By-Pass Sizing Calculator

Often with zoning systems a By-Pass is needed to relieve excess air when only a small zone or number of small zones cannot deliver the required air flow thru the HVAC System. A by-pass is often ducted back into the return air or into non-critical, common conditioned temperature areas such as entry ways, hallways, basements, etc.

Select your Maximum Total System Cubic Feet per Minute (CFM), then enter the CFM of your Smallest Zone to calculate the type of By-Pass Damper you require.

Note: If the By-Pass CFM amount is 30% or less of the Total System CFM, No By-Pass is required.