Dexter Laundry T-30 (On-Premise) - Manual (Page 9)

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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 20' (6m) of straight 8”
diameter pipe be used with two right angle elbows. When more than two elbows are used, 2' (600mm) of straight
pipe should be removed for each additional elbow. No more than four right angle elbows should be used to
exhaust a dryer.
Maintain minimum 1” (25) 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” (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 flow.
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. Figure 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 flow 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 flow; 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 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.