80+ GAS FURNACE

Category I Furnace
*8MPT Two Stage Heating
*8MPV Variable Speed, Two Stage Heating & Supports
Two Stage Cooling Units * Denotes Brands (C, H, T)
See Section 5 for Category I definition.
SAFETY CONSIDERATIONS
Improper installation, adjustment, alteration, service, maintenance, or use can cause explosion, fire, electrical shock, or
other conditions which may cause death, personal injury, or property damage. Consult a qualified installer, service agency,
or your distributor or branch for information or assistance. The qualified installer or agency must use factory authorized kits
or accessories when modifying this product. Refer to the individual instructions packaged with the kits or accessories when
installing.
Follow all safety codes. Wear safety glasses, protective clothing, and work gloves. Use quenching cloth for brazing
operations. Have fire extinguisher available. Read these instructions thoroughly and follow all warnings or cautions
included in literature and attached to the unit. Consult local building codes, the current editions of the National Fuel Gas
Code (NFCG) NFPA 54/ANSI Z223.1, and the National Electrical Code (NEC) NFPA 70.
In Canada refer to the current editions of the National standards of Canada CAN/CSA B149.1 and .2 Natural Gas and
Propane Installation Codes, and Canadian Electrical Code CSA C22.1.
Recognize safety information. This is the safety alert symbol . When you see this symbol on the unit and in instructions
or manuals, be alert to the potential for personal injury. Understand these signal words; DANGER, WARNING, and
CAUTION. These words are used with the safety alert symbol. DANGER identifies the most serious hazards which will
result in severe personal injury or death. WARNING signifies hazards which could result in personal injury or death.
CAUTION is used to identify unsafe practices which may result in minor personal injury or product and property damage.
NOTE is used to highlight suggestions which will result in enhanced installation, reliability, or operation.

INSTALLER: Affix these instructions on or

adjacent to the furnace.

CONSUMER: Retain these instructions for

future reference.
International Comfort Products, LLC
Lewisburg, TN. 37091 Table of Contents
1. Safe Installation Requirements . . . . . . . . . . . . . . . . . . 5 10. Ductwork and Filter (Upflow/Horizontal) . . . . . . . . . 25
2. Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 11. Ductwork and Filter (Downflow) . . . . . . . . . . . . . . . 27
3. Side Venting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 12. Checks and Adjustments . . . . . . . . . . . . . . . . . . . . 30
4. Combustion & Ventilation Air . . . . . . . . . . . . . . . . . . . 9 13. Furnace Maintenance . . . . . . . . . . . . . . . . . . . . . . . 34
5. Gas Vent Installation . . . . . . . . . . . . . . . . . . . . . . . . . 12 14. Sequence of Operation & Diagnostic (*8MPT) . . . . . 35
6. Horizontal Venting . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 15. Wiring Diagram (*8MPT) . . . . . . . . . . . . . . . . . . . . . 37
7. Chimney Adapter Venting . . . . . . . . . . . . . . . . . . . . . . 17 16. Sequence of Operation & Diagnostic (*8MPV) . . . . . 38
8. Gas Supply and Piping . . . . . . . . . . . . . . . . . . . . . . . . 18 17. Wiring Diagram (*8MPV) . . . . . . . . . . . . . . . . . . . . . 40
9. Electrical Wiring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 18. Thermostat Wiring Guide . . . . . . . . . . . . . . . . . . . . 41

! WARNING ! WARNING
CARBON MONOXIDE POISONING AND FIRE
ELECTRIC SHOCK HAZARD HAZARD.
Failure to follow this warning Failure to follow this warning could result in
could result in personal injury personal injury, death and/or property dam-
and/or death. age.
Turn Off All Power Before This furnace is not designed for use in mobile
Servicing. homes, trailers or recreational vehicles.
Portions of the text and tables are reprinted from NFPA 54 / ANSI Z223.1 2006, with permission of National Fire Protection Association, Quincy, MA 02269 and American Gas Association,
Washington, DC 20001. This reprinted material is not the complete and official position of the NFPA or ANSI, on the referenced subject, which is represented only by the standard in its
entirety.

Specifications are subject to change without notice 441 01 2023 01 Nov 2008
 START UP CHECK SHEET
For PSC Models *8MPT
(This sheet is optional. Keep for future reference.)
Date of Start Up: Calculated Input (BTU) Rate: (See Checks and Adjust-
ments Section).
Dealer Name:
Heating Check

Address: Measured Line Pressure During High Heat:

Measured Manifold Pressure: High Heat

City, State(Province), Zip or Postal Code:
Low Heat

Temperature of Supply Air: High Heat

Phone: Low Heat

Temperature of Return Air:

Owner Name:
Temperature Rise (Supply Return): High Heat
Address: Low Heat

City, State(Province), Zip or Postal Code: In Rise Range (see furnace rating plate)?

Static Pressure (Ducts) High Heat: Supply

Return
The Blower Speed Tap used for: High Heat
Model Number:
Low Heat
Optional Check: CO?
Serial Number:
CO2?
Setup Checks Cooling Check

Check the box when task is complete. Temperature of Supply Air:

Temperature of Return Air:

All Electrical Connections Tight?
Temperature Difference:
Manual Gas Shut off Upstream of Furnace/Drip Leg Static Pressure (Ducts) Cooling: Supply

Gas Valve turned ON? Return

The Blower Speed Tap used for: Cooling

Type of Gas: Natural: LP: Dealer Comments:

Filter Type and Size:

Shade in Heating Fan “Time OFF” Setting and Thermo-

stat Type setting:

441 01 2023 01 Specifications are subject to change without notice 2

 START UP CHECK SHEET
For Variable Speed Models *8MPV
(This sheet is optional. Keep for future reference.)
Date of Start Up: Calculated Input (BTU) Rate: (See Checks and Adjust-
ments Section).
Dealer Name:
Heating Check

Address: Measured Line Pressure During High Heat:

Measured Manifold Pressure: High Heat

City, State(Province), Zip or Postal Code:
Low Heat

Temperature of Supply Air: High Heat

Phone:
Low Heat
Owner Name:
Temperature of Return Air:

Address: Temperature Rise (Supply Return): High Heat

City, State(Province), Zip or Postal Code: Low Heat

In Rise Range (see furnace rating plate)?

Static Pressure (Ducts) High Heat: Supply

Model Number:
Return
Serial Number:
Optional Check: CO?
Setup Checks CO2?
Check the box when task is complete. Cooling Check

All Electrical Connections Tight? Temperature of Supply Air:

Temperature of Return Air:

Manual Gas Shut off Upstream of Furnace/Drip Leg
Temperature Difference:
Gas Valve turned ON? Static Pressure (Ducts) Cooling: Supply

Return
Type of Gas: Natural: LP:

Filter Type and Size: Dealer Comments:

Shade in Final Furnace Settings Below:

441 01 2023 01
3 Specifications are subject to change without notice
1. Safe Installation Requirements
• Seal around supply and return air ducts.
! WARNING
FIRE, EXPLOSION, AND CARBON MONOXIDE • Install correct filter type and size.
POISONING HAZARD
• Unit MUST be installed so electrical components are pro-
Improper adjustment, alteration, service, tected from direct contact with water.
maintenance or installation could result in personal
injury, death and/or property damage. Safety Rules
Installation or repairs made by unqualified persons
could result in hazards to you and others. Your unit is built to provide many years of safe and dependable
Installation MUST conform with local codes or, in service providing it is properly installed and maintained. However,
the absence of local codes, with codes of all abuse and/or improper use can shorten the life of the unit and
governmental authorities having jurisdiction. create hazards for you, the owner.
The information contained in this manual is
intended for use by a qualified service agency that is A. The U.S. Consumer Product Safety Commission encourages
experienced in such work, is familiar with all installation of carbon monoxide alarms. There can be various
precautions and safety procedures required in such sources of carbon monoxide in a building or dwelling. The
work, and is equipped with the proper tools and test sources could be gas fired clothes dryers, gas cooking
stoves, water heaters, furnaces, gas fired fireplaces, wood
instruments.
fireplaces.

NOTE: This furnace is design certified by the CSA International Carbon monoxide can cause serious bodily injury and/or
(formerly AGA and CGA) for installation in the United States and death. Carbon monoxide or “CO” is a colorless and odorless
Canada. Refer to the appropriate codes, along with this manual, gas produced when fuel is not burned completely or when the
for proper installation. flame does not receive sufficient oxygen.
• Use only the Type of gas approved for this furnace (see
Therefore, to help alert people of potentially dangerous car-
Rating Plate on unit). Overfiring will result in failure of heat bon monoxide levels, you should have a commercially avail-
exchanger and cause dangerous operation. (Furnaces able carbon monoxide alarm that is listed by a nationally
can be converted to Propane gas with approved kit.) recognized testing agency in accordance with Underwriters
• Install this furnace only in a location and position as speci- Laboratories Inc. Standard for Single and Multiple Station
fied in “Installation” of these instructions. Carbon Monoxide Alarms, ANSI/UL 2034 or the CSA 6.19 01
Residential Carbon Alarming Devices installed and main-
• Provide adequate combustion and ventilation air to the tained in the building or dwelling concurrently with the gas
furnace as specified in “Combustion and Ventilation Air” of fired furnace installation (see Note below). The alarm should
these instructions. be installed as recommended by the alarm manufacturer’s
• Combustion products must be discharged outdoors. Con- installation instructions.
nect this furnace to an approved vent system only, as spe-
cified in “Combustion and Ventilation Air, Horizontal B. There can be numerous sources of fire or smoke in a building
Venting and Chimney Adapter Venting” of these instruc- or dwelling. Fire or smoke can cause serious bodily injury,
tions. death, and/or property damage. Therefore, in order to alert
people of potentially dangerous fire or smoke, you should
• Never test for gas leaks with an open flame. Use a com-
have fire extinguisher and smoke alarms listed by Underwrit-
mercially available soap solution made specifically for the ers Laboratories installed and maintained in the building or
detection of leaks to check all connections, as specified in dwelling (see Note below).
“Gas Supply and Piping, Final Gas Piping Check” of these
instructions.
Note: The manufacturer of your furnace does not test any alarms
• Always install furnace to operate within the furnace’s in- and makes no representations regarding any brand or type
tended temperature rise range with a duct system which of alarms.
has an external static pressure within the allowable range,
as specified in “Technical Support Manual” of these in-
C. To ensure safe and efficient operation of your unit, you should
structions. See furnace rating plate.
do the following:
• When a furnace is installed so that supply ducts carry air
circulated by the furnace to areas outside the space con-
taining the furnace, the return air shall also be handled by 1. Thoroughly read this manual and labels on the unit. This
will help you understand how your unit operates and the haz-
a duct(s) sealed to the furnace casing and terminating out-
ards involved with gas and electricity.
side the space containing the furnace.
• A gas fired furnace for installation in a residential garage
2. Do not use this unit if any part has been under water. Im-
must be installed as specified in “Installation” of these in-
mediately call a qualified service technician to inspect the unit
structions.
and to replace any part of the control system and any gas
• This furnace is not to be used for temporary heating of control which has been under water.
buildings or structures under construction. See “Installa-
tion”, item 10.
3. Never obstruct the vent grilles, or any ducts that provide
• This furnace is NOT approved for installation in mo- air to the unit. Air must be provided for proper combustion
bile homes, trailers or recreation vehicles. and ventilation of flue gases.

441 01 2023 01 Specifications are subject to change without notice

4
Frozen Water Pipe Hazard If your furnace remains off for an extended time, the pipes in your
home could freeze and burst, resulting in serious water damage.

! CAUTION If the structure will be unattended during cold weather you should
take these precautions.
WATER DAMAGE TO PROPERTY HAZARD
1. Turn off the water supply to the structure and drain the water
Failure to protect against the risk of freezing could
lines if possible and add an antifreeze for potable water to
result in property damage. drain traps and toilet tanks. Open faucets in appropriate
Do not leave your home unattended for long periods areas.
during freezing weather without turning off water
supply and draining water pipes or otherwise or
protecting against the risk of frozen pipes and 2. Have someone check the structure frequently during cold
resultant damage. weather to make sure it is warm enough to prevent pipes
from freezing. Instruct them on a service agency to call to
Your furnace is designed solely to provide a safe and comfortable provide service, if required.
living environment. The furnace is NOT designed to ensure that or
water pipes will not freeze. It is equipped with several safety de-
vices that are designed to turn the furnace off and prevent it from 3. Install a reliable remote sensing device that will notify
restarting in the event of various potentially unsafe conditions. somebody of freezing conditions within the home.

2. Installation
5. Do NOT install furnace directly on carpeting, tile or other com-
! WARNING bustible material other than wood flooring.

CARBON MONOXIDE POISONING HAZARD 6. Maintain clearance for fire safety and servicing. A front clear-
ance of 24″ (610 mm) is minimum for access to the burner,
Failure to properly vent this furnace or other controls and filter. See clearance requirements in Figure 1.
appliances could result in personal injury or death.
7. Use a raised base if the floor is damp or wet at times.
If this furnace is replacing a previously common-
vented furnace, it may be necessary to resize the 8. Residential garage installations require:
existing vent system to prevent oversizing • Burners and ignition sources installed at least 18″ (457 mm)
problems for the other remaining appliances(s). above the floor.
See Venting and Combustion Air Check in the Gas
Vent Installation section of this instruction. • Furnace must be located or physically protected from pos-
sible damage by a vehicle.
9. If the furnace is to be suspended from the floor joists in a
Location and Clearances basement or a crawl space or the rafters in an attic, it is nec-
essary to use steel pipe straps or an angle iron frame to rigidly
If furnace is a replacement, it is usually best to install the furnace attach the furnace to prevent movement. These straps
where the old one was. Choose the location or evaluate the exist- should be attached to the furnace with sheet metal screws
ing location based upon the minimum clearance and furnace di- and to the rafters or joists with bolts. The preferred method is
mensions (Figure 1). to use an angle iron frame bolted to the rafters or joists.
10. This furnace may be used for construction heat provided that:
! WARNING • The furnace is permanently installed with all electrical
wiring, piping, venting and ducting installed according to
CARBON MONOXIDE POISONING HAZARD
these installation instructions. A return air duct is pro-
Failure to follow this warning could result in vided, sealed to the furnace casing, and terminated out-
personal injury or death. side the space containing the furnace. This prevents a
Do NOT operate furnace in a corrosive atmosphere negative pressure condition as created by the circulating
containing chlorine, fluorine or any other air blower, causing a flame rollout and/or drawing com-
damaging chemicals, which could shorten furnace bustion products into the structure.
life. • The furnace is controlled by a thermostat. It may not be
Refer to Combustion & Ventilation Air section, “hot wired” to provide heat continuously to the structure
without thermostatic control.
Contaminated Combustion Air for combustion air
evaluation and remedy. • Clean outside air is provided for combustion. This is to
minimize the corrosive effects of adhesives, sealers and
other construction materials. It also prevents the en-
Installation Requirements trainment of drywall dust into combustion air, which can
cause fouling and plugging of furnace components.
1. Install furnace level.
• The temperature of the return air to the furnace is main-
2. This furnace is NOT to be used for temporary heat of build- tained between 55° F (13° C) and 80° F (27° C) , with no
ings or structures under construction. evening setback or shutdown. The use of the furnace
while the structure is under construction is deemed to be
3. Install furnace as centralized as practical with respect to the intermittent operation per our installation instructions.
heat distribution system.
• The air temperature rise is within the rated rise range on
4. Install the vent pipes as short as practical. (See Gas Vent the furnace rating plate, and the firing rate has been set
Installation section). to the rating plate value.

5 Specifications are subject to change without notice 441 01 2023 01

 • The filters used to clean the circulating air during the • After construction is complete,verify proper furnace op-
construction process must be either changed or thor- erating conditions including ignition, gas input rate, air
oughly cleaned prior to occupancy. temperature rise, and venting according to these instal-
• The furnace, ductwork and filters are cleaned as neces- lation instructions.
sary to remove drywall dust and construction debris from
all HVAC system components after construction is com-
pleted.

