Page 1
INSTALLATION
INSTRUCTIONS
SLP99UHV
507999-01
10/2021
Supersedes 08/2021
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.
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.
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.
NOTICE
A thermostat is not included and must be ordered
separately.
• A communicating thermostat must be used in
communicating applications.
• In non-communicating applications, the Lennox
ComfortSense
®
7500 thermostat may be used, as well
as other non-communicating thermostats.
In all cases, setup is critical to ensure proper system
operation.
Field wiring for both communicating and non-
communicating applications is illustrated in diagrams,
which begin on Page 35
©
2021 Lennox Industries Inc.
Dallas, Texas USA
DAVE LENNOX SIGNATURE
®
COLLECTION GAS FURNACES
UP/FLOW HORIZONTAL AIR DISCHARGE
Contents
Unit Dimensions .............................................................2
Parts Arrangement..........................................................3
SLP99UHV Gas Furnace ...............................................4
Shipping and Packing List ..............................................4
Safety Information ..........................................................4
Use of Furnace as Construction Heater .........................5
General ...........................................................................6
Installation - Setting Equipment ......................................6
Filters ............................................................................10
Duct System .................................................................10
Pipe Fittings Specications...........................................13
Joint Cementing Procedure .......................................... 14
Venting Practices ..........................................................15
Vent Pipe Guidelines ....................................................15
Gas Piping ....................................................................30
Electrical .......................................................................33
Integrated Control .........................................................41
Unit Start-Up .................................................................50
Gas Pressure Measurement ........................................51
Operating Pressure Signal Measurement ....................52
Proper Combustion.......................................................53
High Altitude Information ..............................................53
Other Unit Adjustments.................................................53
Heating Sequence of Operation ...................................54
Service..........................................................................56
Repair Parts List ...........................................................58
Integrated Control Diagnostic Codes............................59
Conguring Unit Size Codes ........................................62
Troubleshooting: Heating Sequence of Operation .......63
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