Lennox ELITE EL297DFXV045P36B User manual

Page 1
INSTALLATION
INSTRUCTIONS
EL297DFV
508410-01
09/2023
©2023 Lennox Industries Inc.
Dallas, Texas USA
ELITE®SERIES GAS FURNACE
DOWNFLOW AIR DISCHARGE
Contents
Unit Dimensions - inches (mm) ......................................2
EL297DFV Gas Furnace ................................................3
Shipping and Packing List ..............................................3
Safety Information ..........................................................3
Use of Furnace as Construction Heater .........................4
General...........................................................................5
Combustion, Dilution & Ventilation Air ............................5
Setting Equipment ..........................................................8
Filters............................................................................12
Duct System .................................................................12
Pipe Fittings Specications...........................................12
Venting Options ............................................................13
Joint Cementing Procedure..........................................16
Venting Practices..........................................................16
Vent Piping Guidelines ................................................18
Gas Piping ...................................................................35
Electrical ......................................................................37
Integrated Control ........................................................47
Blower Motor Performance ..........................................52
Unit Start Up ................................................................56
Gas Pressure Measurement ........................................57
Proper Combustion / High Altitude ..............................58
Heating Sequence of Operation ..................................60
Service .........................................................................61
Program Unit Capacity Size Mode ...............................63
Repair Parts List...........................................................65
Start-Up Checklist.........................................................67
THIS MANUAL MUST BE LEFT WITH THE
HOMEOWNER FOR FUTURE REFERENCE
This is a safety alert symbol and should never be
ignored. When you see this symbol on labels or in man-
uals, be alert to the potential for personal injury or death.
WARNING
Improper installation, adjustment, alteration, service
or maintenance can cause property damage, personal
injury or loss of life. Installation and service must be
performed by a licensed professional HVAC installer (or
equivalent), service agency or the gas supplier.
NOTICE
A thermostat is not included and must be ordered
separately.
• A communicating thermostat must be used in
communicating applications.
•In non-communicating applications, the Lennox
ComfortSense® 7500 thermostat may be used, as well
as other non-communicating thermostats.
In all cases, setup is critical to ensure proper system
operation.
Field wiring for both communicating and non-
communicating applications is illustrated in diagrams,
which begin on Page 39.
CAUTION
As with any mechanical equipment, personal injury can
result from contact with sharp sheet metal edges. Be
careful when you handle this equipment.

Page 2
Unit Dimensions - inches (mm)
AIR
EXHAUST AIR
OUTLET
COMBUSTION
AIR INTAKE
FLOW
2-1/16 (52)
GAS PIPING INLET
(Either Side)
RETURN AIR
OPENING
FRONT VIEW SIDE VIEW
TOP VIEW
A
B
C3/4
(19)
27-3/4
(705)
19-1/4
(489)
9-1/8 (232) Right
6-9/16 (167) Left
2 (51)
Either Side
33
(838)
3/4
(19)
B
Supply
Air
Supply
Air
9/16
(14)
9/16
(14)
9/16
(14)
9/16
(14)
19-7/16
(494)
3/4
(19)
CONDENSATE
TRAP CONNECTION
5
(127)
6-7/16 (163)
Either Side
9 (229)
Either Side
2-1/4
(57)
(Either Side)
1-1/2 (38)
Front Panel
1-7/8 (48)
1 (25)
6-1/4
(157)
15
(381)
4-1/2
(114)
2-1/16
(52)
5-3/16
(132)
OPTIONAL LEFT SIDE
VENT LOCATION
(Kit Required)
ALTERNATE RIGHT SIDE
VENT LOCATION
(Parts Furnished)
ELECTRICAL INLET
(Either Side)
ELECTRICAL INLET
(Either Side)
Flue Condensate Trap Assembly
Furnished for external
field installation
on either side of unit.
(See installation instructions
for additional
information.)
7
(178)
Model No. A
in. (mm)
B
in. (mm)
C
in. (mm)
EL297DFXV045P36B
EL297DFXV070P48B 17-1/2 (446) 16-3/8 (416) 16 (406)
EL297DFXV090P60C
EL297DFXV110P60C 21 (533) 19-7/8 (505) 19-1/2 (495)

Page 3
EL297DFV Gas Furnace
The EL297DFV Category IV gas furnace is shipped ready for
installation in the downow position.
The furnace is equipped for installation in natural gas applica-
tions. A conversion kit (ordered separately) is required for use in
propane/LP gas applications.
The EL297DFV can be installed as a Direct Vent or
Non- Direct Vent gas central furnace.
NOTE - In Direct Vent installations, combustion air is taken
from outdoors and ue gases are discharged outdoors. In
Non-Direct Vent installations, combustion air is taken from
indoors or ventilated attic or crawlspace and ue gases
are discharged outdoors. See FIGURE 1 and FIGURE 2
for applications involving roof termination.
DIRECT VENT INSTALLATION NON-DIRECT VENT
INSTALLATION
EXHAUST
OUTLET
COMBUSTION
AIR INTAKE OUTSIDE
OF HOUSE
COMBUSTION
AIR INTAKE
INSIDE
OF HOUSE
EXHAUST OUTLET
FIGURE 1
NON-DIRECT VENT
INSTALLATION
NON-DIRECT VENT
INSTALLATION
COMBUSTION
AIR INTAKE INSIDE
VENTILATED
CRAWL SPACE
COMBUSTION
AIR INTAKE INSIDE
VENTILATED
ATTIC SPACE
EXHAUST
OUTLET
EXHAUST
OUTLET
FIGURE 2
Shipping and Packing List
Package 1 of 1 contains
1 - Assembled EL297DFV unit
1 - Bag assembly containing the following:
1 - Snap bushing
1 - Snap plug
1 - Wire tie
1 - Condensate trap
1 - Condensate trap cap
1 - Condensate trap clamp
1 - 2” diameter Air intake screen
1 - 3/4” Threaded street elbow
2 - 2” Street elbows
2 - Side vent sealing plates
2 - Side vent sealing gaskets
6 - Sheet metal screws
DANGER
Danger of explosion.
There are circumstances in which odorant used with LP/
propane gas can lose its scent. In case of a leak, LP/
propane gas will settle close to the oor and may be
di󰀩cult to smell. An LP/propane leak detector should be
installed in all LP applications.
Check equipment for shipping damage. If you nd any
damage, immediately contact the last carrier.
The following items may also be ordered separately:
1 - Thermostat
1 - LP/Propane changeover kit
1 - High altitude pressure switch
Safety
WARNING
Improper installation, adjustment, alteration, service
or maintenance can cause property damage, personal
injury or loss of life. Installation and service must be
performed by a licensed professional installer (or
equivalent), service agency or the gas supplier.
CAUTION
As with any mechanical equipment, personal injury can
result from contact with sharp sheet metal edges. Be
careful when you handle this equipment.
Use only the type of gas approved for use with this fur-
nace. Refer to unit nameplate.
EL297DFV units are CSA International certied to ANSI
Z21.47 and CSA 2.3 standards.

