Filter And Return Duct Sizing - International comfort products R9MSB0801716 Installation Instructions Manual

INSTALLATION INSTRUCTIONS
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, see Figure 24 and Figure 25.
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.) Where required by code, seal
bottom closure to furnace with tape, mastic or other durable
sealing method.
Filter Arrangement
WARNING
!
FIRE, CARBON MONOXIDE AND POISONING
HAZARD
Failure to follow this warning could result in fire,
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 rack in these
furnaces. An external filter 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.
Figure 27.
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 20 and Figure 28.
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.
440 01 6001 05
See Figure 19, Figure 20,
Specifications subject to change without notice.
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.
Refer to the instructions supplied with filter rack or accessory
air filter for additional assembly and installation options.
See Table 5 for filter size details.
Table 5 – Filter Size Information − in. (mm)
FILTER SIZE
FURNACE
SIDE
CASING
RETURN
WIDTH
14−3/16{
16 x 25 x 3/4
(360) (406 x 635 x 19)
17−1/2
16 x 25 x 3/4
(445) (406 x 635 x 19)
16 x 25 x 3/4
21 (533)
(406 x 635 x 19)
24−1/2
16 x 25 x 3/4
(622) (406 x 635 x 19)
* Recommended to maintain air filter face velocity. See Specification Sheet for
part number.
{ Not all families have these models.

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 6 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:
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
factory-accessory duct adapters.
Gas Furnace: R9MSB
BOTTOM
FILTER
RETURN
TYPE
14 x 25 x 3/4
Washable*
(356 x 635 x 19)
16 x 25 x 3/4
Washable*
(406 x 635 x 19)
20 x 25 x 3/4
Washable*
(508 x 635 x 19)
24 x 25 x 3/4
Washable*
(610 x 635 x 19)
Install a media cabinet capable
instructions supplied with
23