING

BEFORE LIGHTING smell all around the appliance area for

gas. Be sure to smell next to the floor because some gas is heavier than air and will settle on the floor.

Use only your hand to turn the gas control knob. Never use tools. If the knob will not turn by hand, do not try to repair it, call a qualified service technician. Force or attempted repair may result in a fire or explosion.

Placing Furnace Into Operation

G24M furnaces are equipped with a SureLight ignition system. Do not attempt to manually light burners on these furnaces. Each time the thermostat calls for heat, the burn ers will automatically light.

WARNING

If you do not follow these instructions exactly, a fire or explosion may result causing property damage, personal injury or death.

Gas Valve Operation (Figures 23 and 24)

1 - STOP! Read the safety information at the beginning of

this section.

2 - Set the thermostat to the lowest setting.

3 - Turn off all electrical power to the unit. 4 - This furnace is equipped with an ignition device which

automatically lights the burners. Do not try to light the burners by hand.

5 - Remove the access panel.

6 - White Rodgers 36E Gas Valve - Switch gas valve le

ver to OFF. See figure 23. Honeywell VR8205 Gas Valve - Turn knob on gas

valve clockwise to OFF. Do not force. See figure

24.

7 - Wait five minutes to clear out any gas. If you then smell

gas, STOP! Immediately call your gas supplier from a neighbor's phone. Follow the gas supplier's instructions. If you do not smell gas go to next step.

WHITE RODGERS 36E Series Gas Valve

MANIFOLD PRESSURE

ADJUSTMENT

SCREW

MANIFOLD

PRESSURE

OUTLET

GAS VALVE SHOWN IN OFF POSITION

FIGURE 23

HONEYWELL VR8205 Series Gas Valve

MANIFOLD

PRESSURE

ADJUSTMENT

SCREW

OFF

GAS VALVE SHOWN IN OFF POSITION

FIGURE 24

8 - White Rodgers 36E Gas Valve - Switch gas valve lever

to ON. Honeywell VR8205 Gas Valve - Turn knob on gas valve

counterclockwise to ON. Do not force.

9 - Replace the access panel.

10 - Turn on all electrical power to the unit.

11 - Set the thermostat to desired setting.

MANIFOLD

PRESSURE

OUTLET

NOTE – When unit is initially started, steps 1 through 11 may need to be repeated to purge air from gas line.

12 - If the appliance will not operate, follow the instructions

Turning Off Gas to Unit" and call your service techni cian or gas supplier.

Turning Off Gas to Unit

1 - Set the thermostat to the lowest setting. 2 - Turn off all electrical power to the unit if service is to be

performed. 3 - Remove the access panel. 4 - White Rodgers 36E Gas Valve - Switch gas valve le

ver to OFF.

Honeywell VR8205 Gas Valve - Turn knob on gas

valve clockwise to OFF. Do not force. 5 - Replace the access panel.

Page 24

Page 25

Heating Sequence Of Operation

NAT

3.5

3.5 (0.87)*

3.4 (0.85)

3.3 (0.82)

3.2 (0.80)

9.5

1 - When thermostat calls for heat, combustion air blower

starts.

2 - Combustion air pressure switch proves blower opera

tion. Switch is factory set and requires no adjustment.

3 - After a 15 second prepurge, hot surface ignitor ener

gizes.

4 - After a 20 second ignitor warm-up period, gas valve

solenoid opens.

5 - Gas is ignited, ignition sensor proves the flame and

combustion process continues.

6 - If flame is not detected after first ignition trial, ignition

control will repeat steps 3 and 4 four more times before locking out the gas valve (WATCHGUARD" flame fail ure mode). Ignition control will then automatically re peat steps 3, 4, 5 and 6 after 60 minutes.

7 - To interrupt the 60-minute WATCHGUARD" period,

move thermostat from Heat" to OFF" then back to Heat." Heating sequence then restarts at step 1.

