Armstrong G1D80BT User manual

# 45465K005 Page 1
INSTALLATION INSTRUCTIONS
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 prop-
erty damage, personal injury, or death.
WARNING
Manufactured By
A.A.C.
A Lennox International Inc. Company
421 Monroe Street
Bellevue, OH 44811
TABLE OF CONTENTS
SAFETY ................................................. 2
INSTALLATION....................................... 3
START-UP ............................................ 19
OPERATION ........................................ 20
MAINTENANCE ................................... 25
CONTROL DIAGNOSTICS .................. 26
REPAIR PARTS .................................... 27
WIRING DIAGRAMS ............................ 28
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.
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
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.
IMPORTANT
Save these instructions for future reference
G1D80BT, G1D80BR, G2D80CT, & G2D80CR
80% Gas Furnace
with System Sentry™ Control System
*45465K005*

# 45465K005
Page 2
IMPORTANT SAFETY INFORMATION
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 4 of
these instructions.
3. Provide adequate combustion and ventilation air to
the furnace space as specified in the Combustion
and Ventilation Air section beginning on page 4
of these instructions.
4. Combustion products must be discharged outdoors.
Connect this furnace to an approved vent system
only, as specified in Venting beginning on page 6
of these instructions.
5. Never test for gas leaks with an open flame. Use a
commercially available soap solution made specifi-
cally for the detection of leaks to check all connec-
tions, as specified in Gas Supply and Piping
beginning on page 15 of these instructions.
6. 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 23 of these instructions. See furnace rating plate.
7. 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 12 of these instructions.
8. A gas-fired furnace for installation in a residential
garage must be installed as specified in the Loca-
tion section on page 4 of these instructions.
9. The furnace is permitted to be used for temporary
heating of buildings or structures under construc-
tion as specified in the Location section on page 4
of these instructions.
In the State of Massachusetts:
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.

# 45465K005 Page 3
These instructions must be placed on or near the
furnace in a conspicuous place.
This furnace is design certified by CSA International as a
Category I furnace using air from inside the structure for
combustion.The combustion system is fan-assisted, which
means it is equipped with an integral mechanical means to
draw products of combustion through the heat exchanger.
G1D80BT and G2D80CT models may be installed as
upflow furnaces or horizontal furnaces. G1D80BR and
G2D80CR models may be installed as counterflow
(downflow) furnaces 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
Figure 1
INSTALLATION
Locate Screw Here When Horizontal
Installation is Airflow Right to Left
Return
Supply
Locate Screw Here When Horizontal
Installation is Airflow Left to Right
G1D80BR/ ModelsG2D80CR
Return
Supply
Locate Screw Here When Horizontal
Installation is Airflow Left to Right
Locate Screw Here When Horizontal
Installation is Airflow Right to Left
G1D80BT/ ModelsG2D80CT
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.
Check the rating plate for correct model number, type of
gas, and input.
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.
All models are suitable for installation at reduced clear-
ances to combustibles as noted in the tables in Figure 2.
Minimum Clearances to Combustibles
(all measurements in inches)
1May be 2" when Type B-1 vent pipe is used.
2May be 1" when Type B-1 vent pipe is used.
3Where values greater than 0 are shown, may be 0"
when Type B-1 vent pipe is used.
Figure 2
Upflow and Counterflow Installations
Horizontal Installations
(G1D80BR models)
Horizontal Installations
(G2D80CR, G1D80BT, and G2D80CT models)
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# 45465K005
Page 4
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.
WARNING
Where servicing clearances are greater than clearances
to combustibles, servicing clearances take precedence.
G1D80BT, G2D80CT, and horizontally installed G1D80BR
and G2D80CR models may be installed on wood flooring,
but shall not be installed directly on carpeting, tile, or other
combustible material other than wood flooring.
G1D80BR and G2D80CR models installed as counterflow
(downflow) units may be installed on combustible flooring
provided a special combustible floor base is used. See
Counterflow (Downflow) Installations on page 14 for
more information. Refer to unit rating plate for combustible
floor base part number.
Location
All models are suitable for closet or utility room installation.
The furnace must be installed so that electrical compo-
nents are protected from water.
The furnace is suitable for installation in buildings con-
structed 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 to 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 construc-
tion 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 struc-
tures 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.
• 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 construc-
tion.Temporary ducting may supply outdoor air to the
furnace. Do not connect duct directly to the furnace. Size
the temporary duct following the instructions given on the
next page in the Combustion and Ventilation Air
section regarding confined space with air from outside.
• The furnace heat exchanger, components, duct
system, air filters, and evaporator coils must be thor-
oughly 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.
G1D80BR, G1D80BT, G2D80CR, and G2D80CT 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. When a furnace is installed in
conjunction with an evaporator coil in an attic or above a
finished ceiling where condensate overflow could result
in property damage, a drain pan should be provided
under the units as specified by most local building codes.
These furnaces may be installed as suspended units in the
horizontal position.These furnaces are not designed for
direct attachment of suspension rods to the furnace casing.
The suspending means must be field fabricated, and
should consist of two “cradles” made by attaching two
rods to a length of angle iron or suitable gauge steel.
Locate the cradles as close as possible to the ends of the
furnace (this will provide access for removal of major
components such as the blower assembly). Provide
enough clearance between the suspension rods and the
furnace to allow removal of access panels.
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 provi-
sions of the local building codes.

