Combustion Air
18
COMBUSTION AND VENTILATION AIR (cont.)
It is also acceptable to run the condensate drain (or refriger-
ant) line access over the air intake hole as long as a 1" mini-
mum 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 block-
age.
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 furnace
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 combustion
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.
CAUTION
!
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
USE OF SHEET METAL
AIR INTAKE PIPE INSTEAD
OF PVC MAY RESULT IN
NOISE ISSUES.
FIGURE 14
COMBUSTION AIR FITTING – OPTIONAL ATTIC COMBUSTION AIR PULL
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