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If the exhaust pipe passes through a wall, a metal sleeve of slightly larger diameter should be set
in the wall and the exhaust pipe passed through this sleeve. This practice is required by some local codes
and is recommended in all cases to protect the wall. This type of installation should have a means provid-
ed to prevent rain and high winds from entering the exhaust when the dryer is not in use. A hood with a
hinged damper can be used for this purpose. Another method would be to point the outlet end of the pipe
downward to prevent entrance of wind and rain. In either case, the outlet should be kept clear, by at least
24” (610), of any objects which would cause an air restriction.
Never install a protective screen over the exhaust outlet. When exhausting a dryer straight up
through a roof, the overall length of the duct has the same limits as exhausting through a wall. A rain cap
must be placed on top of the exhaust and must be of such a type as to be free from clogging. The type
using a cone shaped “roof” over the pipe is suitable for this application.
Exhausting the dryer into a chimney or under a building is not permitted. In either case there is a
danger of lint build-up which can be highly combustible.
Installation of several dryers, where a main discharge duct is necessary, will need the following
considerations for installation (see Fig. 2). Individual 8” (200mm) ducts from the dryers into the main
discharge duct should be at a 45 degree angle in the direction of discharge air ow.
NOTE: Never install the individual 8” ducts at a right angle into the main discharge duct. The
individual ducts from the dryers can enter at the sides or bottom of the main discharge duct. Fig ure 2
indicates the various round main duct diameter to use with the individual dryer ducts. The main duct can
be rectangular or round, provided adequate air ow is maintained. For each individual dryer, the total
exhausting (main discharge duct plus duct outlet from the dryer) should not exceed the equivalent of 20
feet (6m) and two elbows. The diameter of the main discharge duct at the last dryer must be maintained
to exhaust end.
NOTE: A small diameter duct will restrict air ow; a large diameter duct will reduce air velocity –
both contributing to lint build up. An inspection door should be provided for periodic clean-out of the main
duct.
NOTE: STATIC BACK PRESSURE should be a maximum of 0.3 in. w.c (7.6 mm w.c) at the rear
exhaust outlet of the dryer. If multiple dryers are connected to the common duct, ensure the back draft
damper is installed properly.
NOTE: The following illustration shows the various round main duct diameters to use with
the individual dryer ducts. The main duct can be rectangular or round, provided adequate air
ow is maintained. For each individual cylinder the total exhausting (main discharge duct plus
duct outlet from the dryer) should not exceed the equivalent of 14 feet and two elbows. The
diameter of the main discharge duct at the last dryer must be maintained to exhaust end.
Part # 8533-088-001 7/21
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