# 45465K005 Page 5
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.”
Confined Space Installation/Air from Inside Structure
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
(see Figure 3). 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.
Figure 3
Note: Each opening shall have a free area of at least one square
inch per 1000 BTU per hour of the total input rating of all
equipment in the enclosure, but not less than 100 square
inches.
Water
Heater
Chimney or
Gas Vent
Openings
Furnace
Equipment in Confined Space
All Air From Inside
Confined Space Installation/Air from Outside Structure
If air from outside is brought in for combustion, the confined
space shall be provided with two permanent openings. One
opening shall be within 12" of the ceiling and one opening
within 12" of the floor. Several methods can be used to
bring the outside air in through these openings. The open-
ings shall open directly or by ducts with the outdoors,
through spaces (crawl space or attic) that freely open to the
outdoors, or indirectly through vertical ducts (see Figures 4
and 5). If any of these methods are used, 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.
Another option is to use horizontal combustion ducts
(see Figure 6 on page 6). If horizontal combustion ducts
are run, 1 square inch per 2000 BTU/HR is required.
Figure 5
Figure 4
Equipment in Confined Space
All Air from Outside
(Inlet Air from Crawl Space and
Outlet Air to Ventilated Attic)
Chimney or
Gas Vent
Ventilation Louvers
(Each end of attic)
Water
Heater
Furnace
Outlet
Air
Inlet
Air
Ventilation
Louvers
(For unheated
crawl space)
Note: The inlet and outlet air opening shall each have a free area of
at least one square inch per 4000 BTU per hour of the total
input rating of all equipment in the enclosure.
Chimney or
Gas Vent
Ventilation Louvers
(Each end of attic)
Inlet Air
(Ends 12”
above bottom)
Outlet Air
Water
Heater
Furnace
Equipment in Confined Space
All Air from Outside
(All Air Through Ventilated Attic)
Note: The inlet and outlet air opening shall each have a free area of
at least one square inch per 4000 BTU per hour of the total
input rating of all equipment in the enclosure.

