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2. If combustion air is taken from outdoors through horizontal
ducts, the openings and ducts MUST have at least 1 sq in.
of free area per 2000 Btuh of the total input for all
equipment within the confined space. (See Fig. 13.)
3. When ducts are used, they must be of the same cross-
sectional area as the free area of the openings to which they
connect. The minimum dimension of ducts must not be less
than 3 in. (See Fig. 13.)
INSTALLATION
I. LEVELING LEGS (IF DESIRED)
When furnace is used in upflow position with side inlet(s), leveling
legs may be desired. (See Fig. 14.) Install field-supplied,
corrosion-resistant 5/16-in. machine bolts and nuts.
NOTE: The maximum length of bolt should not exceed 1-1/2 in.
1. Position furnace on its back. Locate and drill a 5/16-in.
diameter hole in each bottom corner of furnace. (See Fig.
14.) Holes in bottom closure panel may be used as guide
locations.
2. For each hole, install nut on bolt and then install bolt and
nut in hole. (Install flat washer if desired.)
Fig. 12—Confined Space: Air for Combustion and
Ventilation from an Unconfined Space
A96185
SUPPLY
AIR
3″ MIN
(FRONT)
RETURN AIR
VENT THROUGH ROOF
OR SIDEWALL
1 SQ IN.
PER 1000
BTUH
*
IN DOOR
OR WALL
12″ MAX
1 SQ IN.
PER 1000
BTUH
*
IN DOOR
OR WALL
12″ MAX
INTERIOR
HEATED
SPACE
* Minimum opening size is 100 sq. in. with
minimum dimensions of 3-In.
NOTE:
UNCONFINED
SPACE
CONFINED
SPACE
Side clearance required as needed for
combustion-air pipe and termination,
vent pipe, and gas and electrical connections.
Fig. 13—Confined Space: Air for Combustion and
Ventilation from Outdoors
A96186
DUCTS
TO
OUTDOORS
1 SQ IN.
PER 4000
BTUH
*
SUPPLY
AIR
VENT
THROUGH
ROOF
D
B
A
C
E
1 SQ IN.
PER 4000
BTUH
*
DUCT
TO
OUTDOORS
RETURN AIR
1 SQ IN.
PER 2000
BTUH
*
1 SQ IN.
PER 2000
BTUH
*
DUCTS
TO
OUTDOORS
12″ MAX
12
″ MAX
12″ MAX
1. Use any of the following
combinations of openings:
A & B C & D D & E F & G
2. Side clearance required as needed for
combustion-air pipe and termination,
vent pipe, and gas and electrical connections.
NOTES:
*
Minimum dimensions of 3-In.
CONFINED
SPACE
12″
MAX
12″
MAX
OUTDOORS
1 SQ IN.
PER 4000
BTUH
*
F
G
1 SQ IN.
PER 4000
BTUH
*
OR
SIDEWALL
For Example:
COMBUSTION AIR FROM OUTDOORS THROUGH
VERTICAL DUCTS
345MAV Furnace
Input Btuh
Free Area per Opening
(Sq In.)
Round Pipe
(In. Dia)
40,000 10.0 4
60,000 15.0 5
80,000 20.0 6
100,000 25.0 6
120,000 30.0 7
For Example:
COMBUSTION AIR FROM OUTDOORS THROUGH
HORIZONTAL DUCTS
345MAV Furnace
Input Btuh
Free Area per Opening
(Sq In.)
Round Pipe
(In. Dia)
40,000 20.0 6
60,000 30.0 7
80,000 40.0 8
100,000 50.0 8
120,000 60.0 9
—14—