12
wall require a 6” clearance from the wall to the furnace
so that the air may enter the front grille of the furnace.
In addition, all return air systems, including the floor and
ceiling systems, must meet the following conditions:
• The return air opening, regardless of its location in the
closet, must not be smaller than size specified on unit
data label. If located in the floor, the opening must be
provided with a means of preventing its inadvertent
closure by flat object(s) placed over the opening.
• The return-air opening into the closet, regardless of its
location, must have an open free area of 200 in
2
(1290
cm
2
) minimum.
• The cross-sectional area of the return duct system (in
floor or ceiling) leading into the closet must not be less
than 200 in
2
(1290 cm
2
).
• The total free area of the openings in the floor or the
ceiling registers serving the return air duct system must
not be not less than 300 in
2
(1935 cm
2
).
• Materials located in the return duct system shall have
a flame spread classification of 200 or less.
• Noncombustible pans having one inch upturned flanges
are located beneath openings in a floor return duct
system.
• Hollow spaces used as ducts or plenums for
environmental air may contain mineral-insulated metal
sheathed cable, aluminum sheathed cable, electrical
metallic tubing, rigid metal conduit, flexible metal
conduit (not to exceed 4 ft), or metal-clad cables. Wiring
materials, fixtures, are to be suitable for the expected
ambient temperatures to which they will be subjected.
• The negative pressure in the closet must not be less
than minus 0.05 inches water column with the closet
door closed and the fan operating at high speed. A
reading below minus 0.05” indicates a dirty filter or a
restricted return air system.
• For floor return systems, the manufactured housing
manufacturer or installer shall affix a prominent
marking on or near the appliance where it is easily
read when the closet door is open. The marking shall
read: “CAUTION, HAZARD OF ASPHYXIATION. DO
NOT COVER OR RESTRICT FLOOR RETURN AIR
OPENING.” or equivalent.
• For closet installation with less than 6” front clearance,
but not less than 1”, a louvered door must be used
having a minimum 200 in
2
(1290 cm
2
) free area opening
directly in line with openings in the furnace door. A fully
louvered door having the minimum free area is also
permitted if the front tolerance is not less than 4”.
Furnace Filter
WARNING:
Never operate the furnace without a filter in
place. Accumulating dust in the return air can
build up on internal components, resulting
in loss of efficiency, equipment damage, and
possible fire.
•
CMF95 furnaces are supplied with a single air filter
when shipped from the factory.
Accessing the filter does
not require tools and can be easily removed from the
inside of the access door. The filter is secured to the
door with a retaining bracket.
It is recommended that
the filter be cleaned or replaced monthly. Newly built or
recently renovated homes may require more frequent
changing until the construction dust has minimized.
•
Replacement filters are available at most local retailers.
Inspect filters frequently and replace when necessary
with filter of same dimensional size.
Filters designed to
remove smaller particles such as pollen, may require
additional maintenance.
Acoustical Treatments
Damping ducts, flexible vibration isolators, or pleated
media-style filters on the return air inlet of the furnace
may be used to reduce the transmission of equipment
noise eminating from the furnace. These treatments can
produce a quieter installation, particularly in the heated
space. However, they can increase the pressure drop in
the duct system. Care must be taken to maintain the proper
maximum pressure rise across the furnace, temperature
rise and flow rate. This may mean increasing the duct size
and/or reducing the blower speed. These treatments must
be constructed and installed in accordance with NFPA and
SMACNA construction standards. Consult with local codes
for special requirements. For best sound performance,
install all the needed gaskets and grommets around
penetrations into the furnace, such as for electrical wiring.
