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RETURN
AIR
INTERIOR
HEATED
SPACE
SUPPLY AIR
* Minimum opening size is 100 sq in. with
minimum dimensions of 3 in.
†
Minimum of 3 in. when type B-1 vent is used.
Fig. 3—Confined Space: Air for Combustion and Ventilation
from an Unconfined Indoor Space
AIR FROM INDOOR
373LAV
UNCONFINED SPACE
FURNACE
Free Area
INPUT
of Opening
(BTUH)
(Sq In.)
46,000
100
69,000
100
92,000
100
115,000
115
135,000
135
* Free area shall be equal to or greater than the sum of the areas of all vent connections in the confined space. Opening area must be increased, if other gas appliances
in the space require combustion air.
III. SUPPLY AIR CONNECTIONS
A. Downflow Furnaces
Connect supply-air duct to supply-air opening (outlet) on furnace.
(See Fig. 1.) The supply-air duct attachment must ONLY be
connected to furnace supply/outlet or air conditioning coil casing
(when used), when installed on non-combustible material. When
installed on combustible material, supply-air duct attachment must
ONLY be connected to an accessory subbase or factory approved
air conditioning coil casing. DO NOT cut main furnace casing to
attach supply side air duct, humidifier, or other accessories. All
accessories MUST be connected external to furnace main casing.
B. Horizontal Furnaces
Connect supply-air duct to supply-air (outlet) opening on furnace.
(See Fig. 1.) The supply-air duct attachment must ONLY be
connected to furnace supply/outlet or air conditioning coil casing
VENT THROUGH ROOF
(CATEGORY I)
12" MAX
1 SQ IN.
PER 1000
BTUH * IN DOOR
OR WALL
UNCONFINED
SPACE
6 " MIN
†
(FRONT)
1 SQ IN.
PER 1000
BTUH * IN DOOR
OR WALL
12" MAX
A93387
TABLE 2—MINIMUM FREE AREA OF COMBUSTION AIR OPENING*
OUTDOOR AIR THROUGH
VERTICAL DUCTS
Free Area of
Opening and Duct
(Sq In.)
11.50
17.25
23.00
28.75
33.75
DUCTS TO
OUTDOORS
12 " MAX
1 SQ IN.
PER 2000
BTUH *
DUCTS
TO
OUTSIDE
1 SQ IN.
PER 2000
BTUH *
12 " MAX
SUPPLY AIR
* Minimum dimensions of 3 in.
NOTE:
Use any of the following
combinations of openings:
A & B
Fig. 4—Confined Space: Air for Combustion and Ventilation
OUTDOOR AIR THROUGH
HORIZONTAL DUCTS
Round
Free Area of
Pipe
Opening and Duct
(In. Dia)
(Sq In.)
4
23.0
5
34.5
6
46.0
7
57.5
7
67.5
(when used). DO NOT cut main furnace casing to attach supply
side air duct, humidifier, or other accessories. All accessories
MUST be connected external to furnace main casing.
IV. RETURN AIR CONNECTIONS
The return-air duct must be connected to return-air opening (inlet)
provided as shown in Fig. 1. DO NOT cut into casing sides or back
to attach any portion of return-air duct. Bypass humidifier connec-
tions should be made at ductwork or coil casing sides exterior to
furnace.
V. DOWNFLOW INSTALLATION
NOTE: This furnace is approved for use on combustible materials
or wood flooring. A factory accessory floor base, as listed on the
furnace rating plate, MUST be used. A factory accessory floor
base is not required when this furnace is installed on manufactur-
er's Coil Assembly Part No. CD5 or CK5, or Coil Box Part No.
KCAKC is used.
—6—
D
RETURN
A
VENT
AIR
F
THROUGH
ROOF
(CATEGORY I)
G
E
B
C
12 " MAX
DUCT
1 SQ IN.
TO
PER 4000
OUTDOORS
BTUH
C & D
D & E
F & G
from Outdoors
OUTDOOR AIR THROUGH
SINGLE DUCT
Round
Free Area of
Pipe
Opening and Duct
(In. Dia)
(Sq In.)
6
15.33
7
23.00
8
30.67
9
38.33
10
45.00
1 SQ IN.
PER 4000
BTUH
*
12"
MAX
1 SQ IN.
PER 4000
BTUH
*
OUTDOORS
1 SQ IN.
PER 4000
BTUH
*
12"
MAX
A93388
Round
Pipe
(In. Dia)
5
6
7
7
8
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