# 45465K005
Page 6
Figure 7
Inlet Air Restrictor Plate
The inlet air restrictor plate must be installed in all
installations using inside air for combustion (non-direct vent).
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 out-
door 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
This furnace has a fan-assisted combustion system designed
for vertical venting into a suitable chimney or listed gas vent,
and is classified as a Category I furnace (negative vent) as
shipped from the factory. This furnace is dual certified as a
direct vent using outside air for combustion or it can use air
from inside the structure. See Figures 14 – 16 on pages 11
and 12 for optional outside combustion air applications.
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 7) is supplied with this
furnace and can be found in the plastic bag containing these
Installation Instructions and the User’s Information Manual.
For installations using inside air for combustion, the inlet air
restrictor plate must be installed as shown in Figure 8.Two
different sized inlet restrictor plates are supplied with the
furnace (2" and 3"). The 3" restrictor plate should be used
with non-direct vented 100K and larger models only; all
other non-direct vented models use the 2" restrictor plate.
Figure 6
Equipment in Confined Space
All Air from Outside
(All Air Through Horizontal Ducts)
Chimney or
Gas Vent
Furnace
Water Heater
Outlet Air
Inlet Air
Note: Each air duct opening shall have a free area of at least one
square inch per 2000 BTU per hour of the total input rating of
all equipment in the enclosure. If the equipment room is
located against an outside wall and the air openings
communicate directly with the outdoors, each opening shall
have a free area of at least one square inch per 4000 BTU
per hour of the total input rating of all other equipment in the
enclosure.

# 45465K005 Page 7
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 do so could
cause improper operation that can result in a
fire hazard or carbon monoxide injury.
WARNING
Sidewall Venting
This furnace can be sidewall (horizontally) vented with a
listed sidewall venter, such as Field Controls Model SWG-
4HD with CK-43 Control Kit, or Tjernlund Model GPAK-JT.
Category I venting classification is maintained when vented
in this manner. The furnace, power venter, and control kit
(where applicable) must be installed in accordance with their
installation instructions and all applicable codes.
The following limitations also apply to the two previously
mentioned venters:
Vent pipe diameter: 4"
Minimum vent pipe length: 4'
Maximum vent pipe length: 25'*
Maximum number of 90° elbows: 4
* When fewer than four elbows are used, maximum vent
pipe length can be increased by 5' per unused elbow.
For Canadian installations, only the Field Controls
venter and control kit are authorized by CSA for use
with this furnace.
See Figures 9 and 10 on pages 8 and 9 for information on
where the sidewall vent terminal can and cannot terminate.
Vertical Venting (Using Inside Air for Combustion)
Category I furnaces must be vented vertically or nearly
vertically. Common venting and multistory venting are
permitted when done in accordance with applicable
codes, such as local and national codes.
The venting system should be designed in accordance with
the “FAN” columns in the venting tables in the latest editions
of the National Fuel Gas Code, ANSI Z223.1/NFPA 54 or the
CSA B149.1, Natural Gas and Propane Installation Codes.
For installations using inside air for combustion, the inlet
air restrictor plate (supplied) must be installed in the air
inlet pipe as shown in Figure 8. See the Venting section
beginning on page 6 for more information.
Figure 8
Inlet Air Restrictor Plate Placement
If this furnace is used to replace an existing furnace, it is
possible that the existing venting system is not suitable
for venting this furnace. Furthermore, the existing venting
system may have to be modified to properly vent any other
gas appliance (such as a water heater) that remains con-
nected to it. Carefully read the Sidewall Venting,Vertical
Venting, and Existing Vent Systems sections that follow to
determine proper venting practices for the installation.
Installation shall be in accordance with Parts 7 and 11 of
the National Fuel Gas Code, ANSI Z223.1/NFPA 54 (latest
edition) and/or Section 7 and Appendix B of the CSA
B149.1, Natural Gas and Propane Installation Codes
(latest edition); local building codes; vent manufacturer
instructions; and these instructions.
1. Consult local building codes for installation requirements.
2. The vent connector should be as short as possible with
the least number of elbows and angles to do the job.
For 100K, 125K, and 150K BTUH input models,
the minimum vent connector diameter is 5". The
transition from 4" diameter flue outlet to 5"
diameter pipe must be made at the flue outlet.
IMPORTANT

