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PIPE SIZE
NUMBER OF 90° ELBOWS
MAXIMUM ALLOWABLE
STRAIGHT LENGTH OF EXHAUST OR INTAKE
2
3
2
3
2
3
2
3
0123456
S - 24” for Service
C - Combustible floor but not carpet or non-ceramic tile
NC - Non-combustible floor or use base kit #30476
MODEL
054
072
090
108
ALL DIMENSIONS IN INCES
70
150
65
140
60
130
55
120
50
110
45
100
40
90
65
140
60
130
55
120
50
110
45
100
40
90
65
140
60
130
55
120
50
110
45
100
40
90
65
140
60
130
55
120
50
110
45
100
40
90
70
150
70
150
70
150
TABLE 4:
VENT LENGTHS- DIRECT/NON-DIRECT VENT LENGTHS
• Count concentric vent fitting as straight pipe.
•
Use medium or long sweep elbows where possible.
•
One 90
°
elbow is equivalent to two 45
°
elbows.
• For direct vent, the above is the length allowed for
each vent (intake and exhaust)
• For non-direct vent, the above is length allowed
for exhaust. The intake should have a two inch
upside down “U” intake installed on the cabinet
intake fitting.
WARNING
DO NOT CONNECT FURNACE TO A CHIMNEY OR FLUE
SERVING OTHER APPLIANCES OR A SOLID FUEL BURN-
ING APPLIANCE.
Recommended clearance for overhangs is a minimum of 1
foot vertically for each foot horizontally up to 6 feet.
As a protection against freezing, do not expose a 3 x 2
reducing coupling to outdoor ambient temperatures.
Any adjacent painted surfaces should be in good condition;
no cracks, peeling paint, etc. If wooden surfaces that may
be periodically exposed to flue gases are present, consider
treating with a sealer.
Calculating Piping Length
When calculating allowable vent lengths, be sure to count
all termination fittings in addition to counting the
concentric vent as a straight pipe. The ventilation pipe
extending through the roof must extend 18” above the
highest point where it extends through the roof, surface
and above any obstruction within an 18” horizontal
distance. The ventilation pipe must extend a minimum of
12” above the anticipated snow level.
Exterior vent pipe greater than 24” should be insulated
with 1/2” insulation to prevent moisture from freezing
within the pipe and accumulating.
Size the ventilation pipe as specified in Table 4 - Direct and
Non-Direct Vent Lengths. This table lists the maximum
allowable length of pipe with respect to the number of 90°
elbows used. For the purposes of this calculation, one 90°
elbow is equivalent to two 45° elbows.
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