Page 4
Building Codes
In the USA, installation of gas furnaces must conform with
local building codes. In the absence of local codes, units
must be installed according to the current National Fuel
Gas Code (ANSI-Z223.1/NFPA 54). The National Fuel
Gas Code is available from the following address:
American National Standards Institute, Inc.
11 West 42nd Street
New York, NY 10036
In Canada, installation must conform with current National
Standard of Canada CSA-B149 Natural Gas and Propane
Installation Codes, local plumbing or waste water codes
and other applicable local codes.
In order to ensure proper unit operation in non-direct vent
applications, combustion and ventilation air supply must
be provided according to the current National Fuel Gas
Code or CSA-B149 standard.
Locations and Clearances
This furnace is CSA International certied for installation
clearances to combustible material as listed on the unit
nameplate and in the table in FIGURE 13. Accessibility
and service clearances must take precedence over re
protection clearances.
For installation in a residential garage, the furnace must
be installed so that the burner(s) and the ignition source
are located no less than 18 inches (457 mm) above the
oor. The furnace must be located or protected to avoid
physical damage by vehicles. When a furnace is installed
in a public garage, hangar, or other building that has a
hazardous atmosphere, the furnace must be installed ac-
cording to recommended good practice requirements and
current National Fuel Gas Code or CSA B149 standards.
NOTE - Furnace must be adjusted to obtain a tempera-
ture rise within the range specied on the unit nameplate.
Failure to do so may cause erratic limit operation and pre-
mature heat
exchanger failure.
This EL297DFV furnace must be installed so that its elec-
trical components are protected from water.
Installation in Combination with a Cooling Coil
When this furnace is used with cooling units (FIGURE 3),
it shall be installed in parallel with, or on the upstream
side of, cooling units to avoid condensation in the heating
compartment. With a parallel ow arrangement, a damper
(or other means to control the ow of air) must adequately
prevent chilled air from entering the furnace. If the damper
is manually operated, it must be equipped to prevent op-
eration of either the heating or the cooling unit, unless it is
in the full HEAT or COOL setting.
When installed, this furnace must be electrically grounded
according to local codes. In addition, in the United States,
installation must conform with the current National Elec-
tric Code, ANSI/NFPA No. 70. The National Electric Code
(ANSI/NFPA No. 70) is available from the following ad-
dress:
National Fire Protection Association
1 Battery March Park
Quincy, MA 02269
In Canada, all electrical wiring and grounding for the unit
must be installed according to the current regulations of
the Canadian Electrical Code Part I (CSA Standard C22.1)
and/or local codes.
AIR HANDLER
GAS UNIT
Dampers
(open during cooling
operation only)
Dampers
(open during heating
operation only)
FIGURE 3
NOTE - This furnace is designed for a minimum continu-
ous return air temperature of 60°F (16°C) or an intermittent
operation down to 55°F (13°C) dry bulb for cases where a
night setback thermostat is used. Return air temperature
must not exceed 85°F (29°C) dry bulb.
The EL297DFV furnace may be installed in alcoves, clos-
ets, attics, basements, garages, utility rooms and crawl
spaces.
This furnace design has not been CSA certied for instal-
lation in mobile homes, recreational vehicles, or outdoors.
Never use an open ame to test for gas leaks. Check all
connections using a commercially available soap solution
made specically for leak detection.
Use of Furnace as Construction Heater
Units may be used for heating of buildings or structures
under construction, if the following conditions are met to
ensure proper operation:
DO NOT USE THE UNIT FOR CONSTRUCTION HEAT
UNLESS ALL OF THE FOLLOWING CRITERIA ARE
MET:
• Furnace must be in its nal location. The vent system
must be permanently installed per these installation in-
structions.
• Furnace must be installed as a two pipe system and
one hundred percent (100%) outdoor air must be pro-
vided for combustion air requirements during construc-
tion.
• A room thermostat must control the furnace. The use
of xed jumpers that will provide continuous heating is
prohibited.
• The input rate and temperature rise must be set per the
furnace rating plate.
• Supply and Return air ducts must be provided and
sealed to the furnace. Return air must be terminated
outside of the space where furnace is installed.

Page 5
• Return air temperature range between 60°F (16°C) and
80°F (27°C) must be maintained.
• MERV 11 or greater air lters must be installed in the
system and must be regularly inspected and maintained
(e.g., regular static checks and replaced at end of life)
during construction.
• Blower and vestibule access panels must be in place
on the furnace at all times.
• The furnace heat exchanger, components, duct system,
and evaporator coils must be thoroughly cleaned follow-
ing nal construction clean−up.
• Air lters must be replaced upon construction comple-
tion.
• All furnace operating conditions (including ignition, in-
put rate, temperature rise and venting) must be veried
in accordance with these installation instructions.
EQUIPMENT MAY EXPERIENCE PREMATURE COM-
PONENT FAILURE AS A RESULT OF FAILURE TO FOL-
LOW THE ABOVE INSTALLATION INSTRUCTIONS.
FAILURE TO FOLLOW THE ABOVE INSTALLATION IN-
STRUCTIONS VOIDS THE MANUFACTURER’S EQUIP-
MENT LIMITED WARRANTY. LENNOX DISCLAIMS
ALL LIABILITY IN CONNECTION WITH INSTALLER’S
FAILURE TO FOLLOW THE ABOVE INSTALLATION IN-
STRUCTIONS.
NOTWITHSTANDING THE FOREGOING, INSTALLER
IS RESPONSIBLE FOR CONFIRMING THAT THE USE
OF CONSTRUCTION HEAT IS CONSISTENT WITH THE
POLICIES AND CODES OF ALL REGULATING ENTI-
TIES. ALL SUCH POLICIES AND CODES MUST BE AD-
HERED TO.
General
These instructions are intended as a general guide and do
not supersede local codes in any way. Consult authorities
having jurisdiction before installation.
In addition to the requirements outlined previously, the
following general recommendations must be considered
when installing a EL297DFV furnace:
• Place the furnace as close to the center of the air distri-
bution system as possible. The furnace should also be
located close to the chimney or vent termination point.
• When the furnace is installed in non-direct vent applica-
tions, do not install the furnace where drafts might blow
directly into it. This could cause improper combustion
and unsafe operation.
• When the furnace is installed in non-direct vent applica-
tions, do not block the furnace combustion air opening
with clothing, boxes, doors, etc. Air is needed for proper
combustion and safe unit operation.
• When the furnace is installed in an attic or other insulat-
ed space, keep insulation away from the furnace.
• When the furnace is installed in an unconditioned
space, consider provisions required to prevent freezing
of condensate drain system.
Combustion, Dilution & Ventilation Air
If the EL297DFV is installed as a Non-Direct Vent Fur-
nace, follow the guidelines in this section.
NOTE - In Non-Direct Vent installations, combustion air is
taken from indoors or ventilated attic or crawlspace and
ue gases are discharged out-doors
.
WARNING
Insu󰀩cient combustion air can cause headaches,
nausea, dizziness or asphyxiation. It will also cause
excess water in the heat exchanger resulting in rusting
and premature heat exchanger failure. Excessive
exposure to contaminated combustion air will result
in safety and performance related problems. Avoid
exposure to the following substances in the combustion
air supply:
Permanent wave solutions
Chlorinated waxes and cleaners
Chlorine base swimming pool chemicals
Water softening chemicals
De-icing salts or chemicals
Carbon tetrachloride
Halogen type refrigerants
Cleaning solvents (such as perchloroethylene)
Printing inks, paint removers, varnishes, etc.
Hydrochloric acid
Cements and glues
Antistatic fabric softeners for clothes dryers
Masonry acid washing materials
In the past, there was no problem in bringing in su󰀩cient
outdoor air for combustion. Inltration provided all the air
that was needed. In today’s homes, tight construction
practices make it necessary to bring in air from outside for
combustion. Take into account that exhaust fans, appli-
ance vents, chimneys, and replaces force additional air
that could be used for combustion out of the house.
Unless outside air is brought into the house for combus-
tion, negative pressure (outside pressure is greater than
inside pressure) will build to the point that a downdraft
can occur in the furnace vent pipe or chimney. As a result,
combustion gases enter the living space creating a poten-
tially dangerous situation.
In the absence of local codes concerning air for combus-
tion and ventilation, use the guidelines and procedures in
this section to install EL297DFV furnaces to ensure e󰀩-
cient and safe operation.