# 45465K005
Page 8 Figure 9
Sidewall Vent Terminal Clearances (Direct Vented Furnaces)
1In accordance with the current CSA B149.1, Natural Gas and
Propane Installation Code
2In 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.
‡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 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.”
†
‡
V
X
Vent Terminal
Air Supply Inlet
Area Where Terminal Is
Not Permitted
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# 45465K005 Page 9
Figure 10
Sidewall Vent Terminal Clearances (Non-Direct Vented Furnaces)
1In accordance with the current CSA B149.1, Natural Gas and
Propane Installation Code
2In 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.
‡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 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.”
†
‡
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Air Supply Inlet
Area Where Terminal Is
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# 45465K005
Page 10
3. It is recommended a minimum of 26 gauge galvanized
flue pipe be used. Use of single-wall vent pipe for the vent
connector is permissible only in conditioned space. Use
Doublewall Type B vent pipe through unconditioned
space such as attics and crawl spaces. The vent
material used should be in accordance with the National
Fuel Gas Code, ANSI Z223.1/NFPA 54 (latest edition) or
the CSA B149.1, Natural Gas and Propane Installation
Codes and local codes. Fan-assisted combustion system
Category I furnaces shall not be vented into single wall
metal vents.
4. The vent connector must have an upward slope
toward the chimney on all horizontal runs of at least
1/4" per foot of horizontal run and should be sup-
ported by a sheet metal strap. The vent pipe connec-
tion must be secured to the induced draft blower
outlet. A single screw is sufficient.
5. All vents passing through floors, ceilings, and walls must
be firestopped according to the requirements of the
National Fuel Gas Code (see Figure 11).
Figure 11
Vent Through Ceiling
Vent Through Floor
Vent Through Wall
6. The furnace shall be connected to a factory-built
chimney or vent complying with a recognized stan-
dard, or a masonry or concrete chimney lined with a
lining material acceptable to the authority with jurisdic-
tion. Venting into an unlined chimney or a single
wall metal vent is prohibited in all cases. A lined
chimney may be used if a draft hood equipped
appliance, such as a water heater, is connected to
the same flue (see Figures 12 and 13).
7. Extend the vent connector into the chimney so that it
is flush with the inside of the flue liner. Seal the joint
between the pipe and the liner.
8. Masonry chimneys serving fireplaces cannot be used
for venting purposes unless the fireplace opening is
permanently sealed.
9. A vent connector serving this appliance must not be
connected into any portion of mechanical draft
systems operating under positive pressure.
10. The vent pipe must not be connected to a chimney
flue serving a solid fuel appliance.
11. A manual damper, barometric draft regulator, or flue
restrictor must not be installed between the furnace
and the chimney.
12. Where local experience indicates that condensate
may be a problem, the vent shall be constructed to
prevent condensation from entering the combustion
blower. Provision shall be made to drain off the
condensate (see Figures 12 and 13).
13. All unused chimney openings should be closed.
14. All vent pipe run through unconditioned areas or
outside shall be constructed of factory-built chimney
sections (see Figure 13).
15. Multistory venting is allowed as permitted by the
National Fuel Gas Code or local codes.
16. Install all vents in accordance with the vent
manufacturer’s instructions. For unlisted material,
install in accordance with the National Fuel Gas Code.
17. Vent terminals must be installed in accordance with
the vent terminals listing or in accordance with the
National Fuel Gas Code, ANSI Z223.1/NFPA 54
(latest edition) or the CSA B149.1, Natural Gas and
Propane Installation Codes, and local codes.
Vertical Venting (Using Optional Outside Fresh Air for
Combustion)
Consult local codes for any requirements relating to a
fresh air inlet to the furnace. In the absence of local codes

