Lennox SLP98UHV SERIES User manual

Page 1
03/14
*2P0314*
507026-01
*P507026-01*
E2014 Lennox Industries Inc.
Dallas, Texas, USA
AIR FLOW
UPFLOW
AIR FLOW
AIR FLOW
HORIZONTAL RIGHT
HORIZONTAL LEFT
WARNING
Improper installation, adjustment, alteration, service
or maintenance can cause property damage, person
al injury or loss of life. Installation and service must
be performed by a licensed professional HVAC in
staller (or equivalent), service agency or the gas sup
plier.
INSTALLATION
INSTRUCTIONS
SLP98UHV
DAVE LENNOX SIGNATURE®
COLLECTION GAS FURNACE
UPFLOW / HORIZONTAL AIR DISCHARGE
507026-01
03/2014
Supersedes 01/2014
THIS MANUAL MUST BE LEFT WITH THE
HOMEOWNER FOR FUTURE REFERENCE
This a safety alert symbol and should never be ignored.
When you see this symbol on labels or in manuals, be alert
to the potential for personal injury or death.
CAUTION
As with any mechanical equipment, personal injury
can result from contact with sharp sheet metal
edges. Be careful when you handle this equipment.
NOTICE
A thermostat is not included and must be ordered
separately.
The Lennox icomfort Wi-Fi®thermostat must be
used in communicating applications.
In non-communicating applications, the Lennox
ComfortSense®7000 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-com
municating applications is illustrated in diagrams,
which begin on Page 32.
Table of Contents
Unit Dimensions 2................................
Parts Arrangement 3..............................
Gas Furnace 4...................................
Shipping and Packing List 4........................
Safety Information 4...............................
Use of Furnace as a Construction Heater 5...........
General 6........................................
Setting Equipment 6...............................
Filters 10..........................................
Duct System 11....................................
Pipe and Fittings Specifications 11...................
Joint Cementing Procedure 12.......................
Venting Practices 13...............................
Vent Piping Guidelines 13...........................
Gas Piping 27.....................................
Electrical 30.......................................
Integrated Control 38...............................
Blower Motor Performance 42.......................
Unit Start Up 47....................................
Gas Pressure Measurement 48......................
High Altitude Information 50.........................
Proper Combustion 50..............................
Other Unit Adjustments 50..........................
Heating Sequence of Operation 51...................
Service 53........................................
Repair Parts List 54................................
Integrated Control Diagnostic Codes 55...............
Configuring Unit Size Codes 58......................
Troubleshooting 59.................................
Litho U.S.A.

Page 2
Unit Dimensions - inches (mm)
AIR FLOW
6−9/16 (167)
Left
9 (229)
Right
23
(584)
(19)
3/4
(19) 1Bottom Return
Air Opening
GAS PIPING INLET
(Either Side)
Side Return
Air Opening
(Either Side)
1Bottom Return
Air Opening
EXHAUSTAIR
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)
(Either Side)
2OPTIONAL
EXTERNAL
SIDE RETURN
AIR FILTER KIT
(Either Side)
16
(406)
14−3/4
(375)
2OPTIONAL
EXTERNAL
SIDE RETURN
AIR FILTER KIT
(Either Side)
2
Optional External Side Return Air Filter Kit is not for use
with the optional RAB Return Air Base.
1NOTE − 60C and 60D size units that require second stage
air volumes over 1800 cfm (850 L/s) must have one
of the following:
1. Single side return air with transition, to accommodate
20 x 25 x 1 in. (508 x 635 x 25 mm) cleanable air
filter. Required to maintain proper air velocity.
2. Single side return air with optional return air base
3. Bottom return air.
4. Return air from both sides.
5. Bottom and one side return air
See blower performance tables for more information.
A B C D
SLP98UH Model No. in. mm in. mm in. mm in. mm
17−1/2 446 16−3/8 416 16 406 7−5/8 194
21 533 19−7/8 505 19−1/2 495 9−3/8 238
24−1/2 622 23−3/8 594 23 584 11−1/8 283
5/8
(16)
1
3−1/4
(83)
23−3/4
(603)
25
(635)
D
1−1/2 (38)
Front Panel
COMBUSTION
AIR INTAKE
2 (51)
(Either Side)
1−7/8 (48)
CONDENSATE
TRAP CONNECTION
(Either Side)
070XV36B
090XV36C
090XV48C
090XV60C
110XV60C
135XV60D

