B&C Technologies DP-250 Industrial - Manual (Page 21)

INSTALLATION PROCEDURES
3-7
3. Multiple Dryer (Common) Venting
If it is not feasible to provide separate exhaust ducts for each dryer, ducts from individual
dryers may be channeled into a "common main duct." The individual ducts should enter the bottom
or side of the main duct at an angle not more than 45° in the direction of air flow and should be
spaced at least 48-3/8 inches apart. The main duct should be tapered, with the diameter increasing
before each individual 1
8-inch (minimum for gas dryers or 72 Kw electric dryers) or 18-inch
(minimum for steam dryers or 80 Kw electric dryers) duct is added.
IMPORTANT: The DP is not provided with a back draft damper. When exhausted into a multiple
(common) exhaust line, a back draft damper must be installed at each dryer duct.
IMPORTANT: No more than four (4) dryers should be connected to one main common duct.
The main duct may be any shape or cross sectional area, so long as the minimum cross
section area is provided. These figures must be increased 10 square inches when rectangular main
ducting is used, and the ratio of duct width to depth should not be greater than 3-1/2 to 1. These
figures must be increased in proportion if the main duct run to the last dryer to where it exhausts to
the outdoors is unusually long (over twenty [20] feet) or has numerous elbows (more than two [2])
in it. In calculating duct work size, the cross section area of a square or rectangular duct must be
increased twenty (20) percent for each additional twenty (20) feet. The diameter of a round exhaust
must be increased ten (10) percent for each additional twenty (20) feet. Each 90° elbow is
equivalent to an additional thirty- (30) feet and each 45° elbow is equivalent to an additional fifteen
(15) feet.
IMPORTANT: For extended duct work runs, the cross section area of the duct work can only be
increased to an extent. Maximum proportional duct work runs cannot exceed
twenty (20) feet more than the original limitations of twenty (20) feet with two (2)
elbows. When the duct work approaches the maximum limits as noted in this
manual, a professional HV AC firm should be consulted for proper venting
information.
IMPORTANT: Exhaust back pressure measured by a manometer at each dryer exhaust duct area
should not exceed 0.3 inches of water column.
The duct work should be smooth inside with no projections from sheet metal screws or
other obstructions which will collect lint. When adding ducts, the duct to be added should overlap
the duct to which it is to be connected. ALL duct work joints must be taped to prevent moisture
and lint from escaping into the building. Inspection doors should be installed at strategic points in
the exhaust duct work for periodic inspection and clean-out of lint from the duct work.
NOTE: Where the exhaust passes through a wall, ceiling, or roof made of combustible materials,
the opening must be 2-inches larger (all the way around) than the duct. The duct must be
centered within this opening.
Outside Duct Work Protection
To protect the outside end of horizontal duct work from the weather, a 90° elbow bent
downward should be installed where the exhaust exits the building. If the exhaust duct work travels
vertically up through the roof, it should be protected from the weather by using a 180° turn to point
the opening downward. In either case, allow at least twice the diameter of the duct between the duct
opening and nearest obstruction.
IMPORTANT: DO NOT use screens, louvers, or caps on the outside of opening of exhaust duct
work.