# 45465K005 Page 11
Liner
Masonry
Chimney
Cleanout
Masonry Chimney Venting
Figure 12
Factory-Built
Chimney
Cleanout
Factory-Built Chimney Venting
Figure 13
and for more information on the provisions for fresh air to
furnaces, refer to the latest edition of the National Fuel
Gas Code, ANSI Z223.1/NFPA 54.
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.
The following venting options are available:
1. The vertically vented furnace can have “Fresh Air”
brought directly to the inlet (see Figure 14) by means
of a 2" or 3" plastic (PVC) drain pipe, schedule 40
Figure 14
Typical Installation
Vertical Vent with Outdoor Fresh Air
Keep inlet
away from
obstructions
Max. 65'*
6" Min.
Height to provide
12 clearance to
average snowfall
"
PVC Inlet
Pipe
See Chart
Approved Vent
System
* Equivalent vent length
PVC, ABS, single wall galvanized, or single wall
stainless steel pipe (see Table 1). This configuration is
for informational purposes and might not exactly
reflect your installation. Some modifications may be
required to accommodate the unit location, inlet pipe,
and building structure. The inlet pipe must be free
from any obstructions and anticipated snow fall, since
all air for combustion is through this pipe.
* The inlet air lengths listed are maximum “equivalent
pipe lengths.”
Note: One 90° elbow or two 45° elbows are the
equivalent of 5' of pipe.
Inlet Pipe Specifications
Table 1
2. Outside air may also be brought to the furnace by
means of a well ventilated attic as shown in Figure 15
on page 12, using 2" or 3" plastic (PVC) drain pipe,
schedule 40 PVC, ABS, single wall galvanized, or
single wall stainless steel pipe (see Table 1). It is
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# 45465K005
Page 12
Figure 16
Optional Outside Air
Gas
Water
Heater
Soffit
Vents
Joist and Insulation
Gas
Furnace
Gable Vent 16 Min.”
important that the inlet terminate in the attic 12" above
the ceiling joist or attic insulation, which ever is the
highest. It is required that the attic have proper
ventilation so that adequate combustion air be avail-
able. If ventilation is not provided, the furnace may not
operate properly.
3. An additional method for bringing combustion air to the
furnace is shown in Figure 16. A single 2" or 3" plastic
(PVC) drain pipe, schedule 40 PVC, ABS, single wall
galvanized, or single wall stainless steel inlet pipe (see
Table 1 on page 11) can be installed from the furnace
through the roof terminating at the same height as the
vent. These pipes should be installed no closer than
16". A 180° elbow must be installed on the inlet pipe to
prevent rain and snow from entering the pipe. The
actual height of the roof termination should be 12"
above the average recorded snow accumulation.
Existing Venting Systems
When an existing Category I furnace is removed or
replaced, the original venting system may no longer be
sized to properly vent the attached appliances. An improp-
erly sized venting system can result in spillage of flue
products into the living space, the formation of conden-
sate, leakage, etc. See the WARNING box on page 13 for
proper test procedure.
Circulating Air Supply
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
Joist and Insulation
Soffit
Vents
Gas
Water
Heater Gas
Furnace
Gable Vent
12” Min.
Attic Must Be
Well Ventilated
Note:
Optional Attic Inlet Air
Figure 15
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 furnace casing and run, full
size, to a location outside the utility room or space housing
furnace to prevent a negative pressure on venting system.
When installing a CAM coil in a horizontal position with a
horizontal gas furnace, always keep the open end of the
A-coil facing the supply air outlet of the furnace (blow into
the open end of the A-coil). The A-coil should point away
from the supply air outlet of the furnace (see Figure 17).
If a cooling coil is not installed with the furnace, then a
removable access panel should be provided in the supply
plenum for purposes of inspecting the heat exchanger.
This opening shall be accessible when the furnace is
installed, and shall be of such size that the heat ex-
When an air conditioning unit is used in
conjunction with the furnace, the evaporator
coil must be installed in the discharge (sup-
ply) air. Do not install an evaporator coil in
the return air; excessive condensation will
occur within the furnace.
CAUTION