Page 3
Parts Arrangement
FIGURE 1
BURNER BOX ASSEMBLY
VARIABLE
CAPACITY
GAS VALVE
HEAT EXCHANGER
ACCESS PANEL
CONTROL BOX
(includes variable capacity integrated control
transformer, circuit breaker and door switch)
VARIABLE SPEED BLOWER MOTOR
BAG ASSEMBLIES
(shipping location)
COLD END HEADER
BOX
PRESSURE SWITCHES
VARIABLE SPEED
COMBUSTION AIR
INDUCER
INNER BLOWER
ACCESS PANEL
SIGHT GLASS
PRIMARY LIMIT
SHIPPING BLOCK
(-135 UNITS ONLY)

Page 4
SLP98UHV Gas Furnace
The SLP98UHV category IV gas furnace is equipped with a
variable-capacity, variable-speed integrated control. This
control ensures compatibility with the Lennox icomfort Wi-
Fi®thermostat, the Harmony IIItzone control system, or a
thermostat which provides humidity control. Each
SLP98UHV is shipped ready for installation in the upflow,
horizontal left air discharge or horizontal right air discharge
position.
The furnace is equipped for installation in natural gas ap
plications only. A changeover kit may be ordered for LP ap
plications.
The SLP98UHV must be installed only as a Direct Vent
gas furnace.
NOTE - In Direct Vent installations, combustion air is taken
from outdoors and flue gases are discharged outdoors.
See figure 2 for applications including roof termination.
FIGURE 2
DIRECT VENT INSTALLATION
EXHAUST OUTLET
COMBUSTION
AIR INTAKE
OUTSIDE OF
HOUSE
Shipping and Packing List
Package 1 of 1 contains
1 - Assembled SLP98UHV 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 cap clamp
1 - 3/4” Threaded street elbow
Check equipment for shipping damage. If you find any
damage, immediately contact the last carrier.
The following items may also be ordered separately:
1 - Thermostat
1 - Natural to LP gas conversion kit
1 - High altitude kit
1 - Horizontal suspension kit
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 floor and may
be difficult to smell. An LP/propane leak detector
should be installed in all LP applications.
Safety Information
WARNING
Improper installation, adjustment, alteration, service
or maintenance can cause property damage, person
al 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 furnace.
Refer to unit nameplate.
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
Installed Locations
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.
This furnace is designed for installation clearances to com
bustible material as listed on the unit nameplate and in the
tables in figures 10 and 11. Accessibility and service clear
ances must take precedence over fire protection clear
ances.
NOTE - For installation on combustible floors, the furnace
shall not be installed directly on carpeting, tile, or other
combustible material other than wood flooring.
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 floor.
The furnace must be located or protected to avoid physical
damage by vehicles. When a furnace is installed in a public

Page 5
garage, hangar, or other building that has a hazardous at
mosphere, the furnace must be installed according to rec
ommended good practice requirements and current Na
tional Fuel Gas Code or CSA B149 standard.
NOTE - NOTE - Furnace must be adjusted to obtain a tem
perature rise (100% percent capacity) within the range(s)
specified on the unit nameplate. Failure to do so may cause
erratic limit operation and may also result in premature
heat exchanger failure.
This SLP98UHV furnace must be installed so that its elec
trical components are protected from water.
Installed in Combination with a Cooling Coil
When this furnace is used with cooling units, 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 flow arrangement, a damper (or other
means to control the flow of air) must adequately prevent
chilled air from entering the furnace. If the damper is manu
ally operated, it must be equipped to prevent operation of
either the heating or the cooling unit, unless it is in the full
HEAT or COOL setting. See figure 3.
FIGURE 3
Gas Unit
Heating Unit Installed Upstream of Cooling Unit
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
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 Electric
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
NOTE - This furnace is designed for a minimum continuous
return air temperature of 60°F (16°C) or an intermittent op
eration 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.
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.
CAUTION
Do not set thermostat below 60°F (16°C) in heating
mode. Setting thermostat below 60°F (16°C) reduces
the number of heating cycles. Damage to the unit
may occur that is not covered by the warranty.
The SLP98UHV furnace may be installed in alcoves, clos
ets, attics, basements, garages, and utility rooms.
This furnace is not designed for installation in mobile
homes, recreational vehicles, or outdoors.
Never use an open flame to test for gas leaks. Check all
connections using a commercially available soap solution
made specifically for leak detection.
Use of Furnace as Construction Heater
Lennox does not recommend the use of SLP98UHV units
as a construction heater during any phase of construction.
Very low return air temperatures, harmful vapors and op
eration of the unit with clogged or misplaced filters will dam
age the unit.
SLP98UHV units may be used for heating of buildings or
structures under construction, if the following conditions
are met:
DThe vent system must be permanently installed per
these installation instructions.
DA room thermostat must control the furnace. The use of
fixed jumpers that will provide continuous heating is not
allowed.
DThe return air duct must be provided and sealed to the
furnace.
DReturn air temperature range between 60°F (16°C) and
80°F (27°C) must be maintained.
DAir filters must be installed in the system and must be
maintained during construction.
DAir filters must be replaced upon construction comple
tion.
DThe input rate and temperature rise must be set per the
furnace rating plate.
DOne hundred percent (100%) outdoor air must be pro
vided for combustion air requirements during construc
tion. Temporary ducting may supply outdoor air to the
furnace. Do not connect duct directly to the furnace.
DThe furnace heat exchanger, components, duct sys
tem, air filters and evaporator coils must be thoroughly
cleaned following final construction clean-up.
DAll furnace operating conditions (including ignition, in
put rate, temperature rise and venting) must be verified
according to these installation instructions.

