Lennox DAVE LENNOX SIGNATURE SL297UHNV User manual

Page 1
INSTALLATION
INSTRUCTIONS
SL297UHNV
507760-04
09/2019
Supersedes 507760-03
NOTICE
A thermostat is not included and must be ordered
separately.
A communicating thermostat must be used in
communicating applications.
In non-communicating applications, any Lennox
conventional 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 34.
IMPORTANT
DO NOT use the heat exchanger tubes to lift, drag or
pull the furnace to its installation location.
Doing so will damage the tubes causing noise and or
unsafe operation.
© 2019 Lennox Industries Inc.
Dallas, Texas USA
DAVE LENNOX SIGNATURE®
GAS FURNACE UPFLOW / HORIZONTAL
AIR DISCHARGE
Contents
Unit Dimensions - inches (mm) ......................................2
Parts Arrangement..........................................................3
SLP297UHNV Gas Furnace...........................................4
Shipping and Packing List ..............................................4
Safety .............................................................................4
Use of Furnace as a Construction Heaterl .....................5
General...........................................................................6
Combustion, Dilution, Ventilation Air...............................6
Setting Equipment ..........................................................6
Filters............................................................................ 11
Duct System ................................................................. 11
Pipe Fittings Specications...........................................12
Joint Cementing Procedure..........................................13
Venting Practices..........................................................14
Gas Piping....................................................................29
Electrical.......................................................................32
Integrated Control.........................................................41
Blower Motor Performance...........................................44
Unit Start-Up.................................................................48
Gas Pressure Measurement.........................................49
Proper Combustion.......................................................50
High Altitude .................................................................50
Repair Parts Lsit...........................................................50
Sequence of Operation.................................................51
Service..........................................................................53
Program Unit Capacity Size Mode ...............................61
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.
Heatexchanger Tubes

Page 2
SL297UHNV Unit Dimensions - inches (mm)
AIR FLOW
23
(584)
(19)
3/4
(19)
1Bottom Return
Air Opening
GAS PIPING INLET
(Right Side Only)
Side Return
Air Opening
(Either Side)
1
Bottom Return
Air Opening
EXHAUST AIR
OUTLET
ELECTRICAL
INLET
(Either Side)
SUPPLY AIR
OPENING
FRONT VIEW SIDE VIEW
TOP VIEW
A
B9/16 (14)
C
3/4
27-3/4
(705)
19-7/16
(494)
23-1/2
(597)
1-1/2
(38)
6-1/2 (165)
(Either Side)
33
(838)
3-1/4
(83)
1-15/16 (49)
14
(356)
9/16
(14)
12-5/8
(321)
2OPTIONAL
SIDE RETURN
AIR FILTER KIT
(Either Side)
16
(406)
14-3/4
(375)
2OPTIONAL
SIDE RETURN
AIR FILTER KIT
(Either Side)
5/8
(16)
1
3-1/4
(83)
23-3/4
(603)
25
(635)
1-1/2 (38)
Front Panel
COMBUSTION
AIR INTAKE
1-7/8 (48)
CONDENSATE
TRAP CONNECTION
(Either Side)
INTAKE AIR
2-1/4
(57)
2-7/8
(73)
6-5/8
(168)
Not Used
2
Optional Side Return Air Filter Kit is not for use
with the Optional Return Air Base.
1
NOTE - 60C size units that require air volumes over
1800 cfm must have one of the following:
1. Single side return air and Optional Return Air Base
with transition that must accommodate required
20 x 25 x 1 inch (508 x 635 x 25 mm) air filter to
maintain proper velocity.
2. Bottom return air.
3. Return air from both sides.
4. Bottom and one side return air.
See Blower Performance Tables for additional information.
Model No. A
in - mm
B
in - mm
C
in - mm
SL297UH040NV36B
SL297UH060NV36B 17-1/2 - 446 16-3/8 - 416 16 - 406
SL297UH080NV48C
SL297UH080NV60C 21 - 533 19-7/8 - 505 19-1/2 - 495