# 45465K005 Page 13
Failure to follow the steps outlined below for each
appliance connected to the venting system being
placed into operation could result in carbon monox-
ide 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 thermo-
stat so appliance is operating continuously.
7. Test for spillage from draft hood equipped appli-
ances 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 Installa-
tion 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 appli-
ance to their previous conditions of use.
CARBON MONOXIDE POISONING HAZARD
WARNING
Figure 17
Correct Positioning of CAM Coil in the
Horizontal Position with a Gas Furnace
Return
Supply
Incorrect
Return
Supply
Correct
changer can be viewed for possible openings using light
assistance or a probe can be inserted for sampling the air
stream. The cover for the opening shall be leaktight.
Upflow Installations
G1D80BT and G2D80CT series furnaces can be installed
as upflow units with either a side or bottom air return. For
bottom return applications, G2D80CT furnaces are
designed with a special knockout base. If desired, bottom
filter kit AFILT529 can be used.
For side return installation, a full-size return air opening
must be cut in the side panel. Corner embossments are
provided in each side.
When side return is desired on a furnace
with an open bottom, the bottom must be
sealed with a piece of sheet metal large
enough to cover the entire opening. Failure
to connect a return air duct to the bottom, or
to enclose the bottom when side return is
desired, may result in combustion products
being drawn into the circulating air stream
which could result in asphyxiation.
WARNING
To provide sufficient filter area for installations requiring
more than 1600 CFM nominal air delivery, return air will
have to be brought through both sides of the furnace,
through one side and the bottom, or optional external filter
AMB20A may be used.

# 45465K005
Page 14
Figure 19
Filter Rack Mounting Hole
Screw
Filter Rack
Corner Embossments
Front of Cabinet
Filter Rack Installation
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).
4. Install the filter(s) in the rack(s), mesh side of filter
towards furnace.
Model AMB20A external filter is available for single
side return air connection in installations requiring
more than 1600 CFM nominal air delivery.
Horizontal Installations
These furnaces can be horizontally installed for airflow
right to left or left to right. They are to be installed so that
the burner and blower access panels are in a vertical
plane; they are NOT to be installed such that these panels
are in a horizontal plane (see Figure 1 on page 3).
Never install any furnace on its back.
Counterflow (Downflow) Installations
G1D80BR and G2D80CR furnaces may be installed
directly on the supply plenum or coil cabinet if the furnace
is installed on a noncombustible floor.
For installations on combustible flooring, a special base
must be ordered and used (refer to the furnace rating
plate for the appropriate base model number). Refer to the
following instructions and Figure 18:
1. Cut a hole in the floor, sized to provide 1" clearance
between all four sides of the duct and the edge of the
flooring. The four angles on the base assembly should
recess into the floor joists and the base should rest on
all four outside flanges.
2. Construct duct connections with 1" to 1-3/4" right
angle flanges, and long enough to extend below the
floor joists.
3. Drop the duct connections through the top of the base
assembly with the right angle flanges in good contact
with the glass tape on top of the base assembly.
4. Carefully position the furnace over the right angle duct
flanges.
Filters
If a filter other than one supplied by the furnace
manufacturer is used, it must be sized according to
information provided in Table 2.
Filters are not supplied with G1D80BR and G2D80CR
series furnaces but their use if required (see Counterflow
Applications on page 15).
Side Return
A filter rack and cleanable 16" x 25" x 1/2" filter are
supplied with each G1D80BT and G2D80CT furnace.
(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. Refer to Figure 19 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).
Figure 18
Combustible Floor Installation
(Counterflow Models Only)
1"
Combustible
Flooring
Woven
Glass Tape
Base
Assembly
Duct
Furnace

