Lennox G1D91BT, G1D93BT, CG90TB Installation Instructions Manual

INSTALLATION INSTRUCTIONS

G1D91BT, CG90TB, & G1D93BT

High Efficiency 90+ Condensing Gas Furnace

WARNING

Improper installation, adjustment, alteration, service, or maintenance can cause
injury or property damage. Refer to this manual. For assistance or additional informa­tion, consult a qualified installer, service agency, or the gas supplier.

WARNING

Do not store combustible materials, including
gasoline and other flammable vapors and
liquids, near the furnace, vent pipe, or warm
air ducts. The homeowner should be cau­tioned that the furnace area must not be
used as a broom closet or for any other
storage purposes. Such uses may result in
actions that could cause property damage,
personal injury, or death.

SAFETY ................................................. 2

INSTALLATION ...................................... 3

START-UP ............................................ 21

OPERATION ........................................ 22

MAINTENANCE ................................... 24

TABLE OF CONTENTS

CONTROL SYSTEM DIAGNOSTICS .. 25

WARNING

This furnace is not approved for installation in
a mobile home. Do not install this furnace in
a mobile home. Installation in a mobile home
could result in actions that could cause prop­erty damage, personal injury, or death.

REPAIR PARTS ................................... 25

WIRING DIAGRAMS............................ 27

Manufactured By

A.A.C.

A Lennox International Company

421 Monroe Street

Bellevue, OH 44811

*47860A005*

IMPORTANT

The installation of the furnace, wiring, warm air ducts, venting, etc. must conform to the requirements of the
National Fire Protection Association; the National Fuel Gas Code, ANSI Z223.1/NFPA No. 54 (latest edi­tion) and the National Electrical Code, ANSI/NFPA No. 70 (latest edition) in the United States; CSA B149.1
(latest edition) Natural Gas and Propane Installation Codes and the Canadian Electrical Code Part 1, CSA

22.1 (latest edition) in Canada; and any state or provincial laws, local ordinances (including plumbing or
wastewater codes), or local gas utility requirements. Local authorities having jurisdiction should be con­sulted before installation is made. Such applicable regulations or requirements take precedence over the
general instructions in this manual.

# 47860A005 Page 1

SAFETY

The following is a list of safety rules and precautions that
must be followed when installing this furnace.

WARNING

In the State of Massachusetts:

1. Use only with the type of gas approved for this
furnace. Refer to the furnace rating plate.

2. Install this furnace only in a location and position as
specified in the Location section on page 3 of these
instructions.

3. Provide adequate combustion and ventilation air to the
furnace space as specified in the Combustion and
Ventilation Air section on page 4 of these instructions.

4. Adequate clearance must be provided around the
vent-air intake terminals as specified in the Venting
section beginning on page 5 of these instructions.

5. Combustion products must be discharged outdoors.
Connect this furnace to an approved vent system only,
as specified in the Venting section beginning on page 5
of these instructions.

6. Never test for gas leaks with an open flame. Use a
commercially available soap solution made specifi­cally for the detection of leaks to check all connec­tions, as specified in Gas Supply and Piping
beginning on page 18 of these instructions.

This product must be installed by a licensed
Plumber or Gas Fitter. When flexible connec­tors are used, the maximum length shall not
exceed 36". When lever-type gas shutoffs are
used, they shall be T-handle type.

7. Always install furnace to operate within the furnace’s
intended temperature-rise range with a duct system
which has an external static pressure within the allow­able range, as specified in Temperature Rise on page
24 of these instructions. See furnace rating plate.

8. When a furnace is installed so that the supply ducts
carry air circulated by the furnace to areas outside the
space containing the furnace, the return air shall also
be handled by duct(s) sealed to the furnace casing
and terminating outside the space containing the
furnace. See Circulating Air Supply on page 18 of
these instructions.

9. A gas-fired furnace for installation in a residential
garage must be installed as specified in the Location
section on page 3 of these instructions.

10. The furnace is not to be used for temporary heating of
buildings or structures under construction as specified
in the Location section on page 3 of these instructions.

# 47860A005Page 2

INSTALLATION

Location

These instructions must be placed on or near the
furnace in a conspicuous place.

The furnace design is certified by CSA International as a
Category IV furnace in compliance with the latest edition
of American National Standard Z21.47/CSA Standard 2.3
for Gas-Fired Central Furnaces, for operation with natural
gas or propane. Consult the rating plate on the furnace for
gas type before installing.

The maximum hourly heat loss of space shall be calcu­lated in accordance with the procedure described in the
current manuals of Air Conditioning Contractors of
America, or by any other recognized method which is
suitable for local conditions, provided the results obtained
are in substantial agreement with, and not less than, those
obtained using the procedure described in the manuals.

G1D91BT, G1D93BT, and CG90TB furnaces may be installed
as upflow or horizontal furnaces. When installed horizon­tally, the installer must install a sheet metal screw to retain
the upper door as shown in Figure 1.

Never install any furnace on its back.

Horizontal Installations

To provide proper operation and satisfactory performance,
care must be taken in choosing the location for this furnace.
The atmosphere in which the furnace operates must be free
of contaminants such as chlorides and sulfates.

The furnace must be installed so that electrical compo­nents are protected from water. Unit must be level for

proper condensate drainage.

CAUTION

The condensate system must not be ex­posed to temperatures under 32°F. The

condensate system must be insulated if ex­posed to temperatures under 32°F. Use of heat
tape is permissible provided the rate tempera­ture of the tape does not exceed 155°F.

All models are suitable for closet or utility room installation.

The furnace is suitable for installation in buildings con­structed on-site. The furnace should be centralized in
respect to the heat distribution system as much as
practicable. When installed in a utility room, the door
should be wide enough to allow the largest part of the
furnace to enter, or permit the replacement of another
appliance, such as a water heater.

Figure 1

Inspection of Shipment

This furnace is shipped in one package, completely
assembled and wired. The thermostat is shipped in a

separate carton when ordered.

Upon receipt of equipment, carefully inspect it for possible
shipping damage. If damage is found, it should be noted
on the carrier’s freight bill. Damage claims should be filed
with the carrier immediately. Claims of shortages should
be filed with the seller within 5 days.

A gas-fired furnace for installation in a residential garage
must be installed so the burner(s) and the ignition source
are located not less than 18" above the floor. The furnace
is to be located or protected to avoid physical damage by
vehicles.

CAUTION

Do not use the furnace as a heater in a
building under construction. The furnace can
be severely damaged due to the abnormal
environment caused by construction. Chlo­rides from sources such as paint, stain, or
varnish; tile and counter cements; adhesives;
and foam insulation are abundant in a struc­ture under construction and can be highly
corrosive. Low return air temperature can
cause condensation in the furnace and other
damage that can shorten the life of the unit.

# 47860A005 Page 3

G1D91BT, G1D93BT, and CG90TB models installed in the
horizontal position are approved for attic installations. If the

furnace is to be installed in an attic or other insulated
space, it must be kept free and clear of insulating
materials.

To avoid property damage caused by condensate drain
blockage, install a field-fabricated auxiliary drain pan with
a separate drain line to the outside under the entire
furnace and drain system. Install according to local codes.

Clearances

WARNING

Insufficient combustion air can cause head­aches, nausea, dizziness, or asphyxiation.
When considering combustion air require­ments, enough air must also be provided to
meet the needs of all fuel-burning appliances
and exhaust fans.

All servicing and cleaning of the furnace can be performed
from the front. If installed in a closet or utility room,
provide 18" clearance in front for service if the door to the
room is not in line with the front of the furnace.