Page 3
Parts Arrangement
FIGURE 1
Heat Exchanger
Gas Valve
Combustion
Air Inducer
Indoor Blower
Two-Stage Control
Cabinet
Panel
Inner Panel
Gas Pipe Inlet
(right side only)
Inlet Vent Pipe
Exhaust Vent Pipe
Exhaust Coupling
Intake Air Assembly
Rollout Switch
Burner Assembly

Page 4
SL297UHNV Gas Furnace
The SL297UHNV Category IV gas furnace is shipped
ready for installation in the upow or horizontal position.
The furnace is shipped with the bottom panel in place. The
bottom panel must be removed if the unit is to be installed
in horizontal or upow applications with bottom return air.
The SL297UHNV is to be installed as Direct Vent gas
central furnace only. The furnace is equipped for in-
stallation in natural gas applications only.
NOTE - In Direct Vent installations, combustion air is tak-
en from outdoors and ue gases are discharged outdoors.
DIRECT VENT INSTALLATION
EXHAUST OUTLET
COMBUSTION
A
IR INTAKE
OUTSIDE OF
HOUSE
FIGURE 2
Shipping and Packing List
Package 1 of 1 contains
1 - Assembled SL297UHNV 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 debris screen
1 - 3/4” Threaded street elbow
Check equipment for shipping damage. If you nd any
damage, immediately contact the last carrier. The follow-
ing items may also be ordered separately:
1 - Thermostat
1 - Return air base kit
1 - Horizontal suspension kit
Safety Information
CAUTION
As with any mechanical equipment, contact with sharp
sheet metal edges can result in personal injury. Take
care while handling this equipment and wear gloves and
protective clothing.
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.
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.
Use only the type of gas approved for use with this fur-
nace. Refer to unit nameplate.
SL297UHNV units are CSA International certied to ANSI
Z21.47 and CSA 2.3 standards.
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.
Installation Locations
This furnace is CSA International certied for installation
clearances to combustible material as listed on the unit
nameplate and in the table in gure 6. Accessibility and
service clearances must take precedence over re protec-
tion clearances.
NOTE - For installation on combustible oors, the furnace
shall not be installed directly on carpeting, tile, or other
combustible material other than wood ooring.
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 temperature
rise within the range specied on the unit nameplate. Fail-
ure to do so may cause erratic limit operation and prema-
ture heat exchanger failure.
This SL297UHNV furnace must be installed so that its
electrical components are protected from water.

Page 5
Installed in Combination with a Cooling Coil
When this furnace is used with cooling coils (gure 3), it
shall be installed in parallel with, or on the upstream side
of, cooling coils to avoid condensation in the heating com-
partment. 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.
Gas Unit
Heating Unit Installed Upstream of Cooling Coil
Gas Unit
Dampers
(open during heating operation only)
Dampers
(open during cooling operation only)
Heating Unit Installed Parallel to Air Handler Unit
Air Handler Unit
Cooling Coil
AIR FLOWAIR FLOW
AIR FLOW AIR FLOW
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 SL297UHNV furnace may be installed in alcoves,
closets, attics, basements, garages, crawl spaces and
utility rooms in the upow or horizontal position.
This furnace design has not been CSA certied for instal-
lation in mobile homes, recreational vehicles, or outdoors.
Use of Furnace as Construction Heater
Construction heat is not allowed with this furnace.
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 SL297UHNV furnace:
• Place the furnace as close to the center of the air
distribution system as possible. The furnace should
also be located close to the vent termination point.
• When the furnace is installed in an attic or other
insulated space, keep insulation away from the fur-
nace.
• When the furnace is installed in an unconditioned
space, consider provisions required to prevent
freezing of condensate drain system.
• Please consult the manufacturer of your evaporator
coil for their recommendations on distance required
between the heat exchanger and their drain pan.
Adequate space must be provided between the
drain pan and the furnace heat exchanger.
CAUTION
SL297UHNV unit should not be installed in areas
normally subject to freezing temperatures.
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 gure 4. The bolt and washer must
be removed before the furnace is placed into opera-
tion. 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 4

