Page 1
INSTALLATION
INSTRUCTIONS
SL280UHNV
507649-04
08/2021
Supersedes 507649-03
NOTICE
A thermostat is not included and must be ordered
separately.
• A communicating thermostat must be used in
communicating applications.
• In non-communicating applications, 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 23
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.
© 2021 Lennox Industries Inc.
Dallas, Texas USA
Table of Contents
Unit Dimensions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Parts Arrangement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
SL280UHNV Gas Furnace . . . . . . . . . . . . . . . . . . . . . . . . . 4
Shipping and Packing List . . . . . . . . . . . . . . . . . . . . . . . . 4
Safety Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Use of Furnace as a Construction Heater . . . . . . . . . . . 5
General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Combustion, Dilution & Ventilation Air . . . . . . . . . . . . . . 6
Setting Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Filters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Duct System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Venting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Gas Piping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Electrical . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Integrated Control. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
Blower Performance Data . . . . . . . . . . . . . . . . . . . . . . . . 35
Unit Start-Up . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
Proper Combustion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
Rate Check . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
High Altitude . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
Other Unit Adjustments . . . . . . . . . . . . . . . . . . . . . . . . . . 41
Heating Sequence of Operation . . . . . . . . . . . . . . . . . . . 40
Service . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
Repair Parts List . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
Integrated Control Diagnostic Modes . . . . . . . . . . . . . . . 46
Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
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.
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