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98618/035-20009-001
Rev. B (1205)
MANUFATURED
(MOBILE)
HOME
AND
MODULAR
HOME
UPFLOW
RETURN
PLENUM
CONNECTION
Return air may enter the furnace through the side(s) or bottom depend-
ing on the type of application.
Return air may not be connected
into the
rear panel of the unit. For single return application,
see data and notes
on blower performance
data tables in this manual.
BOTTOM
RETURN
AND
ATTIC
INSTALLATIONS
Bottom return applications
normally pull return air through a base plat-
form or return air plenum. Be sure the return platform structure or return
air plenum is suitable to support the weight of the furnace.
The return air ducts to the furnace
must have a total cross sectional
area of not less than two square inches per 1000 BTUH (12.9 cm 2 per
0.29 kW) of furnace input rating for heating operation. If air conditioning
is to be installed with the furnace,
larger return air ducts may be
required, depending on the capacity of the air conditioner
and the air-
flow required. The return air opening in the top of the furnace
is large
enough for the largest capacity air conditioner
for which the furnace
blower is rated. The return air duct or plenum can be connected to the
furnace by performing the following steps:
1.
Bend the 3/4" flanges that will be used to attach the return air ple-
num using the scribe marks in the furnace base.
2.
Be sure to seal the furnace to plenum connections
to prevent air
leakage. Refer to Figure 1 for unit and plenum dimensions.
Attic installations
must meet all minimum clearances
to combustibles,
and have floor support with required furnace accessibility.
INSTALLATION
RECOMMENDATIONS
FLOOR INSTALLATIONS
As shown below in Figure 2, the furnace may be installed directly on the
floor of the home, using a side return air connection.
A short duct
should be connected to the side cutout in the furnace casing. The other
end of the return air duct should be connected to a minimum 25" x 16"
filter grille. If a Blend Air ventilation system is to be installed, the return
air duct must be long enough so that the Blend Air damper can be
mounted in the top of the duct.
I ,
PLENUM
/
, ITHOAB'NET
_1
I t [A BLEND AIR
/DAMPER
I
14:
25"x 16"
I
b_"
FILTER
--
GRILLE
FIGURE 2: Floor Installation
PLATFORM
INSTALLATIONS
As shown in Figure 3, the furnace may be installed on a raised platform.
The platform must be a minimum of 20" in height and a filter grille with a
minimum area of 25" x 16" must be mounted in the front, back or side of
the platform. If a Blend Air ventilation system is to be installed, the plat-
form must be wide
enough
so that the Blend Air damper can be
mounted in the top of the platform.
FIGURE 3: Platform Installation
SECTION
IIh
FILTERS
FILTER
INSTALLATION
All applications
require the use of a filter. All models must have a field-
supplied filter and mounting hardware. Replacement
filter size is shown
in Table 5.
SIDE
RETURN/BOTTOM
EXTERNAL
INSTALLATION
Locate and knock out the square corner Iocators. These indicate the
size of the cutout to be made in the furnace side panel. Refer to Figure 4.
__
FRONT
OF
FURNACE
ER
' '
' '
Iv//
MARKINGS
FIGURE 4: Side Return Cutout Markings
Install the side filter rack following the instructions
provided with that
accessory.
If a filter(s) is provided at another location in the return air
system, the ductwork
may be directly
attached
to the furnace
side
panel. An accessory
filter rack is available for mounting the filter exter-
nal to the cabinet.
Some accessories
such as electronic air cleaners
and pleated media
may require a larger side opening. Follow the instructions supplied with
that accessory
for side opening requirements.
Do not cut the opening
larger than the dimensions shown in Figure 1.
6
Unitary Products Group
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