7
Unconditioned Spaces
All duct work passing through unconditioned space must
be properly insulated to minimize duct losses and prevent
condensation. Use insulation with an outer vapor barrier.
Refer to local codes for insulation material requirements
Closed-Off Spaces
Living space not served by, and closed off from the return air
ducts to the furnace (by doors, sliding partitions, and other
means) must be provided with permanent, uncloseable
openings in the doors or partitions to allow air to return to
the furnace from all parts of the home. Return air grilles,
with a minimum open area of one square inch for every
five square feet of living space closed off from the furnace,
must be provided in the door or room partition.
Filtering Methods - Downflow Furnaces
Non-Ducted Return Air
For unducted return air systems, either the optional grille
and frame assembly or the optional wall mount grille is
recommended.
Without A/C or H/P uncased coil:
• Use the lter supplied with the furnace. Make sure
the filter is installed mat side down between the filter
retainer and furnace top. See Figure 2.
With A/C or H/P uncased coil:
• Usetheoptionalcoillters;theltersuppliedwiththe
furnace isnotused; REMOVEANDDISCARDTHIS
FILTER.
With optional coil housing:
• See coil cabinet instructions for specic ltering
methods.
Ducted Return Air
For ducted return air systems with air conditioners or heat
pumps, either providing an access panel in the duct or
using the optional coil cabinet (Figure 3) is recommended.
The duct system must be properly sized to account for
any additional external static pressure produced from the
chosen filtering method.
NOTE: Install a filter with a minimum unrestricted medium
area of 324 in
2
in the duct above the coil that is accessible
for monthly cleaning or replacement by homeowner.
Filtering Methods - Upflow Furnaces
Non-Ducted Return Air
Furnaces may be installed with unducted or ducted return
air. For unducted systems with air conditioners or heat
pumps, the following optional equipment is recommended:
upflow stand, coil cabinet, upflow duct connector, and
wall mount grille.
Without optional upflow stand:
• Installalterwithaminimumunrestrictedmediumarea
of 324 in
2
below the coil cabinet/furnace assembly that
is accessible for monthly cleaning or replacement by
the homeowner
With optional upflow stand:
• Stand (Figure 4 (page 8)) must use two filters:
one is supplied with the stand and the other MUST
be removed from the furnace and placed in the stand.
See instructions supplied with the upflow stand for
additional details.
Ducted Return Air
For ducted systems with air conditioners or heat pumps,
the following optional equipment is recommended: coil
cabinet and upflow duct connector.
• Installalterwithaminimumunrestrictedmediumarea
of 324 in
2
below the coil cabinet/furnace assembly that
is accessible for monthly cleaning or replacement by
the homeowner
Figure 2.
Frame
Top of
Furnace
Fasteners (4)
Grille
Furnace Filter
(not used with
A/C or H/P)
20" (508 mm)
Cabinet
Insulation
23 3/4" (603 mm)
29"
(737 mm)
Figure 3.
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