Page 6
General
WARNING
The State of California has determined that this prod
uct may contain or produce a chemical or chemicals,
in very low doses, which may cause serious illness
or death. It may also cause cancer, birth defects or
reproductive harm.
CAUTION
SLP98UHV unit should not be installed in areas nor
mally subject to freezing temperatures.
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 fol
lowing general recommendations must be considered
when installing a SLP98UHV furnace:
•Place the furnace as close to the center of the air dis
tribution system as possible. The furnace should also be
located close to the chimney or vent termination point.
•When the furnace is installed in an attic or other insu
lated 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.
•The “A” coil drain pan is high quality engineering poly
mer with a maximum service temperature of 500° F.
However, adequate space must be provided between
the drain pan and the furnace heat exchanger. At least
2” space is required for sectionalized heat exchanger
and and 4” for drum-type or oil-fired furnace exchanger.
Closer spacing may damage the drain pan and cause
leaking.
Installation - Setting Equipment
WARNING
Do not connect the return air ducts to the back of the
furnace. Doing so will adversely affect the operation
of the safety control devices, which could result in
personal injury or death.
FIGURE 4
WARNING
Do not install the furnace on its front or back.
See figure 4.
Front Back
Upflow Applications
The SLP98UHV gas furnace can be installed as shipped in
the upflow position. Refer to figure 10 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. Unit may be posi
tioned from level to 1/2” toward the front to aid in draining.
See figure 5.

Page 7
FIGURE 5
SETTING EQUIPMENT
HORIZONTAL APPLICATION
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
Side Return Air
(with transition and filter)
FIGURE 6
Return
Air
Plenum
Transition
20” X 25” X 1”
(508mmX635mmX25mm)
Air Filter
1−1/2”
SLP98UHV 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 feet) re
quire either a return air base or field-fabricated transi
tion to accommodate an optional IAQ accessory taller
than 14.5”. See figure 6.
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 figure 7.
Removing the Bottom Panel
FIGURE 7
Screw
Bottom Panel
Bottom Cap

Page 8
FIGURE 8
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)
123 (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
UNITAND
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)
NOTE - Units with 1/2 hp blower motor are equipped with
three flexible legs and one rigid leg. The rigid leg is
equipped with a shipping bolt and a flat white plastic wash
er (rather than the rubber mounting grommet used with a
flexible mounting leg). See figure 9. The bolt and washer
must be removed before the furnace is placed into op
eration. After the bolt and washer have been removed, the
rigid leg will not touch the blower housing.
FIGURE 9
RIGID LEG
remove shipping bolt and washer
SLP98UHV070V36B and
SL98UH090V036C WITH 1/2 HP
BLOWER MOTOR
Allow for clearances to combustible materials as indicated
on the unit nameplate. Minimum clearances for closet or al
cove installations are shown in figures 10 and 11.
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.
WARNING
Improper installation of the furnace can result in per
sonal injury or death. Combustion and flue 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 fur
nace should be sealed airtight to the return air ple
num. 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. Al
low absolutely no sagging, cracks, gaps, etc.
For no reason should return and supply air duct sys
tems ever be connected to or from other heating de
vices such as a fireplace or stove, etc. Fire, explo
sion, carbon monoxide poisoning, personal injury
and/or property damage could result.

