INSTALLATION INSTRUCTIONS
Gas Furnace: (F/G)9MVT, (F/G)9MXT, (F/G)9MXE
24
440 01 4001 05
Specifications subject to change without notice.
Roll
−
Out Protection
Provide a minimum 12
−
in. x 22
−
in. (305 x 559 mm) piece of
sheet metal for flame roll
−
out protection in front of burner area
for furnaces closer than 12
−
in. (305 mm) above the
combustible deck or suspended furnaces closer than 12
−
in.
(305mm) to joists. The sheet metal MUST extend underneath
the furnace casing by 1
−
in. (25mm) with the door removed.
The bottom closure panel may be used for flame roll
−
out
protection when bottom of furnace is used for return air
connection. See
Figure 26
for proper orientation of roll
−
out
shield.
Supply Air Connections
For a furnace not equipped with a cooling coil, the outlet duct
shall be provided with a removable access panel. This opening
shall be accessible when the furnace is installed and shall be of
such a size that the heat exchanger can be viewed for possible
openings using light assistance or a probe can be inserted for
sampling the air stream. The cover attachment shall prevent
leaks.
Connect supply
−
air duct to flanges on furnace supply
−
air
outlet. Bend flange upward to 90
with wide duct pliers. (See
Figure 22
) The supply
−
air duct must be connected to ONLY
the furnace supply
−
outlet
−
air duct flanges or air conditioning
coil casing (when used). DO NOT cut main furnace casing side
to attach supply air duct, humidifier, or other accessories. All
supply
−
side accessories MUST be connected to duct external
to furnace main casing.
Return Air Connections
The return
−
air duct may be connected to bottom of the furnace.
The side of casing that faces downward may also be used for
return air connection. A combination of the bottom and
downward facing side may also be used. The upward facing
side of the casing cannot be used as a return air connection.
(See
Figure 29
)
Bottom Return Air Inlet
These furnaces are shipped with bottom closure panel installed
in bottom return
−
air opening. Remove and discard this panel
when bottom return air is used. To remove bottom closure
panel, perform the following:
1. Tilt or raise furnace and remove four (4) screws holding
bottom plate. (See
Figure 19
)
2. Remove bottom plate.
3. Remove bottom closure panel.
4. Reinstall bottom plate and screws.
Side Return Air Inlet
These furnaces are shipped with bottom closure panel installed
in bottom return
−
air opening. This panel MUST be in place
when side return air inlet(s) are used without a bottom return air
inlet.
Not all horizontal furnaces are approved for side return air
connections (See
Figure 29
)
Filter Arrangement
WARNING
!
FIRE, CARBON MONOXIDE AND POISONING
HAZARD
Failure to follow this warning could result in personal
injury, or death.
Never operate a furnace without a filter or filtration device
installed. Never operate a furnace with filter or filtration
device access doors removed.
Furnaces shipped without a filter rack:
There are no provisions for an internal filter in these furnaces.
An external filter rack is required and is purchased separately.
A field supplied accessory air cleaner may also be used in
place of the filter rack.
For upflow applications, the filter can be installed on either side
of the furnace, the bottom of the furnace or any combination of
side and bottom of the furnace. (See
Figure 28
,
Figure 31
, and
Figure 30
)
For downflow applications, the filter rack (or field supplied
accessory air cleaner) must only be connected to the bottom
opening on the furnace (See
Figure 27
and
Figure 30
and
Table 9
).
For horizontal applications, the filter rack (or field supplied
accessory air cleaner) can be connected to the bottom opening
on the furnace. For side return use in the horizontal position,
refer to
Figure 29
. If both side and bottom openings are used in
Figure 29
, each opening used will require a filter.
A filter rack or any field supplied accessory air cleaner can also
be installed in the common return duct prior to entering the
return air opening in any orientation.
See
Table 6
for recommended filter size details.
Table 6
Filter Size Information
−
in. (mm)
FURNACE
CASING
WIDTH
FILTER SIZE
FILTER
TYPE
SIDE RETURN
BOTTOM
RETURN
14-3/16
(360)
16 x 25 x 3/4
(406 x 635 x 19)
14 x 25 x 3/4
(356 x 635 x 19)
Washable*
17-1/2
(445)
16 x 25 x 3/4
(406 x 635 x 19)
16 x 25 x 3/4
(406 x 635 x 19)
Washable*
21
(533)
16 x 25 x 3/4
(406 x 635 x 19)
20 x 25 x 3/4
(508 x 635 x 19)
Washable*
24-1/2
(622)
16 x 25 x 3/4
(406 x 635 x 19)
24 x 25 x 3/4
(610 x 635 x 19)
Washable*
* Recommended to maintain air filter face velocity. See Product Data for part
number.
Refer to the instructions supplied with the Filter Rack or
accessory air filter
for additional assembly and installation
options
.
Filter and Return Duct Sizing
Pressure drop must be taken into account when sizing filters,
filter racks, IAQ devices, and associated system ductwork. See
Table 7
for a comparison of Pressure Drop (initial/clean
resistance to airflow) versus Airflow for a variety of filter media
types and sizes. These are representative numbers. Consult
the filter or IAQ device manufacturers’ specification sheet for
performance data for a particular filter media or IAQ device.
Design the filter and associated ductwork for the best match of
pressure drop versus filter size. Best practice usually chooses
filter systems with pressure drops under 0.2 in. w.c. (50 Pa),
with the best blower electrical efficiency and system airflow
performance occurring with filter pressure drops under 0.1 in.
w.c. (25 Pa).
Due to the relatively high pressure drops of 1-in (25 mm) thick
after-market filter media, it is recommended that the filtration
system be designed for at least 2-in (51 mm) thick media.
TIPS FROM CONTRACTORS:
Install a media cabinet capable
of incorporating a 4-in (102 mm) thick media filter. This allows
room for future upgrades to other IAQ devices.
NOTICE
Design the duct system FIRST to determine how much
pressure drop may be allowed in the filter system. See
the AIR DUCTS section. Excessive filter pressure drop
often compromises system airflow and duct perform-
ance, causes inadequate airflow to the furthest ends of
the duct system, as well as causes excess noise and
higher than anticipated electrical consumption.
Provide duct transitions, as required, to smoothly transition
airflow from the return duct system to the filter (or IAQ device)
to the furnace when the dimensions of the ductwork or furnace
return air opening do not match the required filter or IAQ device
dimensions. See the instructions supplied with
factory-accessory duct adapters.