Page 6
Installation - Setting Equipment
WARNING
Do not connect the return air duct 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.
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.
Upow Applications
The SL297UHNV gas furnace can be installed as shipped
in the upow position. Refer to gure 6 for clearances.
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. The unit may be
positioned from level to ½” toward the front. See gure 5.
Allow for clearances to combustible materials as indicated
on the unit nameplate.
SETTING EQUIPMENT
HORIZONTAL APPLICAT ION
FRONT VIEW
AIR FLOW
END VIEW
UNIT
FRONT
1/2”
max.
Unit must be level side-to-side. Unit may be positioned from level to 1/2” toward the front to aid in draining.
FRONT VIEW SIDE VIEW
1/2” max.
AIR FLOW
UNIT
FRONT
SIDE VIEW
UNIT
FRONT
UPFLOW APPLICATION
Figure 5

Page 7
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 injuryand/or property
damage could result.
Installation Clearances
Top
Bottom (Floor)
Left Side Right Side
Top/Plenum 1 in. (25 mm)
*Front 1
Back 1
Sides 1†
Vent 1
Floor 0‡
*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.
‡For installations on a combustible floor, do not install the furnace
directly on carpeting, tile or other combustible materials other
than wood flooring.
FIGURE 6
Return Air Guidelines
Return air can be brought in through the bottom or either
side of the furnace installed in an upow application. If the
furnace is installed on a platform with bottom return, make
an airtight seal between the bottom of the furnace and the
platform to ensure that the furnace operates properly and
safely. The furnace is equipped with a removable bottom
panel to facilitate installation.
Markings are provided on both sides of the furnace cab-
inet for installations that require side return air. Cut the
furnace cabinet at the maximum dimensions shown on
page 2.
Refer to Engineering Handbook for additional information.
SL297UHNV applications which include side return air
and a condensate trap installed on the same side of the
cabinet (trap can be installed remotely within 5 ft.) require
either a return air base or eld-fabricated transition to ac-
commodate an optional IAQ accessory taller than 14.5”.
See gure 7.
Side Return Air
(with transition and filter)
Return
Air
Plenum
Transition
20” X 25” X 1”
(508mmX635mmX 25mm)
Air Filter
FIGURE 7

Page 8
Figure 8
Removing the Bottom Panel
Screw
Bottom Panel
Bottom Cap
FIGURE 9
Removing the Bottom Panel
Remove the two screws that secure the bottom cap to the
furnace. Pivot the bottom cap down to release the bottom
panel. Once the bottom panel has been removed, reinstall
the bottom cap. See gure 9.
Horizontal Applications
WARNING
Do not install the furnace on its front or back. See gure
10.
See figure 4.
Front Back
FIGURE 10
Optional Return Air Base
(Upflow Applications Only)
NOTE- Optional side return air filter kits are not for use with return air base.
1Both the unit return air opening and the base return air opening must be covered by a single plenum or IAQ cabinet.
Minimum unit side return air opening dimensions for units requiring 1800 cfm or more of air (W x H): 23 x 11 in. (584 x 279 mm).
The opening can be cut as needed to accommodate plenum or IAQ cabinet while maintaining dimensions shown.
Side return air openings must be cut in the field. There are cutting guides stenciled on the cabinet for the side return air
opening. The size of the opening must not extend beyond the markings on the furnace cabinet.
2To minimize pressure drop, the largest opening height possible (up to 14 inches) is preferred.
FRONT VIEW
1Unit side return air
Opening
SIDE VIEW
3−1/4
(83)
1
23 (584)
Overall
(Maximum)
(584)
23
3/4
(19)
122−7/16
(570)
Overall
(Maximum)
SIDE RETURN
AIR OPENINGS
(Either Side)
5−5/8
(143)
1Minimum
11 (279)
2Maximum
14 (356)
(683)
26−7/8
7−1/4
(184)
FURNACE
FRONT
AIR FLOW
IF BASE
IS USED
WITHOUT
IAQ CABINET,
A SINGLE
RETURN AIR
PLENUM
MUST
COVER BOTH
UNIT AND
RETURN
AIR BASE
OPENINGS
INDOOR AIR
QUALITY
CABINET
(PCO, Filter
Cabinet, etc.)
AIR BASE
OPTIONAL
RETURN
CONDENSATE
TRAP
17−1/2 (446) B Width (50W98)
21 (533) C Width (50W99)
24−1/2 (622) D Width (51W00)

