Allied Air A97USMV Installation Instructions Manual page 15

EXHAUST PIPE
Horizontal Application
NOTE: All horizontal runs of exhaust pipe must slope back toward unit.
A minimum of 1/4" (6 mm) drop for each 12" (305 mm) of horizontal
run is mandatory for drainage.
NOTE: Exhaust pipe MUST be glued to furnace exhaust fittings.
NOTE: Exhaust piping should be checked carefully to make sure
there are no sags or low spots.
Figure 16
NOTE: The exhaust collar on all models is sized to
accommodate 2" Schedule 40 vent pipe. In horizontal
applications, transition to exhaust pipe larger than 2" must
be made in vertical runs of the pipe. A 2" elbow must be
added before the pipe is transitioned to any size larger than
2". This elbow must be added to the elbow count used
to determine acceptable vent lengths. Contact Allied Air
Technical Service for more information concerning sizing
of vent systems which include multiple pipe sizes.
IMPORTANT
Do not use screens or perforated metal in exhaust or
intake terminations. Doing so will cause freeze-ups and
may block the terminations.
MINIMUM VENT PIPE LENGTHS
* Any approved termination may be added to the minimum equivalent
length listed.
507028-03
Table 4
Issue 1622
Figure 17
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