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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
outdoors having free area of at least 1--in.
2
/4,000 Btuh of
total input rating forall gas appliances in the space.
3. In spaces that use the Indoor Combustion Air Method,
infiltration should be adequate to provide air for
combustion, permanent ventilation and dilution of flue
gases. However, in buildings with unusually tight
construction, 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. Openingsare gasketed
or sealed and
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 AT 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 ---B1vent isused.
A03175
Fig. 8 -- Air for Combustion, Ventilation, and Dilution from
Indoors
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, e tc.
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 menioned 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.
A02098
Fig. 9 -- Removing Bottom Closure Panel
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
multipliedbyreduction Factorinb.above.Theminimum
dimension of air openingsshall 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 two screws holding
bottom filler panel. (See Fig. 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.
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 Desir
ed)
In upflow 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.
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.
To install leveling legs:
1. Position furnace on its back. Locate and drill a hole in
each bottom corner of furnace. (See Fig. 10.)
2. For each leg, install nut on bolt and then install bolt and
nut in hole. (Install flat washer if desired.)
3. Install another nut on other side of furnace base. (Install
flat washer if desired.)
58PHA