8
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
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 A
T LEAST 3 IN.
(305mm)
(152mm)
(305mm)
*Minimum opening size is 100 in.
2
with minimum dimensions of 3 in. (76 mm).
*Minimum of 3 in. (76 mm), when type ---B1 vent is used.
A03175
Fig. 8 -- Air for Combustion, Ventilation, and Dilution from
Indoors
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 minimum
required volume for the space.
Table 3 -- Minimum Space Volumes
were determined by using
the following equations from the current edition of National Fuel
Gas Code ANSI Z223.1/NFPA 54, 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:
I
other
= combined input of all other than fan--assisted appliances
in Btuh/hr
I
fan
= 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 ceil-
ing and the second opening shall commence within 12”
(300 mm) of the floor. The minimum dimension of air
openings shall be at least 3 in. (80 mm). (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 per-
manent openings in doors or floors having free area of
at least 2 in.
2
/1,000 Btuh (4,400 mm
2
/kW) of total input
rating of all gas appliances.
2. An attic or crawlspace may be considered a space that
freely communicates with the outdoors provided there are
adequate permanent ventilation openings directly to out-
doors having free area of at least 1--in.
2
/4,000 Btuh of total
input rating for all gas appliances in the space.
3. In spaces that use the Indoor
Combustion Air Method
,
infiltration should be adequate to provide air for combus-
tion, permanent ventilation and dilution of flue gases.
However, in buildings with unusually tight construction,
additional air MUST be provided using the methods de-
scribed in the
Outdoor Combustion Air
Method section.
Unusually tight construction is defined as construction with:
a. Walls and ceilings exposed to the outdoors have a contin-
uous, sealed vapor barrier. Openings are gasketed or
sealed and
b. Doors and openable windows are weatherstripped and
c. Other openings are caulked or sealed. These include
joints around window and door frames, between sole
plates and floors, between wall--ceiling joints, between
wall panels, at penetrations for plumbing, electrical and
gas lines, etc.
Combination of Indoor and Outdoor Air
1. Indoor openings shall comply with the Indoor
Combustion Air Method below and,
2. Outdoor openings shall be located as required in the
Outdoor Combustion
Air Method mentioned previously
and,
3. Outdoor openings shall be sized as follows:
a. Calculate the Ratio of all Indoor Space volume divided
by required volume for
Indoor Combustion Air
Method below.
