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IMPORTANT: DO NOT use screens, louvers, or caps on the outside opening of the exhaust
ductwork.
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 as long as the minimum cross section area is
provided.
IMPORTANT: The minimum duct size for a gas unit is 16-inches (40.64 cm), (12-inches [30.4 cm]
for MLG-122DR), for a round duct and 14-1/4” x 14-1/4” (36.2 cm x 36.2 cm),
(10-3/4 x 10-3/4 [27.3 cm x 27.3 cm] for MLG-122DR), for a square duct. THE
DUCT SIZE MUST NOT BE REDUCED ANYWHERE DOWNSTREAM
OF THE DRYER.
IMPORTANT: Exhaust back pressure measured by a manometer/magnehelic in the exhaust duct
must be no less than 0 and must not exceed 0.3 in WC (0.74 mb).
NOTE: It is recommended that exhaust or booster fans not be used in the exhaust ductwork system
except where necessary to maintain exhaust back pressure (in the exhaust duct) between zero
and 0.3 inch water column. Where employed, booster fans must not activate the dryer airflow
proving switch (sail switch) when the dryer is not in operation.
It is suggested that the ductwork from each dryer not exceed 20 feet (6.09 meters) with no more than two
(2) elbows (excluding dryer connections). If the ductwork exceeds 20 feet (6.09 meters) or has numerous
elbows, the cross-sectional area of the ductwork must be increased in proportion to the length and number
of elbows in it. In calculating duct size, the cross-sectional area of a square or rectangular duct must be
increased twenty percent (20%) for each additional 20 feet (6.09 meters). The diameter of a round
exhaust duct should be increased ten percent (10%) for each additional 15 feet (4.57 meters). Each 90°
elbow is equivalent to an additional 40 feet (12.19 meters), and each 45° elbow is equivalent to an additional
20 feet (6.09 meters).
SINGLE DRYER VENTING