Page 9
The SL297UHNV furnace can be installed in horizontal
applications with either right- or left-hand air discharge.
Refer to gure 11 for clearances in horizontal applications.
Horizontal Application
Installation Clearances
dnEthgiRdnEtfeL
Right-Hand Discharge
Left-Hand Discharge
Top
Bottom (Floor)**
Bottom (Floor)**
dnEthgiRdnEtfeL
Air
Flow
Air
Flow
Air
Flow
Air
Flow
Top 1
Front* 1
Back 1
Ends 1
Vent 1
Floor 1‡
*Front clearance in alcove installation must be 24 in. (610 mm).
Maintain a minimum of 24 in. (610 mm) for front service access.
**An 8” service clearance must be maintained below the unit to
provide for servicing of the condensate trap.
‡For installations on a combustible floor, do not install the furnace
directly on carpeting, tile or other combustible materials other
than wood flooring.
FIGURE 11
Suspended Installation of Horizontal Unit
This furnace may be installed in either an attic or a crawl-
space. Either suspend the furnace from roof rafters or
oor joists, as shown in gure 12, or install the furnace on
a platform, as shown in gure 13. A horizontal suspension
kit (51W10) may be ordered from Lennox or use equiva-
lent.
NOTE - Heavy-gauge sheet metal straps may be used to
suspend the unit from roof rafters or ceiling joists. When
straps are used to suspend the unit in this way, support
must be provided for both the ends. The straps must not
interfere with the plenum or exhaust piping installation.
Cooling coils and supply and return air plenums must
be supported separately.
HORIZONTAL SUSPENSION KIT
Bracket
(typical)
Metal Strap
(typical)
Air
Flow
Internal Brace
(provided with kit)
FIGURE 12
NOTE - When the furnace is installed on a platform or with
the horizontal suspension kit in a crawlspace, it must be
elevated enough to avoid water damage, accommodate
drain trap and to allow the evaporator coil to drain.
Platform Installation of Horizontal Unit
1 - Select location for unit keeping in mind service and
other necessary clearances. See gure 11.
2 - Construct a raised wooden frame and cover frame
with a plywood sheet. If unit is installed above
nished space, install an an auxiliary drain pan
under unit. Set unit in drain pan as shown in gure
13. Leave 8 inches for service clearance below unit
for condensate trap.
3 - Provide a service platform in front of unit. When
installing the unit in a crawl space, a proper support
platform may be created using cement blocks.
4 - Route auxiliary drain line so that water draining from
this outlet will be easily noticed by the homeowner.
5 - Ifnecessary, runthe condensatelineinto acondensate
pump to meet drain line slope requirements. The
pump must be rated for use with condensing
furnaces. Protect the condensate discharge line
from the pump to the outside to avoid freezing.
6 - Continue with exhaust, condensate and intake piping
installation according to instructions.
*Gas connector may be
used for Canadian
able by local authority
having jurisdiction.
*GAS CONNECTION
RAISED
PLATFORM
SERVICE PLATFORM
INTAKE PIPE
EXHAUST PIPE
FIGURE 13

Page 10
Return Air -- Horizontal Applications
Return air may be brought in only through the end of a
furnace installed in the horizontal position. The furnace is
equipped with a removable bottom panel to facilitate in-
stallation. See gure 9.
Filters
This unit is not equipped with a lter or rack. A eld-pro-
vided high velocity rated lter is required for the unit to
operate properly. Table 1 lists recommended lter sizes. 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 1
Furnace
Cabinet Width
Filter Size
Side Return Bottom Return
17-1/2” 16 X 25 X 1 (1) 16 X 25 X 1 (1)
21” 16 X 25 X 1 (1) 20 X 25 X 1 (1)
Duct System
Use industry-approved standards to size and install the
supply and return air duct system. Figure 14 shows the
correct supply and return duct installation. Refer to ACCA
Manual D. This will result in a quiet and low-static system
that has uniform air distribution.
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.
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. For horizontal units, in-
stall self tapping screws in the three evaporator coil screw
holes made for horizontal applications to seal the top cap
to the vestibule panel.
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 de-
vice (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.
Return air can be brought in through the bottom or either
side of the furnace (return air brought into either side of
furnace allowed only in upow applications). If a furnace
with bottom return air is installed on a platform, make an
airtight seal between the bottom of the furnace and the
platform to ensure that the unit operates properly and
safely. Use berglass sealing strips, caulking, or equiva-
lent sealing 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.
HORIZONTAL UNIT
SUPPLY
AIR
SUPPLY
AIR Install self tapping screws
to seal any potential air
leaks
UPFLOW UNIT
Figure 14