Gas Pressure Adjustment

Gas Flow

To check for proper gas flow to the combustion chamber, de termine the Btu (kW) input from the unit rating plate. Divide this input rating by the Btu (kW) per cubic foot (cubic meter) of available gas. The result is the required number of cubic feet (cubic meter) per hour. Determine the flow of gas through the gas meter for two minutes and multiply by 30 to get the hourly flow of gas.

Gas Pressure

1 - Check the gas line pressure with the unit firing at maxi

mum rate. A minimum of 4.5 in. w.c. for natural gas or

11.0 in. w.c. for LP/propane gas should be maintained.

2 - After the line pressure has been checked and ad

justed, check the regulator pressure. Manifold pres sures are given in table 11. See figures 23 and 24 for manifold pressure adjustment screw location.

Note - A natural gas to LP/propane gas changeover kit is required to convert the unit.

High Altitude Information

Refer to table 11 for manifold pressure settings for installa tions at different altitudes and for different fuels.

TABLE 11

MANIFOLD ABSOLUTE PRESSURE (OUTLET) IN. W.C. (KPA)

Altitude - feet (m) above sea level

FUEL

0-2000

(0-610)

3.5

(0.87)

9.5

(2.36)

2000-4500 (610-1372)

9.5 (2.36

4500-5500

(1372-1676)

5500-6500

(1676-1981)

9.2 (2.29) 8.9 (2.21) 8.6 (2.14)

6500-7500

(1981-2286)

*No adjustment required. NOTE - In Canada, certification for installations at eleva tions over 4500 feet (1372 m) is the jurisdiction of local au thorities.

The combustion air pressure switches are factory-set and require no adjustment.

At elevations of 4500 feet (1372 m) or greater, replace the factoryinstalled pressure switch with the switch listed in table 12.

TABLE 12

Unit Model

G24M-45 NO CHANGE

G24M-60 NO CHANGE

G24M-75 88J8001

G24M-100 18L2401

G24M-120 18L2401

G24M-140-7 NO CHANGE

Pressure Switch

Part Number

Other Unit Adjustments

Primary and Secondary Limits

The primary limit is located on the heating compartment ves tibule panel. Two secondary limits are located in the blower compartment, behind the blower. These limits are factory-set and require no adjustment.

Flame Rollout Switches (Two)

These manually reset switches are located just above the burner box. If tripped, a check for adequate combustion air should be made before resetting.

Combustion Air Pressure Switch

The combustion air pressure switch is located on the heat ing compartment vestibule panel. This switch checks for proper combustion air blower operation before allowing ignition trial. The switch is factory-set and requires no ad justment.

Fan Control

The fan on time of 45 seconds is not adjustable. Fan off time (time that the blower operates after the heat demand has been satisfied) can be adjusted by flipping the dip switches located on the Surelight integrated control. The unit is shipped with a factory fan off setting of 90 seconds. Fan off time will affect comfort and is adjustable to satisfy individual applications. See figure 25.

Page 25

Page 26

FANOFF TIME ADJUSTMENT

60sec. 90sec. 120sec. 180sec.

To adjust fan-off timing, flip dip switch to desired setting.

FIGURE 25

Temperature Rise

Check the temperature rise and, if necessary, adjust the blower speed to maintain the temperature rise within the range shown on the unit rating plate.

Thermostat Heat Anticipation

Set the thermostat heat anticipation:

0.50 amps White Rodgers gas valves

0.70 amps Honeywell gas valves

Electrical

1 - Check all wiring for loose connections.

2 - Check for the correct voltage at the furnace (furnace

operating).

3 - Check ampdraw on the blower motor.

Motor Nameplate__________Actual__________

Flue And Chimney

1 - Check flue pipe, chimney and all connections for tight

ness and to make sure there is no blockage. 2 - Check unit for proper draft. 3 - Is pressure switch closed? Obstructed flue will cause

unit to shut off at pressure switch. Check flue and out

let for blockages. 4 - Reset manual flame rollout switches on burner box

cover.

Burner Flame Adjustment

The G24M burner flame is not adjustable; however, the flame should be inspected at the beginning of each heating season. If necessary, clean the burners. The burner flame should be blue when burning natural gas, and blue/yellow when burning propane gas. See figure 26.