Page 6
You must consider combustion air needs and require-
ments for exhaust vents and gas pip-ing. A portion of this
information has been reprinted with permission from the
National Fuel Gas Code (ANSI Z223.1/NFPA 54). This re-
printed material is not the complete and o󰀩cial position of
the ANSI on the referenced subject, which is represented
only by the standard in its entirety.
In Canada, refer to the CSA B149 installation codes.
CAUTION
EL297DFV unit should not be installed in areas normally
subject to freezing temperatures.
All gas-red appliances require air for the combustion
process. If su󰀩cient combustion air is not available, the
furnace or other appliance will operate ine󰀩ciently and
unsafely. Enough air must be provided to meet the needs
of all fuel-burning appliances and appliances such as ex-
haust fans which force air out of the house. When replac-
es, exhaust fans, or clothes dryers are used at the same
time as the furnace, much more air is required to ensure
proper combustion and to prevent a downdraft. Insu󰀩-
cient air causes incomplete combustion which can result
in carbon monoxide
In addition to providing combustion air, fresh outdoor air
dilutes contaminants in the indoor air. These contaminants
may include bleaches, adhesives, detergents, solvents
and other contaminants which can corrode furnace com-
ponents.
The requirements for providing air for combustion and
ventilation depend largely on whether the furnace is in-
stalled in an unconned or a conned space.
Unconned Space
An unconned space is an area such as a basement or
large equipment room with a volume greater than 50 cubic
feet (1.42 m3) per 1,000 Btu (.29 kW) per hour of the com-
bined input rating of all appliances installed in that space.
This space also includes adjacent rooms which are not
separated by a door. Though an area may appear to be
unconned, it might be necessary to bring in outdoor air
for combustion if the structure does not provide enough air
by inltration. If the furnace is located in a building of tight
construction with weather stripping and caulking around
the windows and doors, follow the procedures in the air
from outside section.
Conned Space
A conned space is an area with a volume less than 50
cubic feet (1.42 m3) per 1,000 Btu (.29 kW) per hour of
the combined input rating of all appliances installed in that
space. This denition includes furnace closets or small
equipment rooms. When the furnace is installed so that
supply ducts carry air circulated by the furnace to areas
outside the space containing the furnace, the return air
must be handled by ducts which are sealed to the furnace
casing and which terminate outside the space containing
the furnace. This is especially important when the furnace
is mounted on a platform in a conned space such as a
closet or small equipment room. Even a small leak around
the base of the unit at the platform or at the return air duct
connection can cause a potentially dangerous negative
pressure condition. Air for combustion and ventilation can
be brought into the conned space either from inside the
building or from outside.
Air from Inside
If the conned space that houses the furnace adjoins a
space categorized as unconned, air can be brought in by
providing two permanent openings between the two spac-
es. Each opening must have a minimum free area of 1
square inch (645 mm2) per 1,000 Btu (.29 kW) per hour of
total input rating of all gas-red equipment in the conned
space. Each opening must be at least 100 square inches
(64516 mm2). One opening shall be within 12 inches (305
mm) of the top of the enclosure and one opening within 12
inches (305 mm) of the bottom. See FIGURE 4.
EQUIPMENT IN CONFINED SPACE - ALL AIR FROM INSIDE
OPENINGS
(To Adjacent
Unconfined
Space)
NOTE
- Each opening shall have a free area of at least one square inch
per
1,000 Btu (645mm2per .29kW) per hour of the total input rating of
all
equipment in the enclosure, but not less than 100 square inches
(64516mm.
2).
ROOF TERMINATED
EXHAUST PIPE
SIDE WALL
TERMINATED
EXHAUST PIPE
(ALTERNATE
LOCATION)
FIGURE 4

Page 7
Air from Outside
If air from outside is brought in for combustion and ventila-
tion, the conned space shall be provided with two perma-
nent openings. One opening shall be within 12” (305mm)
of the top of the enclosure and one within 12” (305mm) of
the bottom. These openings must communicate directly or
by ducts with the outdoors or spaces (crawl or attic) that
freely communicate with the outdoors or indirectly through
vertical ducts. Each opening shall have a minimum free
area of 1 square inch per 4,000 Btu (645mm2 per 1.17kW)
per hour of total input rating of all equipment in the en-
closure. When communicating with the outdoors through
horizontal ducts, each opening shall have a minimum free
area of 1 square inch per 2,000 Btu (645mm2 per .59kW)
per total input rating of all equipment in the enclosure (See
FIGURE 5). It is also permissible to bring in air for com-
bustion from a ventilated attic (FIGURE 6) or ventilated
crawl space (FIGURE 7).
EQUIPMENT IN CONFINED SPACE - ALL AIR FROM OUTSIDE
(Inlet Air from Crawl Space and Outlet Air to Outside)
NOTE-The inlet and outlet air openings shall each have a free area
of at least one square inch per 4,000 Btu (645mm2per 1.17kW) per
hour of the total input rating of all equipment in the enclosure.
OUTLET
AIR
INLET
AIR
VENTILATION
LOUVERS
(For unheated
crawl space)
FURNACE
ROOF TERMINATED
EXHAUST PIPE
VENTILATION LOUVERS
(Each end of attic)
SIDE WALL
TERMINATED
EXHAUST PIPE
(ALTERNATE
LOCATION)
FIGURE 5
EQUIPMENT IN CONFINED SPACE
(Inlet Air from Ventilated Attic and Outlet Air to Outside)
NOTE
-The inlet and outlet air openings shall each have a free area
of at least one square inch per 4,000 Btu (645m
m2per 1.17kW) per
hour of the total input rating of all equipment in the enclosure.
Ventilation Louvers
Inlet Air
(Minimum
12 in.(305mm) Abov
e
attic floor)
Roof Terminated
Exhaust Pipe
Furnace
*Intake Debris
Screen
(Provided)
FIGURE 6
NOTE-The inlet and outlet air openings shall each have a free area
of at least one square inch per 4,000 Btu (645mm2per 1.17kW) per
hour of the total input rating of all equipment in the enclosure.
EQUIPMENT IN CONFINED SPACE
(Inlet Air from Ventilated Crawlspace and Outlet Air to Outside)
Roof Terminated
Exhaust Pipe
Furnace
Ventilation
Louvers
(Crawl space)
*Intake Debris Screen Provided)
Inlet Air
(Minimum
12 in.(305mm)
Above crawl
space floor)
Coupling or
3 in. to 2 in.
Transition
(Field Provided)
FIGURE 7
If air from outside is brought in for combustion and ventila-
tion, the conned space must have two permanent open-
ings. One opening shall be within 12 inches (305 mm) of
the top of the enclosure and one opening within 12 inches
(305 mm) of the bottom. These openings must communi-
cate directly or by ducts with the outdoors or spaces (crawl
or attic) that freely communicate with the outdoors or in-
directly through vertical ducts. Each opening shall have a
minimum free area of 1 square inch (645 mm2) per 4,000
Btu (1.17 kW) per hour of total input rating of all equip-
ment in the enclosure. See FIGURE 5 and FIGURE 8.
When communicating with the outdoors through horizon-
tal ducts, each opening shall have a minimum free area of
1 square inch (645 mm2) per 2,000 Btu (.56 kW) per total
input rating of all equipment in the enclosure. See gure 9.
When ducts are used, they shall be of the same cross-sec-
tional area as the free area of the openings to which they
connect. The minimum dimension of rectangular air ducts
shall be no less than 3 inches (75 mm). In calculating free
area, the blocking e󰀨ect of louvers, grilles, or screens
must be considered. If the design and free area of protec-
tive covering is not known for calculating the size opening
required, it may be assumed that wood louvers will have
20 to 25 percent free area and metal louvers and grilles
will have 60 to 75 percent free area. Louvers and grilles
must be xed in the open position or interlocked with the
equipment so that they are opened automatically during
equipment operation.