Figure 1 Dimensions and Clearances (*8MPT/*8MPV) in(mm)

MINIMUM CLEARANCES TO
COMBUSTIBLE MATERIALS FOR ALL UNITS
TOP
REAR 0
FRONT (combustion air openings in 3″ (76 mm)
F furnace and in structure)
51/3 (135) Required For Service *24″ (610 mm)
5 (127) ALL SIDES Of SUPPLY PLENUM 1″ (25 mm)
24″ (610) min.
1 (25) SIDES 0
LEFT SIDE VENT
33/4 (95)
(365) A
Single Wall Vent 6″ (76 mm)
38 B Type B 1 Double Wall Vent 1″ (25 mm)
(826) TOP OF FURNACE 1″ (25 mm)
321/2
7 *30″ (762 mm) clearance recommended for furnace removal.
(178) (708) FRONT
277/8

21/4(57) (699) Horizontal position: Line contact is permissible only between lines
271/2 formed by intersections of top and two sides of furnace jacket, and
131/4 Plugged starting hole (440) building joists, studs or framing.
(337) to cut side duct opening.. 175/16

281/2 (724)
213/4 (552) 47/8 11/2 (38) 33/4 (95)
17/8 (124) 181/2 (470)
3/ (19)
(48) 265/8 (676) 2
4
(51)

BOTTOM RIGHT SIDE

D
(940)
37 1 (25)
(851)

41/16 (103) 331/2 7 40

231/8 (587) (178)
C (781) (1016)

ALL DIMENSIONS - IN(MM) 303/4 J 1

2 /4 (57)
H
1 in = 25.4 mm (749)
291/2 Plugged starting hole 131/4
(440) to cut side duct opening.. (337)
175/16
DIMENSIONAL INFORMATION
Furnace Cabinet Top Bottom Return Air
Capacity A B F C D Opening 11/2 47/8 215/8 (542)
(38) (124)
17/8 (48)
151/2 14 6 13/8 125/8 261/2 (673)
*8MPT/V050B H
(76) (356) (152) (1.4) (321) 25-23-44a3

*8MPT/V075F14 191/8 171/2 73/4 21/8 143/4

J NOTE: Evaporator “A” coil drain pan dimensions may vary from furnace duct opening size. Always
*8MPT100F14 (486) (445) (197) (54) (15) consult evaporator specifications for duct size requirements.
Furnace is designed for bottom return or side return.
*8MPT/V100J20 223/4 211/4 91/2 115/16 183/4
J Return air through back of furnace is NOT allowed.
*8MPT/V125J20 (578) (540) (241) (49) (476)

* Denotes Brand Drawing is representative, but some models may vary

Installation Positions Furnace Installation

This furnace can be installed in an upflow, horizontal (either left or Inspect the rating plate to be certain the model number begins with
right) or downflow airflow position. DO NOT install this furnace on “*8MPV” or “*8MPT”. This identifies the unit as a multi position
its back. For the upflow position, the return air ductwork can be at- furnace and can be installed in a Upflow, Horizontal Right, Hori-
tached to either the left or right side panel and/or the bottom. For zontal Left or Downflow position.
horizontal and downflow positions, the return air ductwork must be
attached to the bottom. The return air ductwork must never be at- Upflow
tached to the back of the furnace.
No modifications are required for upflow installation. (See
Figure 2)

441 01 2023 01 Specifications are subject to change without notice

6
 The horizontal furnaces may be installed directly on combustible
Figure 2 Typical Upflow Installation wood flooring or supports, however, it is recommended for further
fire protection cement board or sheet metal is placed between the
SUPPLY
furnace and the combustible wood floor and extend 12″ (305 mm)
AIR beyond the front of the furnace louver door. (This is a recommen-
dation only, not a requirement).
This furnace MUST NOT be installed directly on carpeting, tile or

VENT
other combustible material other than wood flooring or supports.

Downflow
RETURN
AIR
GAS SUPPLY
! WARNING
FIRE HAZARD
25 23 17 Failure to install furnace on noncombustible
subbase could result in personal injury, death
and/or property damage.
Horizontal Place furnace on noncombustible subbase on
If you purchased a multi position furnace, it can be installed hori- downflow applications, unless installing on
zontally in an attic, basement, crawl space, alcove, or suspended noncombustible flooring.
from a ceiling in a basement or utility room in either a right or left
airflow position. (see Figure 3) The Multi position furnace (*8MPT or *8MPV) may be installed in
Horizontally installed furnaces may be vented out the top of the a downflow configuration, (see Figure 4). The minimum clear-
unit or out the side facing up. See “Side Venting” for instructions ances to combustion MUST be maintained between the furnace
to rotate the vent to the side. and adjacent constructions, as shown in Figure 1.

The minimum clearances to combustibles MUST be maintained In addition to clearances in Figure 1, clearance for the vent pipe
between the furnace and adjacent construction, as shown in must be considered.
Figure 1. ONLY the corner of the cabinet is allowed to contact the A subbase for combustible floors MUST be used when the furnace
rafters Figure 3. All other clearances MUST be observed as is installed as a downflow on combustible material. See “Duct-
shown in Figure 1. work and Filter” (Downflow Section). The outlet flange must be
bent flat for downflow installation.

Figure 3 Typical Horizontal Installation When installing a four position furnace in the downflow position,
the logo is to be repositioned so that it is right side up as follows:

RETURN
T8MPT and T8MPV Model Numbers
AIR
1. Find the door hardware kit that is stored in the furnace and
save it.
2. Carefully remove logo from the outside of burner compart-
VENT

ment door and save it.

VENT

SUPPLY
AIR 3. Carefully remove two small plug buttons from outside of
blower compartment door and save them.
4. Remove two thumbscrews from blower compartment door.
GAS SUPPLY Save the two thumbscrews.
5. Install two thumbscrews in holes at other end of blower
compartment door from where thumbscrews were re-
OPTIONAL
VENT LOCATION 25-23-18a moved.
6. Install new strip of rubber gasket on inside of blower
compartment door on edge that does not already have a
If the furnace is to be suspended from the floor joists in a crawl gasket.
space or the rafters in an attic, it is necessary to use steel pipe
straps or an angle iron frame to attach the furnace. These straps 7. Install logo retainer pins into holes in blower compartment
should be attached to the furnace bottom side with sheet metal door from which plug buttons were removed.
screws and to the rafters or joists with bolts. The preferred method 8. Install plug buttons into holes in burner compartment door
is to use an angle iron frame bolted to the rafters or joists. from which logo was removed.
If the furnace is to be installed ground level in a crawl space, con- 9. Install blower compartment door on furnace with bevel
sult local codes. A concrete pad 1″ to 2″ (25.4 to 50.8mm) thick is edge and logo at top.
recommended. 10. Install burner compartment door on furnace with bevel
edge at bottom.
24″ (610 mm) is recommended between the front of the furnace
and adjacent construction or other appliances. This should be C8MPT, C8MPV, H8MPT, and H8MPV Model Numbers
maintained for service clearance. 30″ (762mm) is required to re- 1. Carefully remove logo from burner compartment door and
move furnace. save it.
Keep all insulating materials clear from louvered door. Insulating 2. Turn the logo rightside up, and install the logo retainer pins
materials may be combustible. into holes in burner compartment door

7 Specifications are subject to change without notice 441 01 2023 01

 3. New labels for rightside up application on outside of blower Pressure Switch Relocation
compartment door may be purchased in a kit from your dis-
tributor to cover upside down labels.
If the furnace is installed in the upflow position, the pressure
Typical Downflow Installation switch will remain in the same position as installed by the factory
Figure 4
unless the inducer is rotated. If the furnace is installed in an orien-
tation that places the pressure switch below the pressure tap on
the inducer housing, then the switch MUST be relocated. In order
to relocate the switch, locate 2 mounting holes or drill above the
RETURN
inducer pressure tap. When drilling the 2 holes make sure to keep
AIR the switch and tubing far enough away from the burners or hot sur-
See side venting faces as to not melt the hose, switch, or wires. To prevent possible
for venter rotation
kinking of the pressure switch hose, trim the hose to remove ex-

VENT
cess length (see Figure 5). If additional wire length is needed, cut
the wire tie.
OPTIONAL VENT

Combustible floor base

outlet flange
adapter
Figure 5 Pressure Switch Tube Routing

Vent Shield GAS SUPPLY

Kit MUST BE OPPOSITE
VENT DISCHARGE SIDE
SUPPLY
AIR
25 23 19

Downflow Venting: The combustion venter MUST be rotated to

vent out the side for all downflow installations, (see Figure 4). Bot-
tom venting is not permitted. See “Side venting” for instructions
to rotate the vent to the side. In addition to rotating the vent to the
side, a Vent Pipe Shield (NAHA002VC) is required to shield the
hot vent pipe.

!
BURN HAZARD
WARNING
Vent pipe is HOT and could result in personal
injury.
Hot vent pipe is in reach of small children when
installed in downflow position.
Note: When drilling new holes make sure metal shavings do not
Install vent pipe shield NAHA002VC. fall on or in components, as this can shorten the life of the furnace.

3. Side Venting
This furnace is shipped from the factory with the venter assembly Rotating the Venter Assembly
in an upflow configuration (top vent). The venter assembly can
easily be rotated to a side vent configuration for use in upflow, hori- 1. If gas and electrical power has already been connected to
zontal flow, or downflow application. unit, shut off gas and remove power from unit. Unscrew
screws on burner compartment door and remove burner
compartment door. (See Figure 6.)
When using a side vent configuration (side outlet instead of top
outlet), it may be necessary to relocate the pressure switch to the 2. Disconnect power leads to the venter motor and hose to pres-
alternate position on the opposite side of the top panel. Two screw sure switch. Remove four(4) screws which secure the venter
holes are provided at the alternate position. Route the pressure to the collector box. (See Figure 7.)
switch tubing so the tubing is not kinked and not touching the hot 3. Cut webbing with a pair of snips holding the vent plate to the
collector box, venter housing, or motor. It may be necessary to cabinet on either the left or right side of unit depending on
shorten the length of the tubing to properly route the tubing and right or left venting as desired. Discard vent plate, (see
eliminate kinks. Figure 6).

441 01 2023 01 Specifications are subject to change without notice

8
 Figure 6 Furnace with Screws Figure 7 Venter Gasket

Vent Plate

25-23-52c

4. Replace venter gasket (part # 1013540, if needed) to venter

assembly with adhesive in the same location as the old one.
5. Rotate venter assembly 90° right or left from original location
depending on venting configurations.
Screws (2)
6. Tighten the four(4) screws that secure the venter assembly to
the collector box. Do not overtighten. Do tighten screws
25-23-45 enough to compress venter gasket.
7. Replace power leads to venter motor and reconnect hose to
pressure switch.
NOTE: Unused open vent hole must be covered. A Vent Cover is
supplied with Vent Pipe Shield Kit NAHA002VC. A 55/16″
(135mm) diameter Vent Cover can be fabricated with sheet metal
for all side vent installations.

4. Combustion & Ventilation Air

gens that will result in safety and performance related problems
! WARNING and may harm the furnace. These instances must use only out-
door air for combustion.
CARBON MONOXIDE POISONING HAZARD
Failure to provide adequate combustion and The following areas or types of structures may contain or have ex-
ventilation air could result in personal injury or posure to the substances listed below. The installation must be
death. evaluated carefully as it may be necessary to provide outdoor air
Use methods described here to provide for combustion.
combustion and ventilation air.
• Commercial buildings.
• Buildings with indoor pools.
Furnaces require ventilation openings to provide sufficient air for
proper combustion and ventilation of flue gases. All duct or open-
• Furnaces installed in laundry rooms.
ings for supplying combustion and ventilation air must comply with • Furnaces installed in hobby or craft rooms.
the gas codes, or in the absence of local codes, the applicable na- • Furnaces installed near chemical storage areas.
tional codes. • Permanent wave solutions for hair.
• Chlorinated waxes and cleaners.
Combustion and ventilation air must be supplied in accordance • Chlorine based swimming pool chemicals.
with one of the following:
• Water softening chemicals.
1. Section 9.3, Air for Combustion and Ventilation, of the Nation- • De icing salts or chemicals.
al Fuel Gas Code, National Fuel Gas Code (NFGC), NFPA • Carbon tetrachloride.
54/ANSI Z223.1 2006 in the U.S., • Halogen type refrigerants.
2. Sections 8.2, 8.3, 8.5, 8.6, 8.7, and 8.8 of National Standard • Cleaning solvents (such as perchloroethylene).
of Canada, Natural Gas and Propane Installation Code • Printing inks, paint removers, varnishes, etc..
(NSCNGPIC), CSA B149.1 05 in Canada, • Hydrochloric acid.
3. Applicable provisions of the local building code. • Sulfuric Acid.
• Solvent cements and glues.
When the installation is complete, check that all appliances have • Antistatic fabric softeners for clothes dryers.
adequate combustion air and are venting properly. See Venting • Masonry acid washing materials.
And Combustion Air Check in “Gas Vent Installation” Section in
this manual.
Outdoor Combustion Air Method
Contaminated Combustion Air
A space having less than 50 cubic feet per 1,000 BTUH input rat-
Installations in certain areas or types of structures could cause ex- ing for all gas appliances installed in the space requires outdoor
cessive exposure to contaminated air having chemicals or halo- air for combustion and ventilation.

9 Specifications are subject to change without notice 441 01 2023 01

Air Openings and Connecting Ducts Requirements
1. Total maximum input ratings for all gas appliances in the
space MUST be considered when determining free area of 1. Provide confined space with sufficient air for proper com-
openings. bustion and ventilation of flue gases using horizontal or ver-
2. Connect ducts or openings directly to the outdoors. tical ducts or openings.
3. When screens are used to cover openings, the openings 2. Figure 8 illustrates how to provide combustion and ventila-
MUST be no smaller than 1/4″ (6.4 mm) mesh. tion air when two permanent openings, one inlet and one
4. The minimum dimension of air ducts MUST NOT be less outlet, are used.
than 3″ (76 mm).
5. When sizing grille, louver or screen, use the free area of a. One opening MUST commence within 12″ (305 mm) of
opening. If free area is NOT stamped or marked on grill or the floor and the second opening MUST commence
louver, assume a 20% free area for wood and 60% for met- within 12″ (305 mm) of the ceiling.
al. Screens shall have a mesh size not smaller than 1/4″
(76mm). b. Size openings and ducts per Table 1.

Figure 8 Outdoor Air (This is ONLY a guide. Subject to codes of country having jurisdiction.)

This installation NOT approved in Canada

Gable Vent Gable Vent
Gas Vent Gas Vent
Ventilated Attic Ventilated Attic
Top Above Insulation Top Above Insulation
Optional Inlet Air (1)
Gas Vent
Outlet Air (1) Soffit Vent Soffit Vent
Outlet Air (1)

Inlet Outlet
Air (1) Air (1) Outlet
Inlet Air (2)
Furnace Inlet
Air (1)
Furnace Air (2)

Ventilated Crawl Space

Inlet Furnace
Minimum One Inlet and One Outlet Air Supply is Required Inlet
May be in and Combination Shown Air (1)
Air (2)
Inlet Air Opening Must be Within12″(300mm) of floor
Outlet Air Opening Must be Within12″(300mm) of ceiling
(1) 1 Square Inch (6cm2) per 4000 BTUH
(2) 1 Square Inch (6cm2) per 2000 BTUH

c. Horizontal duct openings require 1 square inch of free The opening shall directly communicate with the outdoors or shall
area per 2,000 BTUH (1,100 mm2/kW) of combined in- communicate through a vertical or horizontal duct to the outdoors
put for all gas appliances in the space (see Table 1). or spaces (crawl or attic) that freely communicate with the out-
d. Vertical duct openings or openings directly communicat- doors.
ing with the outdoors require 1 square inch of free area 4. Combination of Indoor and Outdoor Air shall have:
per 4,000 BTUH (550 mm2/kW) for combined input of all a. Indoor openings that comply with the Indoor Combus-
gas appliances in the space (see Table 1). tion Air Method below and
3. When one permanent outdoor opening is used, the opening b. Outdoor openings located as required in the Outdoor
requires: Combustion Air Method above and
a. 1 sq. in of free area per 3,000 BTUH (700 mm2/kW) for c. Outdoor openings sized as follows.
combined input of all gas appliances in the space (see 1) Calculate the Ratio of all Indoor Space volume
Table 1) and divided by required volume for Indoor Combustion
Air Method.
b. not less than the sum of the areas of all vent connectors 2) Outdoor opening size reduction Factor is 1 minus
in the space.
the Ratio in 1) above.
The opening shall commence within 12″ (305 mm) of the top of the 3) Minimum size of Outdoor openings shall be the size
enclosure. Appliances shall have clearances of at least 1″ (25 required in Outdoor Combustion Air Method
mm) from the sides and back and 6″ (152.4mm) from the front. above multiplied by reduction Factor.

