Lenoxx G1D91BU, G1D93BC, G1D93BT, G1D91BT, G1D93BU Installation Instructions Manual

INSTALLATION INSTRUCTIONS

G1D91BU, G1D91BT, G1D93BU, G1D93BT & G1D93BC

High Efficiency 90+ Condensing Gas Furnace

With System Sentry™ Control System

Save these instructions for future reference

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.

W ARNING

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.

W ARNING

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.

T ABLE OF CONTENTS

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

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

START-UP..........................................................26

OPERATION ......................................................27

MAINTENANCE .................................................30

REP AIR PARTS..................................................31

CONTROL SYSTEM DIAGNOSTICS.................32

WIRING DIAGRAMS..........................................33

Manufactured By

Allied Air Enterprises Inc.

A Lennox International Inc. Company

215 Metropolitan Drive

West Columbia, SC 29170

*506305-01*

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/NFP A 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.

506305-01 Page 1 of 36Issue 0938

WARNING

IMPORT ANT SAFETY INFORMA TION

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

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 vent­air 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 22 of these instructions.

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 28 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 22
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 permitted to be used for temporary
heating of buildings or structures under construction as
specified in the Location section beginning on page 3
of these instructions.

In the State of Massachusett s:

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 lever­type gas shutoffs are used, they shall be T-handle
type.

506305-01Page 2 of 36 Issue 0938

INSTALLATION

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.

Location

T o 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.

WARNING

The condensate drain on this furnace is incorporated
within the furnace and must be primed before start-up.
The condensate system must not be exposed to
temperatures under 32°F. Use of heat tape is
permissible provided the rate temperature of the tape
does not exceed 155°F.

G1D91BU and G1D93BU models shall be installed only as
upflow furnaces. G1D93BC models shall be installed only
as counterflow (downflow) furnaces.

G1D91BT and G1D93BT models may be installed as up flow
or horizontal right to left or left to right airflow furnaces. When
installed horizontally , the inst aller 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

HORIZONTAL RIGHT TO
LEFT AIRFLOW SHOWN

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.

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.

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.

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.

This furnace is not recommended to be used as a construction
heater during any phase of construction. Very low return air
temperatures, harmful vapors, and operation of the unit with
clogged or misplaced filters will damage the unit.

The furnace may be used for heating of buildings or structures
under construction, if the following conditions are met:

• The vent system must be permanently installed per these

installation instructions.

• A room thermostat must control the furnace. The use of

fixed jumpers that will provide continuous heating is not
allowed.

• The return air duct must be provided and sealed to the

furnace.

506305-01 Page 3 of 36Issue 0938

• Return air temperature range between 60°F and 80°F
must be maintained.

• Air filters must be installed in the system and must be
maintained during construction.

• Air filters must be replaced upon construction completion.

• The input rate and temperature rise must be set per the
furnace rating plate.

• One hundred percent (100%) outdoor air must be provided
for combustion air requirements during construction.
Temporary ducting may supply outdoor air to the furnace.
Do not connect duct directly to the furnace. Size the
temporary duct following the instructions provided on this
page in the Combustion and Ventilation Air section
regarding confined space with air from outside.

• The furnace heat exchanger, component s, duct system,
air filters, and evaporator coils must be thoroughly cleaned
following final construction cleanup.

• All furnace operating conditions (including ignition, input
rate, temperature rise, and venting) must be verified
according to these installation instructions.

G1D91BU, G1D91BT , G1D93BU and G1D93BT models may
be installed on wood flooring but shall not be installed directly
on carpeting, tile, or any other combustible material.

G1D93BC counterflow models are certified for installation
on combustible flooring provided a special base assembly
is used. (Refer to the Duct Connection – Counterflow
Models section on page 22 for more information on using
the special base assembly .)

When a counterflow unit is installed on a combustible floor ,
1" clearance must be provided between the supply duct and
the floor.

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

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

Clearances

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 T able 1 for the minimum clearances to combustibles
required for construction and proper unit operation.

Accessibility clearances must take precedence over fire
protection clearances.

Minimum Clearances to Combustibles

Table 1

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.

W ARNING

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.

506305-01Page 4 of 36 Issue 0938

Confined Space

A confined sp ace 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.

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).

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

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

G1D91BU, G1D91BT , G1D93BU, G1D93BT and G1D93BC
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. The inlet

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

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.