Page 11
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.
Referto the table 2 below for approved piping and tting
materials.
TABLE 2
PIPING AND FITTINGS SPECIFICATIONS
Schedule 40 PVC (Pipe) D1785
Schedule 40 PVC (Cellular Core Pipe) F891
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 Cellular Core DWV (Pipe) F628
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
PVC & ABS & NORYL Transition Solvent
Cement WELD-ON 4052
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
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.
IMPORTANT
SL297UHNV 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 2. 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 bonding
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. 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.
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.
NOTE - The intake coupling on the furnace is ABS ma-
terial. Use transitional solvent to make connections to
PVC pipe.
NOTE - Vent pipe must be installed with provided vent
adapter. See gure 17.

Page 12
TABLE 3
OUTDOOR TERMINATION USAGE*
Input Size Vent Pipe
Dia. in.
STANDARD CONCENTRIC
Flush
Mount Kit
Wall Kit Wall Ring
Kit
Field
Fabricated
1-1.2 inch 2 inch 3 inch
2 inch 3 inch 2 inch 71M80
(US)
444W92
(CA)
69M29
(US)
444W92
(CA)
60L46 (US)
444W93 (CA)
51W11
(US)
51W12
(CA)
22G44
(US)
430G28
(CA)
44J40
(US)
481J20
(CA)
15F74
040 23YES YES 1YES 1YES 5YES 2YES
33YES YES 1YES 1YES 5YES 2YES
060 23YES YES 1YES 1YES 5YES 2YES
33YES YES 1YES 1YES 5YES 2YES
080 23YES YES YES 5YES YES YES
33YES YES YES 5YES 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 uses with 040 and 060 input models.
3 Flush mount kits 51W11 and 51W12 includes 1-1/2 in. outdoor exhaust accelerator, required when used with 040, 060 and 080 input models.
4 Termination kits 30G28, 44W92, 4493 and 81J20 are certied to ULC S636 for use in Canada only.
5 See table 8 for vent accelerator requirements.
Joint Cementing Procedure
All cementing of joints should be done according to the
specications outlined in ASTM D 2855.
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.
NOTE - Time is critical at this stage. Do not allow
primer to dry before applying cement.
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.
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.

Page 13
Joint Cementing Procedure
* See Piping and Fittings Specifications table
Piping Suspension Guidelines
NOTE - Isolate piping at the point where it exits the outside wall or
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 15
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 following test while each appliance is oper-
ating and the other 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 re-
quirements 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.

Page 14
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.
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 16
Exhaust Piping (Figures 17, 18, 20 and 21)
The vent adapter must be attached to the exhaust cou-
pling on the furnace top panel. Use provided bands. See
steps below.
1 - Remove the caution tag from vent adapter.
2 - Fully insert vent adapter with both bands loosely
attached on the furnace exhaust coupling
3 - Insert PVC exhaust pipe through vent adapter. Ensure
vent pipe is fully seated into exhaust coupling.
4 - Tighten both top and bottom bands to 40in-lbs. See
gure 17.
NOTE - PVC / ABS / NORYL transition solvent cement
WELD-ON 4052 (or equivalent) must be used for con-
necting PVC exhaust pipe to NORYL furnace exhaust
coupling.
Route piping to outside of structure. Continue with instal-
lation following instructions given in piping termination
section.
Furnace
Top Band
(torque to 40in-lbs)
PVC
Exhaust Pipe
Top Panel
Vent Adaptor To Exhaust Coupling
Bottom Band
(torque to 40in-lbs)
Vent
Adaptor
Furnace
Exhaust Coupling
FIGURE 17
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.
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 Du-
raVent or InnoFlue® by Centrotherm venting system the
vent pipe requirements stated in the unit installation in-
struction – minimum & maximum vent lengths, termination
clearances, etc. – apply and must be followed. Follow the
instructions provided with PoyPro by DuraVent and Inno-
Flue by Centrotherm venting system for assembly or if re-
quirements 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 7.
The SL297UHNV is to be installed as a Direct Vent gas
central furnace.