Burner Flame

FLAME APPEARS BLUE IF

BURNING NAT. GAS; BLUE/

YELLOW FOR PROPANE.

FLAME

HEAT

EXCHANGER

TUBE

Blower Speeds

NOTE - CFM readings are taken external to unit with a dry evaporator coil and without accessories.

1 - Turn off electrical power to furnace. 2 - Remove unit access panel. 3 - Disconnect existing speed tap at control board speed

terminal.

NOTE - TERMINATION OF ANY UNUSED MOTOR LEADS MUST BE INSULATED.

4 - Refer to blower speed selection chart on unit wiring dia

gram for desired heating or cooling speed.

5 - Connect selected speed tap at control board speed

terminal. 6 - Resecure unit access panel. 7 - Turn on electrical power to furnace.

Electronic Ignition

The SureLight integrated control has an added feature of an internal watchguard control. The feature serves as an au tomatic reset device for ignition controls lockedout because the burner has failed to light. This type of nuisance lockout is usually attributed to low gas line pressure. After one hour of continuous thermostat demand for heat, the watchguard will break and remake thermostat demand to the furnace and automatically reset the control to relight the furnace.

BURNER

VEST

PANEL

FIGURE 26

Turbulator

G24M(X) series units include a ceramic fiber turbulator in each heat exchanger inlet. The turbulators lower nitrogen oxide emissions. Prior to unit startup, inspect the turbula tors for shipping damage. The turbulators are fragile; they should be removed only if it is necessary to replace them.

Failure To Operate

If the unit fails to operate, check the following: 1 - Is the thermostat calling for heat? 2 - Are access panels securely in place?

3 - Is the main disconnect switch closed? 4 - Is there a blown fuse? 5 - Is the filter dirty or plugged? Dirty or plugged filters will

cause the limit control to shut the unit off. 6 - Is gas turned on at the meter? 7 - Is the manual main shutoff valve open? 8 - Is the internal manual shutoff valve open? 9 - Is the unit ignition system in lock out? If the unit locks

out again, call the service technician to inspect the unit

for blockages.

Page 26

Page 27

Service

WARNING

5 - Clean the inside of each burner with a bottle brush as

shown in figure 27.

BURNER

Cleaning Burners

Disconnect power before servicing unit.

CAUTION

Label all wires prior to disconnection when servicing controls. Wiring errors can cause improper and danger ous operation. Verify proper operation after servicing.

At the beginning of each heating season, service items A through E as described below:

A - Electrical

1 - Check all wiring for loose connections. 2 - Check for the correct voltage at the furnace (furnace

operating).

3 - Check amp-draw on the blower motor.

Motor Nameplate__________Actual__________

B - Blowers

Check the blower wheels for debris and clean if necessary. The blower motors are prelubricated for extended bearing life. No further lubrication is needed.

C - Filters

All G24M filters are installed external to the unit. Filters should be inspected monthly. Clean or replace the filters when necessary to ensure proper furnace operation. See table 13 for filter sizes. Replacement filters for G24M-45/60/75 units must have a minimum velocity rating of 400 FPM. Replacement filters for G24M-100/120/140 units require a minimum velocity rating of 625 FPM.

TABLE 13

Model Number Filter Size - inches (mm)

G24M-45/60/75 16 X 20 X 1 (406 X 508 X 25)

G24M-100/120/140 20 X 20 X 1 (508 X 508 X 25)

WARNING

D - Flue And Chimney

Check the flue pipe, chimney and all connections for tight ness and to make sure there is no blockage.

E - Burners

Inspect the burners and burner flame at the beginning of each heating season. If necessary, clean the burners as in dicated below:

1 - Turn off the electrical and gas supply to the furnace. 2 - Remove the burner box top. 3 - Remove the burner retaining bracket. 4 - Remove the burners.

BOTTLE

BRUSH

FIGURE 27

6 - Replace the burners and the burner retaining bracket.

Make sure the burners are properly seated in the slots on the tray. The burner orifice must be aligned with the

manifold. 7 - Reinstall the burner box top. 8 - Restore electrical power and gas supply to the furnace.

