CIRCULATING AiR SUPPLY
z WARNING:
Products of combustion must not be
allowed to enter the return air openings
of the furnace or the circulating air
supply, Failure to prevent products of
combustion from being circulated into
the living space can create potentially
hazardous conditions including carbon
monoxide poisoning that could result in
personal injury or death,
The floor or platform on which the furnace
ismounted must provide sound physical
support of the furnace with no gaps,
cracks, or sagging between the furnace
and the floor or platform,
The circulating air ductwork must not be
connected to any other heat producing
device such as a fireplace insert, stove,
etc,
GENERAL
Plenums and air ducts must be installed in
accordance with the Standard for the Installa-
tion of Air Conditioning and Ventilating Systems
(NFPA No. 90A) or the Standard for the Instal-
lation of Warm Air Heating and Air Conditioning
Systems (NFPA No. 90B).
RETURN AIR PROVISIONS
U.S.A. home manufacturers shall comply with
all of the following conditions to have accept-
able return air systems for closet installed
forced air heating appliances:
a. Regardless of the location, the return air
opening into the closet shall not be less than
specified in the appliance's listing.
b. Means shall be provided to prevent inadvert-
ent closure by a flat object placed over the
return air opening when it islocated in the floor
of the closet (versus the vertical front or side
wall).
c. Closet installations must use a Iouvered door
having a minimum free area of 235 sq. in.
when located 6" from furnace. For clearance
between 1" and 6" from furnace, require-
ments are a Iouvered door with minimum of
235 sq. in. free area, with the openings in
closet door directly inline with the Iouvered
openings in the furnace door. For 1" clear-
ance from furnace, use a fully Iouvered door
with at least 400 sq. in. of free airflow area.
d. The cross-sectional area of the return duct
system leading into the closet, when located
in the floor or ceiling shall notbe less than 235
square inches.
e. The total free area of openings in the floor or
ceiling registers serving the return air duct
system must be at least 352 sq. in. At least
one register should be located where it is not
likely to be covered by carpeting, boxes and
other objects.
f. Materials located in the return duct system
must have a flame spread classification of
200 or less. This includes a closet door if the
furnace is in a closet.
g. Noncombustible pans having 1" upturned
flanges are located beneath openings in a
floor duct system.
h. Wiring materials located in the return duct
system shall conform to Articles 300-22 of
the National Electrical Code (ANSI Cl/
NFPA-70).
i. Gas piping is not run in or through the return
duct system.
j. Test the negative pressure in the closet with
the air-circulating fan operating at high speed
and the closet closed. The negative
pressure is to be no more negative than
minus 0.05 inch water column.
k. For floor return systems, the manufactured
home manufacturer shall affix a prominent
marking on or near the appliance where itcan
be easily read when the closet door is open.
The marking shall read:
CAUTION:
HAZARD OF ASPHYXIATION: Do not
cover or restrict return air opening,
I. Air conditioning systems may require more
duct register and open louver area to ob-
tain necessary airflow. Use NORDYNE's
certiduct program to determine proper duct
size for A/C.
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