opening must have a free area of at least 1 sq in. per 1000 Btuh of total input rating but not less than 100 sq in. (See Table 4.)
Table 4—Combustion Air
From Unconfined Space
58CMA FURNACE | FREE AREA PER | |
OPENING | ||
INPUT BTUH | ||
(SQ IN.) | ||
| ||
70,000 | 100 | |
91,000 | 100 | |
105,000 | 105 | |
119,000 | 119 | |
140,000 | 140 | |
154,000 | 154 |
ALL AIR FROM OUTSIDE OF STRUCTURE
If outside air is supplied to a confined space, then the 2 openings must be equal and located as above.
1.If combustion air is taken through a permanent opening directly communicating with the outdoors, the opening shall have a minimum free area of 1 sq in. per 4000 Btuh of total input rating for all equipment in the enclosure.
2.If combustion air is taken from outdoors through vertical ducts, the openings and ducts MUST have at least 1 sq in. of free area per 4000 Btuh of the total input for all equipment within the confined space. (See Table 5.)
Table 5—Combustion Air From Outdoors
Through Vertical Ducts
58CMA FURNACE | FREE AREA PER | ROUND PIPE | |
OPENING | |||
INPUT BTUH | (IN. DIAM) | ||
(SQ IN.) | |||
|
| ||
70,000 | 17.5 | 5 | |
91,000 | 22.8 | 6 | |
105,000 | 26.3 | 6 | |
119,000 | 29.8 | 6 | |
140,000 | 35.0 | 6 | |
154,000 | 38.5 | 6 | |
|
|
|
3.If combustion air is taken from outdoors through horizontal ducts, the openings and ducts MUST have at least 1 sq in. of free area per 2000 Btuh of the total input for all equipment within the confined space. (See Table 6.)
Table 6—Combustion Air From Outdoors
Through Horizontal Ducts
58CMA FURNACE | FREE AREA PER OPENING | ROUND PIPE |
INPUT BTUH | (SQ IN.) | (IN. DIAM) |
70,000 | 35.0 | 7 |
91,000 | 45.5 | 8 |
105,000 | 52.5 | 9 |
119,000 | 59.5 | 9 |
140,000 | 70.0 | 10 |
154,000 | 77.0 | 10 |
When ducts are used to supply air, they must be of the same cross sectional area as free area of openings to which they connect.
The minimum dimension of rectangular air ducts must not be less than 3 in.
DUCT WORK RECOMMENDATIONS
When supply ducts carry air circulated by furnace to areas outside spaces containing furnace, return air MUST also be handled by a duct sealed to furnace casing and terminating outside space containing furnace. Incorrect duct work termi- nation and sealing will create a hazardous condition which could lead to bodily harm.
The proper sizing of warm air ducts is necessary to ensure satisfactory furnace operation. Duct work should be in accordance with the latest editions of
The supply duct work should be attached to flanged front opening provided at discharge end of furnace. The
NOTE: The back (blower access opening) should not be used for return air.
The following recommendations should be followed when install- ing duct work:
1.Install
2.A flexible duct connector of noncombustible material should be installed at unit on both supply- and
3.In cases where
4.When a single air grille is used, duct between grille and furnace must be the same size as return opening in furnace.
VENTING
Venting of furnace should be to the outside and in accordance with local codes or requirements of local utility.
For additional venting information, refer to ANSI/NFPA 211 Chimney, Fireplaces, Vents, and Solid Fuel Burning Appliances and/or CSA B139 Installation Code.
This furnace is certified for use with Type ″ L″ vent (maximum flue gas temperature 575°F).
Vent System Inspection
Before furnace is installed, it is highly recommended that any existing vent system be completely inspected.
For any chimney or vent, this should include the following:
1.Inspection for any deterioration in chimney or vent. If dete- rioration is discovered, chimney must be repaired or vent must be replaced.
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