Follow lighting instructions on the front of the unit.

Check the appearance of the burner flame, burner

pressure, gas flow, and temperature rise. If necessary,

make adjustments. See the other unit adjustments sec

tion.

Heat Exchanger

Periodically inspect the heat exchanger tubes and the flue box for corrosion and soot deposits. If necessary, clean as indicated below:

1 - Turn off the electrical and gas supply to the furnace. 2 - Disconnect the wiring to the combustion air fan. 3 - Remove the screws securing the flue box to the furnace.

Clean the flue box with a wire brush (brassbristle brush

recommended), and rags or a shop vacuum cleaner. 4 - Disconnect the gas supply piping and the ignitor and

sensor wires. Remove the burner assembly from the

furnace. 5 - Since the heat exchanger tubes are crimped in several

locations, a thorough cleaning of the entire length of

each tube is not possible. However, remove any soot

deposits which are accessible with a wire brush (brass

bristle brush recommended), and rags or a shop vacuum

cleaner. 6 - Reinstall the flue box using a new gasket. 7 - Reconnect the combustion air fan wiring. 8 - Reinstall the burner box, ignitor and sensor wires and

the gas supply piping. 9 - Carefully check all piping connections (factory and field)

for gas leaks. Use a leak detecting solution or other pre

ferred means.

IMPORTANT

10 Restore electrical power and gas supply. Follow light

ing instructions on front of unit. Check burner flame

and adjust if necessary.

Page 27

Page 28

Repair Parts List

The following repair parts are available through independent Lennox dealers. When ordering parts, include the complete furnace model number listed on the A.G.A. or C.G.A. rating plate  Example: G24M3-75. Refer to page 3 for parts identification. CABINET PARTS BLOWER PARTS NOx turbulator (60 Hz. X units only) Front access panel Blower wheel Hot Surface Ignitor Blower access panel Motor Flame rollout switch (two) Cabinet cap Blower housing cut-off plate Flame sensor Cabinet bottom Motor capacitor Primary limit Vent adapter HEATING PARTS Secondary limit (two) ELECTRICAL PARTS Heat exchanger Pressure switch Transformer Main burners Wire harness plug / cap Control board (Hot Surface Ignition) Main burner orifices Flue box Door interlock switch Gas manifold/Burner box assembly Combustion air blower

Gas valve Gaskets

Low gas pressure switch (propane only)

Ignition Control Board Diagnostic Codes

DIAGNOSTIC CODES

LED #1 LED #2

SIMULTANEOUS

SLOW FLASH

SIMULTANEOUS

FAST FLASH

SLOW FLASH

OFF

ALTERNATING

SLOW FLASH

ON ON OFF

OFF ON

FAST FLASH

SLOW FLASH

ALTERNATING

FAST FLASH

NOTE - Slow flash equals 1 Hz (one flash per second). Fast flash equals 3 Hz (three flashes per second).

SIMULTANEOUS

SLOW FLASH

SIMULTANEOUS

FAST FLASH

SLOW FLASH

ALTERNATING

SLOW FLASH

FAST FLASH

ALTERNATING

FAST FLASH

OFF

DESCRIPTION

Power on -- Normal operation. Also signaled during cooling and continuous fan.

Normal operation - signaled when heating demand initiated at thermostat.

Primary or secondary limit switch open.

Pressure switch open or has opened 5 times during a single call for heat; OR: Blocked inlet/exhaust vent; OR: Condensate line blocked; OR: Pressure switch closed prior to activation of combustion air blower.

Watchguard -- burners failed to ignite.

Flame sensed without gas valve energized. Rollout switch open. OR: 9pin connector improperly attached.

Circuit board failure or control wired incorrectly.

Main power polarity reversed. Switch line and neutral.

Low flame signal. Measures below .7 microAmps. Replace flame sense rod.

Improper main ground or line voltage below 75 volts; OR: Broken ignitor; OR: Open ignitor circuit.

Minimum flame sense current = 0.15 microAmps.

