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L151 0310A
Ducting Do’s and Don’ts
NEVER
restrict the duct size. The K250 blower unit requires 7” round duct or equivalent (32.5
square inches).
Do not use flexible or corrugated duct. This type of duct will restrict airflow and reduce
performance. Only use smooth, galvanized, metal duct. Observe local codes regarding special
duct requirements and placement of duct against combustibles. Make the duct run as short and
as straight as possible with as few turns as possible. Avoid sharp-angled turns. Instead, use
smooth, gradual turns such as adjustable elbows or 45 degree angled turns. For duct runs over
20 feet, increase the duct diameter by one inch for every ten feet of duct. A 90 degree elbow
is equal to 5 feet of duct. Using Vent-A-Hood ducting products (back page) will ensure proper
efficiency. Airflow must not be restricted at the end of the duct run. Do not use screen wire
or spring-loaded doors on wall louvers or roof jacks. Do not terminate venting into an attic or
chimney. Where possible, seal joints with duct tape. The hood must be ducted to the outdoors
without restrictions.
Blower
Duct Size
Sq. Inch Area
K250
3 1/4” x 10” rectangular or equivalent
32.5”
YES
NO
Smooth Duct
Smooth Gradual Turn
Flexible Duct
Sharp Angled Turns
