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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 open-
ing shall have free area of at least 1 in.
2
(2,000 mm
/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 at
least 3 in. (80 mm). (See Figure 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
(4,400 mm
/kW) of total input rating of all gas appli-
ances.
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 outdoors having free area of at least 1−in.
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 com-
bustion, permanent ventilation and dilution of flue
gases. However, in buildings with unusually tight con-
struction, additional air MUST be provided using the
methods described 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
continuous, sealed vapor barrier. Openings are gas-
keted or sealed and
b. Doors and openable windows are weatherstripped
and
c. Other openings are caulked or sealed. These in-
clude joints around window and door frames,
between sole plates and floors, between wall−ceil-
ing 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 Com-
bustion Air Method below and,
2. Outdoor openings shall be located as required in the
Outdoor Combustion Air Method mentioned previ-
ously and,
3. Outdoor openings shall be sized as follows:
a. Calculate the Ratio of all Indoor Space volume di-
vided by required volume for Indoor Combustion
Air Method below.
b. Outdoor opening size reduction Factor is 1 minus
the Ratio in a. above.
10
UPFLOW INSTALLATION
Bottom Return Air Inlet
These furnaces are shipped with bottom closure panel
installed in bottom return−air opening. Remove and discard
2
/1,000 Btuh
this panel when bottom return air is used. To remove bottom
closure panel, perform the following:
2
2
/1,000 Btuh
BOTTOM
2
/4,000
CLOSURE
PANEL
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.
NOTE: Side return−air openings can be used in UPFLOW
and most HORIZONTAL configurations. Do not use side
return−air openings in DOWNFLOW configuration.
In upflow position with side return inlet(s), leveling legs may
be used. (See Figure 10) Install field−supplied, 5/16 x 1−1/2
in. (8 x 38 mm) (max) corrosion−resistant machine bolts,
washers and nuts.
NOTE: Bottom closure must be used when leveling legs are
used. It may be necessary to remove and reinstall bottom
closure panel to install leveling legs. To remove bottom
closure panel, see Item 1. in Bottom Return Air Inlet section.
c. Minimum size of Outdoor openings shall be the size
required in Outdoor Combustion Air Method
above multiplied by reduction Factor in b. above.
The minimum dimension of air openings shall be
not less than 3 in. (80 mm).
INSTALLATION
1. Tilt or raise furnace and remove 2 screws holding bot-
tom filler panel. (See Figure 9.)
Figure 9 - Removing Bottom Closure Panel
BOTTOM
FILLER PANEL
2. Rotate bottom filler panel downward to release holding
tabs.
3. Remove bottom closure panel.
4. Reinstall bottom filler panel and screws.
441 01 1402 02
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