Page 28

Page 29

Troubleshooting

HEATING SEQUENCE OF OPERATION

NORMAL HEATING MODE ABNORMAL HEATING MODE

COMBUSTION AIR BLOWER ON FOR 1 SECOND.

SIGNAL IMPROPER

GROUND AT LED.

SIGNAL HOLDS

UNTIL UNIT IS

PROPERLY

GROUNDED.

POWER ON

CONTROL SELF-CHECK OKAY?

TURN INDUCER ON FOR 1 SECOND.

IS POLARITY REVERSED?

IS THERE

PROPER GROUND?

ROLLOUT SWITCH CLOSED?

YES

BURNER OFF?

(CONTINUOUS FLAME CHECK)

YES

NORMAL OPERATION:

LED #1 -- SLOW FLASH LED #2 -- SLOW FLASH

YES

IS VOLTAGE

ABOVE 75 VOLTS?

GAS VALVE OFF. COMBUSTION AIR BLOWER OFF.

(RESET CONTROL BY TURNING MAIN POWER OFF.)

GAS VALVE OFF. COMBUSTION AIR BLOWER OFF.

SEQUENCE HOLDS UNTIL ROLLOUT SWITCH CLOSES.

GAS VALVE OFF. COMBUSTION AIR BLOWER ON.

INDOOR BLOWER DELAY OFF.

UNTIL VOLTAGE RISES ABOVE 75 VOLTS.

INDOOR BLOWER OFF WITH DELAY.

LED #1 -- ON. LED #2 -- SLOW FLASH.

INDOOR BLOWER ON HEATING SPEED.

LED #1 ON LED #2 ON

POLARITY REVERSED.

LED #1 -- FAST FLASH

LED #2 -- SLOW FLASH

LOW VOLTAGE SIGNAL AT LED HOLDS

LED #1 -- SLOW FLASH

LED #2 -- OFF

THERMOSTAT CALLS FOR HEAT:

LED #1 -- FAST FLASH LED #2 -- FAST FLASH

YES

IS COMBUSTION AIR

PRESSURE SWITCH OPEN?

YES

IS COMBUSTION AIR BLOWER ENERGIZED?

(HTG. ACC. ENERGIZED WITH CAB.)

YES

HAS COMBUSTION AIR PRESSURE

SWITCH CLOSED IN 2.5 MINUTES?

YES

15SECOND COMBUSTION AIR BLOWER PREPURGE

INITIATED BY CLOSED PRESSURE SWITCH.

YES

CONTINUED NEXT PAGE

PRESSURE SWITCH WATCHGUARD MODE.

GAS VALVE OFF. COMBUSTION AIR BLOWER OFF.

LED #1 -- OFF. LED #2 -- SLOW FLASH.

IS 5MINUTE RESET PERIOD COMPLETE?

COMBUSTION AIR BLOWER OFF.

INDOOR BLOWER OFF WITH DELAY.

(Sequence holds until pressure switch

closes or thermostat resets control.)

INDOOR BLOWER OFF WITH DELAY.

GAS VALVE OFF.

LED #1 OFF

LED #2 SLOW FLASH

Page 29

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Troubleshooting

NORMAL HEATING MODE ABNORMAL HEATING MODE

15SECOND COMBUSTION AIR BLOWER PREPURGE

INITIATED BY CLOSED PRESSURE SWITCH.

YES

IGNITOR WARMUP -- 20 SECONDS.

YES

4SECOND TRIAL FOR IGNITION.

GAS VALVE OPENS. IGNITOR ENERGIZED FOR

1 SECOND AFTER VALVE OPENS.

NO FLAME SENSED DURING THIS PERIOD.

YES

FLAME STABILIZATION PERIOD.

4 SECONDS

FLAME RECTIFICATION CURRENT CHECK

CAN FLAME BE PROVEN WITHIN 4

SECONDS AFTER GAS VALVE OPENS?

(0.15 microamps)

HEATING SEQUENCE CONTINUED

GAS VALVE OFF. COMBUSTION AIR BLOWER ON.