Refer to Table 1 for the minimum clearances to combus­tibles required for construction and proper unit operation.
Where servicing clearances are greater than clearances
to combustibles, servicing clearances take precedence.

G1D91BT, G1D93BT, and CG90TB models may be in­stalled on wood flooring but shall not be installed directly
on carpeting, tile, or any other combustible material.

Minimum Clearances to

Combustibles

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Table 1

Combustion and Ventilation Air

Adequate provisions for combustion air and ventilation of
furnace must be made. Refer to Section 5.3, “Air for
Combustion and Ventilation,” of the National Fuel Gas
Code, ANSI Z223.1/NFPA54 (latest edition), Sections 7.2,

7.3, or 7.4 of CSA B149.1 Natural Gas and Propane

Installation Codes (latest editions), or applicable provi­sions of the local building codes.

WARNING

Air openings in the front of the furnace must
be kept free of obstructions. Any obstruction
may cause improper operation that can result
in a fire hazard or carbon monoxide injury.

Unconfined Space

An unconfined space is defined as “a space whose
volume is more than 50 cubic feet per 1000 BTU per hour
of the combined input rating of all appliances installed in
that space.” When a furnace is installed in an unconfined
space in a building, it can be assumed that the infiltration
will be sufficient to supply the required air. If the furnace is
installed in a ventilated attic or crawl space, it is assumed
that the infiltration is sufficient to supply the required air.
However, in a building of unusually tight construction,
additional outdoor air should be provided.

Confined Space

A confined space is defined as “a space whose volume is
less than 50 cubic feet per 1000 BTU per hour of the
combined input rating of all appliances installed in that
space.”

If the furnace is installed in a confined space within the
building and combustion air is taken from a heated space,
the combustion air and ventilating air must enter and leave
the space through two permanent openings of equal area.
One opening shall be located within 12" of the ceiling and
the other within 12" of the floor, each having a free area of
1 square inch per 1000 BTU/HR of total input rating of all
appliances within the space and not less than 100 square
inches each.

If the furnace is installed in a space within a building of tight
construction, makeup air must be supplied from outdoors. In
this case, one opening shall be within 12" of the ceiling and
one opening within 12" of the floor. If combustion ducts are
vertical, each opening shall have a free area of 1 square
inch per 4000 BTU/HR of the total input rating of all appli­ances within the enclosure. If horizontal combustion ducts
are run, 1 square inch per 2000 BTU/HR is required.

# 47860A005Page 4

Contaminated Combustion Air

Excessive exposure to contaminated combustion air will
result in safety and performance related problems. The
recommended source of combustion air is outdoor air.
However, the use of indoor air in most applications is
acceptable if the following guidelines are followed:

1. If the furnace is installed in a confined space, it is

recommended that the necessary combustion air come
from the outdoors by way of an attic, crawl space, air
duct, or direct opening.

2. If indoor combustion air is used, there must be no

exposure to the substances listed in Item 5.

3. All provisions for indoor combustion air must meet the

requirements for combustion air indicated in the
National Fuel Gas Code, ANSI Z223.1/NFPA 54
(latest edition), and/or any applicable local codes. In
Canada, see CSA B149.1, Natural Gas and Propane
Installation Codes (latest edition).

operation. All venting must be in accordance with the codes
having jurisdiction in the area and these instructions.

G1D91BT, G1D93BT, and CG90TB models can be installed
as either direct vent or non-direct vent units. A direct vent
(two pipe) installation requires that all the air necessary for
combustion be supplied from outside the dwelling through
an air intake pipe. A non-direct vent (one pipe) installation
uses air from inside the dwelling for combustion.

The furnace is shipped with the air inlet pipe terminated to
the top panel for either inside or outside combustion air. An
inlet air restrictor plate (see Figure 2) is supplied with this
furnace and can be found in the plastic bag containing these
Installation Instructions and the User’s Information Manual.
This inlet restrictor plate must be used in all installations
using inside air for combustion (non-direct vent).

To install the inlet restrictor plate:

1. Install the restrictor plate in the inlet pipe collar in the
top panel of the furnace.

4. The following types of installation may require outdoor
air for combustion, due to chemical exposures:

• Commercial buildings

• Buildings with indoor pools

• Furnaces installed in laundry rooms

• Furnaces installed in hobby or craft rooms

• Furnaces installed near chemical storage areas

5. Exposure to the following substances in the combustion
air supply may also require outdoor air for combustion:

• Permanent wave solutions

• Chlorinated waxes and cleaners

• Chlorine-based swimming pool chemicals

• Water softening chemicals

• Deicing salts or chemicals

• Carbon tetrachloride

• Halogen-type refrigerants

• Cleaning solvents (such as perchloroethylene)

• Printing inks, paint removers, varnishes, etc.

• Cements and glues

• Antistatic fabric softeners for clothes dryers

• Masonry acid washing materials

• Chlorinated laundry products

• Hydrochloric acid

2. Insert a 3" section of PVC pipe (field supplied) into the
collar. Use high temperature RTV sealant to attach
PVC pipe to collar.

3. Attach a 90° elbow (field supplied) to the PVC pipe.
Use high temperature RTV sealant to attach elbow to
PVC pipe.

Two different sized inlet restrictor plates are supplied with
the furnace (2" and 3"). Use the proper restrictor plate for
the furnace model.

Inlet Air Restrictor Plate

The inlet air restrictor plate must be
installed in all installations using inside
air for combustion (non-direct vent).

Flue Pipe Screen

The flue pipe screen should be
installed at the termination of the flue
pipe in all installations.

Venting

The high efficiency of this furnace is accomplished by the
removal of both sensible and latent heat from the flue
gases. The removal of latent heat results in the condensa­tion of moisture in the flue gases. This condensation occurs
in the secondary heat exchanger and in the vent system.
Therefore, this furnace requires special venting consider­ations and the instructions must be followed to insure proper

# 47860A005 Page 5

Figure 2

Also included in the plastic bag containing the inlet air
restriction plate is a flue pipe screen (see Figure 2). In all
installations, this screen should be installed at the termina­tion of the flue pipe and is designed to keep objects out of
the flue pipe.

WARNING

If at any time in the future the installation of
this furnace is changed to require outside
fresh air for combustion, the inlet air restrictor
plate must be removed. Failure to remove the
inlet air restrictor could cause improper
operation that can result in a fire hazard or
carbon monoxide injury.

Piping and Fitting Specifications

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For either type of installation (direct or non-direct vent),
special venting considerations must be followed. Refer to
the proper section in pages 10 – 14 for the type of furnace
and venting being installed.

The venting system must be supported with mounting
straps to prevent any weight load from being applied to
the vent blower. Horizontal vent pipe must be supported
every 5' and vertical pipe should be supported every 10' to
prevent sagging and provide rigid support.

When a furnace is installed as direct vent, provisions for
ventilation air should follow the same requirements as if
installed as non-direct vent. Proper ventilation air is
necessary to maintain furnace component temperatures
within acceptable limits.

All vents passing through floors, ceilings, and walls must
be installed in accordance with National Fuel Gas Code,
ANSI Z223.1/NFPA 54 (latest edition).

In all applications where the flue pipe is run through
an unconditioned space, 1/2" Armaflex or equivalent
must be used over the pipe. In extreme cold climates,
3/4" Armaflex is recommended.

Materials

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Table 2

When making ABS joints, pieces can be prepared with a
cleaner. When joining ABS to PVC materials, use PVC
solvent cement as specified in ASTM D3138.

