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Installed in Combination with a Cooling Coil
When this furnace is used with cooling units, it shall be in-
stalled in parallel with, or on the upstream side of, cooling 
units to avoid condensation in the heating compartment. 
See Figure 1. 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.
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 Parallell to Air Handler Unit
Air Handler Unit
Evaporator
Figure 1 
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 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 EL180UHE furnace may be installed in alcoves, clos-
ets, attics, basements, garages, crawl spaces and utility 
rooms in the upow or horizontal position.
This furnace design has not been CSA International 
certied for installation in mobile homes, recreational 
vehicles, or outdoors.
Use of Furnace as Construction Heater
Lennox does not recommend the use of EL180UHE units 
as a construction heater during any phase of construc-
tion. Very low return air temperatures, harmful vapors and 
operation of the unit with clogged or misplaced lters will 
damage the unit.
EL180UHE units may be used for heating of buildings or 
structures under construction, if the following conditions 
are met:
•    The vent system must be permanently installed per 
these installation instructions.
•    A room thermostat must control the furnace. The use 
of xed jumpers that will provide continuous heating is 
not allowed.
•   The return air duct must be provided and sealed to the 
furnace.
•    Return air temperature range between 60°F (16°C) and 
80°F (27°C) must be maintained.
•    Air lters must be installed in the system and must be 
maintained during construction.
•    Air lters must be replaced upon construction comple-
tion.
•   The input rate and temperature rise must be set per the 
furnace rating plate.
•   One 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. 
Size the temporary duct following these instructions in 
section for Combustion, Dilution and Ventilation Air in a 
conned space with air from outside.
•    The furnace heat exchanger, components, duct sys-
tem, air lters and evaporator coils must be thoroughly 
cleaned following nal construction clean-up.
•    All furnace operating conditions (including ignition, in-
put rate, temperature rise and venting) must be veried 
according to these installation instructions.
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 EL180UHE furnace:
•     Place the furnace as close to the center of the air distri-
bution system as possible. The furnace should also be 
located close to the chimney or vent termination point.