ADC AD-115DR Installation Manual page 23

IMPORTANT: Minimum duct size for a gas, electric, or steam dryer with a vertical run and not more
than three (3) elbows (including dryer connection and outside outlets) is 16-inches
(40.64 cm) for a round duct or 14-1/2" by 14-1/2" (36.83 cm by 36.83 cm) for a
square duct. DUCT SIZE MUST NOT BE REDUCED ANYWHERE
DOWNSTREAM OF 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) for AD-115ES
and 0.6 in WC (1.48 mb) for AD-115DR.
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 for AD-115ES and 0.6 inch water column for AD-115DR. 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 (minimum 14-inches [35.56 cm]) not exceed 20 feet (6.09
meters) with no more than three (3) elbows (including dryer connections and outside exhaust outlets). If the
ductwork exceeds 20 feet (6.09 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
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 14-inch (35.56 cm) 90° elbow is equivalent to 30 feet (9.14
meters) and each 16-inch (40.64 cm) 90° elbow is equivalent to 36 feet (10.97 meters).
IMPORTANT: For extended ductwork runs, the cross section area of the duct can only be increased
to an extent. Maximum proportional ductwork runs cannot exceed 20 feet (6.09
meters) more than the original limitations of 20 feet (6.09 meters) with two (2) elbows.
When the ductwork approaches the maximum limits as noted in this manual, a
professional heating, ventilating, and air-conditioning (HVAC) firm should be
consulted for proper venting information.
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