All pipe, fittings, primer, and solvent cement must conform
with American National Standard Institute and the American
Society for Testing and Materials (ANSI/ASTM) standards.
The solvent shall be free flowing and contain no lumps,
undissolved particles, or any foreign matter that adversely
affects the joint strength or chemical resistance of the
cement. The cement shall show no gelation, stratification, or
separation that cannot be removed by stirring.

Refer to Table 2 for approved piping and fitting materials.

The primers and solvents used must also meet ASTM
specifications. PVC primer is specified in ASTM F656. Use
PVC solvent as specified in ASTM D2564 and ABS solvent
cement as specified ASTM D2235. Low temperature solvent
cement is recommended. Metal or plastic strapping may be
used for vent pipe hangers.

Preferred fittings are DWV style or long sweep. Seal all
joints gas tight with appropriate cement. In areas where vent
and air intake pipes are exposed to abnormal stress or are
subject to damage, schedule 80 pipe should be used.

Category IV Furnace Limitations

This furnace shall not be connected to any Type B, BW,
or L vent or vent connector and shall not be connected to
any portion of a factory-built or masonry chimney. This

furnace is not to be common vented with any other
appliance. The vent pipe must not be connected to a
chimney flue serving a separate appliance designed
to burn solid fuel.

# 47860A005Page 6

Concentric Vent Kit

A concentric vent kit (model ACVK2) is available for use
when installing this furnace as a direct vent furnace and the
air intake and vent pipe are to be run through the same hole,
whether horizontally through the wall or vertically through the
roof (see Figure 3). Refer to the instructions included with
the concentric vent kit for installation specifics.

Concentric Vent Kit Dimensions

Figure 3

Vent Pipe Size and Length

The vent pipe and air intake pipe (in direct vent installa­tions) should be sized in accordance with the information
found in the appropriate table in Figure 4. One 90° elbow
is equivalent to 5' of pipe. Two 45° elbows are equivalent
to one 90° elbow. The minimum length certified for use
with this furnace is 5' and one elbow, not including the
vent and air intake terminals.

In the event that the pipe length is in between the lengths
listed in the table, use the next larger length listed. For
example, if a length of pipe needed to install the furnace is
27', use the diameter values for the 30' row in the tables.
For direct vent installations, if the vent and air intake pipe
are not equal in length and number of elbows, then
determine the minimum pipe diameter for both the vent
and air intake. If the results indicate different diameters,
use the larger of the two for both the vent and air intake.

Under no circumstances should the vent and air
intake pipe size be different in diameter. For installation

details, refer to the appropriate section in pages 10 – 14
for the unit model and type of installation.

Horizontal Venting

The vent for this appliance shall not terminate over public
walkways; or near soffit vents or crawl space vents or
other areas where condensate or vapor could create a
nuisance or hazard or cause property damage; or where
condensate vapor could cause damage or could be
detrimental to the operation of regulators, relief valves, or

Vent Tables

(numbers in inches unless specified otherwise)

Minimum Pipe Diameter

40,000 – 80,000 BTU/HR Models

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02

03

04

05

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08

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04

05

06

07

08

09

5

01

02

03

04

05

06

NR = Not Recommended

5.15.1 22222222

5.1 2 2 2 2 2 2 2 2 2
222222222 5.2
2 2 2 2 2 2 2 5.2 5.2 5.2
22222 5.25.25.25.25.2
2 2 5.2 5.2 5.2 5.2 5.2 5.2 5.2 3

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5.2 5.2 5.2 5.2 5.2 3 3 3 3 RN

5.25.25.2 33333 RNRN

5.2 5.2 3 3 3 3 3 RN RN RN

Minimum Pipe Diameter

90,000 – 100,000 BTU/HR Models

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22 5.25.25.2 33333

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Minimum Pipe Diameter

112,000 – 125,000 BTU/HR Models

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Figure 4

other equipment. See Figures 5 and 6 on pages 8 and 9 for
additional information on where the horizontal vent terminal
can and cannot terminate.

For horizontal venting in situations where clearance to
floor joists is limited, see Horizontal Venting – Low
Clearance Installations on page 14.

# 47860A005 Page 7

Sidewall Vent Terminal Clearances (Direct Vented Furnaces)

V

Vent Terminal

Air Supply Inlet

X

Area Where Terminal Is
Not Permitted

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In accordance with the current CSA B149.1, Natural Gas and

Propane Installation Code

2

In accordance with the current ANSI Z2223.1/NFPA 54, National

Fuel Gas Code

†

A vent shall not terminate directly above a sidewalk or paved
driveway that is located between two single family dwellings and
serves both dwellings.

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* For clearances not specified in ANSI Z2223.1/NFPA 54 or CSA

B149.1, the following statement shall be included:
“Clearance in accordance with local installation codes and the
requirements of the gas supplier and the manufacturer’s installation
instructions.”

Figure 5

# 47860A005Page 8

Sidewall Vent Terminal Clearances (Non-Direct Vented Furnaces)

V

X

Area Where Terminal Is
Not Permitted

Vent Terminal

Air Supply Inlet

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1

In accordance with the current CSA B149.1, Natural Gas and

Propane Installation Code

2

In accordance with the current ANSI Z2223.1/NFPA 54, National

Fuel Gas Code

†

A vent shall not terminate directly above a sidewalk or paved
driveway that is located between two single family dwellings and
serves both dwellings.

# 47860A005 Page 9

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‡

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minimum of two sides beneath the floor.

* For clearances not specified in ANSI Z2223.1/NFPA 54 or CSA

B149.1, the following statement shall be included:
“Clearance in accordance with local installation codes and the
requirements of the gas supplier and the manufacturer’s installation
instructions.”

Figure 6

Upflow Direct Vent Installation

An inlet air restrictor plate (see Figure 2 on page 5) is supplied
with this furnace and can be found in the plastic bag containing
these Installation Instructions and the User’s Information Manual.

This restrictor plate is to be used only in non-direct vent
applications. See the non-direct venting sections on pages 11

and 13 for more information on installing the restrictor plate in
non-direct vent applications.

The flue pipe screen (see Figure 2 on page 5) should be
installed at the termination of the flue pipe and is designed
to keep objects out of the flue pipe. An additional screen
should not be placed in the intake termination. If a screen
is installed, the air intake may freeze shut.

For horizontal venting, refer to Figure 7. For vertical venting,
refer to Figure 8. It is permissible to run the vent vertically
through the roof and terminate it as shown in Figure 8, and
to run the combustion air intake pipe horizontally through a
side wall and terminate as shown in Figure 7. The vent pipe
on horizontal runs must slope upward, away from the

furnace, at a minimum pitch of 1/4" per foot of run, to prevent
accumulation of condensate.

Do not cement air intake into the connector on burner
box. Use high temperature RTV silicone sealant so
intake pipe can be removed if service is required.

In horizontal venting applications, the vent and air
intake pipe must be installed on the same side of the
house within the parameters shown in Figure 7.

Prime the trap system by slowly pouring 1 cup of water down
the vent pipe. On initial start-up of the unit, some of the
water used to prime the trap system may run down into the
combustion blower and cause noise.

Upflow Direct Vent – Vertical Venting

Upflow Direct Vent – Horizontal Venting

* The 18" dimension is the minimum

recommended height for ex­tremely cold areas. In these areas,
moisture in the flue gases may
condense and freeze on the air
intake if this height is reduced. In
milder climates, this may be
reduced to a minimum of 6".
Height may be increased as
needed provided total length is not
exceeded.

Overhead View

FLUE PIPE

INTAKE PIPE

IS OPTIONAL.

3” MIN. - 48”MAX.

