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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
£223.1-2009/NFPA 54-2009, 9.3.2.2:
1. For other than fan-assisted
appliances,
such
as a draft
hood-equipped water heater:
|
Volume
= 217% )___" other__
Othe
ACH
11000
Btu/hr
Ao4002
2. For fan-assisted appliances such as this furnace:
|
Volume
— A5ft%)__ fan
Fan
ACH
|1000
Btu/hr
A04008
If: Iother
=
combined
input
of
ail
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 shail 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
mm2/kW) of the total input rating of all gas appliances
in the space, but not less than 100 in.? (0.06 m2), One
opening shall commence within 12 in. (300 mm) of
the ceiling and the second opening shall commence
within 12 in. (300 mm) of the floor. The minimum
dimension of air openings shall be af 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 permanent 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.
. 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.
4. Unusually
tight construction is defined
as Construction
with:
a. Walls and ceilings exposed to the outdoors have a con-
tinuous, 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
wail panels, at penetrations for plumbing, electrical
and gas lines, etc.
Combination of Indoor and Outdoor Air
1. Indoor openings shall comply with the Indoor Combus-
tion Air Method below and,
2. Outdoor openings shall be located as required in the Out-
door Combustion Air Method mentioned previously and,
3. Outdoor openings shail be sized as follows:
a. Calculate the Ratio of all Indoor Space volume divided
by required volume for Indoor Combustion Air
Method below.
b. Outdoor opening size reduction Factor is 1 minus the
Ratio in a. above.
c. Minimum size of Outdoor openings shail be the size
required in Outdoor Combustion Air Method above
multiplied by reduction Factor in b. above. The min-
imum dimension of air openings shall be not less than
3 in. (80 mm).
INSTALLATION
UPFLOW INSTALLATION
Bottom Return Air Inlet
These furnaces are shipped with bottom closure panel installed in
bottom return-air opening. Remove and discard this panel when
bottom
return
air is used.
To
remove
bottom
closure
panel,
perform the following:
1. Tilt or raise furnace and remove 2 screws holding bottom
filler panel. (See Fig. 9.)
. Rotate bottom filler panel downward
to release holding
tabs.
3. Remove bottom closure panel.
4. Reinstall bottom filler panel and screws.
Side Return Air Inlet
These furnaces are shipped with bottom closure panel installed in
bottom return-air opening. This panel MUST
be in place when
only side return air is used.
Bottom
Closure Panel
Bottom Filler Panel
A10278
Fig. 9 - Removing Bottom Closure Panel
NOTE:
Side return-air openings can be used in UPFLOW
and
most HORIZONTAL
configurations. Do not use side return-air
openings in DOWNFLOW
configuration.
Leveling
Legs
(If Desired
In upfiow position with side return inlet(s), leveling legs may be
used, (See Fig. 10.) Install field-supplied, 5/16 X 1-1/2 in. (8 X
38 mm)
(max) corrosion-resistant machine bolts, washers and
nuts.
10
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