IV.
RETURN AIR CONNECTIONS
The return-air duct must be connected to return air opening as
shown in Fig. 1. DO NOT cut into casing sides or back to attach
any portion of return-air duct. Bypass humidifier connections
should be made at ductwork or coil casing sides exterior to
furnace.
WARNING:
Do not install furnace on its back. Safety
control operation will be adversely affected. Never con-
nect return-air ducts to back of furnace. Failure to follow
this warning could result in fire, personal injury, or death.
V.
DOWNFLOW INSTALLATION
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 manufacturer’s Coil
Assembly Part No. CD5 or CK5, or when Coil Box Part No.
KCAKC is used.
1. Determine application being installed from Table 3.
2. Construct hold in floor per dimensions specified in Table 3
and Fig. 5.
3. Construct plenum to dimensions specified in Table 3.
4. If downflow subbase (KGASB) is used, install as shown in
Fig. 6.
If coil assembly CD5, CK5 or Coil Box KCAKC is used,
install as shown in Fig. 7.
VI.
HORIZONTAL ATTIC INSTALLATION
The furnace can be installed on either the left-hand (LH) or
right-hand (RH) side. A typical attic installation is shown in Fig. 8.
RETURN
AIR
6
″
MIN
(FRONT)
†
SUPPLY AIR
VENT THROUGH ROOF
(CATEGORY I)
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.
†
Minimum of 3 in. when type B-1 vent is used.
UNCONFINED
SPACE
A93387
Fig. 3—Confined Space: Air for Combustion and Ventilation
from an Unconfined Indoor Space
DUCTS TO
OUTDOORS
1 SQ IN.
PER 4000
BTUH
*
RETURN
AIR
VENT
THROUGH
ROOF
(CATEGORY I)
D
B
A
C
E
1 SQ IN.
PER 4000
BTUH
DUCT
TO
OUTDOORS
SUPPLY AIR
1 SQ IN.
PER 2000
BTUH*
DUCTS
TO
OUTSIDE
12
″
MAX
12
″
MAX
CONFINED
SPACE
12
″
MAX
12
″
MAX
1 SQ IN.
PER 4000
BTUH
*
OUTDOORS
1 SQ IN.
PER 4000
BTUH
*
1 SQ IN.
PER 2000
BTUH*
12
″
MAX
Use any of the following
combinations of openings:
A & B C & D D & E F & G
NOTE:
*Minimum dimensions of 3 in.
F
G
A93388
Fig. 4—Confined Space: Air for Combustion and Ventilation
from Outdoors
TABLE 2—MINIMUM FREE AREA OF COMBUSTION AIR OPENING*
376CAV
FURNACE
INPUT
(BTUH)
AIR FROM INDOOR
UNCONFINED SPACE
OUTDOOR AIR THROUGH
VERTICAL DUCTS
OUTDOOR AIR THROUGH
HORIZONTAL DUCTS
OUTDOOR AIR THROUGH
SINGLE DUCT
Free Area
of Opening
(Sq. In.)
Free Area of
Opening and Duct
(Sq. In.)
Round
Pipe
(In. Dia.)
Free Area
of Opening and Duct
(Sq. In.)
Round
Pipe
(In. Dia)
Free Area
of Opening and Duct
(Sq. In.)
Round
Pipe
(In. Dia)
46,000
100
11.50
4
23.0
6
15.33
5
69,000
100
17.25
5
34.5
7
23.00
6
92,000
100
23.00
6
46.0
8
30.67
7
115,000
115
28.75
7
57.5
9
38.33
7
135,000
135
33.75
7
67.5
10
45.00
8
* Free area shall be equal to or greater than the sum of the areas of all vent connectors in the confined space. Opening area must be increased if other gas appliances in
the space require combustion air.
—6—