THIS PIECE

Figure 8

Figure 7

# 47860A005Page 10

Upflow Non-Direct Vent Installation

An inlet air restrictor plate (see Figure 2 on page 5) is
supplied with this furnace and can be found in the plastic
bag containing these Installation Instructions and the
User’s Information Manual. This restrictor plate is to be
used only in non-direct vent applications. Place the
restrictor plate into the inlet collar, insert 3" section of PVC
pipe (field supplied), then attach a 90° elbow (field sup­plied) to the PVC pipe in all non-direct vent installations
(see Figures 9 and 10).

Two inlet air restrictor plates are supplied with each
furnace – a 2" plate and a 3" plate. Use the proper
restrictor plate for the furnace model.

The flue pipe screen (see Figure 2 on page 5) should be
installed at the termination of the flue pipe and is designed
to keep objects out of the flue pipe.

For horizontal venting, refer to Figure 9. For vertical
venting, refer to Figure 10. The vent pipe on horizontal
runs must slope upward, away from the furnace, at a
minimum pitch of 1/4" per foot of run, to prevent accumu­lation of condensate.

Upflow Non-Direct Vent

Vertical Venting

Prime the trap system by slowly pouring 1 cup of water
down the vent pipe. On initial start-up of the unit, some of
the water used to prime the trap system may run down into
the combustion blower and cause noise.

Upflow Non-Direct Vent

Horizontal Venting

Figure 10

Horizontal Direct Vent Installation

An inlet air restrictor plate (see Figure 2 on page 5) is supplied
with this furnace and can be found in the plastic bag containing
these Installation Instructions and the User’s Information
Manual. This restrictor plate is to be used only in non-direct
vent applications. See the non-direct venting sections on this
page and page 13 for more information on installing the
restrictor plate in non-direct vent applications.

Figure 9

# 47860A005 Page 11

The flue pipe screen (see Figure 2 on page 5) should be
installed at the termination of the flue pipe and is designed
to keep objects out of the flue pipe. An additional screen
should not be placed in the intake termination. If a screen is
installed, the air intake may freeze shut.

The 18" dimension shown in Figure 11 on page 12 is the
minimum recommended height for extremely cold areas. In

these areas, moisture in the flue gases may condense and

Height to

provide 12

clearance
to average
snow level

"

Drain Tee

(supplied)

3 Long Piece of 2 Diameter Pipe

(supplied)

""

6.5 Min
24 Max

"

"

Vent Pipe

Air Intake Pipe

See table for air intake
length and number of
elbows allowed.

See table for vent

length and number

of elbows allowed.

freeze on the air intake if this height is reduced. In milder
climates, this may be reduced to a minimum of 6". Height
may be increased as needed provided the total length of
pipe to furnace is not exceeded.

For horizontal venting, refer to Figure 11. For vertical
venting, refer to Figure 12. It is permissible to run the vent
vertically through the roof and terminate it as shown in
Figure 12, and to run the combustion air intake pipe
horizontally through a side wall and terminate as shown in
Figure 11. The vent pipe on horizontal runs must slope
upward, away from the furnace, at a minimum pitch of 1/4"
per foot of run, to prevent accumulation of condensate.

Horizontal Direct Vent –

Horizontal Venting

Airflow Right to Left

Do not cement air intake into the connector on burner
box. Use high temperature RTV silicone sealant so
intake pipe can be removed if service is required.

In horizontal venting applications, the vent and air
intake pipe must be installed on the same side of the
house within the parameters shown in Figure 11.

Horizontal Direct Vent –

Vertical Venting

Airflow Right to Left

Airflow Left to Right

3 Long Piece of

"

2 Diameter Pipe

"

(supplied)

Intake may be raised as

shown to obtain minimum snow

clearance requirements.

Drain Tee
(supplied)

Air Intake

Pipe

Overhead View

FLUE PIPE

INTAKE PIPE

THIS PIECE

IS OPTIONAL.

3” MIN. - 48” MAX.

Figure 11

Vent
Pipe

18"

6"

Height to

provide 12

clearance
to average
snow level

Airflow Left to Right

"

Figure 12

# 47860A005Page 12

Prime the trap system by slowly pouring 1 cup of water down

Inlet Air Restrictor Plate
(inside inlet coupler)

Vent
Pipe

Height to

provide 12

clearance
to average
snow level

"

Drain Tee

(supplied)

3 Long Piece of 2 Diameter Pipe

(supplied)

""

See table for

vent length

and number

of elbows

allowed

the vent pipe. On initial start-up of the unit, some of the
water used to prime the trap system may run down into the
combustion blower and cause noise.

For horizontal venting, refer to Figure 13. For vertical venting,
refer to Figure 14. The vent pipe on horizontal runs must
slope upward, away from the furnace, at a minimum pitch of
1/4" per foot of run, to prevent accumulation of condensate.

Horizontal Non-Direct Vent Installation

An inlet air restrictor plate (see Figure 2 on page 5) is
supplied with this furnace and can be found in the plastic
bag containing these Installation Instructions. This
restrictor plate is to be used only in non-direct vent applica­tions. Place the restrictor plate into the inlet collar, insert
3" section of PVC pipe (field supplied), then attach a 90°
elbow (field supplied) to the PVC pipe in all non-direct vent
installations (see Figures 12 and 13).

Two inlet air restrictor plates are supplied with each
furnace – a 2" plate and a 3" plate. Use the proper
restrictor plate for the furnace model.

The flue pipe screen (see Figure 2 on page 5) should be
installed at the termination of the flue pipe and is designed
to keep objects out of the flue pipe.

Horizontal Non-Direct Vent –

Horizontal Venting

Airflow Right to Left

Prime the trap system by slowly pouring 1 cup of water
down the vent pipe. On initial start-up of the unit, some of
the water used to prime the trap system may run down into
the combustion blower and cause noise.

Horizontal Non-Direct Vent –

Vertical Venting

Airflow Right to Left

Airflow Left to Right

3 Long Piece of

"

2 Diameter Pipe

"

(supplied)

Inlet Air Restrictor Plate

(inside inlet coupler)

(supplied with unit)

Figure 13

# 47860A005 Page 13

Drain Tee

Vent
Pipe

6"

Height to

provide 12

clearance
to average
snow level

Airflow Left to Right

"

Figure 14

Horizontal Venting – Low Clearance Installations

Vent pipe on horizontal runs must slope upward, away from
the furnace, at a minimum pitch of 1/4" per foot of run, to
prevent accumulation of condensate. In certain horizontal,
left-to-right airflow applications, the furnace’s close proximity
to the floor joists above the unit may make it difficult to
obtain the required pitch/slope. Figure 15 and 16 show the
accepted vent practice to obtain proper pitch/slope back to
furnace for proper drainage. For direct vent applications,
see Figure 15. For non-direct applications, see Figure 16.

In all applications, minimum clearances to combustibles
must be observed (as shown in Table 1 on page 4) as well
as all other required clearances shown in Figures 11 and
13 on pages 12 and 13.

Existing Venting Systems

When an existing furnace is removed or replaced, the original
venting system may no longer be sized to properly vent the
attached appliances. An improperly sized venting system

Horizontal Direct Vent – Horizontal Venting

Low Clearance Installation

Figure 15

Horizontal Non-Direct Vent –

Horizontal Venting

Low Clearance Installation

can result in spillage of flue products into the living space, the
formation of condensate, leakage, etc. See the WARNING
box below for proper test procedure.

WARNING

CARBON MONOXIDE POISONING HAZARD

Failure to follow the steps outlined below for each
appliance connected to the venting system being
placed into operation could result in carbon monox­ide poisoning or death.

