INSTALLATION INSTRUCTIONS Gas Furnace: WFAR
440 01 7104 02 23
Specifications subject to change without notice.
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 28.)
Filter Arrangement
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.
!
WARNING
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. See Figure 19, Figure 20,
Figure 26.
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 27.
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 28. If both side and bottom openings are used in
Figure 28, 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.
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.
Table5–FilterSizeInformation--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)
Wash-
able*
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)
Wash-
able*
21 (533)
16 x 25 x 3/4
(406 x 635 x
19)
20 x 25 x 3/4
(508 x 635 x
19)
Wash-
able*
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)
Wash-
able*
* Recommended to maintain air filter face velocity. See Product Data 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: 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.
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