Page 8
EQUIPMENT IN CONFINED SPACE - ALL AIR FROM OUTSIDE
(All Air Through Ventilated Attic)
NOTE-The inlet and outlet air openings shall each have a free area of
at least one square inch per 4,000 Btu (645mm2per 1.17kW) per hour
of the total input rating of all equipment in the enclosure.
OUTLET
AIR
VENTILATION LOUVERS
(Each end of attic)
INLET AIR
(Ends 12” above
bottom)
ROOF TERMINATED
EXHAUST PIPE
SIDE WALL
TERMINATED
EXHAUST PIPE
(ALTERNATE
LOCATION)
FURNACE
FIGURE 8
EQUIPMENT IN CONFINED SPACE -
ALL AIR FROM OUTSIDE
OUTLET AIR
INLET AIR
NOTE-Each air duct opening shall have a free area of at least one
square inch per 2,000 Btu (645mm2per .59kW) per hour of the total
input rating of all equipment in the enclosure. If the equipment room
cate directly with the outdoors, each opening shall have a free area
of at least 1 square inch per 4,000 Btu (645mm2per 1.17kW) per
hour of the total input rating of all other equipment in the enclosure.
ROOF TERMINATED
EXHAUST PIPE
SIDE WALL
TERMINATED
EXHAUST PIPE
(ALTERNATE
LOCATION)
FURNACE
FIGURE 9
Shipping Bolt Removal
Units with 1/2 hp blower motor are equipped with three
exible legs and one rigid leg. The rigid leg is equipped
with a shipping bolt and a at white plastic washer (rather
than the rubber mounting grommet used with a exible
mounting leg). See FIGURE 10. The bolt and washer
must be removed before the furnace is placed into
operation. After the bolt and washer have been removed,
the rigid leg will not touch the blower housing.
RIGID LEG
remove shipping bolt and washe
r
UNITS WITH 1/2 HP
BLOWER MOTOR
FIGURE 10
Installation - Setting Equipment
WARNING
Do not install the furnace on its front, back or in the
horizontal position. See FIGURE 12. Do not connect
the return air ducts to the back of the furnace. Doing so
will adversely a󰀨ect the operation of the safety control
devices, which could result in personal injury or death.
Select a location that allows for the required clearances
that are listed on the unit nameplate. Also consider gas
supply connections, electrical supply, vent connection,
condensate trap and drain connections, and installation
and service clearances [24 inches (610 mm) at unit front].
The unit must be level from side to side. Unit may be posi-
tioned from level to 1/2” toward the front to aid in draining.
See FIGURE 11.
Allow for clearances to combustible materials as indicated
on the unit nameplate. Minimum clearances for closet or
alcove installations are shown in FIGURE 13.
WARNING
Blower access panel must be securely in place when
blower and burners are operating. Gas fumes, which
could contain carbon monoxide, can be drawn into living
space resulting in personal injury or death.
SETTING EQUIPMENT
FRONT VIEW SIDE VIEW
AIR FLOW AIR FLOW
1/2”
max.
AIR FLOW
SIDE VIEW
Unit must be level side-to-side. Unit may be positioned
from level to 1/2” toward the front to aid in draining.
FIGURE 11

Page 9
Front
NOTE - Do not install the furnace on its front, back or in the horizontal position
Back Horizontal
FIGURE 12
WARNING
Improper installation of the furnace can result in personal
injury or death. Combustion and ue products must
never be allowed to enter the return air system or air
in the living space. Use sheet metal screws and joint
tape to seal return air system to furnace. In platform
installations with furnace return, the furnace should be
sealed airtight to the return air plenum. A door must
never be used as a portion of the return air duct system.
The base must provide a stable support and an airtight
seal to the furnace. Allow absolutely no sagging, cracks,
gaps, etc. For no reason should return and supply air
duct systems ever be connected to or from other heating
devices such as a replace or stove, etc. Fire, explosion,
carbon monoxide poisoning, personal injury and/or
property damage could result.

Page 10
The unit may be installed three ways in downow applica-
tions: on non-combustible ooring, on combustible oor-
ing using an additive base, or on a reverse-ow cooling
coil cabinet. Do not drag the unit across the oor in the
downow position. Floor and furnace ange damage
will result.
Refer to FIGURE 13 for clearances in downow applica-
tions.
Downflow Application Installation Clearances
Top
Bottom
Left Side Right Side
Top 0
*Front 0
Back 0
Sides 0†
Vent 0
Floor NC‡
*Front clearance in alcove installation must be 24 in. (610 mm).
Maintain a minimum of 24 in. (610 mm) for front service access.
†Allow proper clearances to accommodate condensate trap and
vent pipe installation.
‡
tional base is installed between the furnace and the combustible
floor.
FIGURE 13
Installation on Non-Combustible Flooring FIGURE 14
1 - Cut oor opening keeping in mind clearances listed
on unit rating plate. Also keep in mind gas supply
connections, electrical supply, ue and air intake
connections and su󰀩cient installation and servicing
clearances. See TABLE 1 for correct oor opening
size.
2 - Flange warm air plenum and lower the plenum into
the opening.
3 - Set the unit over the plenum and seal the plenum to
the unit.
4 - Ensure that the seal is adequate.
TABLE 1
NON-COMBUSTIBLE FLOOR OPENING SIZE
Cabinet
Width
Front to Rear Side to Side
in. mm in mm
B (17.5”) 19-3/4 502 16-5/8 422
C (21”) 19-3 4 502 20-1/8 511
NOTE - Floor opening dimensions listed are 1/4 inch (6 mm) larger than
the unit opening. See dimension drawing on page 2.
SUPPLY AIR
PLENUM
PROPERLY
SIZED FLOOR
OPENING
FURNACE
FIGURE 14
Installation on Combustible Flooring FIGURE 15
1 - When unit is installed on a combustible oor,
a downow combustible ooring base must be
installed between the furnace and the oor. The
base must be ordered separately. See TABLE 2 for
opening size to cut in oor.
CAUTION
The furnace and combustible ooring base shall not be
installed directly on carpeting, tile, or other combustible
material other than wood ooring.

