Manual Q: Commercial Low Pressure, Low Velocity Duct System Design

In commercial work, duct runs are sized, fittings are selected and airside devices are specified without prior knowledge of the fan performance. Pressure drip calculations are made after all of the sizes, performance characteristics and locations of the various system components are determined. Finally, the fan, along with a motor and drive, is selected to provide the required flow (CFM) when the fan operates against the estimated system resistance (pressure drop).

This manual provides the basic information that is required to design low velocity, low pressure duct systems. The procedures outlined in this manual apply to commercial work.