HAS CONTROL FAILED TO SENSE FLAME FOR

FIVE CONSECUTIVE TRIES DURING A SINGLE

IGNITION WATCHGUARD MODE. GAS VALVE OFF.

LED #1-- ALT. SLOW FLASH, LED #2 -- ALT. SLOW FLASH.

IS 60MINUTE RESET PERIOD COMPLETE?

INDOOR BLOWER OFF.

HEAT DEMAND?

COMBUSTION AIR BLOWER OFF.

INDOOR BLOWER OFF WITH DELAY

YES

FLAME PRESENT?

YES

FLAME SIGNAL ABOVE 0.7 MICROAMPS?

YES

INDOOR BLOWER ON DELAY BEGINS

(45 seconds.)

YES

INDOOR BLOWER ON ACB HEAT SPEED.

ACC. TERMINAL ENERGIZED

PRIMARY AND SECONDARY LIMIT

SWITCHES CLOSED?

YES

ROLLOUT SWITCH CLOSED?

YES

COMBUSTION AIR PRESSURE

SWITCH CLOSED?

YES

THERMOSTAT DEMAND SATISFIED.

YES

LED #1 & #2 SIMULTANEOUS SLOW FLASHES.

YES

COMB. AIR BLOWER CONTINUES 5SECOND

POST PURGE AFTER T'STAT DEMAND IS SATISFIED.

INDOOR AIR BLOWER COMPLETES SELECTED

OFF" DELAY BEFORE SHUTTING OFF.

COMBUSTION AIR BLOWER DE-ENERGIZED.

INDOOR BLOWER ON UNTIL SWITCH CLOSES.

SEQUENCE HOLDS UNTIL ROLLOUT SWITCH CLOSES.

GAS VALVE DE-ENERGIZED.COMBUSTION AIR BLOWER ON.

HAS CONTROL RESET IGNITION

SEQUENCE FOUR TIMES?

LOW FLAME SIGNAL

(Does not affect operation of control)

LED #1 -- SLOW FLASH

LED #2 -- FAST FLASH

GAS VALVE DE-ENERGIZED.

LED #1 -- SLOW FLASH. LED #2 -- ON.

IS LIMIT SWITCH CLOSED?

LIMIT SWITCH WATCHGUARD MODE.

YES

GAS VALVE OFF. COMBUSTION AIR BLOWER OFF.

INDOOR BLOWER OFF WITH DELAY.

LED #1 -- ON. LED #2 -- SLOW FLASH.

INDOOR BLOWER OFF WITH DELAY

LED #1 -- OFF. LED #2 -- SLOW FLASH.

HAS CAB SWITCH CLOSED IN 2.5 MINUTES?

5MINUTE PRESSURE SWITCH

GAS VALVE OFF. COMBUSTION AIR

BLOWER OFF.

INDOOR BLOWER OFF WITH DELAY

LED #1-- SLOW FLASH, LED #2 -- ON.

IS 60MINUTE RESET PERIOD

COMPLETE?

HAS PRIMARY/SECONDARY

LIMIT AUTOMATIC RESET TIME

EXCEEDED 3 MINUTES?

WATCHGUARD MODE.

YES

Page 30

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Troubleshooting

NORMAL COOLING MODE ABNORMAL COOLING MODE

IGNITION CONTROL MAIN POWER ON.

COOLING SEQUENCE OF OPERATION

POWER ON

SIGNAL IMPROPER

GROUND AT LED.

SIGNAL HOLDS

UNTIL UNIT IS

PROPERLY

GROUNDED.

ROLLOUT SWITCH MONITORED CONTINUOUSLY.

CHECK FOR MAIN BURNER FLAME SENSE.

LED: SLOW FLASH RATE REMAINS UNCHANGED

CONTROL SELF DIAGNOSTIC CHECK.

IS CONTROL OPERATING NORMALLY?

YES

TURN INDUCER ON FOR 1 SECOND.

IS POLARITY REVERSED?

IS ROLLOUT SWITCH CLOSED?

IS MAIN BURNER FLAME OFF?