# 45465K005 Page 15
Bottom Filter Location
Upflow Models
Figure 20
Filter
Base
Side
Bottom Return
G2D80CT series furnaces are designed with a special
knockout base pan for bottom return applications. The
removable pan is perforated and held in place by small
metal tabs that must be detached before removing the
knockout base. No special tools are needed.
Counterflow Applications
Filters are not supplied with G1D80BR and G2D80CR
series furnaces; however, filters must be used. It is the
installer’s responsibility to install properly sized filters in
accordance with Table 2.
If filters are needed at furnace only, use the following kits:
•AFILT529 – bottom return or horizontal applications
•AFILT525 – counterflow applications
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).
To remove the NOxinserts, first take out the burners. After
removing the burners, remove the screw holding each
insert and pull the insert from the combustion chamber
(see Figure 21). The screws must be re-installed in the
vest panel after the inserts are removed.
NOxInsert
Location
Figure 21
When converting a low NOxfurnace (desig-
nated by an “L” in the model number, such as
G1D80BT100D20CL-1A) to propane, the
NOxinserts must be removed. Failure to
remove the inserts can create a situation
where carbon monoxide is produced which
may lead to asphyxiation.
WARNING
Any conversion of a natural gas unit to pro-
pane 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.
WARNING
Table 2
Minimum Filter Requirements
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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# 45465K005
Page 16
Electrical Wiring
Failure to follow the safety warnings exactly
could result in serious injury, death, or prop-
erty damage.
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, per-
sonal injury, or loss of life.
WARNING
FIRE OR EXPLOSION HAZARD
Manual
Gas Valve
Union
Te e
Drip Leg
Cap
1/8" NPT
Plugged
Tapping
Manual
Gas Valve
Union
Te e
Drip Leg
Cap
1/8" NPT
Plugged
Tapping
Gas Connection
Upflow/Counterflow
Installation
Horizontal
Installation
Figure 22
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
(see Figure 22).
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.
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.
The gas valve supplied with this furnace is
rated at 1/2 psig maximum. Any higher pres-
sure may rupture the pressure regulator dia-
phragm and may cause overfiring of the burn-
ers and improper burner operation. The
overfiring may result in the creation of carbon
monoxide which could cause asphyxiation.
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 prop-
erty damage, personal injury, or death.
WARNING

# 45465K005 Page 17
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 the 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 overcurrent 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.
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 integrated ignition/blower
control board as indicated on the wiring diagram.
Single Stage Thermostat Operation
(G2D80CR and G2D80CT Models Only)
The automatic heat staging option allows a single stage
thermostat to be used with two stage furnace models
(G2D80CR or G2D80CT). To activate this option, move the
jumper pin (see Figure 23) to desired setting (5 minutes or
10 minutes). The furnace will start on 1st stage heat and stay
at 1st stage heat for the duration of the selected time before
switching to 2nd stage heat.
W1 on the control board must be connected to W1 on the
thermostat.
Humidifier
Terminals are provided on the integrated ignition/blower
control board for connection to a 120-volt humidifier. The
“HUM” terminal is energized whenever the thermostat
calls for heat. See the furnace wiring diagram for specific
connection information.
Electronic Air Cleaner
Terminals are provided on the integrated ignition/blower
control board for connection of a 120-volt electronic air
cleaner. The “EAC” terminal is energized whenever the
thermostat calls for heat, cooling, or continuous blower. See
furnace wiring diagram for specific connection information.
Continuous Blower Operation
The comfort level of the living space can be enhanced when
using this feature by allowing continuous circulation of air
between calls for cooling or heating.
If continuous blower operation on low speed is desired,
connect the lowest speed motor tap to the “CONT” terminal
on the integrated ignition/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.
Twinning
The integrated ignition/blower control board is designed to
permit “twinning” of furnaces (two furnaces connected to a
common supply and return air system, and controlled by
one thermostat).
When “twinning” two furnaces, each furnace must
have its own dedicated vent system.
G1D80BR and G1D80BT Models – To twin two G1D80BR
or G1D80BT model furnaces, an accessory kit must be
ordered from the manufacturer (see Accessories on page
27). Specific wiring and operating instructions are included
with the kit.
Automatic Heat Staging Jumper
Figure 23

