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From an operational standpoint, incorrect or inadequate exhausting can cause a
cycling of the high limit thermostat, which shuts off the heating elements and results in
inefficient drying.
The exhaust duct connection near the top of the dryer will accept an 8 in. (200 mm)
round duct. Individual exhausting of the dryers is recommended. A pipe of the proper
diameter should be attached to the dryer adapter collar and extended out through an
outside wall to exhaust all heat, moisture, and lint outside. This pipe must be very
smooth on the inside, as rough surfaces tend to collect lint, which will eventually clog
the duct and prevent the dryer from exhausting properly. All elbows must be smooth
on the inside. All joints must be made so the exhaust end of one pipe is inside the next
one downstream. The addition of an exhaust pipe tends to reduce the amount of air
the blower can exhaust. This does not affect the dryer operation if held within practical
limits. For the most efficient operation, it is recommended that no more than 14 ft.
(4.25 m) of straight 8 in. (200 mm) diameter pipe is used with two right angle elbows.
The design of the vent system shall be such that any condensate formed when
operating the dryer from cold shall either be retained and re-evaporated or discharged.
Maintain a minimum of 1” (25mm) clearance between duct and combustible material.
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 provided 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 in. (610 mm), of any objects, which would cause 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. The exhaust
air should not be vented into a wall, a ceiling, or a concealed space of building. In
these cases, there is a danger of lint buildup, which can be highly combustible.
Installation of several dryers, where a main discharge duct is necessary, will need the
following considerations for installation (see Figure 3). Individual ducts from the dryers
into the main discharge duct should be at a 45-degree angle in the direction of
discharge airflow.
NOTE: Never install the individual 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. Figure 3 indicates the various round main duct diameters to use with