441 01 2023 01 Specifications are subject to change without notice

10
 Table 1 Free Area
Minimum Free Area Required for Each Opening or Duct to Outdoors
BTUH
Input Two Vertical Ducts or
Two Horizontal Ducts Single Opening Rd Duct
Rating Openings
(sq. in./2,000 BTUH) (sq. in./3,000 BTUH) (sq. in. /4,000 BTUH)
(sq. in./4,000 BTUH)
50,000 25 sq. in. 16.7 sq. in. 12.5 sq. in. 4″ (102 mm)
75,000 37.5 sq. in. 25 sq. in. 18.75 sq. in. 5″ (127 mm)
100,000 50 sq. in. 33.3 sq. in. 25 sq. in. 6″ (152 mm)
125,000 62.50 sq. in. 41.7 sq. in. 31.25 sq. in. 7″ (178 mm)
150,000 75 sq. in. 50 sq. in. 37.5 sq. in. 7″ (178 mm)
EXAMPLE: Determining Free Area
Furnace Water Heater Total Input
100,000 + 30,000 = (130,000 ÷ 4,000) = 32.5 Sq. In. Vertical
Furnace Water Heater Total Input
100,000 + 30,000 = (130,000 ÷ 2,000) = 65 Sq. In. Horizontal

Indoor Combustion Air The Standard Method may be used, if the space has no less vol-
ume than 50 cubic feet per 1,000 BTUH of the maximum input rat-
Standard and Known-Air-Infiltration Rate Methods ings for all gas appliances installed in the space. The standard
! NFPA & AGA method permits indoor air to be used for combustion and ventila-
Indoor air is permitted for combustion and ventilation, if the Stan- tion air.
dard or Known Air Infiltration Rate Method is used. The Known Air Infiltration Rate Method shall be used if the in-
filtration rate is known to be less than 0.40 air changes per hour
! WARNING (ACH) and equal to or greater than 0.10 ACH. Infiltration rates
greater than 0.60 ACH shall not be used. The minimum required
CARBON MONOXIDE POISONING HAZARD volume of the space varies with the number of ACH and shall be
Failure to supply adequate combustion air could determined per Table 2 or Equations 1 and 2. Determine the
result in personal injury or death. minimum required volume for each appliance in the space, and
Most homes will require additional air from add the volumes together to get the total minimum required vol-
outdoors for combustion and ventilation. A space ume for the space.
with at least 50 cubic feet per 1,000 BTUH input
rating or homes with tight construction may need
outdoor air, supplied through ducts, to supplement
air infiltration for proper combustion and ventilation
of flue gases.

MINIMUM SPACE VOLUME FOR 100% COMBUSTION AND VENTILATION AIR FROM INDOORS (ft3)
Table 2 Other Than Fan-Assisted Total Fan-assisted Total
(1,000's Btuh) (1,000's Btuh)
ACH 30 40 50 50 75 100 125 150
0.60 1,050 1,400 1,750 1,250 1,875 2,500 3,125 3,750
0.50 1,260 1,680 2,100 1,500 2,250 3,000 3,750 4,500
0.40 1,575 2,100 2,625 1,875 2,813 3,750 4,688 5,625
0.30 2,100 2,800 3,500 2,500 3,750 5,000 6,250 7,500
0.20 3,150 4,200 5,250 3,750 5,625 7,500 9,375 11,250
0.10 6,300 8,400 10,500 7,500 11,250 15,000 18,750 22,500
0.00 NP NP NP NP NP NP NP NP

NP = Not Permitted
Table 2 Minimum Space Volumes were determined by using the
following equations from the National Fuel Gas Code NFPA
54/ANSI Z223.1 2006, 9.3.2.2:
Volume
fan =
15 ft3
ACH
( I fan
1000 Btu / hr
)
1. For other than fan assisted appliances such as a draft
hood equipped water heater,

( )
If:
21 ft3 I other I other = combined input of all other than fan assisted
appliances in Btu/hr
Volume
other =
ACH 1000 Btu / hr

I fan = combined input of all fan assisted appliances in Btu/

2. For fan assisted appliances such as this furnace, hr

11 Specifications are subject to change without notice 441 01 2023 01

 • Unusually tight construction is defined as Construction with
ACH = air changes per hour (ACH shall not exceed 0.60)
1. Walls and ceilings exposed to the outdoors have a con-
The following requirements apply to the Standard Method and to tinuous, sealed vapor barrier. Openings are gasketed or
the Known Air Infiltration Rate Method. sealed and
2. Doors and openable windows are weather stripped and
• Adjoining rooms can be considered part of a space, if there
are no closable doors between rooms. 3. Other openings are caulked or sealed. These include
joints around window and door frames, between sole
• An attic or crawl space may be considered a space that freely plates and floors, between wall ceiling joints, between
communicates with the outdoors provided there are ade- wall panels, at penetrations for plumbing, electrical and
quate ventilation openings directly to outdoors. Openings gas lines, etc.
MUST remain open and NOT have any means of being
closed off. Ventilation openings to outdoors MUST be at least Ventilation Air
1 square inch of free area per 4,000 BTUH of total input rating
Some provincial codes and local municipalities require ventilation
for all gas appliances in the space.
or make up air be brought into the conditioned space as replace-
• In spaces that use the Indoor Combustion Air Method, in- ment air. Whichever method is used, the mixed return air tempera-
filtration should be adequate to provide air for combustion, ture across the heat exchanger MUST not fall below 60°
ventilation and dilution of flue gases. However, in buildings continuously, or 55° on an intermittent basis so that flue gases will
with unusually tight construction, additional air MUST not condense excessively in the heat exchanger. Excessive con-
be provided using the methods described in section densation will shorten the life of the heat exchanger and possibly
titled Outdoor Combustion Air Method: void your warranty.

5. Gas Vent Installation

3. Use the same diameter Category I connector or pipe as per-
! WARNING mitted by:
CARBON MONOXIDE POISONING HAZARD • by the National Fuel Gas Code Code (NFGC) NFPA
Failure to properly vent this furnace could result 54/ANSI Z223.1 2006 Sections 12 and 13 venting re-
quirements in the United States
in personal injury or death.
or
Use methods described here to provide combus-
tion and ventilation air. • the National Standard of Canada Natural Gas and Pro-
pane Installation Code (NSCNGPIC) CSA B149.1 05
Section 8 and appendix C venting requirements in Cana-
da.
Install the vent in compliance with codes of the country having ju- 4. Push the vent connector onto the furnace flue collar of the
risdiction, local codes or ordinances and these instructions. venter assembly until it touches the bead (at least 5/8″ over-
lap) and fasten with at least two field supplied, corrosion re-
sistant, sheet metal screws located at least 140° apart.
This Category I furnace is fan assisted. 5. Keep vertical Category I vent pipe or vent connector runs as
short and direct as possible.
Category I furnace definition: A central furnace which operates 6. Vertical outdoor runs of Type B or ANY single wall vent pipe
with a non positive vent static pressure and with a flue loss not below the roof line are NOT permitted.
less than 17 percent. These furnaces are approved for common 7. Slope all horizontal runs upwards from furnace to the vent ter-
venting and multi story venting with other fan assisted or draft minal a minimum of 1/4″ per foot (21 mm/m).
hood equipped appliances in accordance with the NFGC or 8. Rigidly support all horizontal portions of the venting system
NSCNGPIC. every 6′ (1.8m)or less using proper clamps and metal straps
to prevent sagging and ensure there is no movement after
installation.
Category I Safe Venting Requirements 9. Check existing gas vent or chimney to ensure they meet
clearances and local codes. See Figure 1
Category I furnace vent installations shall be in accordance with
Parts 10 and 13 of the National Fuel Gas Code (NFGC), NFPA 10. The furnace MUST be connected to a factory built chimney or
54/ANSI Z223.1 2006; and/or Section 8 and Appendix C of the vent complying with a recognized standard, or a masonry or
CSA B149.1 05, National Standard of Canada, Natural Gas and concrete chimney lined with a lining material acceptable to
Propane Installation Code; the local building codes; furnace and the authority having jurisdiction. Venting into an unlined
vent manufacturer’s instructions. masonry chimney or concrete chimney is prohibited.
See the Masonry Chimney Venting section in these in-
structions.
NOTE: The following instructions comply with the NFPA 54/ANSI 11. Fan assisted combustion system Category I furnaces shall
Z223.1 2006 National Fuel Gas Code and CSA B149.1 Natural not be vented into single wall metal vents.
Gas and Propane Installation code, based on the High Heat
12. Category I furnaces must be vented vertically or nearly verti-
input rate on the furnace rating plate. cally, unless equipped with a listed mechanical venter.
1. If a Category I vent passes through an attic, any concealed 13. Vent connectors serving Category I furnaces shall not be
space or floor, use ONLY Type B or Type L double wall vent connected into any portion of mechanical draft systems oper-
pipe. If vent pipe passes through interior wall, use type B vent ating under positive pressure.
pipe with ventilated thimble ONLY. Venting and Combustion Air Check
2. Do NOT vent furnace into any chimney serving an open fire- NOTE: When an existing Category I furnace is removed or re-
place or solid fuel burning appliance. placed, the original venting system may no longer be sized to

441 01 2023 01 Specifications are subject to change without notice

12
properly vent the attached appliances, and to make sure there is
adequate combustion air for all appliances, MAKE THE FOL- Figure 9 Vent Check
LOWING CHECK.

! WARNING
CARBON MONOXIDE POISONING HAZARD
Vent Pipe Draft Hood

Typical Gas
Failure to follow the steps outlined below for each Water Heater Match
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 NOTE: If flame pulls towards draft hood, this indicates
connected to the venting system being placed into sufficient infiltration air.
operation, while all other appliances connected to the
venting system are not in operation:
1. Seal any unused openings in the venting system.
Venting to Existing Masonry Chimney
2. Inspect the venting system for proper size and horizontal NOTE: The tables and notes referred to below are found in the
pitch, as required in the National Fuel Gas Code, NFPA most recent printing of the NFGC venting tables.
54/ANSI Z223.1 2006 or CSA B149.1, Natural Gas and Pro-
pane Installation Code and these instructions. Determine Use the NFGC or NSCNGPIC Tables to size the chimney or vent.
that there is no blockage or restriction, leakage, corrosion Dedicated venting of one fan assisted furnace into any ma-
and other deficiencies which could cause an unsafe condi- sonry chimney is restricted. A chimney must first be lined with
tion. either Type B vent sized in accordance with NFPA 54/ANSI
3. As far as practical, close all building doors and windows and Z223.1 2006 tables 13.1 or13.2 or a listed, metal lining system,
all doors between the space in which the appliance(s) con- sized in accordance with the NFPA 54/ANSI Z223.1 2006 section
nected to the venting system are located and other spaces of 13.1.7 for a single appliance or 13.2.19 for multiple appliances or
the building. CSA B149.1 05 Annex C; or venting into a masonry chimney is
4. Close fireplace dampers. permitted as outlined with use of an optional listed masonry chim-
5. Turn on clothes dryers and any appliance not connected to ney kit. (See Section 7. Masonry Chimney Venting of these in-
the venting system. Turn on any exhaust fans, such as range structions)
hoods and bathroom exhausts, so they are operating at max- Listed, corrugated metallic chimney liner systems in masonry
imum speed. Do not operate a summer exhaust fan. chimneys shall be sized by using NFPA 54/ANSI Z223.1 2006 or
6. Follow the lighting instructions. Place the appliance being in- CSA B149.1 05 tables for dedicated and common venting with
spected into operation. Adjust the thermostat so appliance is the maximum capacity reduced by 20% (0.80 X maximum capac-
operating continuously. ity) and the minimum capacity as shown in the applicable table.
7. Test for spillage from draft hood equipped appliances at the Corrugated metal vent systems installed with bends or offsets re-
draft hood relief opening after 5 minutes of main burner op- quire additional reduction of 5% of the vent capacity for each bend
eration. Use the flame of a match or candle. (Figure 9) up to 45° and 10% of the vent capacity for each bend from 45° up
8. If improper venting is observed, during any of the above to 90°.
tests, the venting system must be corrected in accordance
with the National Fuel Gas Code, NFPA 54/ANSI NOTE: Two(2) 45° elbows are equivalent to one (1) 90° elbow.
Z223.1 2006 and/or CSA B149.1, Natural Gas and Propane
Installation Code. Combined Venting into a Masonry Chimney
9. After it has been determined that each appliance connected
to the venting system properly vents when tested as outlined Venting into a masonry or concrete chimney is only per-
above, return doors, windows, exhaust fans, mitted as outlined in the NFGC or NSCNGPIC venting tables.
fireplace dampers and any other gas fired burning Follow all safe venting requirements.
appliance to their previous conditions of use.
NOTE: See section 7. Masonry Chimney Venting.

6. Horizontal Venting
Category I Furnaces With External Power Vent Termination
Venters Venting Through a Non-Combustible and
Combustible Wall
In order to maintain a Category I classification of fan assisted fur- Consult External Power Venter manufacturer instructions.
naces when vented horizontally with sidewall termination, a power Select the power venter to match the Btuh input of the furnace be-
venter is REQUIRED to maintain a negative pressure in the vent- ing vented. Follow all of the manufacturer’s installation require-
ing system. ments included with the power venter for:
In the U.S.: Per the NFPA 54/ANSI Z223.1 2006, a listed power • venting installation,
venter may be used, when approved by the authority having juris- • vent terminal location,
diction. • preventing blockage by snow,
In Canada: Only power venters approved by the appliance • protecting building materials from degradation by flue gases,
manufacturer and where allowed by the authority having jurisdic- • see Figure 10 for required vent termination.
tion may be used
NOTE: It is the responsibility of the installer to properly terminate
Please consult the Fields Controls Co. or Tjernlund Products, Inc. the vent and provide adequate shielding. This is essential in order
for power venters certified for use with this furnace. to avoid water/ice damage to building, shrubs and walkways.

13 Specifications are subject to change without notice 441 01 2023 01

Figure 10 Other than Direct Vent Termination Clearance

NFPA 54/ANSI Z223.1

NFPA 54/ANSI Z223.1

A05013

441 01 2023 01 Specifications are subject to change without notice

14
7. Masonry Chimney Venting
Chimney Inspection If a clay tile lined masonry chimney is being used and it is ex-
posed to the outdoors below the roof line, relining might be re-
All masonry chimney construction must conform to Standard quired. Chimneys shall conform to the Standard for Chimneys,
NFPA 211 2006 and to any state or local codes applicable. The Fireplaces, Vents, and Solid Fuel Burning Appliances NFPA
chimney must be in good condition and a complete chimney in- 211 2006 in the United States and to a Provincial or Territorial
spection must be conducted prior to furnace installation. If the in- Building Code in Canada (in its absence, the National Building
spection reveals damage or abnormal conditions, make Code of Canada) and must be in good condition.
necessary repairs or seek expert help. See “The Chimney Inspec-
tion Chart” Figure 11. Measure inside area of tile liner and exact U.S.A. Refer to Sections 13.1.8 and 13.2.20 of the NFPA
height of chimney from the top of the chimney to the highest ap- 54/ANSI Z223.1 2006 or the authority having jurisdiction to deter-
pliance flue collar or drafthood outlet. mine whether relining is required. If relining is required, use a
properly sized listed metal liner, Type B vent, or a listed alterna-
Connector Type tive venting design.
To reduce flue gas heat loss and the chance of condensate prob- NOTE: See the NFPA 54/ANSI Z223.1 2006, 13.1.8 and 13.2.20
lems, the vent connector must be double wall Type B vent except regarding alternative venting design and the exception, which
as specified in the listed kit. cover installations such as the Chimney Adapter Kits
Venting Restrictions for Chimney Types NAHA001DH and NAHA002DH, which are listed for use with
these furnaces.
Interior Chimney has no sides exposed to the outdoors below
the roofline. All installations can be single furnace or common The Chimney Adapter Kit are listed alternative venting design for
vented with another draft hood equipped Category I appliance. these furnaces. See the kit instructions for complete details.

Exterior Chimney has one or more sides exposed to the out- Canada (and U.S.A.) This furnace is permitted to be vented into
doors below the roof line. All installations with a 99% Winter De- a clay tile lined masonry chimney that is exposed to the outdoors
sign Temperature* below 17°F ( 8°C) must be common vented below the roof line, provided:
only with a draft hood equipped Category I appliance.
1. Vent connector is Type B double wall, and
* The 99% Winter Design Dry Bulb (db) temperatures are
found in the 2005 ASHRAE Fundamentals Handbook CD 2. This furnace is common vented with at least 1 draft hood
and Chapter 28. equipped appliance, and
3. The combined appliance input rating is less than the maxi-
! WARNING mum capacity given in Table A, and
CARBON MONOXIDE POISONING, FIRE AND 4. The input rating of each space heating appliance is greater
EXPLOSION HAZARD than the minimum input rating given in Table B for Masonry
Failure to properly vent this furnace could result in Chimneys for the local 99% Winter Design Temperature.
personal injury, death and/or property damage. Chimneys having internal areas greater than 38 square
inches require furnace input ratings greater than the input
These furnaces are CSA (formerly AGA and CGA) ratings of these furnaces. See footnote at bottom of Table
design certified for venting into exterior clay B, and
tile lined masonry chimneys with a factory
accessory Chimney Adapter Kit. Refer to the 5. The authority having jurisdiction approves.
furnace rating plate for correct kit usage. The
Chimney Adapter Kits are for use with ONLY If all of these conditions cannot be met, an alternative venting de-
sign shall be used, such as the listed chimney adapter kit with a
furnaces having a Chimney Adapter Kit number
furnace listed for use with the kit, a listed chimney lining system,
marked on the furnace rating plate. or a Type B vent.

