Bryant 373LAV - Manual (Page 6)

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.
1. Determine application being installed from Table 3.
2. Construct hole 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
WARNING: DO NOT install the furnace on its back;
safety control operation will be adversely affected. Never
connect return-air ducts to the sides or back of the
furnace. Failure to follow this warning could result in fire,
personal injury, or death.
The furnace can be installed horizontally on either the left-hand
(LH) or right-hand (RH) side. A typical attic installation is shown
in Fig. 8.
Fig. 3—Confined Space: Air for Combustion and Ventilation
from an Unconfined Indoor Space
A93387
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
Fig. 4—Confined Space: Air for Combustion and Ventilation
from Outdoors
A93388
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
→
TABLE 2—MINIMUM FREE AREA OF COMBUSTION AIR OPENING*
373LAV
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 connections in the confined space. Opening area must be increased, if other gas appliances
in the space require combustion air.
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