Page 15
NOTE - In Direct Vent installations, combustion air is tak-
en from outdoors and ue gases are discharged outdoors.
Intake and exhaust pipe sizing -- Size pipe according to
tables 4 and 5. Count all elbows inside and outside the
home. Table 4 lists the minimum vent pipe lengths per-
mitted. Table 5 lists the maximum pipe lengths permitted.
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 8.
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.
Horizontal Installation Offset Requirements
NOTE - Exhaust pipe MUST be glued to furnace exhaust fittings.
NOTE -
ward unit. A minimum of 1/4” (6mm) drop for each 12” (305mm)
of horizontal run is mandatory for drainage.
NOTE - Exhaust piping should be checked carefully to make
sure there are no sags or low spots.
12” ma x
of straight pipe
Exhaust Pipe
12”Min.
Horizontal
Gas Furnace
FIGURE 18
TABLE 4
MINIMUM VENT PIPE LENGTHS
SL297UHNV Model MIN. VENT LENGTH*
040, -060, -080 15 ft. or 5 ft. plus 2 elbows
or 10 ft. plus 1 elbow
*Any approved termination may be added to the minimum
length listed.
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?
See table 3.
Which needs
most elbows?
Intake or
exhaust?
How many elbows?
Count all elbows inside
and outside house.
Desired pipe size?
2” or 3”
Use table 5 or 6 to find
max intake or exhaust pipe
length. Includes all vent
pipe and elbows inside
and outside the house.
What is the altitude of
the furnace installation?
7
What is the
furnace capacity?
040, 060, 080?
FIGURE 19
IMPORTANT
Do not use screens or perforated metal in exhaust or
intake terminations. Doing so will cause freeze-ups and
may block the terminations.

Page 16
TABLE 5
NOTE - Size intake and exhaust pipe length separately. Values in table are for Intake OR Exhaust, not combined total.
Both Intake and Exhaust must be same pipe size.
Standard Termination at Elevation 0 - 4500 ft
Number Of 90°
Elbows Used
2” Pipe 3” Pipe
Model Model
040 060 080 040 060 080
1 81 66 44 138 137 118
2 76 61 39 133 132 113
3 71 56 34 128 127 108
4 66 51 29 123 122 103
5 61 46 24 118 117 98
6 56 41 19 113 112 93
7 51 36 14 108 107 88
8 46 31
n/a
103 102 83
9 41 26 98 97 78
10 36 21 93 92 73
TABLE 5 Continued
Maximum Allowable Intake or Exhaust Vent Length in Feet
NOTE - Size intake and exhaust pipe length separately. Values in table are for Intake OR Exhaust, not combined total.
Both Intake and Exhaust must be same pipe size.
Concentric Termination at Elevation 0 - 4500 ft
Number Of 90°
Elbows Used
2” Pipe 3” Pipe
Model Model
040 060 080 040 060 080
1 73 58 42 121 121 114
2 68 53 37 116 116 109
3 63 48 32 111 111 104
4 58 43 27 106 106 99
5 53 38 22 101 101 94
6 48 33 17 96 96 89
7 43 28 12 91 91 84
8 38 23
n/a
86 86 79
9 33 18 81 81 74
10 28 13 76 76 69

Page 17
TABLE 6
Maximum Allowable Exhaust Vent Lengths With Furnace Installed in a
Closet or Basement Using VentilatedAttic or Crawl Space For Intake Air in Feet
NOTE - Size intake and exhaust pipe length separately. Values in table are for Intake OR Exhaust, not combined total.
Both Intake and Exhaust must be same pipe 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
2” Pipe 3” Pipe
Model Model
040 060 080 040 060 080
1 71 56 34 118 117 98
2 66 51 29 113 112 93
3 61 46 24 108 107 88
4 56 41 19 103 102 83
5 51 36 14 98 97 78
6 46 31 9 93 92 73
7 41 26 4 88 87 68
8 36 21
n/a
83 82 63
9 31 16 78 77 58
10 26 11 73 72 53
TYPICAL EXHAUST AND INTAKE PIPE CONNECTIONS IN UPFLOW DIRECT OR
NON-DIRECT VENT APPLICATIONS
TRANSITION
2” 2”
2”
3”
2”
2”
or
DO NOT transition
from smaller to larger
pipe in horizontal runs
of exhaust pipe.
EXHAUST
*2”
* When transitioning up in pipe size, use the shortest length of 2” PVC pipe possible.
INTAKE
TRANSITION
3”
*2”
EXHAUSTINTAKE
2”
Appliance
Adaptor Appliance
Adaptor
Figure 20