Page 9
Installation Clearances
Top
Bottom (Floor)
Left Side Right Side
Top/Plenum 1 in. (25 mm)
*Front 0
Back 0
Sides 0†
Vent 0
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 and
vent pipe installation.
‡For installations on a combustible floor, do not install the fur
nace directly on carpeting, tile or other combustible materials oth
er than wood flooring.
FIGURE 10
Return Air -- Upflow Units
Return air can be brought in through the bottom or either
side of the furnace installed in an upflow 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 cabinet
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.
Setting an Upflow Unit
When the side return air inlets are used in an upflow ap
plication, it may be necessary to install shims on the bottom
of the furnace.
Horizontal Applications
The SLP98UHV furnace can be installed in horizontal ap
plications with either right- or left-hand air discharge.
Refer to figure 11 for clearances in horizontal applications.
Horizontal Application
Installation Clearances
Left End Right End
Right-Hand Discharge
Left-Hand Discharge
Top
Bottom (Floor)**
Bottom (Floor)**
Left End Right End
Air
Flow
Air
Flow
Air
Flow
Air
Flow
Top 0
Front* 0
Back 0
Ends 0
Vent 0
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.
**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 fur
nace directly on carpeting, tile or other combustible materials oth
er 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 floor
joists, as shown in figure 12, or install the furnace on a plat
form, as shown in figure 13. A horizontal suspension kit
(51W10) may be ordered from Lennox or use equivalent.
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 in
terfere with the plenum or exhaust piping installation. Cool
ing coils and supply and return air plenums must be
supported separately.
NOTE - When the furnace is installed on a platform in a
crawlspace, it must be elevated enough to avoid water
damage and to allow the evaporator coil to drain.

Page 10
FIGURE 12
HORIZONTAL SUSPENSION KIT
Bracket
(typical)
Metal Strap
(typical)
Air
Flow
Internal Brace
(provided with kit)
Platform Installation of Horizontal Unit
1 - Select location for unit keeping in mind service and
other necessary clearances. See figure 11.
2 - Construct a raised wooden frame and cover frame
with a plywood sheet. If unit is installed above finished
space, fabricate an auxiliary drain pan to be installed
under unit. Set unit in drain pan as shown in figure 13.
Leave 8 inches for service clearance below unit for
condensate trap.
3 - Provide a service platform in front of unit. When instal
ling 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 - If necessary, run the condensate line into a conden
sate 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.
FIGURE 13
*Gas connector may be
used for Canadian
installation if accept
able by local authority
having jurisdiction.
*GAS CONNECTION
RAISED
PLATFORM
SERVICE PLATFORM
INTAKE PIPE
EXHAUST PIPE
Return Air -- Horizontal Applications
Return air must be brought in through the end of a furnace
installed in the horizontal position. The furnace is equipped
with a removable bottom panel to facilitate installation. See
figure 7.
Filters
This unit is not equipped with a filter or rack. A field-pro
vided filter is required for the unit to operate properly. Table
1 lists recommended filter sizes.
IMPORTANT
If a highefficiency filter is being installed as part of
this system to ensure better indoor air quality, the fil
ter must be properly sized. Highefficiency filters
have a higher static pressure drop than standardef
ficiency glass/foam filters. If the pressure drop is too
great, system capacity and performance may be re
duced. 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 filter with this system, check the
specifications provided by the filter manufacturer
against the data given in the appropriate Lennox
Product Specifications bulletin. Additional informa
tion is provided in Service and Application Note
ACC002 (August 2000).
A filter must be in place when the unit is operating.
NOTE - In upflow applications where side return air fil
ter is installed on same side as the condensate trap,
make sure that clearance is maintained to ensure fu
ture access to the filter access panel.
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)
24-1/2” 16 X 25 X 1 (2) 24 X 25 X 1 (1)

