8
!
WARNING
CARBON MONOXIDE POISONING HAZARD
Failure to follow this warning could result in personal injury
or death.
The operation of exhaust fans, kitchen ventilation fans,
clothes dryers, attic exhaust fans or fireplaces could create a
NEGATIVE PRESSURE CONDITION at the furnace.
Make−up air MUST be provided for the ventilation devices,
in addition to that required by the furnace. Refer to Carbon
Monoxide Poisoning Hazard warning in venting section of
these instructions to determine if an adequate amount of
make−up air is available.
The requirements for combustion and ventilation air depend upon
whether or not the furnace is located in a space having a volume
of at least 50 cubic feet per 1,000 Btuh input rating for all gas
appliances installed in the space.
S Spaces having less than 50 cubic feet per 1,000 Btuh
require the OUTDOOR COMBUSTION AIR
METHOD.
S Spaces having at least 50 cubic feet per 1,000 Btuh
may use the INDOOR COMBUSTION AIR,
STANDARD or KNOWN AIR INFILTRATION
METHOD.
Outdoor Combustion Air Method
1. Provide the space with sufficient air for proper
combustion, ventilation, and dilution of flue gases using
permanent horizontal or vertical duct(s) or opening(s)
directly communicating with the outdoors or spaces that
freely communicate with the outdoors.
2. Fig. 7 illustrates how to provide TWO OUTDOOR
OPENINGS, one inlet and one outlet combustion and
ventilation air opening, to the outdoors.
a. One opening MUST commence within 12−in. (300 mm)
of the ceiling and the second opening MUST commence
within 12−in. (300 mm) of the floor.
b. Size openings and ducts per Fig. 7 and Table 2.
1 SQ IN .
PER
4000
BTUH*
DUCTS
TO
O UTDOORS
1 SQ IN.
PER 4000
BTUH*
C IRCULA TING
AIR DUCTS
VENT
THR OUGH
R OOF
D
B
A
C
E
1 SQ IN.
PER 4000
BTUH*
DUCT
TO
OUTDOORS
CIRCULA TING AIR DUCT S
1 SQ IN.
PER 2000
BTUH*
1 SQ IN.
PER 2000
BTUH*
DUCT S
TO
OUTDOORS
12 ″ MAX
12 ″ MAX
12 ″ MAX
12 ″
MAX
12 ″
MAX
OUTDOORS
1 SQ IN .
PER
4000
BTUH*
F
G
CLEARANCE IN FRONT
OF COMB USTION AIR
OPENINGS SHALL BE
AT LEAST 3 IN .
(305mm)
(305mm)
(305mm)
(305mm)
(305mm)
(76mm)
*Minimum dimensions of 3 in. (76 mm).
NOTE: Use any of the following combinations of openings:
A&B, C&D, D&E, F&G
A03174
Fig. 7 − Air for Combustion, Ventilation, and Dilution from
Outdoors
c. TWO HORIZONTAL DUCTS require 1 square inch of
free area per 2,000 Btuh (1,100 mm
2
/kW) of combined
input for all gas appliances in the space per Fig. 7 and
Table 2.
d. TWO OPENINGS OR VERTICAL DUCTS require 1
square inch of free area per 4,000 Btuh (550 mm
2
/kW)
for combined input of all gas appliances in the space per
Fig. 7 and Table 2.
3. ONE OUTDOOR OPENING requires:
a. 1 square inch of free area per 3,000 Btuh (734 mm
2
/kW)
for combined input of all gas appliances in the space per
Table 2 and
b. Not less than the sum of the areas of all vent connectors
in the space.
The opening shall commence within 12” (300 mm) of the ceiling.
Appliances in the space shall have clearances of at least 1” (25
mm) from the sides and back and 6” (150 mm) from the front.
The opening shall directly communicate with the outdoors or
shall communicate through a vertical or horizontal duct to the
outdoors or spaces (crawl or attic) that freely communicate with
the outdoors.
Indoor Combustion Air − NFPA & AGA
Standard and Known−Air−Infiltration Rate Methods
Indoor air is permitted for combustion, ventilation, and dilution,
if the Standard or Known−Air−Infiltration Method is used.
CARBON MONOXIDE POISONING HAZARD
Failure to follow this warning could result in death and/or
personal injury.
Many homes require air to be supplied from outdoors for
furnace combustion, ventilation, and dilution of flue gases.
The furnace combustion air supply must be provided in
accordance with this instruction manual.
!
WARNING
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 -B1 vent is used.
A03175
Fig. 8 − Air for Combustion, Ventilation, and Dilution from
Indoors
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