506305-01 Page 5 of 36Issue 0938

Figure 2

The inlet restrictor plate must be installed in the air inlet in
one of three ways:

• Restrictor plate in inlet collar: Install the restrictor plate
in the inlet pipe collar in the top panel of the furnace.
Insert a 3" to 36" section of PVC pipe (field supplied)
into the collar. Use high temperature RTV sealant to
attach PVC pipe to collar. A 90° elbow (field supplied)
may be attached to the PVC pipe, but the elbow is not
required. Use high temperature RTV sealant to attach
elbow to PVC pipe (if applicable).

• Restrictor plate in inlet pipe: Insert a 3" to 36" section of
PVC pipe (field supplied) into the collar. Use high
temperature RTV sealant to attach PVC pipe to collar.
Install the restrictor plate in the end of the inlet pipe just
installed. Attach either a field-supplied coupler or 90°
elbow to the end of the PVC pipe to keep the restrictor
plate in place. Use high temperature RTV sealant to
attach the coupler or elbow to PVC pipe.

• Restrictor plate in elbow: Insert a 3" to 36" section of
PVC pipe (field supplied) into the collar. Use high
temperature RTV sealant to attach PVC pipe to collar.
Attach a 90° elbow (field supplied) to the PVC pipe. Use
high temperature RTV sealant to attach elbow to PVC pipe.
Install the restrictor plate into the elbow .

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/NFP A 54 (latest edition).

The length of flue pipe exposed to outdoor conditions should
be kept to a minimum. When the installation requires more
than 3 feet of flue pipe be exposed to outdoor conditions,
insulating the exposed flue pipe with 1/2” Armaflex or
equivalent is recommended. In climates with design
temperatures below zero degrees (F), 3/4” Armaflex or
equivalent is recommended.

Materials

All pipe, fittings, primer, and solvent cement must conform
with American National S tandard 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

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

W ARNING

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 .

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 sould be installed at the termination
of the flue pipe and is designed to keep objects out of the
flue pipe.

For either type of installation (direct or non-direct vent),
special venting considerations must be followed. Refer to
the proper section in pages 11 – 17 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.

Piping and Fitting Specifications

Piping & Fitting

Material

Schedule 40 PVC

(Pipe)

Schedule 40 PVC

(Cellular Core Pipe)

Schedule 40 PVC

(Fittings)

SDR-26

(Pipe)

SDR-26 CPVC

(Pipe)

Schedule 40 ABS

Cellular Core

DWV (Pipe)

Schedule 40 ABS

(Pipe)

Schedule 40 ABS

(Fittings)

Schedule 40 & 80 CPVC

(Pipe)

Schedule 40 & 80 CPVC
(Fittings)

ABS-DWV

Drain Waste & Vent

(Pipe & Fittings)

PVC-DWV

Drain Waste & Vent

(Pipe & Fittings)

Specification

D1785

D2665

T able 2

ASTM

F891

D2466

D2241

F442

F628

D1527

D2468

F441

F438

D2661

506305-01Page 6 of 36 Issue 0938

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.
Canadian Applications Only: PVC pipe, fittings, primer

and solvent cement used to vent this applicance must be
certified to ULC S636 and supplied by a single manufacturer
as part of an approved venting system. In addition, the first
three feet of vent pipe from the furnace flue collar must be
accessible for inspection. Models that may be installed as a
horizontal furnace include a horizontal drain kit. In Canada
this drain kit must be replaced by a locally available IPEX
Drain Kit # 196014. For Local IPEX Canadian Customer

Service Center and Kit abailability call IPEX at 1-866-473-

9462.

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.

When making ABS joint s, pieces can be prepared with a clean
dry cloth to clean inside socket surface of fitting and male end
of pipe to depth of socket. Refer to procedure specified in
ASTM D3138. When joining ABS to PVC materials, use
transition solvent.

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.

Concentric Vent Kit

A concentric vent kit (see Accessories section on p age 31 for
correct kit) 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.

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 11 – 17 for the unit model
and type of installation.

High Altitude Installation: 2” pipe not recommended at
altitude above 4,000 feet. 3” pipe required for altitude above
5,000 feet.

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 other equipment.

Concentric Vent Kit Dimensions

Figure 3

506305-01 Page 7 of 36Issue 0938

See Figures 5 and 6 on pages 9 and 10 for additional
information on where the horizontal vent terminal can and
cannot terminate.

For Massachusetts Installations: The installation must
comply with Massachusetts

248 CMR 5.08 Modifications to

sections of NFP A-54, Chapter10. (See p ages 35 and 36 )

Vent Tables *

(numbers in inches unless specified otherwise)

Minimum Pipe Diameter

45,000 – 75,000 BTU/HR Models

Vent Pipe
Length
(ft.)