Page 11
TABLE 2
COMBUSTIBLE FLOORING BASE OPENING SIZE
Cabinet
Width
Catalog
Number
Front to Rear Side to Side
in mm in mm
B (17.5”) 11M60 22 559 18-3/4 476
C (21”) 11M61 22 559 22-3/4 578
FURNACE
SUPPLY AIR
PLENUM
COMBUSTIBLE
FLOORING BASE
PROPERLY
SIZED FLOOR
OPENING
FIGURE 15
2 - After opening is cut, set the combustible ooring
base into opening.
3 - Check berglass strips on the combustible ooring
base to make sure they are properly glued and
positioned.
4 - Lower supply air plenum into the combustible ooring
base until plenum anges seal against berglass
strips.
NOTE - Be careful not to damage berglass strips.
Check for a tight seal.
5 - Set the furnace over the plenum.
6 - Ensure that the seal between the furnace and
plenumis adequate.
Installation on Cooling Coil Cabinet FIGURE 16
NOTE - Downow combustible ooring kit is not used.
1 - Refer to reverse-ow coil installation instructions for
correctly sized opening in oor and installation of
cabinet.
2 - When cooling cabinet is in place, set and secure
the furnace according to the instructions that are
provided with the cooling coil. Secure the furnace to
the cabinet.
3 - Seal the cabinet and check for air leaks.
COOLING COIL
PLENUM
PROPERLY
SIZED FLOOR
OPENING
FURNACE
FIGURE 16
Return Air Opening -- Downow Units
Return air may be brought in only through the top opening
of a furnace installed in the downow position. The follow-
ing steps should be taken when installing plenum:
1 - Bottom edge of plenum should be anged with a
hemmed edge (See FIGURE 17 or FIGURE 18).
2 - Sealing strips should be used to ensure an airtight
seal between the cabinet and the plenum.
3 - In all cases, plenum should be secured to top of
furnace using sheet metal screws.
4 - Make certain that an adequate seal is made.
SECURE FROM
OUTSIDE CABINET
PLENUM
(Field Provided)
SEALING STRIP
(Field Provided)
Side View
CABINET
SIDE PANEL
FIGURE 17
SECURE FROM
INSIDE CABINET
PLENUM
(Field Provided)
SEALING STRIP
(Field Provided)
Side View
CABINET
SIDE PANEL
FIGURE 18

Page 12
Filters
This unit is not equipped with a lter or rack. A eld-provid-
ed lter is required for the unit to operate properly. TABLE
3 lists recommended minimum lter size.
A lter must be in place whenever the unit is operating.
IMPORTANT
If a highe󰀩ciency lter is being installed as part of this
system to ensure better indoor air quality, the lter must
be properly sized. Highe󰀩ciency lters have a higher
static pressure drop than standarde󰀩ciency glass/foam
lters. If the pressure drop is too great, system capacity
and performance may be reduced. The pressure drop
may also cause the limit to trip more frequently during
the winter and the indoor coil to freeze in the summer,
resulting in an increase in the number of service calls.
Before using any lter with this system, check the
specications provided by the lter manufacturer against
the data given in the appropriate Lennox Product
Specications bulletin. Additional information is provided
in Service and Application Note ACC002
(August 2000).
TABLE 3
Furnace Cabinet Width Minimum Filter Size
16 x 25 x 1 (1)
17-1/2”
21”
Duct System
Use industry-approved standards to size and install the
supply and return air duct system. Refer to ACCA Manual
D. This will result in a quiet and low-static system that has
uniform air distribution. See gure below for proper duct
installation.
NOTE - This furnace is not certied for operation in heat-
ing mode (indoor blower operating at selected heating
speed) with an external static pressure which exceeds 0.8
inches w.c. Operation at these conditions may result in
improper limit operation.
Duct Installation
Down-Flow Unit
SUPPLY
AIR
Supply Air Plenum
If the furnace is installed without a cooling coil, a remov-
able access panel should be installed in the supply air
duct. The access panel should be large enough to per-
mit inspection of the heat exchanger. The furnace access
panel must always be in place when the furnace is oper-
ating and it must not allow leaks into the supply air duct
system.
Return Air Plenum
NOTE - Return air must not be drawn from a room where
this furnace, or any other gas-fueled appliance (i.e., water
heater), or carbon monoxide-producing device (i.e., wood
replace) is installed.
When return air is drawn from a room, a negative pressure
is created in the room. If a gas appliance is operating in
a room with negative pressure, the ue products can be
pulled back down the vent pipe and into the room. This
reverse ow of the ue gas may result in incomplete com-
bustion and the formation of carbon monoxide gas. This
raw gas or toxic fumes might then be distributed through-
out the house by the furnace duct system.
Use berglass sealing strips, caulking, or equivalent seal-
ing method between the plenum and the furnace cabinet
to ensure a tight seal. If a lter is installed, size the return
air duct to t the lter frame.
Pipe & Fittings Specications
All pipe, ttings, primer and solvent cement must conform
with American National Standard Institute and the Ameri-
can Society for Testing and Materials (ANSI/ASTM) stan-
dards. The solvent shall be free owing and contain no
lumps, undissolved particles or any foreign matter that
adversely a󰀨ects the joint strength or chemical resistance
of the cement. The cement shall show no gelation, strati-
cation, or separation that cannot be removed by stirring.
Refer to the table 4 below for approved piping and tting
materials
.
CAUTION
Solvent cements for plastic pipe are ammable liquids
and should be kept away from all sources of ignition.
Do not use excessive amounts of solvent cement when
making joints. Good ventilation should be maintained to
reduce re hazard and to minimize breathing of solvent
vapors. Avoid contact of cement with skin and eyes.

