Vent-a-Hood K250 Installation Instructions - Ducting Do’S and Don’Ts
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L117 1213A
Ducting Do’s and Don’ts
YES
NO
Smooth Duct
Smooth Gradual Turn
Flexible Duct
Sharp Angled Turns
General Requirements
• Observe local codes regarding special duct requirements and placement of duct against combustibles.
• Using Vent-A-Hood transitions (back page) will ensure proper efficiency.
• Using Vent-A-Hood roof jacks or wall louvers (back page) will ensure proper efficiency.
• Where possible, seal joints with duct tape.
• The hood must be ducted to the outdoors without restrictions.
Blower Requirements
• The K250 blower unit requires 7” round duct or equivalent (32.5 square inches).
Blower
Duct Dize
Sq. Inch Area
Vent-A-Hood Transition
K250
3 1/4" x 10" or equivalent
32.5 sq. in.
VP521 (Optional)
Ducting Requirements
• NEVER reduce the duct size.
• Do not use flexible or corrugated duct. This type of duct will restrict airflow and reduce performance.
• Only use smooth, galvanized, metal duct.
• 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.
Termination Requirements
• Airflow must not be restricted at the end of the duct run.
• A wall louver or roof jack is required for each duct run.
• Every wall louver or roof jack must include a gravity damper to prevent back drafts.
• Do not use screen wire or spring-loaded doors on wall louvers or roof jacks.
• Do not terminate venting into an attic or chimney.