15 Specifications are subject to change without notice 441 01 2023 01

 Exterior Masonry Chimney, If the inspection of a previously used tile lined chimney:
a. Shows signs of vent gas condensation, the chimney should
FAN+NAT Installations with be relined in accordance with local codes and the authority
Type B Double Wall Vent Connectors having jurisdiction. The chimney should be relined with a
! NFPA & AGA listed metal liner, Type B vent, or a listed chimney adapter
kit to reduce condensation. If a condensate drain is re-
Table A- quired by local code, refer to the NFPA 54/ANSI
Combined Appliance Z223.1 2006 Section 12.10 for additional information on
Maximum Input Rating in condensate drains.
Thousands of Btu per Hr b. Indicates the chimney exceeds the maximum permissible
size in the tables, the chimney should be rebuilt or relined to
VENT INTERNAL AREA OF CHIMNEY conform to the requirements of the equipment being
HEIGHT SQ IN.(cm)
FT(m) installed and the authority having jurisdiction.
12(77.4) 19(122.6) 28(180.6) 38(245.2)
A chimney without a clay tile liner, which is otherwise in good con-
6(1.8) 74 119 178 257 dition, shall be rebuilt to conform to NFPA 211 or be lined with a UL
8(2.4) 80 130 193 279 listed (ULC listed in Canada) metal liner or UL listed Type B vent.
10(3) 84 138 207 299 Relining with a listed metal liner or Type B vent is considered to
15(4.6) NR 152 233 334 be a vent in a chase.
20(6.1) NR NR 250 368 If a metal liner or Type B vent is used to line a chimney, no other
30(9.1) NR NR NR 404 appliance shall be vented into the annular space between the
chimney and the metal liner.
Table B- Appliance Application Requirements
Minimum Allowable Input Rating of Appliance operation has a significant impact on the performance
Space-Heating Appliance in of the venting system. If the appliances are sized, installed, ad-
Thousands of Btu per Hr justed, and operated properly, the venting system and/or the ap-
pliances should not suffer from condensation and corrosion. The
VENT INTERNAL AREA OF CHIMNEY venting system and all appliances shall be installed in accordance
HEIGHT sq. in(cm) with applicable listings, standards, and codes.
FT(m) 12(77.4) 19(122.6) 28(180.6) 38(245.2) The furnace should be sized to provide 100% of the design heat-
Local 99% Winter Design Temperature: ing load requirement plus any margin that occurs because of fur-
17 to 26"F ( 8 to 3"C)

17 to 26°F ( 8 to 3°C)* nace model size capacity increments. Heating load estimates can
6(1.8) 0 55 99 141 be made using approved methods available from Air Conditioning
8(2.4) 52 74 111 154 Contractors of America (Manual J); American Society of Heating,
10(3) NR 90 125 169
Refrigerating, and Air Conditioning Engineers; or other approved
engineering methods. Excessive oversizing of the furnace could
15(4.6) NR NR 167 212
cause the furnace and/or vent to fail prematurely.
20(6.11) NR NR 212 258
When a metal vent or metal liner is used, the vent or liner must be
30(9.1) NR NR NR 362 in good condition and be installed in accordance with the vent or
Local 99% Winter Design Temperature: liner manufacturer’s instructions.
5 t o 16"F ( 15 to 9"C)

5 to 16°F ( 15 to 9°C)*
To prevent condensation in the furnace and vent system, the fol-
6(1.8) NR 78 121 166 lowing precautions must be observed:
8(2.4) NR 94 135 182 1. The return air temperature must be at least 60°F db except
10(3) NR 111 149 198 for brief periods of time during warm up from setback at no
15(4.6) NR NR 193 247 lower than 55°F db or during initial start up from a standby
condition.
20(6.11) NR NR NR 293
2. Adjust the gas input rate per the installation instructions.
30(9.1) NR NR NR 377 Low gas input rate causes low vent gas temperatures,
Local 99% Winter Design Temperature: causing condensation and corrosion in the furnace and/or
10 to 4"F ( 23 to 16"C)

10 to 4°F ( 23 to 16°C)* venting system. Derating is permitted only for altitudes

6(1.8) NR NR 145 196 above 2000′ (609.6m).
3. Adjust the air temperature rise to the midpoint of the rise
8(2.4) NR NR 159 213
range or slightly above. Low air temperature rise can cause
10(3) NR NR 175 231 low vent gas temperature and potential for condensation
15(4.6) NR NR NR 283 problems.
4. Set the thermostat heat anticipator or cycle rate to reduce
20(6.11) NR NR NR 333
short cycling.
30(9.1) NR NR NR NR Air for combustion must not be contaminated by halogen com-
11°F Local 99% Winter Design Temperature: pounds which include chlorides, fluorides, bromides, and iodides.
( 24°C) 11°F ( 24°C) or lower* These compounds are found in many common home products such
or lower Not recommended for any vent configuration as detergent, paint, glue, aerosol spray, bleach, cleaning solvent,
salt, and air freshener, and can cause corrosion of furnaces and
* The 99% Winter Design Dry Bulb (db) temperatures are vents. Avoid using such products in the combustion air supply. Fur-
found in the 2005 ASHRAE Fundamentals Handbook CD nace use during construction of the building could cause the furnace
and Chapter 28. to be exposed to halogen compounds, causing premature failure of
Inspections before the sale and at the time of installation will deter- the furnace or venting system due to corrosion.
mine the acceptability of the chimney or the need for repair and/or Vent dampers on any appliance connected to the common vent can
(re)lining. Refer to “The Chimney Inspection Chart” to perform a cause condensation and corrosion in the venting system. Do not use
chimney inspection. vent dampers on appliances common vented with this furnace.

441 01 2023 01 Specifications are subject to change without notice

16
Figure 11 CHIMNEY INSPECTION CHART

For additional requirements refer to the National Fuel Gas Code NFPA 54/ANSI Z223.1-2006 and NFPA 211-2006 Chimneys, Fireplaces, Vents, and Solid Fuel Burning Appliances in
the U.S.A. or to the Canadian Installation Code CSA-B149.1 in Canada.

Crown
condition:
Missing mortar
Yes Rebuild
or brick? crown

No

Is
Chimney properly lined
with clay tile No
liner?

Yes

Is Repair
liner and top No liner or top seal Reline
seal in good or reline chimney as
condition necessary.

Yes Repair

Debris in
cleanout? Mortar, tile, Yes Mortar or Remove mortar
metal vent, fuel oil
Yes and tile debris?
tile debris?
residue?

No Remove metal vent or liner.

No

Clay
tile misalignment, missing Yes
sections, gaps?

Consult
Part B of chimney adapt­
No No er venting Not Suitable
instructions for
application
suitability.
Condensate Is Chimney
drainage at bottom Yes lined with properly Suitable
of chimney? sized, listed liner or
Type-B vent? Line chimney with properly
Yes Install chimney sized, listed flexible metal
adapter per liner or Type-B vent per NFGC or
instructions. NSCNGPIC Vent Sizing Tables and lin­
er or vent manufacturer's installation
No instructions.
Yes Not Suitable

Consult
Chimney Part C of chimney
exposed to outdoors be­ Is Chimney to
low roof line? be dedicated to a single
No adapter venting Suitable
Yes instructions for
furnace? application
suitability.
Install chimney
adapter per
No instructions.

Chimney is
acceptable for use

17 Specifications are subject to change without notice 441 01 2023 01

8. Gas Supply and Piping
! WARNING Table 3 Gas Pressures
FIRE AND EXPLOSION HAZARD Gas Type Supply Pressure
Failure to follow this warning could result in Recommended Max. Min.
personal injury, death and/or property damage. Natural 7 in wc 14 in wc 4.5 in wc
Models designated for Natural Gas are to be used (1744 Pa) (3487 Pa) 1121 Pa)
with Natural Gas ONLY, unless properly converted Propane 11 in wc 14 in wc 11 in wc
to use with Propane gas. (2740 Pa) (3487 Pa) (2740 Pa)

Gas Piping Requirements

NOTE: The gas supply line must be installed by a qualified service
technician in accordance with all building codes.
Gas Supply Requirements NOTE: In the state of Massachusetts.
Gas supply pressure should be within minimum and maximum a. Gas supply connections MUST be performed by a li-
values listed on rating plate. Pressures are usually set by gas sup- censed plumber or gas fitter).
pliers. b. When flexible connectors are used, the maximum length
(See Propane Gas Conversion Kit instruction manual for furnaces shall not exceed 36″ (915 mm).
converted to Propane gas) c. When lever handle type manual equipment shutoff
valves are used, they shall be T handle valves.
• Use only the Type of gas approved for this furnace. See rat-
ing plate for approved gas type. d. The use of copper tubing for gas piping is NOT approved
by the state of Massachusetts.
• A 1/8″ NPT plugged tapping, accessible for a test gauge
1. Install gas piping in accordance with local codes, or in the ab-
connection,must be installed immediately upstream of the
sence of local codes, the applicable national codes.
gas supply connection to furnace.
2. It is recommended that a manual equipment shutoff valve be
• Gas supply pressure should be within minimum and maxi- installed in the gas supply line outside the furnace. Locate
mum values listed on rating plate. Pressures are usually set valve as close to the furnace as possible where it is readily
by gas suppliers. accessible. Refer to Figure 12.
• Gas input must not exceed the rated input shown on the rat- 3. Use black iron or steel pipe and fittings or other pipe approved
ing plate. Overfiring will result in failure of heat exchanger by local code.
and cause dangerous operation. 4. Use pipe thread compound which is resistant to natural and
• Do not allow minimum supply pressure to vary downward. Propane gases.
Doing so will decrease input to furnace. Refer to Table 3 for 5. Use ground joint unions and install a drip leg no less than 3″
Gas supply. Refer to Table 5 or Table 4 for manifold pres- long to trap dirt and moisture before it can enter gas control
sures. valve inside furnace.

Figure 12 Typical Gas Piping and Adding Propane Low Pressure Switch

Alternative
installation
Drip Leg and Union, Union* should be outside the Manual shut-off
cabinet. Manual shut-off valve MUST be upstream of valve
dripleg, union, and furnace.

Use elbows and 3# (76.2mm) pipe nipple to con­

nect valve to piping when using right side gas
pipe entry.

ON

Propane Low pressure OFF

switch. REQUIRED
3# (76.2mm)
pipe nipple

ON
OFF

25 24 86

* Union may be installed inside the cabinet when necessary because of clearances.

441 01 2023 01 Specifications are subject to change without notice

18
 ! WARNING Figure 14
Gas Valve with Elbows
(*8MPT/*8MPV)
FIRE HAZARD
Failure to follow this warning could result in
personal injury, death and/or property damage.
Use wrench to hold furnace gas control valve
when turning elbows and gas line to prevent
damage to the gas control valve and furnace.

6. Use two pipe wrenches when making connections to pre-

vent gas valve from turning.
NOTE: If local codes allow the use of a flexible gas appliance con- 25 25 03a

nector, always use a new listed connector. Do not use a connector

which has previously served another gas appliance.
Gas Valve with Elbows
Figure 15
7. Flexible corrugated metal gas connector may NOT be used (*8MPT/*8MPV)
inside the furnace or be secured or supported by the fur-
nace or ductwork.
8. Properly size gas pipe to handle combined appliance load
or run gas pipe directly from gas meter or Propane gas reg-
ulator.
9. Install correct pipe size for run length and furnace rating.
10. Measure pipe length from gas meter or Propane second
stage regulator to determine gas pipe size.

Left Side Gas Supply Piping

Gas line can be installed directly to the gas valve through the hole
provided in the left side of the cabinet. See Figure 12
4. Gas supply line then can be run directly into opening of elbow.
Right Side Gas Supply Piping Piping with Close Nipples and Standard Elbows
Two(2) 90° street elbows or two(2) 90° standard elbows and 1. Assemble elbows and nipples similar to street elbows shown
two(2) close nipples are required for right side gas supply. See in Figure 13.
Figure 12. 2. Follow steps 2 through 4 Piping with Street Elbows.

Piping with Street Elbows

1. Assemble the elbows so that the outlet of one(1) elbow is 90°
!
WARNING
from the inlet of the other. The elbows should be tight enough FIRE OR EXPLOSION HAZARD
to be leak proof. An additional 1/4 turn will be required at the Failure to properly install metal gas connector
end of step 2, see Figure 13. could result in personal injury, death and/or
2. Screw elbow assembly into gas valve far enough to be leak property damage.
proof. Position elbow assembly so that the inlet of the elbow is A flexible corrugated metal gas connector must be
at the bottom of the gas valve. An additional 1/2 turn will be properly installed, shall not extend through the side
required in step 3. Turn open end of inlet elbow to face the of the furnace, and shall not be used inside the
right side of the furnace (1/4 turn), see Figure 14. furnace.
3. Turn assembly an additional 1/2 turn to position inlet near the Black iron pipe shall be installed at the furnace gas
top of the gas valve. In line with gas opening on right side of control valve and extend a minimum of 2# outside
furnace, see Figure 12 and Figure 15. furnace.

Additional Propane Piping Requirements

Figure 13 Elbows (*8MP)
• Have a licensed Propane gas dealer make all connections
at storage tank and check all connections from tank to fur-
nace.
• If copper tubing is used, it MUST comply with limitation set
in local codes, or in the absence of local codes, the gas
codes of the country having jurisdiction.
• Two stage regulation of Propane gas is recommended.
Propane Conversion
25 23 23c An accessory kit shall be used to convert to propane gas use, see
the furnace rating plate for the Propane conversion accessory kit
part number.

19 Specifications are subject to change without notice 441 01 2023 01

 Ensure furnace is equipped with the correct main burner orifices.
! WARNING Refer to Table 5 or Table 4 for correct orifice size and manifold
pressure for a given heating value and specific gravity for natural
CARBON MONOXIDE POISONING HAZARD
and propane gas.
Failure to follow this warning could result in per-
sonal injury, death and/or property damage.
NOx inserts for use with Natural Gas units Operation Above 2000ft (609.6m) Altitude
ONLY. If Propane Gas is required, NOx inserts must
be removed.
! WARNING
FIRE, EXPLOSION, CARBON MONOXIDE
!
WARNING POISONING HAZARD
FIRE, EXPLOSION HAZARD Failure to follow this warning could result in per-
Failure to follow this warning could result in per- sonal injury, death and/or property damage.
sonal injury, death and/or property damage.
This high altitude gas conversion shall be done
A Propane conversion accessory kit is required by a qualified service agency in accordance with
when operating the furnace with Propane gas. the Manufacturer’s instructions and all applicable
codes and requirements, or in the absence of local
codes, the applicable national codes.
For Propane conversion remove screws that secure the NOx in-
sert and discard insert.
These furnaces may be used at full input rating when installed at
Reinstall screws. See Figure 16 altitudes up to 2000ft (609.6m). When installed above 2000ft
(609.6m), the High Heat input must be decreased 2% (natural) or
NOTE: It is very important to reinstall the NOx insert mounting 4% (Propane) for each 1000ft (304.8m) above sea level in the
screws. USA. In Canada, the input rating must be derated 10% (natural) or
5% (Propane) for altitudes of 2000 to 4500ft (609.6 to 1371.6m)
above sea level. This may be accomplished by a simple adjust-
Figure 16 Removing NOx inserts ment of manifold pressure or an orifice change, or a combination
of a pressure adjustment and an orifice change. The changes re-
quired depend on the installation altitude and the heating value of
the fuel. Table 4 and Table 5 show the proper furnace manifold
pressure and gas orifice size to achieve proper performance
based on elevation above sea level for both natural gas and pro-
pane gas.

To use the natural gas table, first consult your local gas utility for
the heating value of the gas supply. Select the heating value in the
vertical column and follow across the table until the appropriate
elevation for the installation is reached. The value in the box at the
intersection of the altitude and heating value provides not only the
25-24-99a manifold pressure but also the orifice size. In the natural gas
tables the factory shipped orifice size is in bold (42). Other sizes
must be obtained from service parts.

! WARNING High Altitude Input Rate =

Nameplate Sea Level Input Rate x (Multiplier) [USA]
FIRE OR EXPLOSION HAZARD Elevation High Altitude Multiplier
An open flame or spark could result in personal ft (m) Natural Gas Propane Gas
injury, death and/or property damage. 2001′ - 3000′
0.95 0.90
Propane gas is heavier than air and will settle and (609.9 914.4)
remain in low areas and open depressions. 3001′ - 4000′
0.93 0.86
(914.7 1219.2)
Thoroughly ventilate area and dissipate gas. Do
4001′ - 5000′
NOT use a match or open flame to test for leaks, or (1219.5 1524)
0.91 0.82
attempt to start up furnace before thoroughly
ventilating area. 5001′ - 6000′
0.89 0.78
(1524.3 1828.8)
6001′ - 7000′
0.87 0.74
(1829.1 2133.6)
Orifice Sizing 7001′ - 8000′
0.85 0.70
(2133.9 2438.4)
NOTE: Factory sized orifices for natural and Propane gas are
listed in the furnace Technical Support Manual. * Based on mid range of elevation.