The following steps shall be followed for each appli­ance connected to the venting system being placed
into operation, while all other appliances connected to
the common venting system are not in operation:

1. Seal any unused openings in the common venting
system.

2. Visually inspect the venting system for proper size
and horizontal pitch, as required in the National
Fuel Gas Code, ANSI Z223.1/NFPA 54 (latest
edition) or the CSA B149.1, Natural Gas and
Propane Installation Codes and these instructions.
Determine that there is no blockage or restriction,
leakage, corrosion, or other deficiencies which
could cause an unsafe condition.

3. As far as practical, close all building doors and
windows between the space in which the
appliance(s) connected to the venting system are
located and other spaces in the building.

4. Close fireplace dampers.

5. Turn on clothes dryers and any appliance not
connected to the venting system. Turn on any
exhaust fans, such as range hoods and bathroom
exhausts, so they are operating at maximum
speed. Do not operate a summer exhaust fan.

6. Follow the lighting instructions. Place the unit
being inspected in operation. Adjust the thermo­stat so appliance is operating continuously.

7. Test for spillage from draft hood equipped appli­ances at the draft hood relief opening after 5
minutes of main burner operation. Use the flame
of a match or candle.

8. If improper venting is observed during any of the
above tests, the venting system must be corrected
in accordance with the National Fuel Gas Code,
ANSI Z223.1/NFPA 54 (latest edition) and/or the
CSA B149.1, Natural Gas and Propane Installa­tion Codes.

9. After it has been determined that each appliance
remaining connected to the venting system
properly vents when tested as outlined above,
return doors, windows, exhaust fans, fireplace
dampers, and any other gas-fired burning appli­ance to their previous conditions of use.

Figure 16

# 47860A005Page 14

Condensate Disposal Installation

The condensate drain should be routed directly to a locally
acceptable disposal area. The condensate drain line
should not be run directly to the outdoors especially in
colder climates where temperatures may cause the
condensate to freeze in the drain line.

In horizontal installations where clearance beneath the
unit is limited, an alternate method for condensate dis­posal trap installation may be used (see Horizontal

Installation – Tight Clearance Below Unit on page 17).

Upflow Installation

Tilt Unit Forward

1/4" Max

Install the condensate drain line to the unit as follows. The
condensate can be drained from either the right or left
side of the furnace. Install the 1/2" NPT x 3/4" PVC
adapter (supplied) in the drain on the side that the draining
will occur. Install the plastic pipe plug opposite of the
drain. Using 3/4" PVC pipe, make a connection from the
adapter just installed to extend just outside the unit. Install
a 3/4" PVC tee as shown in Figure 17. From the tee,
install the drain to the disposal area. The top of the tee
must be left open for proper condensate drainage.

Condensate Disposal – Upflow

THRU.

59.69/56.64

1/2” NPT PLUG

(SUPPLIED)

3/4” PVC

TEE MUST REMAIN

OPEN

1/2” NPT x 3/4” PVC ADAPTER

(SUPPLIED)

Figure 18

Insert Plugs

1/2 NPT Plug
(supplied on unit)

Figure 19

"

1/2 NPT Plug

"

(supplied in kit)

Figure 17

Horizontal Installation – Right to Left Airflow

Furnace must be mounted such that the side through
which the condensate will drain is elevated a minimum of
9" above a surface such as a floor.

Install unit at a slight pitch forward (see Figure 18).

1. Relocate the 1/2" NPT plug installed on the flue pan to
one side of the internal trap assembly (as shown in
Figure 19).

2. Connect the 1/2" NPT plug (supplied) to the opposite
side of the internal trap assembly from the plug
installed in Step 1.

3. Insert trap assembly (supplied) into flue pan (see
Figure 20).

# 47860A005 Page 15

Install Trap Assembly

Flue Pan

1/2 NPT x 1/2 PVC

""

Adapter and Trap Assembly

(supplied)

Figure 20

4. Connect a length of 3/4" PVC pipe (3' minimum) to the
trap assembly (see Figure 21).

Tilt Unit Forward

5. Install 3/4" tee (supplied) as shown in Figure 21.

Completing Condensate

Drain Installation

3/4" Tee

3/8" Vinyl Hose

(supplied)

Be sure to avoid double-trapping the vinyl hose.
Hose must be installed as shown.

1/4 Max."

Figure 22

Insert Plugs

1/2 NPT Plug

"

(supplied in kit)

Figure 21

6. From the tee, connect the drain to disposal area. The
top of the tee must be left open for proper condensate
drainage. The open end of the tee must be oriented so
that condensate does not run out of the opening.

7. Remove 72" vinyl hose supplied with unit and cut in half.
Connect one end of the vinyl hose to the 3/8" barbed
fitting of the 2" x 2" x 1/2" tee in vent and the other end
to the 3/8" barbed fitting on the drain trap assembly.

Horizontal Installation – Left to Right Airflow

Furnace must be mounted such that the side through
which the condensate will drain is elevated a minimum of
9" above a surface such as a floor.

Install unit at a slight pitch forward (see Figure 22).

1. Relocate 1/2" NPT plug installed on flue pan to one side
of the internal trap assembly (as shown in Figure 23).

2. Connect the 1/2" NPT plug (supplied) to the opposite
side of the internal trap assembly from the plug
installed in Step 1.

3. Insert trap assembly (supplied) into flue pan (see
Figure 24).

4. Connect a length of 3/4" PVC pipe (3' minimum) to the
trap assembly (see Figure 25).

1/2 NPT Plug

"

(supplied on unit)

Figure 23

Install Trap Assembly

Flue Pan

1/2 NPT x 1/2 PVC

""

Adapter and Trap Assembly

(supplied)

Figure 24

5. Install 3/4" tee (supplied) as shown in Figure 25.

# 47860A005Page 16

Completing Condensate

Drain Installation

Condensate Drain Trap Installation –

Tight Clearance Below Unit

3/8 Vinyl Hose

"

(supplied)

Be sure to avoid double-trapping the vinyl hose.
Hose must be installed as shown.

3/4 Tee"

Figure 25

6. From the tee, connect the drain to disposal area. The

top of the tee must be left open for proper condensate
drainage. The open end of the tee must be oriented
so that condensate does not run out of the opening.

7. Connect one end of 72" vinyl hose (supplied) to 3/8"

barbed fitting of the 2" x 2" x 1/2" tee in vent and the
other end to 3/8" barbed fitting on drain trap assembly.

Horizontal Installation – Tight Clearance Below Unit

In certain horizontal installations, clearance between unit
and drain pan beneath unit may be limited. In these applica­tions, an alternate method may be used to install the
condensate drain trap assembly. Using two 90° elbows (field
supplied), bring condensate trap out to side of unit beyond
drain pan (see Figure 26). After trap assembly has been
attached using this method, follow proper instructions on the
previous pages for completing condensate drain installation.

CAUTION

To avoid property damage caused by conden­sate drain blockage, install a field-fabricated
auxiliary drain pan with a separate drain line to
the outside under the entire furnace and drain
system, including open vent tees.

Do not install trap assembly any farther than 10" from
the unit. The pressure switch and vent hoses must be
able to reach the barbed fittings on the trap assembly.

Figure 26

the hose must be connected to the flue pan (see Figure

27). Remove and discard the plastic cap plug from 1/4" port
on the flue pan and connect the hose to the port.

Pressure Switch Connection

Upflow Installation

0.10 W.C.

"

Pressure Switch

Black Hose

Pressure Switch Connection

Upflow Installation

The unit is shipped from the manufacturer with a black
hose connected to the pressure switch. The other end of

# 47860A005 Page 17

Figure 27

Horizontal Installation

Circulating Air Supply

The unit is shipped from the manufacturer with a black
hose connected to the pressure switch. The other end of
the hose must be connected to the external drain trap.

