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Provide ample space for servicing and cleaning. Always comply
with minimum fire protection clearances shown on unit’s clear-
ance to combustibles label. (See Fig. 3.) Locate furnace where
available electric power and gas supplies meet specifications on
furnace rating plate.
II. LOW-FIRE ONLY INSTALLATION
This 355MAV furnace can be installed to operate in the low-fire
only heating mode when sized using the low-fire heating capacity.
This is accomplished by placing setup switch SW-2 in the ON
position to provide only low-fire-heat operation. See Fig. 25 and
Table 10. With this setup, high-fire operation will not occur.
When the model no. on the furnace rating plate is followed by an
asterisk (*), the furnace has an alternate low-fire only efficiency
rating as listed in the GAMA and CEC directories. This alternate
rating will be listed as the furnace model number followed by an
(-L) suffix.
CAUTION: The furnace can operate in the high-fire
mode when certain fault conditions occur. The following
precautions should be taken:
1. Size gas piping based on the high-fire input.
2. Check the high-fire input and adjust it per the main
literature instructions.
NEVER assume the high-fire input rate is not important
for low-fire-only installation.
III. FURNACE LOCATION RELATIVE TO COOLING
EQUIPMENT
The cooling coil must be installed parallel with or on downstream
side of furnace to avoid condensation in heat exchanger. When
installed parallel with a furnace, dampers or other means used to
control flow of air must prevent chilled air from entering furnace.
If dampers are manually operated, they must be equipped with a
means to prevent operation of either unit unless damper is in
full-heat or full-cool position.
NOTE: These furnaces are designed for a minimum continuous
return-air temperature of 60°F or intermittent operation down to 55°F
such as when used with a night setback thermostat. Return-air
temperature must not exceed a maximum of 85°F. Failure to follow
these return-air temperature limits may affect reliability of heat
exchangers, motors, and controls.
A93042
FRONT
RETURN
AIR
MAX 85°F MIN 55°F
°F °F
WARNING: Do not install furnace on its back. Safety
control operation will be adversely affected. Never con-
nect return-air ducts to back of furnace. Failure to follow
this warning could result in fire, personal injury, or death.
A93043
FRONT
BACK
FRONT
B
A
C
K
CAUTION: If these furnaces are installed in an uncon-
ditioned space where ambient temperatures may be 32°F
or lower, freeze protection measures must be taken.
A93058
32°F MINIMUM INSTALLED
AMBIENT OR FREEZE
PROTECTION REQUIRED
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