18
Combustion Air
COMBUSTION AND VENTILATION AIR (cont.)
It is also acceptable to run the condensate drain (or refrig-
erant) line access over the air intake hole as long as a 1”
minimum clearance is maintained.
Combustion air openings must not be restricted in any manner.
IMPORTANT: When indoor combustion air is used, the inlet
air opening at the furnace must be protected from accidental
blockage.
IMPORTANT: If the furnace is in a location with an exhaust fan,
there must be sufficient ventilation to prevent the exhaust fan
from creating a negative pressure in the room.
Combustion air openings must NOT BE RESTRICTED in any
manner.
CONSULT LOCAL CODES FOR SPECIAL REQUIREMENTS.
B: Method 3
For the optimum in quiet operation, attic air may be brought di-
rectly to the furnace.
IMPORTANT: In applications using Method 3 for combustion air,
the attic must be ventilated by gable or soffit vents.
COMBUSTION AIR FROM ATTIC
If attic combustion air is used, the inlet air opening at the fur-
nace must be protected from accidental blockage. Install a 90°
elbow pointing horizontally at the top of inlet air pipe. See Figure
14 (maximum of 2, 45° or 90° elbows, allowed).
NOTE: Maximum length of pipe that may be used for combus-
tion air is 10 feet with two elbows. Lengths of more than 10 feet
can result in nuisance pressure switch trips.
!
CAUTION
COMBUSTION AIR INTAKES CANNOT BE TERMINATED
OUTSIDE. DOING SO CAN CAUSE IMPROPER OPERA-
TION OF THE FURNACE.
INCLUDING
HORIZONTAL DIRECTION
ATTACH A 90° ELBOW TO TOP INLET AIR
OPENING TO PREVENT ACCIDENTAL BLOCKAGE
OF INTAKE OPENING.
PVC
ELBOW
#8 SCREWS
#8 SCREW
METAL FLUE PIPE ONLY
10 FT. MAX.
12” MIN. FROM
TOP OF INSULATION
6” MINIMUM
CLEARANCE
PVC
COUPLER
EXHAUST
ATTIC SPACE
INDOOR SPACE
INSULATION
FIGURE 14
COMBUSTION AIR FITTING – OPTIONAL ATTIC COMBUSTION AIR PULL
CAUTION
!
USE OF SHEET METAL
AIR INTAKE PIPE INSTEAD
OF PVC MAY RESULT IN
NOISE ISSUES.
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