Page 13
TABLE 4
PIPING AND FITTINGS SPECIFICATIONS
Schedule 40 PVC (Pipe) D1785
Schedule 40 PVC (Fittings) D2466
Schedule 40 CPVC (Pipe) F441
Schedule 40 CPVC (Fittings) F438
SDR-21 PVC or SDR-26 PVC (Pipe) D2241
SDR-21 CPVC or SDR-26 CPVC (Pipe) F442
Schedule 40 ABS (Pipe) D1527
Schedule 40 ABS (Fittings) D2468
ABS-DWV (Drain Waste & Vent) (Pipe &
Fittings) D2661
PVC-DWV (Drain Waste & Vent) Pipe &
Fittings) D2665
PRIMER & SOLVENT CEMENT ASTM
SPECIFICATION
PVC & CPVC Primer F656
PVC Solvent Cement D2564
CPVC Solvent Cement F493
ABS Solvent Cement D2235
PVC/CPVC/ABS All Purpose Cement
For Fittings & Pipe of the same material
D2564, D2235,
F493
ABS to PVC or CPVC Transition Solvent
Cement D3188
CANADA PIPE & FITTING & SOLVENT
CEMENT MARKING
PVC & CPVC Pipe and Fittings
ULCS636
PVC & CPVC Solvent Cement
ABS to PVC or CPVC Transition
Cement
POLYPROPYLENE VENTING SYSTEM
PolyPro® by Duravent
InnoFlue® by Centrotherm
UL 1738 CERTIFIED GAS VENTING SYSTEM
IPEX System1738 Schedule 40 PVC
Pipes and Fittings UL1738
IPEX System1738 PVC FGV Cement &
Primer
IMPORTANT
EL297DFV exhaust and intake connections are made
of PVC. Use PVC primer and solvent cement when
using PVC vent pipe. When using ABS vent pipe, use
transitional solvent cement to make connections to the
PVC ttings in the unit.
Use PVC primer and solvent cement or ABS solvent ce-
ment meeting ASTM specications, refer to TABLE 4. As
an alternate, use all purpose cement, to bond ABS, PVC,
or CPVC pipe when using ttings and pipe made of the
same materials. Use transition solvent cement when bond-
ing ABS to either PVC or CPVC.Low temperature solvent
cement is recommended during cooler weather. Metal or
plastic strapping may be used for vent pipe hangers. Uni-
formly apply a liberal coat of PVC primer for PVC or use
a clean dry cloth for ABS to clean inside socket surface of
tting and male end of pipe to depth of tting socket.
Canadian Applications Only - Pipe, ttings, primer and
solvent cement used to vent (exhaust) this appliance must
be certied to ULC S636 and supplied by a single manu-
facturer as part of an approved vent (exhaust) system. In
addition, the rst three feet of vent pipe from the furnace
ue collar must be accessible for inspection.
Venting Options
The EL297DFV is shipped with vent exhaust / air intake
connection at the top cap. See FIGURE 19. Using parts
provided, the furnace may be eld modied to have these
connections on the right side of the furnace cabinet. See
FIGURE 22 and follow the steps below. For left side vent-
ing order kit 87W73.
1 - Remove inner blower door.
2 - Loosen hose clamps which attach rubber ttings to
the white PVC pipes inside the vestibule area. See
FIGURE 19.
3 - Loosen the clamp which secures the pipes at the
blower deck. See FIGURE 19.
4 - Remove white PVC pipes, slide up and out thru the
top cap.
5 - Remove the black plastic tting in top cap which
previously aligned the PVC pipes.
6 - Remove the remaining parts of the pipe clamp at the
blower deck.
7 - Remove the sheet metal patch plate on the side
of the cabinet which covers the openings for side
venting option. Save screws for reuse.
8 - Re-use the patch plate to cover the hole in the top
cap. See FIGURE 20. Remove the 2 screws which
secure the top cap to the furnace on the right side
and re-install securing the right edge of the patch
plate and the right side of the top cap to the furnace.
Use 2 self-drilling sheet metal screws (provided) to
nish securing the left edge of the patch plate on the
left side.
9 - Use a utility knife to cut out the cabinet insulation for
the right side vent / air intake.
10 -Install the two 90° street elbows (provided) through
the side of the cabinet. The male side of each
elbow should extend down through the blower deck
and connect to the rubber ttings below. Once the
elbows are properly positioned, tighten each clamp.
11 -Peel protective backing from side vent sealing
gaskets (2) and apply to side vent sealing plates (2)
as shown in FIGURE 22.

Page 14
12 -Install the side vent sealing plates and gaskets on
the exterior of the cabinet as shown in FIGURE
22. Secure with six mounting screws (four reused
and two provided from bag assembly). Holes are
pre-punched in the parts and cabinet, no drilling is
required.
13 -Install sheet metal screws (provided) to seal extra
two holes in cabinet not used with side vent clamps.
IMPORTANT
Side vent sealing plates and side vent sealing gaskets
must be used when converting to right side venting.
Failure to use gaskets and plates may lead to improper
operation of unit.
Top Vent Configuration
Exhaust/Air
Intake Connections
Pipe Clamp
Hose Clamp
FIGURE 19
Sheet Metal
Patch Plate
Patch Plate Top Cap
FIGURE 20
Crawl Space and Extended Horizontal Venting
Lennox provides kit 51W18 (USA) and kit 15Z70 (Cana-
da) to install 2” or 3” PVC exhaust piping through the oor
joists and into the the crawl space. See FIGURE 21. This
kit can also be used as a supplemental drain for installa-
tions with condensate run back in the vent pipe (ie. long
horizontal runs, unconditioned spaces, etc.).
Venting In A Crawl Space
Basement Floor
KIT 51W18
(USA)
KIT 15Z70
(CANADA)
FIGURE 21

Page 15
Right Side Vent Configuration
Side Vent
Sealing Plate
Side Vent
Sealing Gaskets
Street Elbows (2)
Intake
Exhaust
FIGURE 22
TABLE 5
OUTDOOR TERMINATION USAGE*
Input Size Vent Pipe Dia.
in.
STANDARD CONCENTRIC
Flush Mount
Kit Wall Kit
Field
Fabricated
1-1/2 inch 2 inch 3 inch
51W11 (US)
51W12 (CA)
2 inch 3 inch 71M80 (US)
444W92 (CA)
69M29 (US)
444W92 (CA)
60L46 (US)
444W93 (CA)
22G44 (US)
430G28 (CA)
44J40 (US)
481J20 (CA)
045
61-1/2 3YES YES 1YES 5 YES 2YES
23YES YES 1YES 5 YES 2YES
N/A N/A
2-1/2 3YES YES 1YES 5 YES 2YES
33YES YES 1YES 5 YES 2YES
070
61-1/2 3YES YES 1YES 5 YES 2YES
23YES YES 1YES 5 YES 2YES
2-1/2 3YES YES 1YES 5 YES 2YES
33YES YES 1YES 5 YES 2YES
090
23YES
N/A
YES 5 YES
N/A
YES YES
2-1/2 3YES YES 5 YES YES YES
33YES YES 5 YES YES YES
110
2 YES YES 5 YES YES YES
2-1/2 YES YES 5 YES YES YES
3 YES YES 5 YES YES YES
NOTE - Standard Terminations do not include any vent pipe or elbows external to the structure. Any vent pipe or elbows external to the structure must be included in total
vent length calculations. See vent length tables.
* Kits must be properly installed according to kit instructions.
1Requires eld-provided outdoor 1-1/2” exhaust accelerator.
2Concentric kits 71M80 and 44W92 include 1-1/2” outdoor accelerator, when used with 045 and 070 input models. 1-1/2 in pipe must transition to 2 in pipe when used with
a concentric kit.
3 Flush mount kits 51W11 and 51W12 includes 1-1/2 in. outdoor exhaust accelerator, required when used with 045, 070 and 090 input models. 1-1/2 in pipe must transition
to 2 in pipe when used with the ushmount kit.
4 Termination kits 30G28, 44W92, 4493 and 81J20 are certied to ULC S636 for use in Canada only.
5 See table 10 for vent accelerator requirements.
6 2 in to 1-1/2 in reducer required must be eld provided.

