a.OneopeningMUST commence within 12-in. (300 ram)
of the ceiling and the second opening MUST commence
within 12-in. (300 ram) of the floor.
b. Size openings and ducts per Fig. 7 and Table 2.
c. TWO HORIZONTAL DUCTS require 1 square inch of
free area per 2,000 Btuh (1,100 mm2/kW) of combined
input for all gas appliances in the space per Fig. 7 and
Table 2.
d. TWO OPENINGS OR VERTICAL DUCTS require 1
square inch of free area per 4,000 Btuh (550 mm2/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 connectors
in the space.
The opening shall commence within 12" (300 ram) of the ceiling.
Appliances in the space shall have clearances of at least 1" (25
ram) from the sides and back and 6" (150 ram) from the front.
The opening shall directly conmmnicate with the outdoors or
shall conmmnicate through a vertical or horizontal duct to the
outdoors or spaces (crawl or attic) that freely communicate with
the outdoors.
TO
OUTDOORS
1 SQ IN.
PER 4000
BTUH*
(305mm)12"MAXI /
1sQ_a. _1:/
PER2000 I:IB
BTUi*
iiiiiiii_i
DUT%TS
OUTiOORS
1SQIN. I:::l I
PER 2000 & I:IAI
BTUH* f
305mm 12"MAX |
i,
CIRCULATING AIR DUCTS
12" MAX
(305mm)
12_X (305mm)
SQ IN.
PER
4000
BTUH*
03
rr
O
O
C3
F-
O
SQ IN.
PER
4000
BTUH*
12" (305ram)
MAX
1 SQ IN.
TO PER 4000
OUTDOORS BTUH*
*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
Fig. 7 - Air for Combustion, Ventilation, and Dilution from
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 iniury.
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.
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
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 n_ininmm
required volume for the space.
Table 3-Minimum Space Volumes were determined by using
the following equations from the National Fuel Gas Code ANSI
Z223.1-2006/NFPA 54-2006, 9.3.2.2:
1. For other than fan-assisted appliances, such as a draft
hood-equipped water heater:
Vo'" m e Other: A"_'O_ Q 00_ "a-_/h r")
2. For fan-assisted appliances such as this furnace:
_]
V°lumeFan : ACH _000 Btu/hr 3
A04002
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 closable doors between rooms.
b. Combining spaces on same floor level. Each opening
shall have free area of at least 1 in.2/l,000 Btuh (2,000
mm2/kW) of the total input rating of all gas appliances
in the space, but not less than 100 in. 2 (0.06 m2). One
opening shall commence within 12" (300 ram) of the
ceiling and the second opening shall commence within
12" (300 ram) of the floor. The n_ininmm dimension of
air openings shall be at least 3 in. (80 ram). (See Fig. 8.)
c. Combining space on different floor levels. The volumes
of spaces on different floor levels shall be considered as
communicating spaces if connected by one or more
permanent openings in doors or floors having free area
il
To Next Page
Loading...
Need help?
General