MAXIDRY MAXI120, Installation Manual, Page: 13 / 30

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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 elbows. When
the ductwork approaches the maximum limits as noted in
this manual, a professional HVAC firm should be consulted
for proper venting information.
All ductwork 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 ductwork 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 ductwork for periodic inspection
and cleaning of lint from the ductwork.
NOTE: When the exhaust ductwork passes through a wall,
ceiling, or roof made of combustible materials, the opening
must be 2-inches (5.08 cm) larger than the duct (all the
way around). The duct must be centered within this
opening.
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 airflow and should be spaced at least
48-3/4” (123.83 cm) apart. The main duct should be tapered,
with the diameter increasing before each individual dryer
branch duct is added.
IMPORTANT: No more than four dryers should be
connected to one main common duct.
The main duct may be any shape or cross-sectional area, as
long as the minimum cross section area is provided. The
illustration below shows the minimum cross section area for
multiple dryer round or square venting. These figures must
be increased 10 square inches (64.51 square centimeters)
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 20 feet [6.09 meters]) or has numerous
elbows (more than two) in it. In calculating ductwork size,
the cross section area of a square or rectangular duct must
be increased twenty percent for each additional 20 feet (6.09
meters). The diameter of a round exhaust must be increased
ten percent for each additional 20 feet (6.09 meters). Each
90° elbow is equivalent to an additional 15 feet (4.57 meters).
IMPORTANT: Exhaust back pressure measured by a
manometer at each dryer exhaust duct area must be no
less than 0 and must not exceed 0.3 in WC (0.75 mb, 75
Pa).
For extended ductwork runs, the cross section area of the
ductwork 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 elbows. When the ductwork approaches
the maximum limits as noted in this manual, a professional
HVAC firm should be consulted for proper venting
information.
The duct 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 ductwork 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 ductwork for periodic inspection
and cleaning of lint from the ductwork.
MULTIPLE DRYER VENTING
14-INCHES (35.56 CM) DIAMETER, 2,150 CFM (60.88 CMM) EXHAUST CONNECTION AT COMMON DUCT
(GAS, ELECTRIC, AND STEAM MODELS)