9
441 01 1411 04
Specifications are subject to change without notice.
c. TWO HORIZONTAL DUCTS require 1 square inch of
free area per 2,000 Btuh (1,100 mm
2
/kW) of combined
input for all gas appliances in the space per Figure 7
and Table 2.
d. TWO OPENINGS OR VERTICAL DUCTS require 1
square inch of free area per 4,000 Btuh (550 mm
2
/kW)
for combined input of all gas appliances in the space
per Figure 7 and Table 2.
3. ONE OUTDOOR OPENING requires:
a. 1 square inch of free area per 3,000 Btuh (734
mm
2
/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” (300 mm) of the
ceiling. Appliances in the space shall have clearances of at
least 1” (25 mm) from the sides and back and 6” (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.
Figure 7
−
Air for Combustion, Ventilation, and Dilution
from Outdoors
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&B, C&D, D&E, F&G
A03174
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
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 ap-
pliances 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
Infiltration rates greater than 0.60 ACH shall not be used. The
minimum required volume of the space varies with the
number of ACH and shall be determined per Table 3 or
Equations 1 and 2. Determine the minimum required volume
for each appliance in the space and add the volumes
together to get the total minimum required volume for the
space.
Table 3
−
Minimum Space Volumes
were determined by
using the following equations from the National Fuel Gas
Code ANSI Z223.1
−
2012/NFPA 54
−
2012, 9.3.2.2:
1. For
other than fan
−
assisted appliances
, such as a
draft hood
−
equipped water heater:
Volume
Other
= 21ft
3
ACH
I
other
1000 Btu/hr
A04002
2. For
fan
−
assisted appliances
such as this furnace:
Volume
Fan
= 15ft
3
ACH
I
fan
1000 Btu/hr
A004003
If:
Iother = combined input of all other than fan
−
assisted
appliances
in Btuh/hr
Ifan = combined input of all fan
−
assisted appliances in
Btuh/hr
ACH = air changes per hour (ACH shall not exceed 0.60.)
The following requirements apply to the Standard Method
and to the Known Air Infiltration Rate Method.
1. Adjoining rooms can be considered part of a space if:
a. There are no closeable doors between rooms.
b. Combining spaces on same floor level. Each opening
shall have free area of at least 1 in.
2
/1,000 Btuh (2,000
mm
2
/kW) of the total input rating of all gas appliances
in the space, but not less than 100 in.
2
(0.06 m
2
). One
opening shall commence within 12” (300 mm) of the
ceiling and the second opening shall commence with-