441 01 2023 01 Specifications are subject to change without notice

20
MANIFOLD PRESSURE AND ORIFICE SIZE FOR HIGH ALTITUDE APPLICATIONS
NATURAL GAS MANIFOLD PRESSURE (in wc)
Table 4
MEAN ELEVATION FEET ABOVE SEA LEVEL ft(m)
HEATING 0 to 2000 2001 to 3000 3001 to 4000 4001 to 5000 5001 to 6000 6001 to 7000 7001 to 8000
VALUE at (0 to 609.6) (609.9 to 914.4) (914.7 to 1219.2) (1219.5 to 1524) (1524.3 to 1828.8) (1829.1 to 2133.6) (2133.9 to 2438.4)
ALTITUDE Orifice Mnfld Pres­ Orifice Mnfld Pressure Orifice Mnfld Pressure Orifice Mnfld Pressure Orifice Mnfld Pressure Orifice Mnfld Pres­ Orifice Mnfld Pres­
BTU/CU. No. sure No. No. No. No. No. sure No. sure
FT. HI LO HI LO HI LO HI LO HI LO HI LO HI LO
700 41 3.7 1.8
725 41 3.7 1.8 41 3.4 1.7
750 41 3.5 1.7 42 3.6 1.7
775 41 3.6 1.7 42 3.6 1.8 42 3.3 1.6
800 41 3.6 1.8 42 3.7 1.8 42 3.4 1.7 42 3.1 1.5
825 41 3.7 1.8 41 3.4 1.7 42 3.5 1.7 42 3.2 1.6 43 3.6 1.8
850 41 3.5 1.7 42 3.6 1.7 42 3.3 1.6 43 3.7 1.8 43 3.4 1.7
875 41 3.6 1.7 42 3.6 1.8 42 3.4 1.6 42 3.1 1.5 43 3.5 1.7 43 3.2 1.6
900 42 3.7 1.8 42 3.4 1.7 42 3.2 1.6 43 3.6 1.7 43 3.3 1.6 44 3.5 1.7
925 41 3.7 1.8 42 3.5 1.7 42 3.3 1.6 43 3.7 1.8 43 3.4 1.7 43 3.1 1.5 44 3.3 1.6
950 41 3.5 1.7 42 3.3 1.6 42 3.1 1.5 43 3.5 1.7 43 3.2 1.6 44 3.4 1.7 44 3.1 1.5
975 42 3.7 1.8 42 3.2 1.6 43 3.6 1.8 43 3.3 1.6 44 3.5 1.7 44 3.2 1.6 45 3.6 1.7
1000 42 3.5 1.7 43 3.7 1.8 43 3.4 1.7 43 3.1 1.5 44 3.3 1.6 45 3.7 1.8 45 3.4 1.7
1050 42 3.2 1.6 43 3.3 1.6 43 3.1 1.5 44 3.3 1.6 45 3.6 1.8
1100 43 3.6 1.7 44 3.5 1.7 44 3.2 1.6 45 3.6 1.8
Conversion: 1 in wc = 249 Pa
NOTE: Natural gas data is based on 0.60 specific gravity. For fuels with different specific gravity consult the National Fuel Gas Code NFPA 54/
ANSI Z223.1 2006 or National Standard of Canada, Natural Gas and Propane Installation Code CSA B149.1 05.
NOTE: Propane data is based on 1.53 specific gravity. For fuels with different specific gravity consult the National Fuel Gas Code NFPA 54/ANSI
Z223.1 2006 or National Standard of Canada, Natural Gas and Propane Installation Code CSA B149.1 05.
NOTE: The derating of these furnaces at 2% (Natural Gas) and 4% (Propane Gas) has been tested and design certified by CSA.
In Canada, the input rating must be derated 5% (Natural Gas) and 10% (Propane Gas) for altitudes of 2,000 to 4,500 ft (609.6 to 1371.6
m)above sea level. Use the 2001 to 3000 ft (609.9 to 914.4 m) column in Table 4 and Table 5.
The burner orifice part nos. are as follows: High Altitude Air Pressure Switch
Orifice #41 1096942 Orifice #42 1011351
Orifice #43 1011377 Orifice #44 1011352 The factory installed pressure switches need NOT be changed
Orifice #45 1011353 Orifice #54 1011376 for any furnace installations from sea level up to and including
Orifice #55 1011354 Orifice #56 1011355 8,000′ (24.8.4 m) altitude.

Table 5 PROPANE GAS MANIFOLD PRESSURE (in wc)

MEAN ELEVATION FEET ABOVE SEA LEVEL ft(m)
HEATING VALUE 0 to 2000 2001 to 3000 3001 to 4000 4001 to 5000 5001 to 6000 6001 to 7000 7001 to 8000
at ALTITUDE (0 to 609.6) (609.9 to 914.4) (914.7 to 1219.2) (1219.5 to 1524) (1524.3 to 1828.8 (1829.1 to 2133.6) (2133.9 to 2438.4)
BTU/CU. FT.
HI LO HI LO HI LO HI LO HI LO HI LO HI LO
2500 10.0 4.9 10.0 4.9 9.0 4.4 10.0 4.9 9.4 4.6 8.5 4.2 10 4.9
Orifice Size #54 #54 #54 #55 #55 #55 #56
Conversion: 1 in wc = 249 Pa
NOTE: Propane data is based on 1.53 specific gravity. For fuels with different specific gravity consult the National Fuel Gas Code NFPA 54/ANSI
Z223.1 2006 or National Standard of Canada, Natural Gas and Propane Installation Code CSA B149.1 05.
NOTE: The derating of these furnaces at 2% (Natural Gas) and 4% (Propane Gas) has been tested and design certified by CSA.
In Canada, the input rating must be derated 5% (Natural Gas) and 10% (Propane Gas) for altitudes of 2,000 to 4,500 ft (609.6 to 1371.6
m) above sea level. Use the 2001 to 3000 ft (609.9 to 914.4 m) column in Table 4 and Table 5.

21 Specifications are subject to change without notice 441 01 2023 01

 ! WARNING MONOXIDE
FIRE, EXPLOSION, CARBON
Figure 18 Changing Orifices

POISONING HAZARD Measure from face of orifice

to the back side of the
Failure to follow this warning could result in per- manifold.
sonal injury, death and/or property damage. 1.11″ (28.2mm)
1.21″ (30.8mm)

This high altitude gas conversion shall be done

by a qualified service agency in accordance with
the Manufacturer’s instructions and all applicable
codes and requirements, or in the absence of local
codes, the applicable national codes.

Changing Orifices Final Gas Piping Check

1. After disconnecting power and gas supply to the furnace,
remove the burner compartment door, exposing the burner
compartment.
!
WARNING
2. Disconnect gas line from gas valve so manifold can be re- FIRE OR EXPLOSION HAZARD
moved. Failure to follow this warning could result in
3. Disconnect wiring at gas valve. Be sure to note the proper personal injury and/or death.
location of all electrical wiring before being disconnected. Never test for gas leaks with an open flame. Use a
4. Remove the four (4) screws holding the manifold and gas commercially available soap solution made
valve to the manifold supports. Do not discard any screws. specifically for the detection of leaks to check all
See Figure 17. connections.

Figure 17 Manifold ! AVERTISSEMENT

RISQUE D’EXPLOSION ET D’INCENDIE
Le fait de ne pas suivre cet avertissement pourrait
entraîner des dommages corporels et / ou la mort.
Ne jamais examiner pour les fuites de gaz avec une
flamme vive. Utilisez plutôt un savon fait
specifiquement pour la détection des fuites de gaz
pour verifier tous les connections.
1. The furnace and the equipment shut off valve must be dis-
connected from the gas supply piping system during any
pressure testing of that system at test pressures in excess
25-25-00a
of 1/2″ PSIG (3.5 Pa). Close the manual shut off valve be-
fore testing at such pressures.
Some Models may vary 2. The furnace must be isolated from the gas supply system
by closing the equipment shut off valve during any pressure
5. Carefully remove the manifold assembly. testing of the gas supply system at test pressure equal to or
6. Remove the orifices from the manifold and replace them less than 1/2″ PSI (3.5 Pa).
with proper sized orifices. See Figure 18. 3. When installation is complete, test all pipe connections for
7. Tighten orifices so they are seated and gas tight. See leaks with the gas pressure less than 1/2″ PSIG (3.5 Pa) to
Figure 18. the gas valve.
8. Reassemble all parts in reverse order as removed. Be sure 4. Apply a commercial soap solution to all joints to test for
to engage the main burner orifices in the proper openings in leaks. Correct any leaks indicated by bubbles.
the burners. 5. Correct even the smallest leak at once.
9. After reassembling, turn gas on and check all joints for gas 6. Check for leaks at gas valve and orifice connections to the
leaks using a soapy solution. All leaks must be repaired im- burner manifold along with the pilot tube connections to the
mediately. valve and pilot assembly while the furnace is operating.

441 01 2023 01 Specifications are subject to change without notice

22
9. Electrical Wiring
stage thermostat. Failure to change DIP switch with single stage
! WARNING thermostat will result in Low Heat operation ONLY. (See
Figure 21 and wiring diagram)
ELECTRICAL SHOCK HAZARD
Failure to turn off power could result in personal During operation, the furnace will operate on low Heat for up to12
injury or death. minutes. If the heat request exists for more than 12 minutes, the
furnace will automatically shift to the high Heat mode for the re-
Turn OFF electrical power at fuse box or service
maining duration of the heating cycle.
panel before making any electrical connections
and ensure a proper ground connection is made For two stage thermostat installations, the R, W1 and W2 wires
before connecting line voltage. from the thermostat connect to the R, W1 and W2 connections on
the furnace control board. Set TT SW1 DIP switch #3 to ON posi-
tion. During operation, the furnace will shift from Low Heat to High
Power Supply Wiring Heat as requested by the thermostat. (See Figure 19, Figure 20
and wiring diagram)
The furnace MUST be electrically wired and grounded in accor-
dance with local codes, or in the absence of local codes, with the Heat anticipator setting will need to be measured if 24VAC humidi-
National Electrical Code (NEC), NFPA 70 2008 in the U.S., or the fier is installed. Measure current in series from R to W1 at the ther-
Canadian Electrical Code (CEC), CSA C22.1 in Canada. mostat. Be sure 24VAC humidifier is wired up to control. Allow
furnace to operate for two minutes before recording the AC am-
The power supply to the furnace connections must be between perage reading. Set anticipator on thermostat to recorded value.
104 VAC and 127 VAC during furnace operation for acceptable
performance. Thermostat location has an important effect on the operation of
the furnace. Follow instructions included with thermostat for cor-
Field wiring connections must be made inside the furnace connec-
rect mounting and wiring.
tion box. A suitable strain relief should be used at the point the
wires exit the furnace casing. Low voltage connections to furnace must be made on terminal
board to furnace control board. (See Figure 19 and Figure 20)
Copper conductors shall be used. Line voltage wires should
conform to temperature limitation of 35° C rise. Wire and circuit
breaker sizing shall be based on the ampacity of the furnace elec-
Cooling
trical components plus the amps for all installed accessories (1.0 *8MPT
amps total for EAC and HUM). Ampacity can be determined by us-
ing the NEC or CEC. If cooling is used, the Y and G from the thermostat must be con-
nected to the control board Y/Y2 and G to energize cooling blower
NOTE: Furnace will not have normal operation is line polarity is
speed.
reversed. Check ALL field and control connections prior to opera-
tion. NOTE: MPT models are not two stage cooling compatible.
Furnace must be installed so the electrical components are pro-
tected from water and connected to its own separate circuit. *8MPV
Junction Box (J-Box) Relocation If single stage cooling is used, the Y and G from the thermostat
must be connected to the control board Y/Y2 and G to energize
The J Box is installed in the burner compartment on left side of cooling blower speed.
casing. An alternate J Box location on right side can be used.
If two stage cooling is used, the Y1, Y2, G off the thermostat must
1. Remove and save two screws holding J Box to casing. be connected to Y1 of the tap select interface board for Low Cool-
ing, Y/Y2 of the furnace control board for High Cooling and G of the
2. Move large hole plug from right to left J Box location.
furnace control board for continuous fan speed.
3. Clip wire tie holding J Box wires if needed.
Optional Equipment
4. Move J Box to alternate location and attach using two
screws removed from left side location. All wiring from furnace to optional equipment MUST conform to
local codes or, in the absence of local codes with the latest edition
5. Position all wires away from hot surfaces, sharp edges, and
of The National Electric Code, NFPA 70 and/or The Canadian
moving parts. Do not pinch J Box wires or other wires when
Electric Code CSA C22.1. Install wiring in accordance with
reinstalling burner compartment door.
manufacturer’s instructions. The wiring MUST have a minimum
temperature rating of 105° C.
Thermostat
Humidifier/Electronic Air Cleaner
Heating
The furnace is wired for humidifier and/or electronic air cleaner
The two stage furnace control board will operate with either a connection.
single stage or a two stage heating thermostat and will provide
two stage heating operation. HUMIDIFIER The HUM (24V) terminal is energized when
the low pressure switch closes on a call for heat. The HUM
For single stage thermostat installations, the R and W wires
(115V) is energized when the inducer is energized.
from the thermostat connect to the R and W1 connections on the
furnace control board. ELECTRONIC AIR CLEANER EAC is energized when there
Note: The TT (Thermostat Type) SW1 DIP switch # 3 should be in is a blower speed call, except it is NOT energized when blower
the off position for the furnace to operate properly with a single operates in the hard wired continuous fan mode.

23 Specifications are subject to change without notice 441 01 2023 01

 ! CAUTION Figure 20 Electrical Connections
*8MPT
REDUCED FURNACE LIFE HAZARD NOTE: Junction Box can be mounted to either the left or right side.

Failure to follow caution instructions may result in 115V. 60 Hz.

reduced furnace life.

NEUT.
HOT
W
Do NOT exceed 115V/1.0 amp. maximum current BK
load for both the EAC terminal and the HUM G
terminal combined. Connection
Box
Ground

Furnace Control Board LowVoltage

R
C
TerminalBoard
W2
The furnace control board has a fixed blower ON delay of 30 W1
seconds for High Heat calls and 45 seconds for Low Heat calls. Y/Y2
The blower OFF timing is factory preset at 140 seconds. If desired, G
the fan OFF delay can be reset to obtain the longest delay times W
while still maintaining comfort levels. See “Furnace Wiring R G SingleStage
Thermostat
Diagram”.
R
LowVoltage
Dehumidification - Variable Speed ONLY (*8MPV) TerminalBoard
C
W2
W1
The furnace control board has a dehumidification feature which
Y/Y2
reduces cooling airflow by 20% when the DEHUM terminal [1/4” G
(6.4mm) male quick connect] is energized by 24VAC and there is a W2
TwoStage
cooling call. DEHUM may be operated by a thermostat dehumidify R W1
G
Thermostat
(24VAC for dehumidify) command or a dehumidistat (switch 25-25-06a
closes on call for dehumidification) with one terminal connected to NOTE: 115 VAC/60Hz/single-phase
(Y1 for two stage cooling or Y/Y2 for single speed cooling Operating voltage range*: 127 VAC max, 104 VAC min.
applications) and the other terminal connected to DEHUM.
* Permissible limits of voltage at which unit will operate satisfactorily

Figure 19 Electrical Connections

*8MPV
NOTE: Junction Box can be mounted to either the left or right side.
Figure 21 Control Connections
115V. 60 Hz.
NEUT.
HOT

W
BK

G
Connection Diagnostic Light
Box Dip Switch
See “Wiring Diagram”
Ground for switch settings

R
LowVoltage
C
TerminalBoard
W2 24 VAC 115 VAC
W1 HUM HUM
Y/Y2
G
W
R G SingleStage
Thermostat

R FUSE
LowVoltage
C
TerminalBoard EAC
W2 DEHUM
W1
25 24 74
Y/Y2
G
W2 Variable Speed
TwoStage
R W1 Motor Motor
Thermostat
G Control Furnace Control Fuse
NOTE: 115 VAC/60Hz/single-phase 25-25-06
Operating voltage range*: 127 VAC max, 104 VAC min. The 24V circuit contains a 5 amp, automotive type fuse located
on furnace control board. (See Figure 21) Any electrical shorts to
* Permissible limits of voltage at which unit will operate satisfactorily 24V wiring during installation, service, or maintenance may cause
fuse to blow. If fuse replacement is required, use only a fuse of
identical size (5 amp.).

