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8
CARBON MONOXIDE POISONING HAZARD
Failure to follow this warning could result in personal
injury or death.
The operation of exhaust fans, kitchen ventilation fans,
clothes dryers, attic exhaust fans or fireplaces could create a
NEGATIVE PRESSURE CONDITION at the furnace.
Make--up air MUST be provided for the ventilation devices,
in addition to that required by the furnace. Refer to Carbon
Monoxide Poisoning Hazard warning in venting section of
these instructions to determine if an adequate amount of
make--up air is available.
!
WARNING
The requirements for combustion and ventilation air depend
upon whether or not the furnace is located in a space having a
volume of at least 50 cu/ft. per 1,000 Btuh input rating for all gas
appliances installed in the space.
S Spaces having less than 50 cu/ft. per 1,000 Btuh re-
quire the OUTDOOR COMBUSTION AIR
METHOD.
S Spaces having at least 50 cu/ft. per 1,000 Btuh may use
the INDOOR COMBUSTION AIR, STANDARD or
KNOWN AIR INFILTRATION METHOD.
Outdoor Combustion Air Method
1. Provide the space with sufficient air for proper combus-
tion, ventilation, and dilution of flue gases using perman-
ent horizontal or vertical duct(s) or opening(s) directly
communicating with the outdoors or spaces that freely
communicate with the outdoors.
2. Fig. 7 illustrates how to provide TWO OUTDOOR
OPENINGS, one inlet and one outlet combustion and
ventilation air opening, to the outdoors.
e. One opening MUST commence within 12 in. (300
mm) of the ceiling and the second opening MUST
commence within 12 in. (300 mm) of the floor.
f. Size openings and ducts per Fig. 7 and Table 2.
g. TWO HORIZONTAL DUCTS require 1 sq./in. of free
area per 2,000 Btuh (1,100 mm
2
/kW) of combined
input for all gas appliances in the space per Fig. 7 and
Table 2.
h. TWO OPENINGS OR VERTICAL DUCTS require 1
sq./in. of free area per 4,000 Btuh (550 mm
2
/kW) for
combined input of all gas appliances in the space per
Fig. 7 and Table 2.
3. ONE OUTDOOR OPENING requires:
a. 1 square inch of free area per 3,000 Btuh (734
mm2/kW) for combined input of all gas appliances in
the space per Table 2 and
b. Not less than the sum of the areas of all vent connect-
ors in the space.
The opening shall commence within 12 in. (300 mm) of the
ceiling. Appliances in the space shall have clearances of at least 1
in. (25 mm) from the sides and back and 6 in. (150 mm) from the
front. The opening shall directly communicate with the outdoors
or shall communicate through a vertical or horizontal duct to the
outdoors or spaces (crawl or attic) that freely communicate with
the outdoors.
Indoor Combustion Air NFPA & AGA
Standard and Known--Air--Infiltration Rate Methods
Indoor air is permitted for combustion, ventilation, and dilution,
if the Standard or Known--Air--Infiltration Method is used.
CARBON MONOXIDE POISONING HAZARD
Failure to follow this warning could result in death and/or
personal injury.
Many homes require air to be supplied from outdoors for
furnace combustion, ventilation, and dilution of flue gases.
The furnace combustion air supply must be provided in
accordance with this instruction manual.
!
WARNING
Table 2—Minimum Free Area Required for Each Combustion Air Opening of Duct to Outdoors
FURNACE
INPUT
(BTUH)
TWO HORIZONTAL DUCTS SINGLE DUCT OR OPENING
TWO OPENINGS OR VERTICAL
DUCTS
(1 SQ. I N./2,000 BTUH)
(1,100 SQ. MM/KW)
(1 SQ. I N./3,000 BTUH)
(734 SQ. MM/KW)
(1 SQ. I N./4,000 BTUH)
(550 SQ. MM/KW)
Free Area of Open-
ing and Duct
Sq. In. (Sq. mm)
Round Duct
Dia.
In. (mm)
Free Area of Open-
ing and Duct
Sq. In. (Sq. mm)
Round Duct
Dia.
In. (mm)
Free Area of Open-
ing and Duct
Sq. In. (Sq. mm)
Round Duct
Dia.
In. (mm)
44,000 22 (14194) 6 (152) 14.7 (9484) 5 (127) 11 (7096) 4 (102)
66,000 33 (21290) 7 (178) 22.0 (14193) 6 (152) 16.5 (10645) 5 ( 127)
88,000 44 (28387) 8 (203) 29.3 (18903) 7 (178) 22 (14193) 6 (152)
110,000 55 (35484) 9 (229) 36.7 (23677) 7 (178) 27.5 (17742) 6 ( 152)
132,000 66 (42580) 10 (254) 44 .0 (28387) 8 (203) 33 (21290) 7 (178)
154,000 77 (49677) 10 (254) 51.3 (33096) 9 (229) 38.5 (24839) 8 (203)
EXAMPLES: Determining Free Area
FURNACE WATER HEATER TOTAL INPUT
110,000 + 30,000 = (140,000 divided by 4,000) = 35.0 Sq. In. for each two Vertical Ducts or Openings
66,000 + 40,000 = (106,000 divided by 3,000) = 35.3 Sq. In. for a Single Duct or Opening
88,000
+ 30,000 = (118,000 divided by 2,000) = 59.0 Sq. In. for each of two Horizontal Ducts
310AAV