Allied A96US2V - Duct System, Plenum, and Pipe Specifications; Duct System Guidelines

507404-02 Page 13 of 80Issue 1448
Return Air - Horizontal Applications
Return air may be brought in only 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 13.
Filters
This unit is not equipped with a lter or rack. A eld provided
lter is required for the unit to operate properly. Table 1 list
recommended lter sizes.
A lter must be in place whenever the unit is operating.
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: This furnace is not certied for operation in heating
mode (indoor blower operating at selected heating speed)
with an external static pressure which exceeds 0.8 inches
w.c. Operation at these conditions may result in improper
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 reected light) of the heat exchanger for leaks after the
furnace is installed. The furnace access panel must always
be in place when the furnace is operating and it must not
allow leaks into the supply air duct system.
Return Air Plenum
NOTE: 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 replace) 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 ue products can be pulled
back down the vent pipe and into the room. This reverse
ow of the ue gas may result in incomplete combustion
and the formation of carbon monoxide gas. This raw gas or
toxic fumes 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 berglass sealing
strips, caulking, or equivalent sealing method between the
plenum and the furnace cabinet to ensure a tight seal. If a
lter is installed, size the return air duct to t the lter frame.
Pipe & Fittings Specications
All pipe, ttings, primer and solvent cement must conform
with American National Standard Institute and the American
Society for Testing and Materials (ANSI/ASTM) standards.
The solvent shall be free owing and contain no lumps,
undissolved particles or any foreign matter that adversely
affects the joint strength or chemical resistance of the
cement. The cement shall show no gelation, stratication,
or separation that cannot be removed by stirring. Refer to
Table 2 for approved piping and tting materials.
Figure 19
Table 1