Page 18
SIDE VIEW
2”
2”
2”
2”
or
TYPICAL EXHAUST AND INTAKE PIPE CONNECTIONS IN HORIZONTAL DIRECT OR NON-DIRECT VENT
APPLICATIONS (RIGHT HAND DISCHARGE SHOWN)
2”
45°
MAX
45°
MAX
DO NOT transition
from smaller to larger
pipe in horizontal runs
of exhaust pipe.
EXHAUST
12” max.
* When transitioning up in pipe size, use the shortest length of 2” PVC pipe possible.
INTAKE
3”
*2”
*2”
2”
2” 2”
2”
Appliance
Adaptor
Appliance
Adaptor
EXHAUST
INTAKE
Figure 21
General Guidelines for Vent Terminations
In Non-Direct Vent applications, combustion air is taken
from indoors or ventilated attic or crawlspace and the ue
gases are discharged to the outdoors. The SL297UHNV
is then classied as a non-direct vent, Category IV gas
furnace.
In Direct Vent applications, combustion air is taken from
outdoors and the ue gases are discharged to the out-
doors. The SL297UHNV is then classied as a direct vent,
Category IV gas furnace.
In both Non-Direct Vent and Direct Vent applications, the
vent termination is limited by local building codes. In the
absence of local codes, refer to the current National Fuel
Gas Code ANSI Z223-1/NFPA 54 in U.S.A., and current
CSA-B149 Natural Gas and Propane Installation Codes in
Canada for details.
Position termination according to location given in gure
23. In addition, position termination so it is free from any
obstructions and 12” above the average snow accumula-
tion. At vent termination, care must be taken to maintain
protective coatings over building materials (prolonged
exposure to exhaust condensate can destroy protective
coatings). It is recommended that the exhaust outlet not
be located within 6 feet (1.8m) of an outdoor AC unit be-
cause the condensate can damage the painted coating.
NOTE - See table 7 for maximum allowed exhaust pipe
length without insulation in unconditioned space during
winter design temperatures below 32°F (0°C). If required
exhaust pipe should be insulated with 1/2” (13mm) Ar-
maex or equivalent. In extreme cold climate areas, 3/4”
(19mm) Armaex or equivalent may be necessary. Insu-
lation must be protected from deterioration. Armaex with
UV protection is permissable. Basements or other en-
closed areas that are not exposed to the outdoor ambient
temperature and are above 32 degrees F (0°C) are to be
considered conditioned spaces.
IMPORTANT
Do not use screens or perforated metal in exhaust or
intake terminations. Doing so will cause freeze-ups and
may block the terminations.

Page 19
TABLE 7
Maximum Allowable Exhaust Vent Pipe Length (in ft.) Without Insulation In Unconditioned Space For
Winter Design Temperatures Two - Stage High E󰀩ciency Furnace
Winter Design
Temperatures1 °F
(°C)
Vent Pipe
Diameter
Unit Input Size
040 060 080
32 to 21
(0 to -6)
PVC 2PP PVC 2PP PVC 2PP
2 in 21 18 33 30 46 42
3 in 12 12 21 21 30 30
20 to 1
(-7 to -17)
2 in 11 9 19 17 28 25
3 in n/a n/a 9 9 16 16
0 to -20
(-18 to -29)
2 in 6 4 12 10 19 16
3 in n/a n/a n/a n/a 8 8
1Refer to 99% Minimum Design Temperature table provided in the current edition of the ASHRAE Fundamentals Handbook.
2 Poly-Propylene vent pipe (PP) by Duravent and Centrotherm.
NOTE - Concentric terminations are the equivalent of 5’ and should be considered when measuring pipe length.
NOTE - Maximum uninsulated vent lengths listed may include the termination(vent pipe exterior to the structure) and cannot exceed 5 linear feet or
the maximum allowable intake or exhaust vent length listed in table 5 or 6 which ever is less.
NOTE - If insulation is required in an unconditioned space, it must be located on the pipe closest to the furnace. See gure22.
Conditioned
Space Unconditioned
Space
Exhaust
Pipe
Intake
Pipe
Conditioned
Space
Pipe Insulation
Figure 22