441 01 2023 01 Specifications are subject to change without notice

24
Tap Select Interface Board (*8MPV) whether O is energized or not. COMFORT provides a 10%
reduction in airflow when O is not energized with a cooling call).
The Tap Select Interface Board is used with the Variable Speed
The O terminal is available for use for Heat Pump applications, if
motor. There are DIP switches (SW2) for continuous blower
desired.
adjust, heating blower adjust, cooling blower adjust and cooling
on/off delay profiles. There is a jumper (J1) for slight blower The Y1 terminal (if a two stage Air Conditioner or two stage Heat
adjustment, increase (+)/no change (NOM)/decrease ( ). There is Pump is used) will provide low cooling blower speed when
a jumper (J2) for airflow selection of Heat Pump EFFICIENCY or energized. (Only Y/Y2 on the furnace control board is used if a
COMFORT. (EFFICIENCY provides no airflow reduction in airflow single stage Air Conditioner or Heat Pump is installed)

10. Ductwork and Filter (Upflow/Horizontal)

Duct Installation Requirements
! WARNING • When a furnace is installed so that supply ducts carry air cir-
CARBON MONOXIDE POISONING HAZARD culated by the furnace to areas outside of the space con-
Failure to properly seal duct could result in taining the furnace, the return air shall also be handled by
personal injury or death. duct(s) sealed to the furnace casing and terminating out-
side the space containing the furnace.
Do NOT draw return air from inside a closet or utility
room where furnace is located. Return air duct
MUST be sealed to furnace casing.
! WARNING
CARBON MONOXIDE POISONING HAZARD
Duct Connections Failure to follow this warning could result in
This furnace may be installed in only a bottom or side return ap-
personal injury or death.
plication. Return air through the back of the furnace is NOT al- Cool air passing over heat exchanger could cause
lowed. condensate to form resulting in heat exchanger
Side connections can be made by cutting out the embossed area failure.
shown in Figure 22. A plugged hole is provided at each furnace
side duct location to help start cutting the opening.
• When the furnace is used with a cooling unit, the furnace
shall be installed parallel with or on the upstream side of the
Figure 22 Cutting Side Return Air Opening
cooling unit to avoid condensation in the heating element.
• With a parallel flow arrangement, the dampers or other
means used to control flow of air shall be adequate to pre-
vent chilled air from entering the furnace. Chilled air going
through the furnace could cause condensation and shorten
furnace life. Dampers (purchased locally) can be either au-
tomatic or manual. Manually or automatically operated
Knockout
dampers MUST be equipped with a means to prevent fur-
Starting
nace and air conditioning operation, unless damper is in the
Hole
full heat or cool position.
• Installation of locking type dampers is recommended in all
branches, or in individual ducts to balance system’s air
flows.
• Non combustible, flexible duct connectors are recom-
Bottom returns can be made by removing the knockout panel in mended for return and supply connections to furnace.
the furnace base. Do NOT remove knock-out except for a bottom
return. • If air return grille is located close to the fan inlet, install at
least one 90° air turn between fan and inlet grille to reduce
Duct Design noise.

Design and install air distribution system to comply with Air Condi- • Ductwork installed in attic or exposed to outside tempera-
tioning Contractors of America manuals or other approved meth- tures requires a minimum of 2″ (50.8mm) of insulation with
ods that conform to local codes and good trade practices. outdoor type vapor barrier.

When the furnace is located in an area near or adjacent to the liv- • Ductwork installed in an indoor unconditioned space re-
ing area, the system should be carefully designed with returns to quires a minimum of 1″ (25.4mm) of insulation with indoor
minimize noise transmission through the return air grille. Any type vapor barrier.
blower moving a high volume of air will produce audible noise Inspection Panel on some models
which could be objectionable when the furnace is located very
close to a living area. It is often advisable to route the return air For a furnace not equipped with a cooling coil, the outlet duct shall
ducts under the floor or through the attic. be provided with a removable access panel. This opening shall be
accessible when the furnace is installed and shall be of such a size
• Refer to furnace Technical Support Manual (Blower Data)
that the heat exchanger can be viewed for possible openings us-
for air flow information.
ing light assistance or a probe can be inserted for sampling the air
• Size ductwork to handle air flow for heating and air condi- stream. This access cover shall be attached in such a manner as
tioning. to prevent air leaks.

25 Specifications are subject to change without notice 441 01 2023 01

Filters • The furnaces with greater than 1600 CFM to 2000 CFM
may require that bottom return or both (left and right) side
A filter MUST be used. returns are used or for single side return in upflow applica-
Filters are supplied with these furnaces, and additional filters may tion, must use filter rack NAHA001TK. Two side return fil-
be purchased from your distributor. ters and racks are required. Filter racks must be mounted
externally. (See Figure 23 and Figure 24.) If return air
See Table 6 for required high velocity filter sizes. must be on one side only, an optional 20″ x 25″ (508 x
635mm) filter standoff rack kit can be used. (See
Table 6 High Velocity Air Filter Sizes (max. 600 FPM) Figure 23.) For bottom return, an internal filter can be used
Internal or a filter rack kit can be mounted externally.
Cabinet Filter External Filter Rack
Width in(mm) • See Technical Manual, Circulation Air Blower Data for addi-
in (mm)
Bottom Bottom Side+ tional information.
151/2 14 X 25 14 X 25 14 X 25 (355.6 x 635)
(393.7) (355.6 x 635) (355.6 x 635) or 16 X 25 (508 x 635)* NOTE: The 20″ x 25″ (508 x 635mm) standoff side filter rack
191/8 16 X 25 * 16 X 25 16 X 25
gives more filter area but does not provide more air. (See
(485.8) (406.4 x 635) * (406.4 x 635)* (406.4 x 635)* Figure 23.) To achieve 2000 CFM 2 side returns may be required.
(See Figure 25.)
223/4 20 X 25 20 X 25 16 X 25
(577.9) (508 x 635)* (508 x 635)* (508 x 635)*
NOTE: Disposable, low velocity filters may be replaced with
* Greater than 1600 CFM with a maximum of 2000 CFM requires both (left and right) washable, high velocity filters providing they meet the minimum
side return filter racks or for single return in an upflow application, must use filter rack size areas for 300 FPM or less. Washable, high velocity filters
NAHA001TK. See Figure 23. can be replaced ONLY with same type and size filter.
+ Side return air duct(s) is not permitted with horizontal or downflow furnace installa-
tion.

Use either filter type:

Optional Duct Standoff
• Washable, high velocity filters are based on a maximum air Figure 23 NAHA001TK in(mm)
flow rating of 600 FPM.
• Disposable, low velocity filters are based on a maximum air
flow of 300 FPM when used with with external filter grille.

!
REDUCED FURNACE LIFE HAZARD
CAUTION 23 1/2
(570)

25 1/16 22 1/2
20
Failure to follow caution instructions may result in (637) (572)
(508)
18 1/2
reduced furnace life. (470)

Use of excessively dirty and/or restrictive air filters 14.5

may increase furnace operating (368)

temperatures and shorten the life of the furnace.

16
Filters supplied with the furnace are rated at a (406) 25 1/16
maximum of 600 fpm air velocity and sized for the 20 x 25 (508 x 635 mm) 6 7/8
(637)

furnace’s airflow rate. Replacement filters must be Optional Filter Rack (175)
Filter
of equivalent type, size, and rating except as
described below.
Disposable, low velocity filters may be used to
replace washable, high velocity filters, providing Filters Rack Installation
they are sized for 300 FPM or less.
Side Return
• The furnaces with 1600 or less CFM rating are supplied
with a 16″ x 25″ (406 x 635mm) high velocity filter and Center the filter rack on the side panel, flush with the bottom edge
rack. On these models the supplied filter may be installed of the furnace. Mark the fastening holes. Drill the fastening holes
internally for bottom return or the supplied filter and rack in the side panel and fasten the filter rack in place with sheet metal
may be mounted externally for bottom return. screws. See Figure 24 & Figure 25.

441 01 2023 01 Specifications are subject to change without notice

26
 Side Return Filter Rack Figure 26 Bottom Mounted Filter
Figure 24

Center Clip
side-to-side

9″ (152.4mm) 25-24-18-1

Filter 25-23-05-1 Figure 27 Filter Clip Construction in(mm)

11/2″
(38.1)
3″ (76.2)

Figure 25 Filters Installed on Two Sides 11/4″ (31.8)

Using Two
Filter Racks
26 Ga. Galvanized Steel
FAST part number 1008482 11/ ″
16 (27)

Note: If filters are only suitable for heating application, advise

homeowner that filter size may need to be increased if air condi-
tioning is added.

Addition Of Air Conditioning

25-23-05-3
When a refrigeration coil is used in conjunction with this furnace, it
Filter must be installed on the discharge side of the furnace to avoid
Filter condensation on the heat exchanger. All furnaces are designed
with a break away duct flange on the supply air side of the fur-
nace. This allows for installation in the horizontal right or downflow
applications. The coil installation instructions must be consulted
Internal Filter in Bottom Return Installation for proper coil location and installation procedures. With a parallel
flow arrangement, dampers must be installed to prevent chilled air
When installing a bottom mounted filter inside the furnace, install from entering the furnace. If manually operated dampers are
the filter clips on the edge of the bottom duct opening with the wid- used, they must be equipped with a means to prevent operation of
er end of the clips toward the blower, as shown in Figure 26. Clips either unit unless the damper is in full heat or full cool position.
may be obtained from your distributor or fabricated from sheet
metal (Figure 27). Insert filter into side clips first and push filter Copper or plastic tubing may be used for the condensate drain
back until it is fully engaged into back clip. line.

11. Ductwork and Filter (Downflow)

! WARNING ! WARNING
CARBON MONOXIDE POISONING HAZARD FIRE HAZARD
Failure to properly seal duct could result in Side return air duct(s) could cause excessive
personal injury or death. furnace and/or air temperatures, which could
result in personal injury, death and/or property
Do NOT draw return air from inside a closet or utility damage.
room where furnace is located. Return air duct Return air duct is to be connected to only the top of
MUST be sealed to furnace casing. downflow furnace.

27 Specifications are subject to change without notice 441 01 2023 01

 Sub-Bases for Combustible Floors - Furnace Only
! WARNING Note: When using the subbase for combustible floors, the dis-
BURN HAZARD
charge air duct flanges on the furnace MUST be broken down to
Failure to properly install vent shield could result in provide proper fit up to the subbase. Use duct pliers to bend the
personal injury or death. duct flanges flat onto the furnace casing. DO NOT bend the duct
The vent may be hot. flanges inward (toward the heat exchangers) as air flow restric-
tions may occur.
Vent Shield
The Sub base for Combustible Floors MUST be used when a
A vent shield is required for all downflow installations. The vent downflow furnace is set on a combustible floor, even when the fur-
Must exit out the side of the furnace for all downflow installations. nace is installed on a coil box.
This places the hot vent pipe (over 300° F) within reach of children.
The vent shield attaches to side of furnace to cover vent pipe. See 1. Cut the opening in the floor according to the dimensions in
Figure 4 in “2. Installation” section. Table 7 because the base is equipped with locating tabs that
center the base over the opening.
Outlet Duct Flange
The opening in the base is 11/4″ (31.8mm) shorter and 11/8″
Downflow installations with cased coils require the furnace outlet
(28.6mm) narrower than the minimum required size of the
duct flange to be bent outward and flat to mate the outlet of the fur-
opening in the floor. This is done to maintain a 1″ clearance
nace to the cased coil.
between the floor and the plenum.

! WARNING 2. Fabricate the plenum to the dimensions given in Table 7.

Note that the dimensions given are outside dimensions.
FIRE HAZARD
3. Set the base over the opening in the floor, centering the open-
Failure to install furnace on noncombustible
ing in the base over the opening in the floor. Fasten the base
subbase could result in personal injury, death
to the floor with screws or nails. See Figure 28 and
and/or property damage. Figure 29.
Place furnace on noncombustible subbase on
downflow applications, unless installing on 4. Drop the plenum through the opening in the base. The flange
non combustible flooring. of the plenum should rest on top of the combustible floor
base.

Table 7 Sub bases for Combustible Floors Dimensions in(mm)

Sub base for Sub base for Combustible Opening In Typical Plenum
Opening In Floor
Combustible Floors Floor Dimensions Base For Plenum Dimensions
Part Number H* J* K** L M N P R S T
Subbase for Furnace Only
1511/16 161/4 145/8 131/2 131/2
NAHH001SB 283/4 (730.3) 149/16 (369.9) 16(406.4) 15 (381) 15 (381)
(398.5) (412.8) (371.5) (342.9) (342.9)
195/16 161/4 181/4 171/8 171/8
NAHH002SB 283/4 (730.3) 183/16 (462) 16(406.4) 15 (381) 15 (381)
(490.5) (412.8) (463.6) (435.6) (435.6)
2215/16 161/4 217/8 193/4 193/4
NAHH003SB (582.6) 283/4 (730.3) 2113/16 (554) 16(406.4) (412.8) (555.6) 15 (381) (501.7) 15 (381) (501.7)
Subbase for Coil Box
153/4 209/16 161/16 161/4 145/8 131/2 131/2
NAHH004SB (25.4) (522.3) 149/16 (369.9) (408) (412.8) (371.5) 15 (381) (342.9) 15 (381)
(342.9)
193/8 209/16 161/16 161/4 181/4 171/8 171/8
NAHH005SB 183/16 (462) 15 (381) 15 (381)
(181.1) (522.3) (408) (412.8) (463.6) (435.6) (435.6)
209/16 161/16 161/4 217/8 193/4 193/4
NAHH006SB 23 (284.2) (522.3) 2113/16 (554) (408) (412.8) (555.6) 15 (381) (501.7) 15 (381) (501.7)
* Outside Dimension
** Base Spacer Side To Side
Converstion: 1 in = 25.4 mm

441 01 2023 01 Specifications are subject to change without notice

28
 4. Drop the plenum through the opening in the base. The
Exploded View of Sub Base for
Figure 28 flange of the plenum should rest on top of the combustible
Furnace ONLY
floor base
T S A = 4 1/4” (108mm) Minimum
clearance from back of hole Figure 30 Exploded View of Base for
Plenum to wall or other obstruction. Downflow Cased Coil

H
J
2″ (50.8mm)
K R

2″ (50.8mm)
P 1″ (25.4mm) 21/2″ (63.5mm)
L

N M 11/2″ (38.1mm)
Hole in
Floor

A 25-20-46

Sub-base for Combustible Floors- Downflow Coil Figure 31 Setting the Base
Adapter Box
Coil Box
The sub base for combustible floors is not required when a down-
flow furnace, used with a downflow coil box, is set on combus- Subbase
Insulation
tible flooring.

1. Cut the opening in the floor according to the dimensions in

Table 7 because the base is equipped with locating tabs
that center the base over the opening.

The opening in the base is 11/4″ (31.8mm) shorter and 11/8″ Wood Floor
(28.6mm) narrower than the minimum required size of the
opening in the floor. This is done to maintain a 1″ (25.4mm)
Wood Screw Plenum
clearance between the floor and the plenum. 25-20-46A

Consideration must be given to the height of the base to allow for

easy installation of the condensate drain. See Figure 32. This
Figure 29 Setting the Base subbase for combustible floors has been designed so that the
height of the subbase raises the downflow coil off the floor to allow
Furnace easy installation of the condensate drain
Subbase
Insulation
Figure 32 Condensate Line Raised by Base

Wood Floor

Wood Screw Plenum

25-20-46A
25 20 52

Non-Combustible Floor
2. Fabricate the plenum to the dimensions given in Table 7. Set the furnace over the opening in the floor. If necessary, grout
Note that the dimensions given are outside dimensions. around the base to seal air leaks between the base and the floor.
3. Set the base over the opening in the floor, centering the Duct Connections
opening in the base over the opening in the floor. Fasten
the base to the floor with screws or nails. See Figure 30 In the downflow position, the return air duct must be connected to
and Figure 31. only the top of the furnace. Top return connections can be made

29 Specifications are subject to change without notice 441 01 2023 01

by removing the knockout panel in the furnace base. Return air • When a furnace is used with a cooling unit, the furnace
connection through the side(s) or back of the furnace is NOT al- shall be installed parallel with or on the upstream side of the
lowed. cooling unit to avoid condensation in the heating element.
Duct Design • With a parallel flow arrangement, the dampers or other
Design and install the air distribution system to comply with Air means used to control flow of air shall be adequate to pre-
Conditioning Contractors of America manuals or other approved vent chilled air from entering the furnace. Chilled air going
methods that conform to local codes and good trade practices. through the furnace could cause condensation and shorten
furnace life. Dampers (purchased locally) can be either au-
When the furnace is located in an area near or adjacent to the liv- tomatic or manual. Manually or automatically operated
ing area, the system should be carefully designed with returns to dampers MUST be equipped with a means to prevent fur-
minimize noise transmission through the return air grille. Any nace and air conditioning operation, unless damper is in
blower moving a high volume of air will produce audible noise the full heat or cool position.
which, could be objectionable when the furnace is located very
close to a living area. It is often advisable to route the return air • Installation of locking type dampers is recommended in all
ducts under the floor or through the attic. branches, or in individual ducts to balance system’s air
flows.
• Refer to furnace Technical Support Manual (Blower Data)
for air flow information. • Non combustible, flexible duct connectors are recom-
• Size ductwork to handle air flow for heating and air condi- mended for return and supply connections to furnace.
tioning, if used. • If air return grille is located close to the fan inlet, install at
Duct Installation Requirements least one 90° air turn between fan and inlet grille to reduce
noise.
• When a furnace is installed so that supply ducts carry air cir-
culated by the furnace to areas outside of the space con- • Ductwork installed in attic or exposed to outside tempera-
taining the furnace, the return air shall also be handled by tures requires a minimum of 2″ (50.8mm) of insulation with
duct(s) sealed to the furnace casing and terminating out- outdoor type vapor barrier.
side the space containing the furnace. • Ductwork installed in an indoor unconditioned space re-
quires a minimum of 1″ (25.4mm) of insulation with indoor
! WARNING type vapor barrier.
CARBON MONOXIDE POISONING HAZARD
Failure to follow this warning could result in per-
sonal injury or death.
Install cooling coil on furnace discharge. Cool air
passing over heat exchanger could cause
condensate to form resulting in heat exchanger
failure.

