© 2021 Lennox Industries Inc.
Dallas, Texas USA
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.
Contents
Safety .............................................................................4
General ...........................................................................5
Filters ............................................................................ 11
Duct System .................................................................12
Venting .........................................................................12
INSTALLATION
INSTRUCTIONS
SL280DFNV
DAVE LENNOX SIGNATURE
GAS FURNACE DOWNFLOW
AIR DISCHARGE
508150-02
08/2021
Supersedes 508150-01
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.
Improper
installation,
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.
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 21.
Gas Piping ....................................................................17
Electrical .......................................................................19
Unit Start-Up .................................................................37
Service..........................................................................41
Troubleshooting ............................................................51
Page 1
®
WARNING
adjustment,
alteration,
NOTICE