# 45465K005
Page 18
Figure 24
Wiring Connections for Twinning G2D80BR and G2D80BT Furnaces
Two Stage Heating/Two Stage Cooling
Figure 25
Wiring Connections for Twinning G2D80BR and G2D80BT Furnaces
Two Stage Heating/Single Stage Cooling
G2D80CR and G2D80CT Models – To twin two G2D80CR
or G2D80CT furnaces, connect wires as shown in either
Figure 24 or Figure 25.
NOTE: If a single stage thermostat is used, move the
automatic heat staging jumper pin (see Figure 23 on
page 17) from the NONE position to either the 5 or 10
minute setting. Connect rest of wiring as shown in
Figure 24 or Figure 25 except in this single stage stat
configuration, the W2 must remain open (only W1
should be connected).
If the red LED on the control board flashes a “9 flash” fault
code after the units are energized (see Table 6 on page 26),
switch 24V leads on the transformer in one of the units to
bring both transformers into phase.

# 45465K005 Page 19
Should overheating occur or the gas supply
fail to shut off, shut off the manual gas valve
to the appliance before shutting off the elec-
trical supply.
WARNING
START-UP
Lighting Instructions
For Your Safety, Read Before Operating
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.
•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.
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.
CAUTION
If you do not follow these instructions exactly,
a fire or explosion may result causing prop-
erty damage, personal injury, or loss of life.
WARNING
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 room thermostat to a point above room tempera-
ture to light the burners. After the burners have
ignited, set room thermostat to desired temperature.
To Shut Down Furnace:
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 gas by moving gas control knob to “OFF” position.
5. Replace the burner access door.
To Start Furnace:

# 45465K005
Page 20
Sequence of Operation (G1D80BR and G1D80BT
Models)
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 pre-
purge, 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
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.
In the event the unit loses ignition, the control will attempt
to recycle up to five times before it goes into a 1-hour
lockout. Lockout may be manually reset by removing
power from the control for more than 1 second or remov-
ing the thermostat call for heat for more than 3 seconds.
If during a heating cycle the limit control senses an
abnormally high temperature and opens, the circulating air
blower is energized on high speed and continues to run
while the limit is still open.
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 heat speed. The fan remains energized as
long as the thermostat calls for fan “on” operation.
If a call for heat is energized during a fan “on” call, the fan
continues to operate at the heat speed. If a call for cooling is
energized during a fan “on” call, the fan switches to cooling
speed.
At the end of the fan “on” call the thermostat de-energizes
the R-G circuit of the control, causing the fan to be de-
energized immediately.
OPERATION 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 de-
energize 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.
Sequence of Operation (G2D80CR and G2D80CT
Models)
Heating
When the control is in standby mode, it continually moni-
tors thermostat input, rollout switch, and flame sense.
On a call for 1st stage heat, W1 and R are connected. The
control verifies the limit switch is closed and both low and
high pressure switches are open. The control always starts
on low-fire and ignores 2nd stage call for 30 seconds.
The induced draft blower is energized on high speed and
waits for the low pressure switch to close. The inducer
remains on high speed and begins a pre-purge period
when the low pressure switch closes. After a 15-second
pre-purge, the control energizes the hot surface igniter for
a period of 7 seconds (15 seconds on retries) before the
gas valve is energized on 1st stage and main burners
ignite. After a 30-second blower “on” delay, the control
energizes the low heat circulating air blower. Fifteen
seconds after the circulating air blower energizes, the
combustion air blower switches to low speed and runs at
that speed until the thermostat is satisfied.
If the 1st stage is not sufficient to satisfy the heating
demand, the room thermostat initiates call for the 2nd
stage heating (W1 and W2). The control energizes the
combustion blower on high speed and confirms the high-
fire pressure switch contacts are closed. If the contacts
are closed, the gas valve energizes on the 2nd stage and
the high-heat circulating air blower is energized.
If the automatic heat staging option is being used (see
Single Stage Thermostat Operation on page 17), the
furnace does not switch to 2nd stage heat in response to a
call from the thermostat but instead operates at 1st stage
heat for the duration of the selected time before automati-
cally switching to 2nd stage heat.