12. Checks and Adjustments

Startup Manifold Gas Pressure Adjustments
NOTE: Refer to startup procedures in the Users Information (High and Low Heat)
Manual.
NOTE: Make adjustment to manifold pressure with burners oper-
! WARNING ating.

ELECTRICAL SHOCK, FIRE, OR EXPLOSION

HAZARD
Failure to follow this warning could result in injury,
death, and/or property damage.
If any sparks, odors or unusual noises occur,
immediately shut OFF gas and power to furnace.
Check for wiring errors or obstruction to blower.

Gas Supply Pressure

Gas supply pressure should be within minimum and maximum
values listed on rating plate. Pressures are usually set by gas sup-
pliers.

441 01 2023 01 Specifications are subject to change without notice

30
 1. Turn OFF gas supply to all appliances other than furnace
Figure 33 Typical Gas Control Valve Honeywell and start furnace. Use jumper wire on R to W1 and W2 for
High Heat.
Regulator
Adjustment 2. Time how many seconds it takes the smallest dial on the
Under Cap gas meter to make one complete revolution. Refer to Ex-
ample.
HI HONEYWELL 3. Repeat step 2 with jumper wire on R to W1 for Low Heat.
LO
NOTE: If meter uses a 2 cubic foot dial, divide results (sec-
onds) by two.
NOTE: SW1 DIP switch #3 must be in ON position. (See
ON furnace wiring diagram). Return SW1 DIP switch #3 to pre-
vious setting after check.
INLET
Pressure OFF Refer to Example. The Example is based on a natural gas BTU
Tap - 1/8″ OUTLET
Pressure
content of 1,000 BTU’s per cubic foot.
25-24-98a Tap - 1/8″
Example
Natural Gas
BTU Content No. of Seconds Time Per Cubic BTU Per
Per Hour Foot in Seconds Hour
! WARNING per cu. foot
1,000 3,600 48 75,000
FIRE OR EXPLOSION HAZARD 1,000 x 3,600 ÷ 48 = 75,000 BTUH
Failure to turn OFF gas at shut off before 4. Remove jumper wire from R to W1 and W2.
connecting manometer could result in personal
injury, death and/or property damage. 5. Relight all appliances and ensure all pilots are operating.
Turn OFF gas at shut off before connecting
manometer. ! WARNING
CARBON MONOXIDE POISONING HAZARD
1. With gas OFF, connect manometer to manifold pressure
tap on the outlet of gas control valve. See Figure 33. Use a Failure to follow this warning could result in
manometer with a 0 to 12 in wc (0 to 2989 Pa) range. personal injury or death.
2. Turn gas ON. Operate the furnace on High Heat by using a NOx inserts for use with Natural Gas units ONLY.
jumper wire on the R to W1 & W2 thermostat connections If Propane Gas is required, NOx inserts must be
on the furnace control board. removed.
3. Remove manifold pressure adjustment screw cover on fur-
nace gas control valve. Turn adjusting screw counterclock-
wise to decrease the manifold pressure and clockwise to
Main Burner Flame Check
increase pressure. See Figure 33. Allow the furnace to run approximately 10 minutes. Then inspect
the main burner flames. See Figure 34.
NOTE: Adjustment screw cover MUST be replaced on gas control
valve before reading manifold pressure and operating furnace. Check for the following (Figure 34):
4. Set manifold pressure to value shown in Table 5 or Table 4. • Stable and blue flames. Dust may cause orange tips or
wisps of yellow, but flames MUST NOT have solid, yel-
5. Operate the furnace on Low Heat by using a jumper wire on low tips.
the R to W1 thermostat connections on the furnace control • Flames extending directly from burner into heat ex-
board. changer.
Note: The SW1 DIP switch #3 should be in the on position • Flames do NOT touch sides of heat exchanger
to set the Low Heat manifold pressure. (See wiring dia-
gram.) If any problems with main burner flames are noted, it may be nec-
essary to adjust gas pressures or check for drafts.
6. Repeat steps 3 and 4 for Low Heat operation.
7. When the manifold pressures are properly set, replace the Figure 34 Main Burner
adjustment screw covers on the gas control valve.
8. Remove the jumper wires from the thermostat connections
on the furnace control board. Remove manometer connec- Burner Face
tion from manifold pressure tap, and replace plug in gas
valve.
9. Return SW1 DIP switch #3 to previous setting.
10. Check for leaks at plug.

Natural Gas Input Rating Check 10 10 78

The gas meter can be used to measure input to furnace. Check
with gas supplier for actual BTU content. For ignitor location see Figure 35.

31 Specifications are subject to change without notice 441 01 2023 01

 Figure 35 Ignitor Location in(mm)
Blower Adjustments (*8MPT)
21/16(52.4)
Changing Blower Speed
5/ (8)
16
1/ (6.4)
4 !
WARNING
ELECTRICAL SHOCK HAZARD
Failure to follow this warning could result in
personal injury or death.
Turn OFF power to furnace before changing
speed taps.
NOTE: Flame sensor has a different orientation in all 050 models.
NOTE: The speed taps that the manufacturer sets at the factory
Temperature Rise Check for this furnace are based on a nominal 400 CFM per ton for cool-
ing and the basic mid range on the temperature rise for heating.
!
CAUTION Since the manufacturer cannot predict the static pressure
that will be applied to the furnace, it is the responsibility of
the installer dealer/contractor to select the proper blower
REDUCED FURNACE LIFE HAZARD
motor speed leads for the application when the furnace is
Failure to properly set the air temperature rise may installed.
result in reduced furnace life.
If it is necessary to change speeds, refer to steps below.
Use ONLY the blower motor speed taps marked “Y” for
1. Refer to Furnace Wiring Diagram for location of the heating
YES for setting air temperature rise. and cooling speed taps located on the furnace control board
Blower Motor Speed Taps for *8MPT Model Sizes as well as location of unused blower motor speed leads. Use
Model Heat LO M LO M HI HI the chart (Table 8) to determine the blower motor speed set-
Sizes Stage RED BLUE ORN BLK tings.
LO N Y Y Y
050B12
HI N Y Y N Table 8 Blower Speed Chart (*8MPT)
LO N Y Y Y
075F14
HI N Y Y Y Wire Color Motor Speed
LO N Y Y Y Black High
100F14 Orange* Med High
HI N N Y Y
LO Y Y N N Blue Med Low
100J20
HI N N Y Y Red Low
LO N N Y Y * Med High speed may not be provided on all models.
125J20
HI N N Y Y
2. Change the heat or cool blower motor speed by removing the
The blower speed MUST be set to give the correct air temperature motor lead from the “HI HEAT or LO HEAT” or “COOL” termi-
rise through the furnace as marked on the rating plate. Tempera- nal and replace it with the desired motor speed lead from the
ture rise is the difference between supply and return air tempera- “M1” or “M2” location. Connect the wire previously removed
tures. from the “HI HEAT or LO HEAT” or “COOL” terminal to the
To check temperature rise,use the following procedure: vacated “M1” or “M2” terminal.
1. Place thermometers in supply and return air registers as 3. If the same speed must be used for both heating and cooling,
close to furnace as possible, avoiding direct radiant heat remove the undesired motor speed lead from the “HI HEAT
from heat exchangers. or LO HEAT” or “COOL” terminal and connect that lead to
the open terminal at “M1” or “M2” location or tape off. Attach
2. Operate furnace on High Heat for ten minutes with all the
a jumper between the “HI HEAT or LO HEAT” and “COOL”
registers and duct dampers open by using a jumper wire on
terminals and the remaining motor speed lead.
R to W1 and W2 thermostat connections on the furnace
control board. NOTE: When using the same speed on motors with (4) speed
leads, it will be necessary to tape off the terminal of the motor
Note: The SW1 DIP switch #3 should be in the on position.
speed lead removed from the “HI HEAT or LO HEAT” or
(See furnace wiring diagram)
“COOL” terminal with electrical tape since an open terminal
3. Take readings and compare with range specified on rating will not be available at the “M1” or “M2” location.
plate.
4. If the air temperature rise is not in the correct range, the
Continuous-Fan using “G”
blower speed must be changed. A higher blower speed will Energizing the ”G” terminal on the furnace control board provides
lower the temperature rise. A lower blower speed will in- continuous fan operation. This is done by connecting the G
crease the temperature rise. terminal of the thermostat to the G terminal on the furnace control
board. When the FAN switch is turned from auto to ON the fan will
5. Repeat steps 2 thru 4 with the furnace operating on Low
operate continuously at ”LO HEAT” speed. EAC will be energized
Heat for 10 minutes by using a jumper wire on the R to W1
in this mode.
thermostat connections on the furnace control board.
6. Remove the jumper wire after the adjustments are com- NOTE: In heating, the fan will turn off during furnace ignition and
plete. Return SW1 DIP switch #3 to previous setting. warm up then restart at heating speed.

441 01 2023 01 Specifications are subject to change without notice

32
Hard-Wired Continuous Fan NOTE: The blower speeds that the manufacturer sets from the
factory for this product are based on a nominal 400 CFM per ton
A terminal is provided on the furnace control board located in the cooling and the mid range on the temperature rise for heating.
circulating air blower compartment for operation of the continuous Since the manufacturer cannot predict the static pressure
fan option. This connection is intended for the low speed motor tap, that will be applied to the furnace, it is the responsibility of the
and has a lower contact rating (8 amps) than the heat and cool installing dealer/contractor to select the proper speeds for
taps. When the low speed blower lead is connected to this the application when the furnace is installed.
terminal, it will provide low speed blower operation whenever the
other three speeds (“HI HEAT or LO HEAT” or COOL) are not If it is necessary to change speeds, refer to steps below.
energized. 1. The 115 VAC power supply to the furnace must be turned
Thoroughly check the system after modification to ensure the OFF before making adjustments to the motor.
proper operation of the circulating air blower in all modes of opera-
NOTE: Allow at least 1 minute before restoring power to the
tion.
furnace after making Blower Control changes.
Separate Speed Selections for Low Heat, High Heat, 2. The heating, cooling and continuous blower speeds can be
adjusted by changing the SW2 DIP switch settings that are
Cool, and Continuous-Fan located on the Tap Select Interface Board (see Figure 36).
Connect low speed lead from circulating air motor to the “CONT” * Switches #1 and #2 adjust the continuous blower speeds.
terminal at the furnace control board. The appropriate motor leads Switches #3 and #4 adjust the heating speed.
should already be connected to the “HI HEAT and LO HEAT” and Switches #5 and #6 adjust the cooling speed.
“COOL” terminals. Switches #7 and #8 adjust the cooling speed on/off delay
profiles. See the “Technical Support Manual” for the switch
Heating and Continuous-Fan Speed the Same settings for the desired airflow rates for the installation.
The jumper J1 is used to slightly increase (+) or decrease
If it is necessary to operate the Low Heat speed and ( ) or not change (NOM) the blower speed selected from
continuous fan speed using the same blower speed, connect a SW2. J1 effects BOTH cooling and heating airflow.
jumper between the “LO HEAT” and “CONT FAN” terminals on * Continuous blower selection DIP 10 and 11 will cause the
the furnace control board. blower to run in high cooling speed for all low cooling (Y1)
Note: There should be only ONE motor lead going to the “LO calls. Continuous blower DIP settings of 00 and 01 will allow
HEAT” and “CONT FAN” terminals. low cooling (Y1) calls to operate normally.

Blower Adjustments (*8MPV) Continuous-Fan using “G”

Energizing the ”G” terminal on the furnace control board provides
Changing Blower Speed continuous fan operation. This is done by connecting the G
terminal of the thermostat to the G terminal on the furnace control
board. When the FAN switch is turned from auto to ON the fan will
! WARNING operate continuously at airflow selected by DIP SW2 switch #1
and DIP SW2 switch #2. EAC will be energized in this mode.
ELECTRICAL SHOCK HAZARD
Failure to disconnect power could result in NOTE: In heating, the fan will not turn off during furnace ignition
personal injury or death. and warm up.
Turn OFF power to furnace before changing blower Hard Wired Continuous Fan Operation
speed.
Not available for variable speed models.

33 Specifications are subject to change without notice 441 01 2023 01

 Figure 36 Variable Speed (*8MPV) Tap Select Interface Board (TSIB)

TO FURNACE BOARD
J1
P3

BLU WHT + NOM

GRN BLK

BRN YEL
P7
BLOWER ADJUST

TO FURNACE
CONTROL 24VAC
RED J1
+ NOM J2
BLOWER ADJUST AC/HP EFFICIENCY
INCREASE/NO CHANGE/DECREASE
HP COMFORT
SELECTION
HP MODE
SELECT
SW2
1 2 3 4 5 6 7 8
FROM 24V
ON
TRANS RED

OFF J2
O Y1
CONT HEAT COOL COOL
FAN DLY AC/HP EFFICIENCY

HP COMFORT
SELECTION
HP MODE
ON = 1 SELECT

1 8

SW2 HEAT PUMP EFFICIENCY OR

OFF = 0 1 2 3 4 5 6 7 8 HP COMFORT SELECTION

CONT HEAT COOL COOL

FAN DLY

CONTINUOUS HEATING RISE COOLING CFM COOLING ON/OFF

CFM SELECT SELECT SELECT DELAY PROFILES

25 25 54

13. Furnace Maintenance

!
WARNING !
WARNING
FIRE, EXPLOSION, OR CARBON MONOXIDE
ELECTRICAL SHOCK, FIRE OR EXPLOSION
POISONING HAZARD
HAZARD
Failure to have the furnace inspected and
Failure to follow this warning could result in
maintained could result in personal injury, death,
personal injury, death, and/or property damage.
and/or property damage.
It is recommended that the furnace be inspected
and serviced on an annual basis (before the • Before servicing, disconnect all electrical power
heating season) by a qualified service agency. to furnace.
• When servicing controls, label all wires prior to
disconnecting. Reconnect wires correctly.
• Verify proper operation after servicing.

See “User’s Information Manual”.

441 01 2023 01 Specifications are subject to change without notice

34
14. Sequence of Operation & Diagnostics for *8MPT
The following is the normal operating sequence at factory default settings (SW1 OFF/ON/OFF)
Cooling (Y) Request:
24VAC signals applied to Y/Y2 & G terminals of FCB (furnace control board).
• Cool motor speed is energized after 5 second Cool Fan On Delay time.
Y/Y2 & G signals removed from FCB
• Cool motor speed is de energized after 90 second Cool Fan Off Delay time.
NOTE: DEHUM not available on the *8MPT models.

Continuous Circulating Fan (G) Request:

24VAC signal applied to G terminal of FCB.
• Low Heat motor speed is energized without delay.
G signal removed from FCB.
• Low Heat motor speed is de energized after 5 second delay.
NOTE 1) Furnace de energizes the fan during the heat exchanger warm up period on a call for Heating that occurs during a G request
unless a blower motor lead is connected to the CONT FAN terminal on the FCB, in which case see NOTE 2)
NOTE 2) Heating or Cooling requests received during a Fan request cause the fan speed to change to the appropriate heat or cool speed
after the Fan On Delay time expires. The fan returns to continuous circulating speed after the selected Fan Off Delay time expires
following loss of the Heating or Cooling request.

Continuous Circulating Fan Hard-Wired (Cont) Request:

Field selected low speed motor tap installed on ”CONT FAN” terminal.
• Low speed is energized when power applied to furnace. Operates at this speed continuously while there are no other
blower demands from furnace control board. Fan demands from furnace control board for heat, cool or ”G” will override hard wired
speed tap.
NOTE 3) EAC is NOT active for hard wired mode but IS active for fan demands from furnace control board for heat, cool and “G”.

