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D. FRESH AIR SUPPLY REQUIREMENTS
When the dryer is operating, it draws in room air, heats it, passes this air through the basket (tumbler), and
exhausts it out of the building. Therefore, the room air must be continually replenished from the outdoors. If the
make-up air is inadequate, drying time and drying efficiency will be adversely affected. Ignition problems and sail
switch “fluttering” problems may result, as well as premature motor failure from overheating.
Air supply (make-up air) must be given careful consideration to assure proper performance of each dryer. An
unrestricted source of air is necessary for each dryer. An airflow of 2,150 cfm (cubic feet per minute) - 60.88
cmm (cubic meters per minutes) - must be supplied to each gas, electric, and steam dryer. As a general rule, an
unrestricted air entrance from the outdoors (atmosphere) of a minimum of 3 square feet (0.28 square meters) is
required for each gas, electric, and steam dryer.
To compensate for the use of registers or louvers used over the openings, this make-up air area must be
increased by approximately thirty-three percent (33%). Make-up air openings should not be located in an area
directly near where exhaust vents exit the building.
It is not necessary to have a separate make-up air opening for each dryer. Common make-up air openings are
acceptable. However, they must be set up in such a manner that the make-up air is distributed equally to ALL
the dryers. The dryer must be installed with provisions for adequate combustion and make-up air supply.
EXAMPLE: For a bank of six (6) gas dryers, two (2) openings measuring 3 feet by 3 feet (0.91
meters by 0.91 meters) 9 square feet (0.84 square meters) is acceptable.
Allowances must be made for remote or constricting passageways or where dryers are located at excessive
altitudes or predominantly low pressure areas.