5
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 filter supplied with the furnace. Make sure
the filter is installed mat side down between the filter
retainer and furnace top.
With A/C or H/P uncased coil:
• Use the optional coil filters; the filter supplied with the
furnace is not used; REMOVE AND DISCARD THIS
FILTER.
With optional coil housing:
• See coil cabinet instructions for specific filtering
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 1) 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 that meets the application requirements of the furnace
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:
• Install a filter with a minimum unrestricted medium
area that meets the application requirements of the
furnace below the coil cabinet/furnace assembly that
is accessible for monthly cleaning or replacement by
the homeowner
With optional upflow stand:
• Stand (Figure 3 (page 6)) only uses filters that
come in the box. The filter in the furnace must be
removed and discarded. 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.
• Install a filter with a minimum unrestricted medium
area that meets the application requirements of the
furnace below the coil cabinet/furnace assembly that
is accessible for monthly cleaning or replacement by
the homeowner
Figure 1. Upflow Coil Cabinet
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 2. Grille Support Frame & Grille Assembly
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