Route hose through gas line access hole in cabinet. Then
connect to 1/4" barbed fitting on drain trap assembly.

For right to left airflow installations, see Figure 28. For left
to right airflow installations, see Figure 29.

Be sure that the pressure switch hose does not form
a trap to hold condensation that could form from the
flue gas. Hose may be cut shorter to avoid forming a
trap, if required.

Pressure Switch Connection

Horizontal Installation – R to L Airflow

When the furnace is installed so that the supply ducts
carry air circulated by the furnace to areas outside the
space containing the furnace, the return air shall be
handled by a duct or ducts sealed to the furnace casing
and terminated outside the space containing the furnace.
A return air duct system is recommended. If the unit is
installed in a confined space or closet, a return connection
must be run, full size, to a location outside the closet. The
air duct in the closet must be tight to prevent any entrance
of air from the closet into the circulating air.

If there is no complete return air duct system, the return
air connection must be sealed to the furnace casing and
run, full size, to a location outside the utility room or space
housing the furnace to prevent a negative pressure on the
venting system.

CAUTION

When an air conditioning unit is used in con­junction with the furnace, the evaporator coil
must be installed in the discharge (supply) air.
Do not install an evaporator coil in the return
air; excessive condensation will occur within
the furnace.

Figure 28

Pressure Switch Connection

Horizontal Installation – L to R Airflow

Outlet Duct

For installations not equipped with a cooling coil, a remov­able access panel must be provided in the outlet duct. The
opening should be accessible when the furnace is placed
in service. Smoke or reflected light may be observed
inside the casing to indicate the presence of leaks in the
heat exchanger. The cover for the opening shall be
attached in such a manner as to prevent leaks. The
recommended opening size is 6" x 14" for all sizes.

Gas Supply and Piping

Refer to the furnace rating plate to make sure the furnace
is equipped to burn the gas supplied (natural or propane).

WARNING

Any conversion of a natural gas unit to pro­pane gas must be done by qualified person­nel using a conversion kit available from the
manufacturer, following the instructions in the
conversion kit. If done improperly, overfiring
of the burners and improper burner operation
can result. This can create carbon monoxide
which could cause asphyxiation.

Figure 29

# 47860A005Page 18

Gas supply piping should be installed in accordance with
local codes and the regulations of the utility. Piping must be
of adequate size to prevent undue pressure drop. Consult
the local utility or gas supplier for complete details on special
requirements for sizing gas piping.

If local codes allow the use of a flexible gas appliance
connector, always use a new listed connector. Do not use
a connector which has previously serviced another gas
appliance.

Pipe connections must be tight, and a non-hardening pipe
compound resistant to liquefied petroleum gases should
be used.

Connect the gas pipe to the furnace controls providing a
ground joint union as close to the controls as is possible to
facilitate removal of controls and manifold. Provide a drip
leg on the outside of the furnace. A manual shutoff valve
shall be installed in the gas line, outside the unit, 5' above
the floor, or in accordance with any local codes. A test
gauge connection must be installed with a 1/8" NPT
plugged tapping immediately upstream of the shutoff valve
(refer to Figure 30).

Gas Piping Connection

Manual

Gas Valve

Union

Te e

Drip Leg

1/8" NPT
Plugged
Tapping

The furnace must be isolated from the gas supply piping
system by closing the individual manual shutoff valve
during any pressure testing of the gas supply piping
system at test pressure equal to or less than 1/2 psig
(3.5 kPa) or 14" W.C. If the piping system is to be tested
at pressures in excess of 1/2 psig (3.5 kPa), the furnace
and its appliance main gas valve must be disconnected
from the gas supply piping system.

WARNING

The gas valve supplied with this furnace is
rated at 1/2 psig maximum. Any higher pres­sure may rupture the pressure regulator
diaphragm and may cause overfiring of the
burners and improper burner operation. The
overfiring may result in the creation of carbon
monoxide which could cause asphyxiation.

After gas piping is complete, carefully check all piping
connections (factory and field) for gas leaks. Use a leak
detecting solution or other preferred means. Some soaps
used for leak detection are corrosive to certain metals.
Carefully rinse piping thoroughly after leak detection has
been completed.

WARNING

FIRE OR EXPLOSION HAZARD

Failure to follow the safety warnings exactly
could result in serious injury, death, or prop­erty damage.

Cap

Upflow

Installation

Figure 30

# 47860A005 Page 19

Horizontal

Installation

Never test for gas leaks with an open flame.
Use a commercially available soap solution
made specifically for the detection of leaks to
check all connections. A fire or explosion may
result causing property damage, personal
injury, or loss of life.

Electrical Wiring

WARNING

Risk of electrical shock. Disconnect electrical
power at the circuit breaker or service panel
before making electrical connections. Failure
to disconnect power supplies can result in
property damage, personal injury, or death.

The furnace must be grounded and wired in accordance
with local codes or, in the absence of local codes, with the
National Electrical Code ANSI/NFPA No. 70 (latest edition)
and/or CSA C22.1 Electrical Code (latest edition) if an
external electrical source is utilized.

In all instances, other than wiring for thermostat, the wiring
to be done and any replacement of wire shall conform with
the temperature limitation for Type T wire –63°F (35°C) rise.
Connect a sufficiently sized wire with ground to the furnace’s
line voltage connections and ground lug. Refer to the
furnace rating plate for electrical characteristics to be used
in sizing field supply wiring and over-current protection.

The line voltage supply should be routed through a readily
accessible disconnect located within sight of the furnace.
A junction box on the furnace side panel is provided for
line voltage connections. Refer to the furnace wiring
diagram for specific connection information.

Electronic Air Cleaner

Terminals are provided on the blower control board for
connection of a 120-volt electronic air cleaner. The “EAC”
terminal is energized whenever the thermostat is calling for
heat, cooling, or continuous blower. Refer to the furnace
wiring diagram for specific connection information.

Twinning

The blower control board is designed to permit “twinning” of
furnaces (two furnaces connected to common supply and
return air system, and controlled by one thermostat). An
accessory kit must be ordered from manufacturer. Specific
wiring and operating instructions are included with the kit.

Each furnace must have its own dedicated vent system.

Filters

Proper polarity of the supply connections (“HOT”
and “NEUTRAL”) must be observed to ensure that
safety controls provide the protection intended.

A connection to the ground lug and actual earth ground
(typically a ground stake or buried steel pipe) must be
maintained for proper operation.

Thermostat

Install a room thermostat according to the instructions
furnished with it. Select a location on an inside wall that is
not subject to drafts, direct sunshine, or other heat
sources. The initial heat anticipator setting should be
equal to the total current draw of the control circuit.

Low voltage thermostat connections are to be made to the
blower control board as indicated on the wiring diagram.

Continuous Low Speed Blower

If continuous blower operation on low speed is desired,
connect the lowest speed motor tap to the “CONT”
terminal on the blower control board (refer to the furnace
wiring diagram.) The blower will operate on low speed
whenever main power is connected to the furnace, except
when it operates on heating or cooling speed during
thermostat call for heat or cooling. This constant air
terminal is intended for low speed only. If a motor is
wired for a higher speed, the increased amp draw could
cause the board control to fail and void the warranty.

Humidifier

Terminals are provided on the blower control board for
connection to a 120-volt humidifier. The “HUM” terminal is
energized whenever the thermostat calls for heat. Refer to
furnace wiring diagram for specific connection information.

