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Figure 4.
Figure 3.
13 1/4"
10 1/4"
19”
19"
Top View
of Duct
Connector
x
SUPPLY AIR DUCT
FLOOR CAVITY
(depth equal to "X" in Figure 5 and Table 5)
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 is located in the
floor of the closet (versus the vertical front
or side wall).
c. Closet installations must use a louvered
door having a minimum free area of 235 sq.
in. when located 6” from furnace. For clear-
ance between 1” and 6” from furnace, re-
quirements are a louvered door with mini-
mum of 235 sq. in. free area, with the open-
ings in closet door directly inline with the
louvered openings in the furnace door. For
1” clearance from furnace, use a fully lou-
vered 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
Figure 2. Non-Platinum
Supply Duct System
A Single trunk duct
B
Dual trunk duct
w/crossover connector
C
Transition duct
w/branches
Table 5. Duct Connectors
Use Duct Connector
If "X" (Floor Cavity) is: Model Part Number:
English Metric
(
mm
)
Finger Tab Screw Down
7/8" 22 901987 904008
2" 51 901988 904009
4 1/4" 108 901989 904010
6 1/4" 150 901990 904011
8 1/4" 210 901991 904012
10 1/4" 260 901992 904013
12 1/4" 311 901993 904014
in the floor or ceiling shall not be 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 C1/
NFPA-70).