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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 Fig.
24.
Horizontal Installation
NOTE: The furnace must be pitched forward as shown in Fig. 19
for proper condensate drainage.
The furnace can be installed horizontally in an attic or crawlspace
on either the left- -hand (LH) or right- -hand (RH) side. The furnace
can be hung from floor joists, rafters or trusses or installed on a
non- -combustible platform, blocks, bricks or pad.
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 Fig. 20. 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 Fig. 23.
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 Fig.
24.
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 Fig. 23. 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.
The furnace may be used with an optional external media filter
cabinet. The optional media filter cabinet uses either a standard
1-in. (25 mm) filter or 4-in. (102 mm) wide media filter which can
be purchased separately. A field supplied accessory air cleaner may
also be used in place of the media cabinet.
The optional media cabinet is sized for bottom return applications
for use in upflow, downflow and horizontal applications. A 16- -in.
(406 mm) media cabinet may be used with the 14- -3/16-in. (360
mm) furnace and includes block-off plates
Table 6 – Air Filter Selection and Duct Sizing - - In. (mm)
FURNACE
CASING
SIDE
WIDTH
RETURN
16 x 25 x 3/4
14---3/16
{
(406 x 635 x
(360)
19)
(1) 16 x 25 x
17---1/2
3/4
(445)
(406 x 635 x
19)
(1) 16 x 25 x
3/4
21 (533)
(406 x 635 x
19)
(1) 16 x 25 x
24---1/2
3/4
(622)
(406 x 635 x
19)
* Filters with a side return ---air may have a different filter size. Measure the
filter to obtain the correct size.
* Recommended to maintain air filter face velocity. See Product Data for
part number.
{ Not all families have these models.
Refer to the instructions supplied with Media Cabinet or accessory
air filter for assembly and other details.
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
compromises system airflow and duct performance, 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.
19
FILTER SIZE
FILTER TYPE
BOTTOM
RETURN
14 x 25 x 3/4
(356 x 635 x
Washable*
19)
(1) 16 x 25 x
3/4
Washable*
(406 x 635 x
19)
(1) 20 x 25 x
3/4
Washable*
(508 x 635 x
19)
(1) 24 x 25 x
3/4
Washable*
(610 x 635 x
19)
filter
pressure
drop
often
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