Carrier 58CMA - Manual (Page 5)

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.)
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.)
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.)
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.
Return-air grilles and warm air registers MUST NOT be
obstructed. Failure to follow this caution will result in
premature failure of the heat exchanger.
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 NFPA-90A (Installation of Air Condi-
tioning and Ventilating Systems) and NFPA-90B (Warm Air
Heating and Air Conditioning Systems) or Canadian equivalent.
The supply duct work should be attached to flanged front opening
provided at discharge end of furnace. The return-air duct work
should be attached to flanged rear opening of furnace. See Fig. 2
for dimensions of these openings.
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 locking-type dampers in all branches of individual
ducts to balance out system. Dampers should be adjusted to
impose proper static at outlet of furnace.
2. A flexible duct connector of noncombustible material should
be installed at unit on both supply- and return-air systems. In
applications where extremely quiet operation is necessary, the
first 10 ft (if possible) of supply and return ducts should be
internally lined with acoustical material.
3. In cases where return-air grille is located close to fan inlet,
there should be at least one 90° air turn between fan inlet and
grille. Further reduction in sound level can be accomplished
by installing acoustical air turning vanes or lining duct as
described in item 2 above.
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.
OIL-FIRED APPLIANCES SHALL BE CONNECTED TO
FLUES HAVING SUFFICIENT DRAFT AT ALL TIMES TO
ENSURE SAFE AND PROPER OPERATION OF APPLIANCE.
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.
Table 4—Combustion Air
From Unconfined Space
58CMA FURNACE
INPUT BTUH
FREE AREA PER
OPENING
(SQ IN.)
70,000 100
91,000 100
105,000 105
119,000 119
140,000 140
154,000 154
Table 5—Combustion Air From Outdoors
Through Vertical Ducts
58CMA FURNACE
INPUT BTUH
FREE AREA PER
OPENING
(SQ IN.)
ROUND PIPE
(IN. DIAM)
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
Table 6—Combustion Air From Outdoors
Through Horizontal Ducts
58CMA FURNACE
INPUT BTUH
FREE AREA PER OPENING
(SQ IN.)
ROUND PIPE
(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
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