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
A Single trunk duct | ||
B | Dual trunk duct | |
w/crossover connector | ||
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| Transition duct | |
C | w/branches | |
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Figure 2. Non-Platinum
Supply Duct System
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
19” |
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13 1/4" |
| Top View | ||
| of Duct | |||
10 | 1/4" | 19" | ||
Connector | ||||
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| Figure 4. |
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| 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 | |
Table 5. Duct Connectors
FLOOR CAVITY
(depth equal to "X" in Figure 5 and Table 5)
x
SUPPLY AIR DUCT
Figure 3.
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