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2. Single Dryer Venting
Where possible, it is suggested to provide a separate exhaust duct for each dryer. The exhaust duct should
be laid out in such a way that the ductwork travels as directly as possible to the outdoors with as few turns
as possible. It is suggested that the use of 90° turns in the ducting be avoided; use 30° and/or 45° angles
instead. The shape of the exhaust ductwork is not critical so long as the minimum cross section area is
provided.
IMPORTANT: Minimum duct size for a dryer is 14-inches (35.56 cm) for a round duct or
12-1/2” x 12-1/2” (31.75 cm x 31.75 cm) for a square duct. THE DUCT SIZE
MUST NOT BE REDUCED ANYWHERE DOWNSTREAM OF THE
DRYER.
IMPORTANT: Exhaust back pressure measured by a manometer at each basket (tumbler) exhaust
duct area must be no less than 0 and must not exceed 0.3 inches (0.74 mb) of water
column (W.C.).
It is suggested that the ductwork from each dryer not exceed 15 feet (4.57 meters) with no more than two
(2) elbows (excluding dryer connections and outside exhaust outlets). If the ductwork exceeds 15 feet
(4.57 meters) or has numerous elbows, the cross section area of the ductwork must be increased in
proportion to the length and number of elbows in it. In calculating duct size, the cross section area of a
square or rectangular duct must be increased by twenty percent (20%) for each additional 15 feet (4.57
meters). The diameter of a round exhaust duct should be increased ten percent (10%) for each additional
15 feet (4.57 meters). Each 90º elbow is equivalent to an additional 30 feet (9.14 meters), and each 45º
elbow is equivalent to an additional 15 feet (4.57 meters).