Page 20
Figure 23
VENT TERMINATION CLEARANCES
FOR DIRECT VENT INSTALLATIONS IN THE USA AND CANADA
K
D
E
L
B
C
F
G
A
B
J
A
M
I
H
INSIDE CORNER
DETAIL
VENT TERMINAL AIR SUPPLY INLETAREA WHERE TERMINAL
IS NOT PERMITTED
Fixed
Closed
Operable
B
Fixed
Closed
Operable
B
B
A =
B =
C =
D =
E =
F =
G =
H =
I =
J =
K =
L =
M =
US Installations1Canadian Installations2
12 inches (305mm) or 12 in. (305mm)
above average snow accumulation.
12 inches (305mm) or 12 in. (305mm)
above average snow accumulation.
Clearance above grade, veranda,
porch, deck or balcony
Clearance to window or
door that may be opened
6 inches (152mm) for appliances <10,000
pliances > 10,000 Btuh (3kw) and <50,000
pliances > 50,000 Btuh (15kw)
6 inches (152mm) for appliances <10,000
Btuh (3kw), 12 inches (305mm) for
appliances > 10,000 Btuh (3kw) and
<100,000 Btuh (30kw), 36 inches (.9m)
for appliances > 100,000 Btuh (30kw)
Clearance to permanently
closed window
Vertical clearance to ventilated soffit
located above the terminal within a
horizontal distance of 2 feet (610mm)
from the center line of the terminal
Clearance to unventilated soffit
Clearance to outside corner
Clearance to inside corner
tended above meter / regulator assembly
Clearance to service regulator
vent outlet
Clearance to non-mechanical air
pliance
ply inlet
Clearance above paved sidewalk or
paved driveway located on public property
Clearance under veranda, porch, deck or balcony
* 12”
*
*
* 7 feet (2.1m)
3 feet (.9m) within a height 15 feet (4.5m)
above the meter / regulator assembly
3 feet (.9m)
6 inches (152mm) for appliances <10,000
pliances > 10,000 Btuh (3kw) and <50,000
pliances > 50,000 Btuh (15kw)
6 inches (152mm) for appliances <10,000
Btuh (3kw), 12 inches (305mm) for
appliances > 10,000 Btuh (3kw) and
<100,000 Btuh (30kw), 36 inches (.9m)
for appliances > 100,000 Btuh (30kw)
3 feet (.9m) above if within 10 feet
(3m) horizontally
6 feet (1.8m)
7 feet (2.1m)†
12 inches (305mm)‡
1In accordance with the current ANSI Z223.1/NFPA 54 Natural Fuel Gas Code
2In accordance with the current CSA B149.1, Natural Gas and Propane Installation Code
*For clearances not specified in ANSI Z223.1/NFPA 54 or CSA
B149.1, clearance will be in accordance with local installation
codes and the requirements of the gas supplier and these
installation instructions.”
† A vent shall not terminate directly above a sidewalk or paved driveway that is located
between two single family dwellings and serves both dwellings.
‡ Permitted only if veranda, porch, deck or balcony is fully open on a minimum of
two sides beneath the floor. Lennox recommends avoiding this location if possible.
* 12”
* Equal to or greater than soffit depth* Equal to or greater than soffit depth* Equal to or greater than soffit depth
* Equal to or greater than soffit depth*Equal to or greater than soffit depth
* No minimum to outside corner * No minimum to outside corner
3 feet (.9m) within a height 15 feet (4.5m)
above the meter / regulator assembly
3 feet (.9m)
*
*12 inches (305mm)‡