Page 11
Duct System
Use industry‐approved standards to size and install the
supply and return air duct system. This will result in a quiet
and low‐static system that has uniform air distribution.
NOTE - Operation of this furnace in heating mode (indoor
blower operating at selected heating speed) with an exter
nal static pressure which exceeds 0.8 inches w.c. may re
sult in erratic limit operation.
Supply Air Plenum
If the furnace is installed without a cooling coil, a removable
access panel should be installed in the supply air duct. The
access panel should be large enough to permit inspection
(by reflected light) of the heat exchanger for leaks after the
furnace is installed. If present, this access panel must al
ways be in place when the furnace is operating and it must
not allow leaks into the supply air duct system.
Return Air Plenum
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 fireplace) 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 pres
sure, the flue products can be pulled back down the vent
pipe and into the room. This reverse flow of the flue gas
may result in incomplete combustion and the formation of
carbon monoxide gas. This toxic gas might then be distrib
uted throughout 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 in through either side
of the furnace allowed in upflow applications only). If a fur
nace 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 safe
ly. Use fiberglass sealing strips, caulking, or equivalent
sealing method between the plenum and the furnace cabi
net to ensure a tight seal. If a filter is installed, size the re
turn air duct to fit the filter frame.
Pipe & Fittings Specifications
All pipe, fittings, 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-flowing and contain no
lumps, undissolved particles or any foreign matter that ad
versely affects the joint strength or chemical resistance of
the cement. The cement shall show no gelation, stratifica
tion, or separation that cannot be removed by stirring. Re
fer to table 2 for approved piping and fitting 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 D3138
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 ULC-S636
PolyPro by Duravent
CAUTION
Solvent cements for plastic pipe are flammable liq
uids 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 fire hazard and to minimize
breathing of solvent vapors. Avoid contact of ce
ment with skin and eyes.
IMPORTANT
SLP98UHV 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 con
nections to the PVC fittings in the unit.

Page 12
Use PVC primer and solvent cement or ABS solvent ce
ment meeting ASTM specifications, refer to Table 2. As an
alternate, use all purpose cement, to bond ABS, PVC, or
CPVC pipe when using fittings 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. Metal
or plastic strapping may be used for vent pipe hangers.
Uniformly apply a liberal coat of PVC primer for PVC
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
51W11
(US)
51W12
(CA)
22G44 (US)
430G28 (CA)
44J40
(US)
481J20 (CA)
15F74
71M80
(US)
444W92
(CA)
69M29
(US)
444W92
(CA)
60L46 (US)
444W93 (CA)
045
23YES YES 1YES 1YES 5YES 2YES
2-1/2 3YES YES 1YES 1YES 5YES 2YES
33YES YES 1YES 1YES 5YES 2YES
070
23YES YES 1YES 1YES 5YES 2YES
2-1/2 3YES YES 1YES 1YES 5YES 2YES
33YES YES 1YES 1YES 5YES 2YES
090
23YES YES YES 5YES YES YES
2-1/2 3YES YES YES 5YES YES YES
33YES YES YES 5YES YES YES
110
2 YES YES YES 5YES YES YES
2-1/2 YES YES 5YES YES YES
3 YES YES 5YES YES YES
135 3 YES YES 5YES 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 field-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.
3Flush mount kits 51W11 and 51W12 includes 1-1/2 in. outdoor exhaust accelerator, required when used with 045, 070 and 090 input models.
4Termination kits 30G28, 44W92, 4493 and 81J20 are certified to ULC S636 for use in Canada only.
5See table 7 for vent accelerator requirements.
Joint Cementing Procedure
All cementing of joints should be done according to the
specifications outlined in ASTM D 2855.
NOTE - A sheet metal screw may be used to secure the in
take pipe to the connector, if desired. Use a drill or self tap
ping 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 fitting 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 fit joint and mark depth of fitting 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 fitting and male end of pipe to depth of fitting
socket.

Page 13
6 - Promptly apply solvent cement to end of pipe and in
side socket surface of fitting. Cement should be ap
plied 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 prim
er 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 dur
ing assembly (but not after pipe is fully inserted) to dis
tribute cement evenly. DO NOT turn ABS or cellular
core pipe.
NOTE - Assembly should be completed within 20 sec
onds 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 fitting socket. A properly made joint will show a bead
around its entire perimeter. Any gaps may indicate a
defective assembly due to insufficient solvent.
9 - Handle joints carefully until completely set.
Venting Practices
FIGURE 14
* See table2 for allowable pipe.
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 --
Support every 5 feet.
All other pipe* --
Support every 3 feet.
Wall
inside outside
24” maximum
3/4” minimum
Wall Thickness Guidelines
1 - In areas where piping penetrates joists or interior
walls, hole must be large enou`gh 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 conden
sate collection trap and lines.
Exhaust Piping (Figures 18 and 19)
3 - Route piping to outside of structure. Continue with
installation following instructions given in piping ter
mination section.
Intake Piping (Figures 18 and 19)
The SLP98UHV furnace may be installed only in direct
vent applications.
The SLP98UHV is designed for combustion air intake
through an inlet in the unit's top cap. Intake air piping is in
dependent of exhaust piping.
If an SLP98UHV furnace replaces 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.
FIGURE 15
REPLACING FURNACE THAT WAS PART OF A
COMMON VENT SYSTEM
CHIMNEY
OR GAS
VENT
(Check sizing
for water
heater only)
FURNACE
(Replaced
by SLP98)
WATER
HEATER
OPENINGS
(To Adjacent
Room)
CAUTION
Do not discharge exhaust into an existing stack or
stack that also serves another gas appliance. If verti
cal discharge through an existing unused stack is re
quired, 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 pres
sure and must be completely sealed to prevent leak
age of combustion products into the living space.
Vent Piping Guidelines
NOTE - Lennox has approved the use of DuraVent®manu
factured vent pipe and terminations as an option to PVC.
When using the PolyPro®by DuraVent venting system the
vent pipe requirements stated in the unit installation in
struction – minimum & maximum vent lengths, termination