5
10
20

30

40

50
60
70
80

90

Vent Pipe
Length
(ft.)

5

10

20

30

40

50

60

70

80

90

0123456789

1.5

1.5

1.5
2

2222222

22 222

2

2

2.5

2.52.5

2.5

2.5

2.52.5

90,000 – 100,000 BTU/HR Models

0123456789

NR

222222

2
222 333

2NR2

2.5

2.5

2.5
3333
33
33

Number of 90° Elbows

22222222
222222222

22222222

2.5 2.5

2.5

2

2.5 2.5

2.5
33333

2.5 2.5 2.5 2.5

2.5 2.5

2.52.52.5

3

3

2.5

2.5

2.5
3333
33

NR

3

3

2.5 2.5

2.5

NR NR

NR

Minimum Pipe Diameter

Number of 90° Elbows

2.5

2222222

2

2

2.5

2.5

3 3

3

NR NR NR

22

2.5 2.5 2.5 2.5

2.5
3

3

NR

2.5 2.5 2.5 2.5

2.5

3 3

33333

3

3

3

NR

NR

NR

NR

NR

NR

2.5 2.5

3

2.5

2.5

3

NR NR NR

NR NR

NRNR

NRNRNR

2.5

2.5

32.5 2.5

3

3

NR

NR

2.5

2.5
3

33

NR

NR

NR

Minimum Pipe Diameter

112,000 – 125,000 BTU/HR Models

Vent Pipe
Length
(ft.)

5

10

20
30

40

50

60

0123456789

2.5

2.5

2.5

2.5 2.5

2.5 2.5

2.5
3

Number of 90° Elbows

2.5

2.52.5

2.5

2.5

2.5

33

3

2.5

2.5

NR

2.5

2.5 2.5

2.5
NR

NR

2.5

2.52.52.5

2.5

2.5

2.5

NR

3

NR

NR

NR NR

2.52.52.5

2.5 2.5

2.5
33

NR
NR NR NR

NR

NR

NR

NR = Not Recommended
* 2” not recommended at altitude above 4,000 feet
3” required for altitude above 5,000 feet

Figure 4

2.52.5

3

2.5
3

3

NR

NRNR

NR

NR
NR
NR

NR

.

NR

506305-01Page 8 of 36 Issue 0938

Sidewall Vent Terminal Clearances (Direct Vented Furnaces)

A ** Minimum 12” (30 cm) above grade or
12” (30 cm) above average snow accumulation.

V

Vent Terminal

Air Supply Inlet

X

Area Where Terminal Is
Not Permitted

1

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

Propane Installation Code

2

In accordance with the current ANSI Z223.1/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.

506305-01 Page 9 of 36Issue 0938

‡

Permitted only if veranda, porch, deck, or balcony is fully open on a
minimum of two sides beneath the floor.

* For clearances not specified in ANSI Z223.1/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

Sidewall Vent Terminal Clearances (Non-Direct Vented Furnaces)

A ** Minimum 12” (30 cm) above grade or
12” (30 cm) above average snow accumulation.

V

X

Area Where Terminal Is
Not Permitted

Vent Terminal

Air Supply Inlet

1

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

Propane Installation Code

2

In accordance with the current ANSI Z223.1/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.

‡

Permitted only if veranda, porch, deck, or balcony is fully open on a
minimum of two sides beneath the floor.

* For clearances not specified in ANSI Z223.1/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

506305-01Page 10 of 36 Issue 0938

G1D91BU, G1D91BT, G1D93BU and G1D93BT Upflow
Models – 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 pages 5 and 6 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 int ake
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 V ent – Vertical Venting

(G1D91BU, G1D91BT, G1D93BU & G1D93BT Only)

Upflow Direct Vent – Horizontal Venting

(G1D91BU, G1D91BT, G1D93BU & G1D93BT Only)

* Maintaining a vertical separation

between the flue outlet and the
air intake of at least 18” is highly
recommended to minimize the
chance of flue gases
recirculating and freezing in the
air intake pipe. This distance
may be reduced in milder
climates or where wind is
unlikely to blow flue products to
the intake pipe, but should not
be less than 6”.

Overhead View

FLUE PIPE

INTAKE PIPE

IS OPTIONAL.

3” MIN. - 48”MAX.

THIS PIECE

Figure 8

Figure 7

506305-01 Page 11 of 36Issue 0938