Page 16
Joint Cementing Procedure
All cementing of joints should be done according to the
specications outlined in ASTM D 2855.
NOTE - A sheet metal screw may be used to secure the
intake pipe to the connector, if desired. Use a drill or self
tapping screw to make a pilot hole.
DANGER
DANGER OF EXPLOSION!
Fumes from PVC glue may ignite during system check.
Allow fumes to dissipate for at least 5 minutes before
placing unit into operation.
1 - Measure and cut vent pipe to desired length.
2 - Debur and chamfer end of pipe, removing any ridges
or rough edges. If end is not chamfered, edge of pipe
may remove cement from tting socket and result in
a leaking joint.
NOTE - Check the inside of vent pipe thoroughly for
any obstruction that may alter furnace operation.
3 - Clean and dry surfaces to be joined.
4 - Test t joint and mark depth of tting on outside of
pipe. 5 - Uniformly apply a liberal coat of PVC primer
for PVC or use a clean dry cloth for ABS to clean
inside socket surface of tting and male end of pipe
to depth of tting socket.
6 - Promptly apply solvent cement to end of pipe and
inside socket surface of tting. Cement should be
applied lightly but uniformly to inside of socket. Take
care to keep excess cement out of socket. Apply
second coat to end of pipe.
NOTE - Time is critical at this stage. Do not allow
primer to dry before applying cement.
7 - Immediately after applying last coat of cement to
pipe, and while both inside socket surface and end
of pipe are wet with cement, forcefully insert end of
pipe into socket until it bottoms out. Turn PVC pipe
1/4 turn during assembly (but not after pipe is fully
inserted) to distribute cement evenly. DO NOT turn
ABS or cellular core pipe.
NOTE - Assembly should be completed within 20
seconds after last application of cement. Hammer
blows should not be used when inserting pipe.
8 - After assembly, wipe excess cement from pipe at
end of tting socket. A properly made joint will show
a bead around its entire perimeter. Any gaps may
indicate an improper assembly due to insu󰀩cient
solvent.
9 - Handle joints carefully until completely set.
Venting Practices
* See Piping and Fittings Specifications table
Piping Suspension Guidelines
NOTE - Isolate piping at the point where it exits the outside wall o
r
roof in order to prevent transmission of vibration to the structure.
SCHEDULE 40
PVC - 5'
all other pipe* - 3'
Wall edistuoedisni
24” maximum
3/4” minimum
Wall Thickness Guidelines
FIGURE 23
If replacing a furnace which was
commonly vented with another gas appliance, the size
of the existing vent pipe for that gas appliance must be
checked. Without the heat of the original furnace flue
products, the existing vent pipe is probably oversized for
the single water heater or other appliance. The vent
should be checked for proper draw with the remaining
appliance.
REPLACING FURNACE THAT WAS PART OF A
COMMON VENT SYSTEM
CHIMNEY
OR GAS
VENT
(Check sizing
for water
heater only)
FURNACE
(Replaced)
WATER
HEATER
OPENINGS
(To Adjacent
Room)
FIGURE 24

Page 17
1 - In areas where piping penetrates joists or interior
walls, hole must be large enough to allow clearance
on all sides of pipe through center of hole using a
hanger.
2 - When furnace is installed in a residence where unit
is shut down for an extended period of time, such
as a vacation home, make provisions for draining
condensate collection trap and lines.
Removal of the Furnace from Common Vent
In the event that an existing furnace is removed from a
venting system commonly run with separate gas applianc-
es, the venting system is likely to be too large to properly
vent the remaining attached appliances. Conduct the fol-
lowing test while each appliance is operating and the oth-
er appliances (which are not operating) remain connected
to the common venting system. If the venting system has
been installed improperly, you must correct the system as
indicated in the general venting requirements section.
.
WARNING
CARBON MONOXIDE POISONING HAZARD
Failure to follow the steps outlined below for each
appliance connected to the venting system being placed
into operation could result in carbon monoxide poisoning
or death.
The following steps shall be followed for each appliance
connected to the venting system being placed into
operation, while all other appliances connected to the
venting system are not in operation:
1 - Seal any unused openings in the common venting
system.
2 - Inspect the venting system for proper size and
horizontal pitch. Determine that there is no blockage,
restriction, leakage, corrosion, or other deciencies
which could cause an unsafe condition.
3 - Close all building doors and windows and all
doors between the space in which the appliances
remaining connected to the common venting system
are located and other spaces of the building. Turn on
clothes dryers and any appliances not connected to
the common venting system. Turn on any exhaust
fans, such as range hoods and bathroom exhausts,
so they will operate at maximum speed. Do not
operate a summer exhaust fan. Close replace
dampers.
4 - Follow the lighting instructions. Turn on the appliance
that is being inspected. Adjust the thermostat so that
the appliance operates continuously.
5 - After the main burner has operated for 5 minutes,
test for leaks of ue gases at the draft hood relief
opening. Use the ame of a match or candle.
6 - After determining that each appliance connected to
the common venting system is venting properly, (step
3) return all doors, widows, exhaust fans, replace
dampers, and any other gas-burning appliances to
their previous mode of operation.
7 - If a venting problem is found during any of the
preceding tests, the common venting system must
be modied to correct the problem. Resize the
common venting system to the minimum vent pipe
size determined by using the appropriate tables in
Appendix G. (These are in the current standards of
the National Fuel Gas Code ANSI Z223.1.
Exhaust Piping (FIGURE 26 and FIGURE 27)
Route piping to outside of structure. Continue with instal-
lation following instructions given in piping termination
section.
WARNING
Carbon Monoxide Poisoning Hazard
Cutting or altering exhaust or air intake pipes, which
are located in the blower compartment, could result in
Carbon Monoxide Poisoning or Death.
CAUTION
Do not discharge exhaust into an existing stack or
stack that also serves another gas appliance. If vertical
discharge through an existing unused stack is required,
insert PVC pipe inside the stack until the end is even
with the top or outlet end of the metal stack.
CAUTION
The exhaust vent pipe operates under positive pressure
and must be completely sealed to prevent leakage of
combustion products into the living space.

Page 18
Vent Piping Guidelines
NOTE - Lennox has approved the use of DuraVent® and
Centrotherm manufactured vent pipe and terminations as
an option to PVC. When using the PolyPro® by DuraVent
or InnoFlue® by Centrotherm venting system the vent pipe
requirements stated in the unit installation instruction –
minimum & maximum vent lengths, termination clearanc-
es, etc. – apply and must be followed. Follow the instruc-
tions provided with PoyPro by DuraVent and InnoFlue by
Centrotherm venting system for assembly or if require-
ments are more restrictive. The PolyPro by Duravent and
InnoFlue by Centrotherm venting system must also follow
the uninsulated and unconditioned space criteria listed in
table 8.
The EL297DFV can be installed as either a Non-Direct
Vent or a Direct Vent gas central furnace.
NOTE - In Non-Direct Vent installations, combustion air is
taken from indoors or ventilated attic or crawlspace and
ue gases are discharged outdoors. In Direct Vent instal-
lations, combustion air is taken from outdoors and ue
gases are discharged outdoors.
Intake and exhaust pipe sizing -- Size pipe according to
TABLE 6 (minimum pipe lengths) and TABLE 7 (maxim-
mum pipe lengths). Count all elbows inside and outside
the home.
TABLE 6
MINIMUM VENT PIPE LENGTHS
EL297DFV MODEL MIN. VENT LENGTH*
045, 070, 090, 110 15 ft or 5ft plus 2 elbows or
10 ft plus 1 elbow
*Any approved termination may be added to the minimum
length listed. Two 45 degree elbows are the equivalent to
one 90 degree elbow.
Regardless of the diameter of pipe used, the standard roof
and wall terminations described in section Exhaust Piping
Terminations should be used. Exhaust vent termination
pipe is sized to optimize the velocity of the exhaust gas as
it exits the termination. Refer to TABLE 10.
In some applications which permit the use of several dif-
ferent sizes of vent pipe, a combination vent pipe may be
used. Contact Lennox’ Application Department for assis-
tance in sizing vent pipe in these applications.
IMPORTANT
Do not use screens or perforated metal in exhaust or
intake terminations. Doing so will cause freeze-ups and
may block the terminations.
NOTE - It is acceptable to use any pipe size which ts
within the guidelines allowed in TABLE 7.
NOTE - All horizontal runs of exhaust pipe must slope
backtoward unit. A minimum of 1/4” (6mm) drop for each
12” (305mm) of horizontal run is mandatory for drainage.
NOTE - Lennox oers a glueless vent adapter kit 17H92
as an option for exhaust exiting at the furnace top cap
coupling.
NOTE - Exhaust pipe MUST be glued to furnace exhaust
ttings.
NOTE - Exhaust piping should be checked carefully to
make sure there are no sags or low spots.
NOTE - If right side venting option is used, you must in-
clude the elbow at the furnace in the elbow count. If tran-
sitioning to 3” dia pipe, this elbow equates to 20’ of equiv-
alent vent length for all models.
Use the following steps to correctly size vent pipe diam-
eter.
Piping Size Process
1
2
3
4
5
6
Which style termination
being used?
Standard or concentric?
.
Which needs
most elbows?
Intake or
exhaust?
How many elbows?
Count all elbows inside
and outside house.
Desired pipe size?
What is the altitude of
the furnace installation?
7
What is the
furnace capacity?
See max and min length
tables. Include all vent pipe
and elbows inside and
outside the hpouse
FIGURE 25