Filters are not supplied with CG90TB series furnaces but
their use if required. G1D91BT and G1D93BT furnaces come
with a filter rack and cleanable 16" x 25" x 1/2" filter. (Models
designed for more than 1600 CFM nominal air delivery
include two of each.) The filter rack is to be installed between
the return air duct and the side of the furnace.

If a filter other than one supplied by the furnace
manufacturer is used, it must be sized according to
information provided in Table 3.

Refer to Figure 31 and the following instructions to install
the filter rack:

1. Using the corner embossments as a guide, mark and
cut a full-size opening in the side panel(s).

2. Using the filter rack as a template, mark and drill four
7/64" diameter screw holes in the side panel(s).

3. With the filter access opening toward the front of the
furnace, use sheet metal screws to fasten the rack(s)
to the side panel(s).

The filter slides in the rack from the front of the unit. Install
the filter(s) with the mesh side towards furnace.

For units that do not include a side return filter rack, kit
AFILT524 can be used. Single side filter frame kit
AFILTHA7 is available for single side return air connection
in installations requiring more than 1600 CFM nominal air
delivery. Bottom return filter kit AFILT529 is also available
from the manufacturer.

# 47860A005Page 20

Minimum Filter Requirements

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1. The Airflow Descriptor is the two digits following
the “D” in the model number.

2. Areas and dimensions shown for cleanable filters
are based on filters rated at 600 feet per minute
face velocity.

3. Typical filter sizes are shown; however, any
combination of filters whose area equals or
exceeds the minimum area shown is satisfactory.

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START-UP

Lighting Instructions

For Your Safety, Read Before Operating

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WARNING

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

These furnaces are equipped with an ignition device
which automatically lights the burners. Do not try to light

the burners by hand.

Before operating, 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.

What to do if you smell gas:

• Do not try to light any appliances.

Filter Rack Installation

Front of Cabinet

Bottom Filter Location

Table 3

Filter Rack Mounting Hole

Corner Embossments

Figure 31

Side

Screw

Filter Rack

• Extinguish any open flame.

• Do not touch any electric switch; do not use any

phone in your building.

• Immediately call your gas supplier from a neighbor’s

phone. Follow the gas supplier’s instructions.

• If you cannot reach your gas supplier, call the fire

department.

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

IMPORTANT: Refer to the Lighting Instruction label on
the furnace for instructions on operating the specific
controls used on your unit.

To Start Furnace:

CAUTION

Base

Filter

Figure 32

# 47860A005 Page 21

Be sure the manual gas control has been in
the “OFF” position for at least 5 minutes
before starting the unit. Do not attempt to
manually light the burners.

1. Set the room thermostat to lowest setting.

2. Remove burner access door.

3. Move the gas control knob to the “ON” position. Use
only your hand to turn the gas control knob; never use
tools. If the knob will not turn by hand, don’t try to
repair it; call a qualified service technician. Force or

attempted repair may result in a fire or explosion.

4. Replace the burner access door.

5. Turn on the electrical power to the furnace.

6. Set the room thermostat to a point above room
temperature to light the main burners. After the
burners have ignited, set the room thermostat to
desired temperature.

To Shut Down Furnace:

shuts off after a 15-second post-purge delay. The circulating
air blower will continue to operate until the user-selectable
heat blower “off” delay expires. The control return to standby
mode once the heat blower “off” delay expires.

Fan “On”

During a fan “on” call, the thermostat energizes the R-G
circuit of the control board, immediately causing the fan to
energize the COOL speed. The fan remains energized as
long as the thermostat calls for fan “on” operation.

If a call for cooling is energized during a fan “on” call, the fan
continues to operate at the COOL speed. If a call for heat is
energized during a fan “on” call, the control de-energizes the
fan immediately and begins the heat call/ignition sequence.

1. Set the room thermostat to the lowest setting.

2. Turn off all electric power to the furnace.

3. Remove burner access door.

4. Shut off the gas by moving the gas control knob to the
“OFF” position.

5. Replace the burner access door.

WARNING

Should overheating occur or the gas supply
fail to shut off, shut off the manual gas valve
to the appliance before shutting off the
electrical supply.

OPERATION

Sequence of Operation

Heating

During a call for heat the thermostat closes the R-W
circuit of the control board. The control board verifies limit
switches are closed and pressure switch is open. The
induced draft blower relay closes causing the blower to
run. As vent pressure is developed by the induced draft
blower, the pressure switch closes. After a 15-second pre­purge, the control energizes the hot surface ignitor. After
the 7-second warmup time, the control energizes the main
gas valve causing the main burners to ignite. The hot
surface ignitor is de-energized 3 seconds after the main
valve opens. If flame is sensed during this time the main
valve remains energized and the control starts the
30-second heat blower “on” delay.

As heating demand is met, the thermostat de-energizes the
R-W circuit. The control de-energizes the main valve
causing the burners to shut off. The induced draft blower

At the end of the fan “on” call the thermostat de-energizes
the R-G circuit of the control, causing the fan to be de­energized immediately.

Cooling

During a call for cooling, the thermostat energizes the R-Y
circuit of the control board. After a 1-second cooling “on”
delay, the control energizes the cooling fan speed. If the fan
is already energized, it remains running and does not de­energize for the 1-second cooling fan “on” delay.

The call for cooling has priority over continuous fan
operation while a call for heating has priority over both a
call for cooling or continuous fan. Ignition lockouts for any
reason do not affect cooling operation.

As cooling demand is met, the thermostat de-energizes
the R-Y circuit of the control board. After a 60-second
cooling “off” delay, the control de-energizes the cooling
speed fan. At the end of the cooling “off” delay period, the
control returns to the standby mode.

Controls

Following is a description of the operation of some of the
controls used in this furnace. All models use one of each
control, except as noted.

Pressure Switch

The pressure switch is a normally open switch that
monitors combustion air flow. Inadequate air flow resulting
from excessive venting system restriction or a failed
combustion blower will cause the switch to remain open.

Rollout Switch

The rollout switch is a normally closed switch that opens
when abnormal temperatures exist in the burner area.
This can be caused by a restricted heat exchanger
causing main burner flame to “roll out” into the vestibule
area or burner box. These units have two rollout switches.

# 47860A005Page 22

Primary Limit Control

This is a normally closed control that opens if abnormally
high circulating air temperatures occur. It is an automatic
reset control.

Auxiliary Limit Control

This is a normally closed control that opens under abnor­mal “reverse air flow” conditions that could occur in a
counterflow or horizontal installation if the circulating
blower fails. It is an automatic reset control.

Interlock (Blower Door) Switch

When the blower door is removed, the interlock switch
breaks the power supply to the burner controls and blower
motor. The switch operation must be checked to confirm it
is operating correctly.

Blower Control Board

The blower control board operates the circulating air
blower, the combustion blower and any accessories
connected to it. These models feature user-selectable
blower “off” delay times (60, 90, 120, and 180 seconds)
that are factory set to provide a 120-second blower “off”
delay on heating (see wiring diagram on page 27).

Gas input must never exceed the value shown on the
furnace rating plate. The furnace is equipped for rated
input at manifold pressures of 3.5" W.C. for natural gas or

10.0" W.C. for propane gas.

To measure the manifold pressure, disconnect the hose
and remove the barbed fitting in the downstream side of
the gas valve and connect a water manometer or gauge
(see Figure 33).

Checking and Adjusting

Gas Input

Refer to the furnace wiring diagram while using the
following procedure to change motor speed:

1. Turn off electrical power to the unit.

2. Connect the desired speed tap for cooling on the

blower control board.