Page 14
clearances, etc. – apply and must be followed. Follow the
instructions provided with PoyPro by DuraVent venting
system for assembly or if requirements are more restrict
ive. The PolyPro by Duravent venting system must also fol
low the uninsulated and unconditioned space criteria listed
in table 6.
The SLP98UHV is installed only as a Direct Vent gas
central furnace.
NOTE - In Direct Vent installations, combustion air is taken
from outdoors and flue 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 7.
In some applications which permit the use of several differ
ent 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.
Use the steps in figure 17 to correctly size vent pipe diame
ter.
NOTE - It is acceptable to use any pipe size which fits within
the guidelines allowed in table 5.
FIGURE 16
Exhaust Pipe
NOTE - Exhaust pipe MUST be glued to furnace exhaust fittings.
NOTE - All horizontal runs of exhaust pipe must slope back to
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” max
of straight pip e
Exhaust Pipe
12” Min.
Horizontal
Gas Furnace
NOTE - The exhaust collar on all models is sized to accom
modate 2” Schedule 40 vent pipe. In horizontal applica
tions, any transition to exhaust pipe larger than 2” must be
made in vertical runs of the pipe. Therefore a 2” elbow must
be added before the pipe is transitioned to any size larger
than 2”. This elbow must be added to the elbow count used
to determine acceptable vent lengths. Contact the Applica
tion Department for more information concerning sizing of
vent systems which include multiple pipe sizes.
IMPORTANT
Do not use screens or perforated metal in exhaust or
intake terminations. Doing so will cause freeze-ups
and may block the terminations.
FIGURE 17
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”, 2-1/2”, 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?
045, 070, 090,
110 or 135?
TABLE 4
MINIMUM VENT PIPE LENGTHS
SLP98UHV
MODEL
MIN. EQUIV.
VENT
LENGTH
EXAMPLE
070, 090, 110
15 ft.*
5 ft. plus 2 elbows of 2”, 2-1/2”
or 3” diameter pipe
135 5 ft. plus 2 elbows of 3”
diameter pipe
*Any approved termination may be added to the minimum equivalent
length listed.

Page 15
TABLE 5
Maximum Allowable Intake or Exhaust Vent Length in Feet
*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 - 7500'
Number Of
90° Elbows
Used
2” Pipe 2-1/2” Pipe 3” Pipe
Model Model Model
070 090 110 135 070 090 110 135 070 090 110 135
1 91 69 14
n/a
140 93 43
n/a
162 143 118 114
2 86 64 9 135 88 38 157 138 113 109
3 81 59
n/a
130 83 33 152 133 108 104
4 76 54 125 78 28 147 128 103 99
5 71 49 120 73 23 142 123 98 94
6 66 44 115 68 18 137 118 93 89
7 61 39 110 63 13 132 113 88 84
8 56 34 105 58
n/a
127 108 83 79
9 51 29 100 53 122 103 78 74
10 46 24 95 48 117 98 73 69
Standard Termination at Elevation 7501' - 10,000'
Number Of
90° Elbows
Used
2” Pipe 2-1/2” Pipe 3” Pipe
Model Model Model
070 090 110 135 070 090 110 135 070 090 110 135
1 66 44
n/a n/a
115 68
n/a n/a
137 118 93 89
2 61 39 110 63 132 113 88 84
3 56 34 105 58 127 108 83 79
4 51 29 100 53 122 103 78 74
5 46 24 95 48 117 98 73 69
6 41 19 90 43 112 93 68 64
7 36 14 85 38 107 88 63 59
8 31
n/a
80 33 102 83 58 54
9 26 75 28 97 78 53 49
10 21 70 23 92 73 48 44
Concentric Termination at Elevation 0 - 7500'
Number Of
90° Ebows
Used
2” Pipe 2-1/2” Pipe 3” Pipe
Mode Model Model
070 090 110 135 070 090 110 135 070 090 110 135
1 83 67 12
n/a
130 89 39
n/a
146 139 114 105
2 78 62 7 125 84 34 141 134 109 100
3 73 57
n/a
120 79 29 136 129 104 95
4 68 52 115 74 24 131 124 99 90
5 63 47 110 69 19 126 119 94 85
6 58 42 105 64 14 121 114 89 80
7 53 37 100 59
n/a
116 109 84 75
8 48 32 95 54 111 104 79 70
9 43 27 90 49 106 99 74 65
10 38 22 85 44 101 94 69 60
Concentric Termination at Elevation 7501' - 10,000'
Number Of
90° Elbows
Used
2” Pipe 2-1/2” Pipe 3” Pipe
Model Model Model
070 090 110 135 070 090 110 135 070 090 110 135
1 58 42
n/a n/a
105 64
n/a n/a
121 114 89 80
2 53 37 100 59 116 109 84 75
3 48 32 95 54 111 104 79 70
4 43 27 90 49 106 99 74 65
5 38 22 85 44 101 94 69 60
6 33 17 80 39 96 89 64 55
7 28 12 75 34 91 84 59 50
8 23
n/a
70 29 86 79 54 45
9 18 65 24 81 74 49 40
10 13 60 19 76 69 44 35

