Filters; Duct System - Allied Air A97USMV Installation Instructions Manual

* Gas Connector may be used for Canadian installation if acceptable
by local authority having jurisdiction.
Figure 13
Return Air - Horizontal Applications
Return air must be brought in through the end of a furnace
installed in the horizontal position. The furnace is equipped
with a removable bottom panel to facilitate installation. See
Figure 7.

Filters

This unit is not equipped with a filter or rack. A field provided
filter is required for the unit to operate properly. Table 1 lists
recommended filter sizes.
A filter must be in place when the unit is operating!
NOTE: In upflow applications where side return air filter is
installed on same side as the condensate trap, make sure
that clearance is maintained to ensure future access to the
filter access panel.
507028-03
Table 1

Duct System

Use industry approved standards to size and install the
supply and return air duct system. This will result in a quiet
and low static system that has uniform air distribution.
NOTE: Operation of this furnace in heating mode (indoor
blower operating at selected heating speed) with an external
static pressure which exceeds 0.8 inches w.c. may result in
erratic limit operation.
Supply Air Plenum
If the furnace is installed without a cooling coil, a removable
access panel should be installed in the supply air duct. The
access panel should be large enough to permit inspection
(by reflected light) of the heat exchanger for leaks after
the furnace is installed. If present, this access panel must
always be in place when the furnace is operating and it
must not allow leaks into or from the supply air duct system.
Return Air Plenum
Return air must not be drawn from a room where this
furnace, or any other gas fueled appliance (i.e., water
heater), or carbon monoxide producing device (i.e., wood
fireplace) is installed. When return air is drawn from a
room, a negative pressure is created in the room. If a gas
appliance is operating in a room with negative pressure,
the flue products can be pulled back down the vent pipe
and into the room. This reverse flow of the flue gas may
result in incomplete combustion and the formation of carbon
monoxide gas. This toxic gas might then be distributed
throughout the house by the furnace duct system.
Return air can be brought in through the bottom or either
side of the furnace. If a furnace with bottom return air is
installed on a platform, make an airtight seal between the
bottom of the furnace and the platform to ensure that the
unit operates properly and safely. Use fiberglass sealing
strips, caulking, or equivalent sealing method between the
plenum and the furnace cabinet to ensure a tight seal. If a
filter is installed, size the return air duct to fit the filter frame.
Issue 1622 Page 11 of 74