Page 18
Use the following steps to correctly size vent pipe diam-
eter.
Piping Size Process
1
2
3
4
5
6
Which style termination
being used?
Standard or
concentric?.
Which needs
most elbows?
Intake or
exhaust?
How many elbows?
Count all elbows inside
and outside house.
Desired pipe size?
Find max intake or
exhaust pipe length.
Includes all vent pipe and
elbows inside and outside
the house.
What is the altitude of
the furnace installation?
7
What is the
furnace capacity?
Figure 24
IMPORTANT
Do not use screens or perforated metal in exhaust or
intake terminations. Doing so will cause freeze-ups and
may block the terminations.
TABLE 4
MINIMUM VENT PIPE LENGTHS
ML196UHE Model MIN. VENT LENGTH*
030, 045, -070, -090, 110, 135
15 ft. or 5 ft. plus 2 elbows
or 10 ft. plus 1 elbow
*Any approved termination may be added to the minimum
length listed. Two 45 degree elbows are the equivalent of one
90 degree elbow.
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