Page 16
FIGURE 18
TYPICAL EXHAUST AND INTAKE PIPE CONNECTIONS IN UPFLOW APPLICATIONS
2”
DO NOT transition
from smaller to larger
pipe size in horizontal
runs of exhaust pipe.
* When transitioning up in pipe size, use the shortest length of 2” PVC pipe possible.
*2”
2”
Exhaust Intake Exhaust Intake
*2”
2” 2”
2” 2”
or
FIGURE 19
TRANSITION
SIDE VIEW
2” 2”
2”
2”
or
TYPICAL EXHAUST AND INTAKE PIPE CONNECTIONS IN HORIZONTAL AIR APPLICATIONS
(RIGHT HAND DISCHARGE SHOWN)
3”
2”
45°
MAX
45°
MAX
DO NOT transition
from smaller to larger
pipe size in horizontal
runs of exhaust pipe.
*2”
*2”
12” max.
* When transitioning up in pipe size, use the shortest length of 2” PVC pipe possible.
Intake
Exhaust
Intake
Exhaust
3”
*2”
*2”
2”
2”
or
2”

Page 17
FIGURE 20
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 INLET AREA 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
Btuh (3kw), 9 inches (228mm) for ap
pliances > 10,000 Btuh (3kw) and <50,000
Btuh (15 kw), 12 inches (305mm) for ap
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
Clearance to each side of center line ex
tended above meter / regulator assembly
Clearance to service regulator
vent outlet
Clearance to non-mechanical air
supply inlet to building or the com
bustion air inlet to any other ap
pliance
Clearance to mechanical air sup
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
Btuh (3kw), 9 inches (228mm) for ap
pliances > 10,000 Btuh (3kw) and <50,000
Btuh (15 kw), 12 inches (305mm) for ap
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)‡

Page 18
General Guidelines for Vent Terminations
In Direct Vent applications, combustion air is taken from
outdoors and the flue gases are discharged to the out
doors. The SLP98UHV is classified as a direct vent, Cate
gory IV gas furnace.
In 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 Pro
pane Installation Codes in Canada for details.
Position termination according to location given in figure
20. In addition, position termination so it is free from any ob
structions and 12” above the average snow accumulation.
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 because
the condensate can damage the painted coating.
NOTE - See table 6 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) Arma
flex or equivalent. In extreme cold climate areas, 3/4”
(19mm) Armaflex or equivalent may be necessary. Insula
tion must be protected from deterioration. Armaflex 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
terminations. Doing so will cause freeze-ups and
may block the terminations.
IMPORTANT
For Canadian Installations Only:
In accordance to CSA International B149 installation
codes, the minimum allowed distance between the
combustion air intake inlet and the exhaust outlet of
other appliances shall not be less than 12 inches
(305mm).