Heating (W1) Request (single stage thermostat operation, SW1 DIP switch #3 must be in OFF
position) (see furnace wiring diagram):
24VAC signal applied to W1 terminal of FCB.
• Inducer motor turns on at high speed.
• Following a 15 second prepurge delay after the low pressure switch closes, the ignitor begins a 17 second warm up.
• The gas valve is energized, the main burners light at Low Heat rate and flame is sensed.
• The ignitor is de energized, and the inducer drops to low speed after the main burners ignite.
• The FCB will delay Low Heat blower operation for the 45 second Low Heat Fan On Delay time, timed from
the opening of the gas valve.
• If the W1 request is still present after 12 minutes, timed from the opening of the gas valve, the inducer switches to high speed,
closing the high pressure switch, then the High Heat solenoid energizes, and the fan switches to High Heat speed.
W1 signal removed from FCB.
• The gas valve de energizes and the main burners go out.
• The inducer runs at its present speed for a 15 second postpurge period.
• The fan runs at its present speed.
• The fan de energizes after the selected Heat Fan Off Delay time expires, timed from the gas valve de energizing.
NOTE 4) If a new Heating request arrives while the control is waiting in the Heat Fan Off Delay time, the FCB will wait for the selected Heat
Fan Off Delay then start a new heating cycle as long as the heat call remains.
Heating Request (W1 & W2) (two-stage thermostat operation, SW1 DIP switch #3 must be in ON
position) (see furnace wiring diagram):
24VAC signal applied to W1 terminal of FCB.
• Same response as single stage thermostat operation (fan uses Low Stage Heat On Delay) described above except the control
will not go to High Heat rate, and High Heat Fan speed unless a W2 signal is applied.
24VAC signal applied to W1 and W2 terminals of FCB.
• Same light off routine as described for the signal stage thermostat operation except main burners light at High Heat rate, the
inducer remains on high speed after ignition, and the FCB will delay blower operation at the High Heat Fan speed for 30 second
On Delay time.
NOTE 5) The FCB responds without delay to the presence or loss of W2 (with W1 constant). W1 & W2 result in high inducer, High Heat
rate, and High Heat Fan speed. W1 only results in low inducer, Low Heat rate, and Low Heat Fan speed.

35 Specifications are subject to change without notice 441 01 2023 01

Heating Request with Gas Shut Off:
24 VAC signal applied to W1 terminal of FCB.
The FCB will attempt 4 cycles for ignition then go to soft lockout for 3 hours, and then try for ignition again as long as the heat call
remains. Power reset will clear lockout.
• Inducer motor turns on at high speed.
• Following a 15 second prepurge delay, the ignitor begins warm up.
• The ignitor glows red hot for 22 seconds, then turns off. The FCB flashes error code 6.
• The ignitor stays off for 17 seconds, then begins to warm up again.
• The ignitor glows red hot for 22 seconds then turns off. The FCB continues flashing error code 6.
• The ignitor stays off for 17 seconds, then begins to warm up again.
• The ignitor glows red hot for 22 seconds then turns off. The FCB continues flashing error code 6.
• The ignitor stays off for 17 seconds, then begins to warm up again.
• The ignitor glows red hot for 22 seconds then turns off. The FCB proceeds to soft lockout. Stops flashing
error code 6, and begins flashing error code 6 + 1.
· The inducer motor de energizes after a 15 second post purge.

Furnace Control Board Diagnostic Codes (See Figure 37):

OFF = 24VAC or 115VAC is off, fuse is open
Heartbeat = Normal operation or no previous Diagnostic Code
ON SOLID = Soft Lockout Furnace Control Error (1 hr delay)
If code repeats immediately following power reset then replace control
1 Flash = Not used
2 Flashes = Pressure switch(es) closed when should be open
3 Flashes = Low pressure switch open when should be closed
4 Flashes = Limit or flame roll out switch open (less than 2 minutes)
5 Flashes = Flame sensed out of sequence
6 Flashes = Failure to ignite or flame sense lost while running
6 + 1 Flashes = Soft Lockout Max of four trials for ignition reached (3hr delay)
7 Flashes = Soft Lockout Limit or flame roll out switch open longer than 2 minutes (1 hr delay)
(roll out switch requires manual reset)
8 Flashes = Permanent Lockout Gas valve relay contact stuck closed or miswired gas valve (power reset only)
9 Flashes = High pressure switch open when should be closed
10 Flashes = Line voltage polarity or improper transformer phasing on twinned applications
NOTE: The 6 + 1 designation indicates a combination of flash
codes. Figure 37 Control Board
* If status code recall is needed, briefly (2 3 seconds) remove then
reconnect one limit switch wire (main or rollout) to display last
stored status code. Do not remove power or blower door before
initiating status code recall or code will be lost. Code is Diagnostic Light
automatically cleared after 72 hours or upon power reset. DIP Switch
See “Wiring Diagram”
for switch settings
* Proper flame sense microamps: 0.7 microamps D.C. minimum,
2.0 4.0 microamps nominal
24 VAC 115
HUM VAC
HUM

EAC
FUSE
DEHUM
25 24 74

HUMIDIFIER The 24VAC HUM is energized when the low pressure switch closes on a call for heat. The 115V HUM (called HUM on
Control) is energized when the inducer is energized.
ELECTRONIC AIR CLEANER EAC is energized when there is a blower speed call. It is NOT energized when blower operates in
the hard wired continuous fan mode.

441 01 2023 01 Specifications are subject to change without notice

36
15. Wiring Diagram *8MPT (Two Stage Heating with PSC Motor)
37 Specifications are subject to change without notice 441 01 2023 01
16. Sequence of Operation & Diagnostics for *8MPV
The following is the normal operating sequence at factory default settings (SW1 OFF/ON/OFF, SW2 all OFF)
NOTE: SW1 DIP switches (G, Y/Y2, W1, W2 thermostat terminals) and DEHUM (1/4” male quick connect terminal) are located on the
FCB.
SW2 DIP switches and Y1 and O thermostat terminals are located on the TSIB.
Low Cooling (Y1) Request:
24VAC signals applied to Y1 & G terminals of TSIB (Tap Select Interface Board) and FCB (Furnace Control Board), respectively.
• Low Cooling motor speed is energized after 5 second Cool Fan On Delay time.
Y1 & G signals removed from TSIB and FCB
• Low Cooling motor speed is de energized after 90 second Cool Fan Off Delay time.
Cooling (Y1) and dehumidification (DEHUM) requests:
• 24 VAC signals applied to Y1, DEHUM & G terminals of TSIB and FCB.
• Same operation as the cooling (Y1) request, except the cooling airflow is reduced 20% to compensate for high
humidity conditions during cooling operation. The low cooling airflow returns to the normal setting after the DEHUM signal is
removed.

High Cooling (Y1 & Y/Y2) or (Y/Y2) Request:

24VAC signals applied to Y1 & Y/Y2 & G or Y/Y2 & G terminals of FCB (Furnace Control Board).
• High Cooling motor speed is energized after 5 second Cool Fan On Delay time.
Y1 & Y/Y2 & G or Y/Y2 & G signals removed from TSIB and FCB
• High Cooling motor speed is de energized after 90 second Cool Fan Off Delay time.
High Cooling (Y1 & Y/Y2 or Y/Y2) and dehumidification (DEHUM) requests:
• 24 VAC signals applied to Y1 & Y/Y2 or Y/Y2, DEHUM, & G terminals of and FCB.
• Same operation as the high cooling (Y1 & Y/Y2 or Y/Y2) request, except the cooling airflow is reduced 20% to compensate for high
humidity conditions during cooling operation. The high cooling airflow returns to the normal setting after the DEHUM signal is
removed.
Low or high cooling and O terminal (Heat Pump mode):
• If the J2 jumper is in the AC/HP EFFICIENCY position, there will be no change in blower airflow regardless of the O terminal being
energized or de energized.
• If the J2 jumper is in the HP COMFORT position, then there will be a 10% reduction in airflow when the O terminal is de energized
(HP heating) and no airflow reduction when O is energized (HP cooling).
NOTE 1) The motor has been set up to recognize the O terminal as energized during cooling calls (reversing valve energized for cooling).
Continuous Circulating Fan (G) Request:
24VAC signal applied to G terminal of FCB.
• Continuous fan speed is energized without delay.
G signal removed from FCB.
• Continuous fan speed is de energized after 5 second delay.
NOTE 2) Heat or Cooling requests received during a Fan request, cause the fan speed to change to the appropriate heat or cool speed
after the Fan On Delay time expires. The fan returns to continuous circulating speed after the selected Fan Off Delay time expires
following loss of the Heating or Cooling request.
NOTE 3) Hard wire option not available for variable speed models.
NOTE 4) Continuous blower selection DIP 10 and 11 will cause the blower to run in high cooling speed for all low cooling (Y1) calls.
Continuous blower DIP settings of 00 and 01 will allow low cooling (Y1) calls to operate normally.
Heating (W1) Request (single stage thermostat operation, SW1 DIP switch #3 on the FCB must
be in OFF position) (see furnace wiring diagram):
24VAC signal applied to W1 terminal of FCB.
• Inducer motor turns on at high speed.
• Following a 15 second prepurge delay after the low pressure switch closes, the ignitor begins a 17 second warm up.
• The gas valve is energized, the main burners light at Low Heat rate.
• The ignitor is de energized, and the inducer drops to low speed after the main burners ignite.
• The FCB will delay Low Heat blower operation for the 45 second Low Heat Fan On Delay time timed from the opening of the gas
valve.
• If the W1 request is still present after 12 minutes, timed from the opening of the gas valve, the inducer switches to high speed,
closing the high pressure switch, then the High Heat solenoid energizes, and the fan switches to High Heat speed.

441 01 2023 01 Specifications are subject to change without notice

38
 W1 signal removed from FCB.
• The gas valve de energizes and the main burners go out.
• The inducer runs at its present speed for a 15 second postpurge period.
• The fan runs at its present speed.
• The blower de energizes after the selected Heat Fan Off Delay time expires timed from the gas valve de energizing.
NOTE 5) If a new Heating request arrives while the control is waiting for the Heat Fan Off Delay time to expire, the FCB will wait for the
selected Heat Fan Off Delay, and then start a new heating cycle.

Heating (W1 & W2) Request (two-stage thermostat operation, SW1 DIP switch #3 must be in ON
position) (see furnace wiring diagram):
24VAC signals applied to W1 terminal of FCB.
• Same response as single stage thermostat operation described above except the burners, inducer, and blower will not go to high
heat rate, and High Heat Fan speed unless a W2 signal is applied.
24VAC signal applied to W1 and W2 terminals of FCB.
• Same light off routine as described for the signal stage thermostat operation except burners light at High Heat rate, the inducer
remains on high speed after ignition, and the FCB will delay High Heat blower operation for the 30 second High Heat Fan
On Delay.
NOTE 6) The FCB responds without delay to the presence or loss of W2 (with W1 constant). W1 & W2 result in high inducer, High Heat
rate, and High Heat Fan speed. W1 only results in low speed inducer, Low Heat rate, and Low Heat Fan speed.
Heating Request with Gas Shut Off:
24 VAC signals applied to W1 terminal of FCB.
The FCB will attempt 4 cycles for ignition then go to soft lockout for 3 hours, and then try for ignition again as long as the heat call
remains. Power reset will clear lockout.
• Inducer motor turns on at high speed.
• Following a 15 second prepurge delay after the low pressure switch closes, the ignitor begins warm up.
• The ignitor glows red hot for 22 seconds, then turns off. The FCB flashes error code 6.
• The ignitor stays off for 17 seconds, then begins to warm up again.
• The ignitor glows red hot for 22 seconds then turns off. The FCB continues flashing error code 6.
• The ignitor stays off for 17 seconds, then begins to warm up again.
• The ignitor glows red hot for 22 seconds then turns off. The FCB continues flashing error code 6.
• The ignitor stays off for 17 seconds, then begins to warm up again.
• The ignitor glows red hot for 22 seconds then turns off. The FCB proceeds to soft lockout. Stops flashing
error code 6, and begins flashing error code 6 + 1.
• The inducer motor de energizes 15 seconds after error code 6 + 1 starts flashing.
Furnace Control Board Diagnostic Codes (See Figure 37):
OFF = 24VAC or 115VAC is off, fuse is open
Heartbeat = Normal operation or no previous Diagnostic Code
ON SOLID = Soft Lockout Furnace Control Error (1 hr delay)
If code repeats immediately following power reset then replace control
1 Flash = Not used
2 Flashes = Pressure switch(es) closed when should be open
3 Flashes = Low pressure switch open when should be closed
4 Flashes = Limit or flame roll out switch open (less than 2 minutes)
5 Flashes = Flame sensed out of sequence
6 Flashes = Failure to ignite or flame sense lost while running
6 + 1 Flashes = Soft Lockout Max of four trials for ignition reached (3 hr delay)
7 Flashes = Soft Lockout Limit or flame roll out switch open longer than 2 minutes (1 hr delay)
(roll out switch requires manual reset)
8 Flashes = Permanent Lockout Gas valve relay contact stuck closed or miswired gas valve (power reset only)
9 Flashes = High pressure switch open when should be closed
10 Flashes = Improper transformer phasing on twinned applications or improper line voltage polarity.
* If status code recall is needed, briefly (2 3 seconds) remove then reconnect one limit switch wire (main or rollout) to display last stored
status code. Do not remove power or blower door before initiating status code recall or code will be lost. Code is automatically cleared
after 72 hours or upon power reset.
* Proper flame sense microamps: 0.7 microamps D.C. minimum, 2.0 4.0 microamps nominal
NOTE 7) Continuous blower selection DIP 10 and 11 will cause the blower to run in high cooling speed for all low cooling (Y1) calls.
Continuous blower DIP settings of 00 and 01 will allow low cooling (Y1) calls to operate normally.
HUMIDIFIER The 24VAC HUM is energized when the low pressure switch closes on a call for heat. The 115V HUM (called HUM on
Control) is energized when the inducer is energized.
ELECTRONIC AIR CLEANER EAC is energized when there is a blower speed call. It is NOT energized when blower operates in
the hard wired continuous fan mode.

39 Specifications are subject to change without notice 441 01 2023 01

17. Wiring Diagram *8MPV (Variable Speed Blower Motor)

441 01 2023 01 Specifications are subject to change without notice

40
18. Thermostat Wiring Guide
1. These diagrams are for reference. See thermostat 8. 24V HUM terminal on furnace control is used to power
wiring instructions for specific terminal assignments, a humidifier (on call for heat and pressure switch
connections or operation. closed) if no HUM thermostat option is available.
2. Humidifier/humidistat is optional and not included 9. DEHUM provides a 20% reduction in airflow (when Y1
with the furnace. or Y1 + Y2 is energized) when the furnace control DE-
3. Dehumidify feature (MPV models only) requires ther- HUM terminal is energized with 24V.
mostat with DEHUM feature or a separate dehumidis- 10. If no DEHUM thermostat option is available, a dehu-
tat to get the dehumidification operation. Dehumidis- midistat that has closed contacts on a call for dehu-
tat is optional and not included with the furnace. midify may be used
4. Underlined terminal indicates intended use for multi-
11. O provides a 10% reduction in airflow when Y1 or Y1 +
ple function terminals.
Y2 is energized and O is NOT energized. (J2 jumper
5. TSIB terminals only available on MPV models. on TSIB must be in HP COMFORT position to get this
6. Two stage Air Conditioning or two stage Heat Pump function. AC/HP EFFICIENCY position results in no
capability only available with MPV models. reduction of airflow for Y1 or Y1 + Y2 calls regardless
of O being energized or not.)
7. W2 furnace operation is from furnace control algo-
rithm SW1 DIP switch #3 (TT) set to OFF. Furnace 12. For Heat Pump/Furnace systems, refer to Fossil Fuel
runs in Low Heat for 12 minutes then switches to High Kit or Dual Fuel Thermostat Installation Instructions
Heat if heating call still exists. for wiring.

HUM and DEHUM Terminal available from Thermostat. Humidifier Wiring (*MPT/MPV)
Figure 38
Models and Dehumidify Wiring (*MPV Models only)

41 Specifications are subject to change without notice 441 01 2023 01

 No HUM and/or DEHUM Terminal available from thermostat. Humidifier Wiring (*MPT/MPV models)
Figure 39
Dehumidify wiring (*MPV models only)

Single Stage Thermostat with Two Stage or Variable Speed Furnace (*MPT/MPV Models) and
Figure 40
Single Stage Air Conditioner

441 01 2023 01 Specifications are subject to change without notice

42
 Two Stage Thermostat with Two Stage Furnace or Variable Speed Furnace (*MPT/MPV Models)
Figure 41
and Single Stage Air Conditioner

Two Stage Thermostat with Variable Speed Furnace (*MPV Models only) and Two Stage Air
Figure 42
Conditioner

43 Specifications are subject to change without notice 441 01 2023 01

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INTENTIONALLY

441 01 2023 01 Specifications are subject to change without notice

44