3. For heating speed, check the temperature rise and, if

necessary, adjust the blower speed tap to maintain
temperature rise within the range shown on the
furnace rating plate.

To use the same speed tap for both heating and
cooling, install a piggyback terminal on the speed tap
using a short jumper. Wire 1/4" quick connect termi­nals on both ends to jumper the “HEAT” and “COOL”
speed on the blower control board.

4. The remaining speed taps must be connected to

dummy terminals marked “PARK” on the blower
control board.

Checking and Adjusting Gas Input

Figure 33

To adjust the regulator, turn the adjusting screw(s) on the
regulator clockwise to increase pressure and input; coun­terclockwise to decrease pressure and input.

Replace the barbed fitting and reconnect the hose after
measuring and/or adjusting the regulator.

CAUTION

The furnace rate must be within +/- 2% of the
appliance rating input.

For Natural Gas: Check the furnace rate by observing
the gas meter, when available, making sure all other gas
appliances are turned off. The test hand on the meter
should be timed for at least one revolution. Note the
number of seconds for one revolution.

Cubic Feet Per RevolutionBTU/HR

INPUT # Seconds Per Revolution

=

x 3600 x

Heating

Value

The minimum permissible gas supply pressure for the
purpose of input adjustment is 5" W.C. for natural gas and
11" W.C. for propane gas. This furnace requires conversion
for use with propane (see Accessories section on page 26
for correct kit). The maximum inlet gas supply pressure is

10.5" W.C. for natural gas and 13" W.C. for propane.

# 47860A005 Page 23

The heating value of the gas can be obtained from the local
utility company.

For Propane Gas: The only check for the furnace rate is to
properly adjust the manifold pressure using a manometer

and Table 4. Typical manifold set point for installations at
altitudes from 0 to 4500 feet above sea level is 10.0" W.C.

MAINTENANCE

Temperature Rise

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

High Altitude

In both the United States and Canada, this furnace is
approved for operation at altitudes from 0 to 4500 feet
above sea level without any required modifications. From
4500 to 7500 feet, the gas manifold pressure needs to be
adjusted according to the information shown in Table 4.

To adjust the manifold pressure, refer to Checking and
Adjusting Gas Input on page 23. For installations above
7500 feet, call Technical Service at 1-800-448-5872 ext.
2610 for assistance.

Manifold Pressure vs. Altitude

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000594892.3930214.90098.0

0055 338 72.3 0002 53.9 0978.0

000681852.3469192.90868.0

0056 208 32.3 7291 42.9 0758.0

000778712.3198181.90648.0

0057 177 91.3 3581 21.9 0538.0

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WARNING

ELECTRICAL SHOCK, FIRE,

OR EXPLOSION HAZARD

Failure to follow the safety warnings exactly
could result in dangerous operation, serious
injury, death, or property damage.

Improper servicing could result in dangerous
operation, serious injury, death, or property
damage.

• Before servicing, disconnect all electrical

power to furnace.

• When servicing controls, label all wires prior

to disconnecting. Reconnect wires correctly.

• Verify proper operation after servicing.

It is recommended that this furnace be inspected by a
qualified service technician at the beginning of each
heating season.

Filters

Filters should be checked at least every 6 weeks. Dispos­able filters should be replaced when dirty, and cleanable
filters should be cleaned regularly. It is important to keep the
air filters clean, as dirty filters can restrict airflow and the
blower and induced draft motors depend upon sufficient air
flowing across and through them to keep from overheating.

Lubrication

The blower motor and induced draft motor are pre-lubri­cated by the manufacturer and do not require further
lubricating attention. However, the motors should be
cleaned periodically to prevent the possibility of overheating
due to an accumulation of dust and dirt on the windings or
on the motor exterior.

Furnace Input = Input Factor x Nameplate Input

Above 7500 feet, call Technical Services at 1-800­448-5872 ext. 2610.

Table 4

Condensate Collection and Disposal System

Check the condensate drain line periodically for blockage.
Visual inspection of condensate flow can be done easily
while the furnace is in operation. Use a flashlight to
illuminate the discharge end of the condensate drain that
is placed in the sewer opening. If the condensate drain
line becomes blocked or plugged, the furnace will not
operate properly.

# 47860A005Page 24

Main Burners

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Light the burners and allow to operate for a few minutes to
establish normal burning conditions. Observe the main
burner flames. Compare this observation to Figure 34 to
determine if proper flame adjustment is present. Flame
should be predominantly blue in color and strong in appear­ance. Check that all burners are lit, and that the flame does
not impinge on the sides of the heat exchanger.

Distorted flame or yellow tipping of the natural gas main
burner flame, or long yellow tips on propane, may be
caused by lint accumulation or dirt inside the burner or
burner ports, at the air inlet between the burner and
manifold pipe, or obstructions over the main burner orifice.

The furnace has a built-in, self-diagnostic capability. If a
system problem occurs, a fault code is shown by an LED
on the control board. The control continuously monitors its
own operation and the operation of the system. If a failure
occurs, the LED will indicate the failure code. The flash
codes are presented in Table 5.

Fault Code History Button

The control stores the last five fault codes in memory. A
pushbutton switch is located on the control (see Figure 35
on page 27). When the pushbutton switch is pressed and
released, the control flashes the stored fault codes. The
most recent fault code is flashed first; the oldest fault code
is flashed last.

Use a soft brush or vacuum to clean the affected areas.

Typical Flame Appearance

(Main Burners)

Heat

Exchanger

Burner

Gas

Manifold

Burner

Flame

(Blue Only)

Figure 34

CONTROL SYSTEM DIAGNOSTICS

Troubleshooting

To clear the fault code history, press and hold pushbutton
switch in for more than 5 seconds before releasing.

Failure Codes

The following visual checks should be made before
troubleshooting:

1. Check to see that the power to the furnace and the

blower control board is on.

2. The manual shutoff valves in the gas line to the

furnace must be open.

3. Make sure all wiring connections are secure.

4. Review the Sequence of Operation (see page 22).

Start the system by setting the thermostat above the room
temperature. Observe the system’s response. Then use
the information provided in this section to check the
system’s operation.

# 47860A005 Page 25

Table 5

REPAIR PARTS

The following repair parts are available from the local
distributor. When ordering parts, include the complete
furnace model number and serial number which are
printed on the rating plate located on the furnace.

Control Group

Transformer
High limit control
Auxiliary limit (if used)

Control Group (cont.)

Gas valve
Ignition/blower control board
Flame sensor
Pressure switch
Blower door interlock switch
Combustion blower assembly
Flame rollout protector switch
Hot surface igniter

Heat Exchanger Group

Heat exchanger – primary
Heat exchanger – secondary
Condensate drain pan

Blower Group

Blower housing assembly
Blower wheel
Blower motor
Blower motor mount
Blower motor capacitor

Burner Group

Gas manifold
Main burner orifices
Main burners

Accessories

ALPKT572 Natural Gas to Propane Conversion Kit

(G1D91BT and CG90TB)

ALPKT574 Natural Gas to Propane Conversion Kit

(G1D93BT)
AFILTHA7 Single Side Filter Frame Kit
AFILT524 Side Return Filter Kit
AFILT529 Bottom Return Filter Kit
ANGKT557 Propane to Natural Gas Conversion Kit

(G1D91BT and CG90TB)
ANGKT556 Propane to Natural Gas Conversion Kit

(G1D93BT)
ATWIN579 Twinning Kit
ACVK2 Concentric Vent Kit

# 47860A005Page 26

Connection Diagram

P/N 45198-006

# 47860A005 Page 27

Figure 35

Schematic Diagram

P/N 45198-006

Figure 36

# 47860A005Page 28