Page 19
TABLE 6
Maximum Allowable Vent Pipe Length (in ft.) Without Insulation In Unconditioned Space For
Winter Design Temperatures Modulating High Efficiency Furnace
Winter Design
Temperatures1°F (°C)
Vent Pipe
Diameter
Unit Input Size
070 090 110 135
32 to 21
(0 to -6)
PVC 2PP PVC 2PP PVC 2PP PVC 2PP
2 in. 8 8 14 13 16 15 N/A N/A
2-1/2 in. 6 N/A 9 N/A 12 N/A N/A N/A
3 in. 4 3 6 5 8 7 12 11
20 to 1
(-7 to -17)
2 in 5 5 7 6 8 7 N/A N/A
2-1/2 in. 4 N/A 5 N/A 6 N/A N/A N/A
3 in. 2 2 2 2 4 3 6 5
0 to -20
(-18 to -29)
2 in. 3 3 4 4 5 4 N/A N/A
2-1/2 in. 2 N/A 2 N/A 3 N/A N/A N/A
3 in. 1 1 1 1 1 1 2 1
1Refer to 99% Minimum Design Temperature table provided in the current edition of the ASHRAE Fundamentals Handbook.
2Poly-Propylene vent pipe (PP)
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 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 figure21.
FIGURE 21
Conditioned
Space Unconditioned
Space
Exhaust
Pipe
Intake
Pipe
Conditioned
Space
Pipe Insulation

Page 20
Details of Intake and Exhaust Piping Terminations for
Direct Vent Installations
NOTE - In Direct Vent installations, combustion air is taken
from outdoors and flue gases are discharged to outdoors.
NOTE - Flue gas may be slightly acidic and may adversely
affect some building materials. If any vent termination is
used and the flue gasses may impinge on the building ma
terial, a corrosion-resistant shield (minimum 24 inches
square) should be used to protect the wall surface. If the
optional tee is used, the protective shield is recommended.
The shield should be constructed using wood, plastic,
sheet metal or other suitable material. All seams, joints,
cracks, etc. in the affected area should be sealed using an
appropriate sealant. See figure 29.
Intake and exhaust pipes may be routed either horizontally
through an outside wall or vertically through the roof. In at
tic or closet installations, vertical termination through the
roof is preferred. Figures 22 through 30 show typical ter
minations.
1 - Intake and exhaust terminations are not required to be
in the same pressure zone. You may exit the intake on
one side of the structure and the exhaust on another
side (figure 23). You may exit the exhaust out the roof
and the intake out the side of the structure (figure 24).
2 - Intake and exhaust pipes should be placed as close
together as possible at termination end (refer to il
lustrations). Maximum separation is 3” (76mm) on roof
terminations and 6” (152mm) on side wall termina
tions.
NOTE - When venting in different pressure zones, the
maximum separation requirement of intake and ex
haust pipe DOES NOT apply.
3 - On roof terminations, the intake piping should termi
nate straight down using two 90° elbows (See figure
22).
4 - Exhaust piping must terminate straight out or up as
shown. A reducer may be required on the exhaust pip
ing at the point where it exits the structure to improve
the velocity of exhaust away from the intake piping.
See table 7.
NOTE - Care must be taken to avoid recirculation of
exhaust back into intake pipe.
5 - On field-supplied terminations for side wall exit, ex
haust piping may extend a maximum of 12 inches
(305mm) for 2” PVC and 20 inches (508mm) for 3”
(76mm) PVC beyond the outside wall. Intake piping
should be as short as possible. See figure 29.
6 - On field-supplied terminations, a minimum distance
between the end of the exhaust pipe and the end of the
intake pipe without a termination elbow is 8” and a
minimum distance of 6” with a termination elbow. See
figure 29.
FIGURE 22
UNCONDITIONED
ATTIC SPACE
SIZE TERMINATION
PIPE PER TABLE 7.
3”(76mm) MAX.
12” (305mm) ABOVE
AVERAGE SNOW
ACCUMULATION
3” (76mm) OR
2” (51mm) PVC
PROVIDE SUPPORT
FOR INTAKE AND
EXHAUST LINES
8” (203mm) MIN
Inches(mm)
DIRECT VENT ROOF TERMINATION KIT
(15F75 or 44J41)
FIGURE 23
Exhaust
Pipe Furnace
Exiting Exhaust and Intake Vent
(different pressure zone)
Inlet Air
(Minimum 12 in.
305 MM) above
grade or snow
accumulation
FIGURE 24
Roof Terminated
Exhaust Pipe
Furnace
Exiting Exhaust and Intake Vent
(different pressure zone)
Inlet Air
(Minimum 12 in.
305 MM) above
grade or snow
accumulation
TABLE 7
EXHAUST PIPE TERMINATION SIZE REDUCTION
SLP98UHV
MODEL Termination Pipe Size
*070 1-1/2”
*090 2”
110 2”
135 2”
*SLP98UH-070 and -090 units with the flush-mount termination must use
the 1-1/2”accelerator supplied with the kit.