Page 19
TABLE 7
Maximum Allowable Intake or Exhaust Vent Length
Size intake and exhaust pipe length separately. Values in table are for Intake OR Exhaust, not combined total. Intake and Exhaust must be same size.
NOTE - Additional vent pipe and elbows used to terminate the vent pipe outside the structure must be included in the total vent length calculation.
Standard Termination at Elevation 0 - 4500 ft
Number
Of 90°
Elbows
Used
1-1/2” Pipe 2” Pipe 2-1/2” Pipe 3” Pipe
Model Model Model Model
045 070 090 110 045 070 090 110 045 070 090 110 045 070 090 110
1 20 15
n/a n/a
71 56 34 14 105 105 83 48 128 127 108 108
2 15 10 66 51 29 9 100 100 78 43 123 122 103 103
3 10
n/a
61 46 24 4 95 95 73 38 118 117 98 98
4
n/a
56 41 19
n/a
90 90 68 33 113 112 93 93
5 51 36 14 85 85 63 28 108 107 88 88
6 46 31 9 80 80 58 23 101 102 83 83
7 41 26 4 75 75 53 18 98 97 78 78
8 36 21
n/a
70 70 48 13 93 92 73 73
9 31 16 65 65 43 8 88 87 68 68
10 26 11 60 60 38 3 83 82 63 63
Standard Termination Elevation 4501 - 10,000 ft
Number
Of 90°
Elbows
Used
1-1/2” Pipe 2” Pipe 2-1/2” Pipe 3” Pipe
Model Model Model Model
045 070 090 110 045 070 090 110 045 070 090 110 045 070 090 110
1 20 15
n/a n/a
71 56 34
n/a
105 105 83 48 128 127 108 108
2 15 10 66 51 29 100 100 78 43 123 122 103 103
3 10
n/a
61 46 24 95 95 73 38 118 117 98 98
4
n/a
56 41 19 90 90 68 33 113 112 93 93
5 51 36 14 85 85 63 28 108 107 88 88
6 46 31 9 80 80 58 23 103 102 83 83
7 41 26 4 75 75 53 18 98 97 78 78
8 36 21
n/a
70 70 48 13 93 92 73 73
9 31 16 65 65 43 8 87 87 68 68
10 26 11 60 60 38 5 83 82 63 63

Page 20
TABLE 7 CONT.
Maximum Allowable Intake or Exhaust Vent Length
Size intake and exhaust pipe length separately. Values in table are for Intake OR Exhaust, not combined total. Intake and Exhaust must be same size.
NOTE - Additional vent pipe and elbows used to terminate the vent pipe outside the structure must be included in the total vent length calculation.
Concentric Termination at Elevation 0 - 4500 ft
Number
Of 90°
Elbows
Used
1-1/2” Pipe 2” Pipe 2-1/2” Pipe 3” Pipe
Model Model Model Model
045 070 090 110 045 070 090 110 045 070 090 110 045 070 090 110
115 10
n/a n/a
63 48 32 12 95 95 79 44 111 111 104 104
210
n/a
58 43 27 7 90 90 74 39 106 106 99 99
3
n/a
53 38 22 2 85 85 69 34 101 101 94 94
4 48 33 17
n/a
80 80 64 29 96 96 89 89
5 43 28 12 75 75 59 24 91 91 84 84
6 38 23 7 70 70 54 19 86 86 79 79
7 33 18 2 65 65 49 14 81 81 74 74
8 28 13
n/a
60 60 44 9 76 76 69 69
9 23 8 55 55 39 4 71 71 64 64
10 18 3 50 50 34 n/a 66 66 59 59
Concentric Termination Elevation 4501 - 10,000 ft
Number
Of 90°
Elbows
Used
1-1/2” Pipe 2” Pipe 2-1/2” Pipe 3” Pipe
Model Model Model Model
045 070 090 110 045 070 090 110 045 070 090 110 045 070 090 110
115 10
n/a n/a
63 48 32
n/a
95 95 79 44 111 111 104 94
210
n/a
58 43 27 90 90 74 39 106 106 99 99
3
n/a
53 38 22 85 85 69 34 101 101 94 94
4 48 33 17 80 80 64 29 96 96 89 89
5 43 28 12 75 75 59 24 91 91 84 84
6 38 23 7 70 70 54 19 86 86 79 79
7 33 18 2 65 65 49 14 81 81 74 74
8 28 13
n/a
60 60 44 9 76 76 69 69
9 23 8 55 55 39 4 71 71 64 64
10 18 3 50 50 34 n/a 66 66 59 59
TABLE 8
Maximum Allowable Exhaust Vent Length Using Ventilated Attic or Crawl Space For Intake Air in Feet
NOTE - Additional vent pipe and elbows used to terminate the vent pipe outside the structure must be included in the total vent length calculation.
Standard Termination at Elevation 0 - 10,000 ft
Number
Of 90°
Elbows
Used
1-1/2 2” Pipe 2-1/2” Pipe 3” Pipe
Model Model Model Model
045 070 090 110 045 070 090 110 045 070 090 110 045 070 090 110
115 10
n/a n/a
61 46 24
n/a
90 90 68 33 108 107 88 88
210
n/a
56 41 19 85 85 63 28 103 102 83 83
3
n/a
51 36 14 80 80 58 23 98 97 78 78
4 46 31 9 75 75 53 18 93 92 73 73
5 41 26 4 70 70 48 13 88 87 68 68
6 36 21
n/a
65 65 43 8 81 82 63 63
7 31 16 60 60 38 3 78 77 58 58
8 26 11 55 55 33
n/a
73 72 53 53
9 21 6 50 50 28 68 67 48 48
10 16 1 45 45 23 63 62 43 43