Installation Manual

12
exchanges with the living area of the home. A partially
louvered door may also be used across the opening. Grilles
placed in a side wall require a 6” clearance from the wall
to the furnace so that the air may enter the front grille
of the furnace. 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 cross-sectional area of the return duct system (in
floor or ceiling) leading into the closet must not be less
than 235 in
2
(1,516 cm
2
).
CAUTION:
HAZARD OF ASPHYXIATION: Negative pressure
inside the closet, with closet door closed and
the furnace blower operating on high speed,
shall be no more negative than minus 0.05 inch
water column.
Test the negative pressure in the closet with the air-
circulating fan operating at high speed and the closet
closed. 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.
The negative pressure is to be no more negative than
minus 0.05” water column as this indicates a dirty filter
or a restricted return air system.
For closet installation with less than 6” front clearance,
but not less than 1”, a louvered door must be used
having a minimum 250 in
2
(1,613 cm
2
) free area opening
directly in line with openings in the furnace door. For 1”
clearance from furnace, use a fully louvered door with
at least 400 in
2
(2,580 cm
2
) of free airflow area.
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.
MG2R furnaces designed for front return are supplied
with a single reusable 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.
MG2R furnaces designed for top return are shipped
with a non-reusable single 18”x18”x1” air filter from
the factory. Accessing the filter does not require tools
and can be easily removed from inside the blower
compartment. The filter is secured with a U-shaped
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.
Combustion Air Pipe
Blower
Assembly
Insert filter between
blower assembly &
combustion air pipe
Blower
Assembly
Angle the filter into place
above the blower assembly
Combustion Air Pipe
Filter
Blower
Assembly
Combustion Air Pipe
Align the filter
over the opening and
secure with filter retainer
Filter
Blower
Assembly
Figure 7. Filter Installation