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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 out-
doors having free area of at least 1−in.
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, ad-
ditional 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
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−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 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 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.
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 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 Figure 9)
2. 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.
10
2
/1,000 Btuh
2
/4,000 Btuh of total
Specifications are subject to change without notice.
Figure 9 − Removing Bottom Closure Panel
BOTTOM
CLOSURE
PANEL
BOTTOM
FILLER 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 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 in Step 1
above.
To install leveling legs:
1. Position furnace on its back. Locate and drill a hole in each
bottom corner of furnace. (See Figure 10)
Figure 10 − Leveling Legs
5/ 16
"
(8mm)
1
3
/
"
4
(44mm)
(8mm)
5
/
"
16
(44mm)
1
3/ 4
"
1
(44mm)
2. For each leg, install nut on bolt and then install bolt with
nut in hole. (Install flat washer if desired.)
3. Install another nut on other side of furnace base. (Install
flat washer if desired.)
4. Adjust outside nut to provide desired height, and tighten
inside nut to secure arrangement.
(8mm)
5/ 16
"
1
3
/
"
4
(44mm)
(8mm)
5/ 16
"
3/ 4
"
441 01 2122 01
A89014
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