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9
1 SQ IN .
PER
4000
BTUH*
DUCTS
TO
O UTDOORS
1 SQ IN.
PER 4000
BTUH*
C IRCULA TING
AIR DUCTS
VENT
THR OUGH
R OOF
D
B
A
C
E
1 SQ IN.
PER 4000
BTUH*
DUCT
TO
OUTDOORS
CIRCULA TING AIR DUCT S
1 SQ IN.
PER 2000
BTUH*
1 SQ IN.
PER 2000
BTUH*
DUCT S
TO
OUTDOORS
12 ″ MAX
12 ″ MAX
12 ″ MAX
12 ″
MAX
12 ″
MAX
OUTDOORS
1 SQ IN .
PER
4000
BTUH*
F
G
CLEARANCE IN FRONT
OF COMB USTION AIR
OPENINGS SHALL BE
AT LEAST 3 IN .
(305mm)
(305mm)
(305mm)
(305mm)
(305mm)
(76mm)
*Minimum dimensions of 3---in. (76 mm).
NOTE: Use any of the following combinations of openings:
A&BC&DD&EF&G
A03174
Fig. 7 -- Air for Combustion, Ventilation, and Dilution for
Outdoors
S Spaces having at least 50 cubic feet 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. (645
sq. mm) 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. (645 sq. mm) 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 sq. in. (645 sq. mm) of free area per 3,000 Btuh
(734 mm
2
/kW) for combined input of all gas appli-
ances in the space per Table 2 and
b. Not less than the sum of the areas of all vent connect-
ors in the space.
CIRCULATING AIR
DUCTS
6" MIN
(FRONT)
Ü
CIRCULATING AIR DUCTS
VENT THROUGH ROOF
1 SQ IN.
PER 1000
BTUH* IN DOOR
OR WALL
12" MAX
1 SQ IN.
PER 1000
BTUH* IN DOOR
OR WALL
12" MA X
UNCONFINED
SPACE
INTERIOR
HEATED
SPACE
CLEARANCE IN FRONT OF COMBUSTION AIR
OPENINGS SHALL BE AT LEAST 3 IN.
(305mm)
(152mm)
(305mm)
* Minimum opening size is 100 sq in. (64516 sq. mm)with minimum dimensions
of3in.(76mm)
†Minimumof3in.(76mm)whentype-B1ventisused.
A03175
Fig. 8 -- Air for Combustion, Ventilation, and Dilution from
Indoors
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 AirE 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 personal
injury or death.
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
The Standard Method:
1. The space has no less volume than 50 cubic feet per 1,000
Btuh of the maximum input ratings for all gas appliances
installed in the space and
2. The air infiltration rate is not known to be less than 0.40
air changes per hour (ACH).
The Known Air Infiltration Rate Method shall be used, if the
infiltration rate is known to be:
1. Less than 0.40 ACH and
2. Equal to or greater than 0.10 ACH
315AAV