THROUGHOUT COOLING CYCLE.

THERMOSTAT CALLS FOR COOLING.

IS THERE

PROPER GROUND?

YES

IS VOLTAGE

ABOVE 75 VOLTS?

GAS VALVE OFF. COMBUSTION AIR BLOWER OFF.

INDOOR BLOWER OFF WITH NORMAL DELAY.

SIGNAL CIRCUIT BOARD FAILURE AT LED.

INTERRUPT MAIN POWER TO RESET CONTROL.

SIGNAL POLARITY REVERSED AT LED.

GAS VALVE OFF. COMBUSTION AIR BLOWER OFF.

INDOOR BLOWER OFF WITH NORMAL DELAY.

SIGNAL CIRCUIT BOARD FAILURE AT LED.

SEQUENCE HOLDS UNTIL ROLLOUT SWITCH CLOSES.

GAS VALVE OFF. COMBUSTION AIR BLOWER OFF.

INDOOR BLOWER OFF WITH NORMAL DELAY.

SIGNAL CIRCUIT BOARD FAILURE AT LED.

SEQUENCE HOLDS UNTIL FLAME IS NOT SENSED.

LOW VOLTAGE SIGNAL AT LET HOLDS

UNTIL VOLTAGE RISES ABOVE 75 VOLTS.

COMPRESSOR CONTACTOR AND SYSTEM FAN

ENERGIZED WITH 0SECOND DELAY.

ACB COOL SPEED ENERGIZED. ACC. TERM. ENERGIZED.

THERMOSTAT OPENS.

COMPRESSOR OFF.

SYSTEM FAN AND ACC. TERM. OFF

WITH 0SECOND DELAY.

Page 31

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Troubleshooting

CONTINUOUS LOW SPEED FAN SEQUENCE OF OPERATION

LED: SLOW FLASH RATE REMAINS

UNCHANGED THROUGHOUT SEQUENCE.

MANUAL FAN SELECTION MADE AT THERMOSTAT.

CONTROL (G) ENERGIZES SYSTEM FAN AT CONTINUOUS

ACB LOW SPEED. ACC. TERM. ENERGIZED.

THERMOSTAT CALLS FOR HEAT (W).

NO YES

THERMOSTAT CALLS FOR COOLING.

YES

SYSTEM FAN SWITCHED TO ACB COOL

SPEED. ACC. TERM. REMAINS ON.

THERMOSTAT OPENS.

MANUAL FAN SELECTION MADE AT THERMOSTAT.

CONTROL (G) ENERGIZES SYSTEM FAN AT CONTINUOUS

ACB LOW SPEED. ACC. TERM. ENERGIZED.

SYSTEM FAN ENERGIZES ON ACB HEAT SPEED

AFTER NORMAL DELAY

THERMOSTAT OPENS.

SYSTEM FAN OFF. ACC. TERM. OFF.

(AFTER OFF DELAY COMPLETED).

HTGACC. TERM. ENERGIZES WITH COMB. AIR BLOWER.

G24M Start-up and Performance Check List

START-UP AND PERFORMANCE CHECK LIST

Job Name Job Number Date Job Location City State/Province Installer

City State/Province

Unit Model Number Serial Number Service Technician

HEATING SECTION

Electrical Connections Tight? Supply Voltage Blower Motor Amps Blower Motor Horsepower/kw Gas Piping Connections Tight & Leaks Tested? Fuel Type: Natural Gas? LP/Propane Gas? Furnace Btu (kW) Input Line Pressure Regulator Pressure w.c./Pa -- Nat. w.c/Pa -- LP/Propane Connections Tight? Proper Draft? Fan Control Setting (45 Seconds Fixed On) Fan Control Off Setting Temperature Rise Filter Clean & Secure? Vent Clear?

Calibrated? Heat Anticipator Properly Set? Level?

THERMOSTAT

Page 32

Lennox G24M2-45, G24M3-75, G24M2-60, G24M4-75, G24M3/4-100 Installation Instructions Manual

Specifications and Main Features

Frequently Asked Questions

User Manual