(PDF) Duct Size Chart

Download free duct sizing chart pdf according to ASHRAE standard. These duct chart are based on equal friction method with a friction loss value = 0.1 inch/100ft. Duct size chart calculate duct dimensions for both rectangular and round ducts.

How to use Duct Size Chart:

1. Identify the volume of air that will be passing through the duct
2. Select the duct size from the table that can carry that volume of air
3. If desired airflow exceeds the CFM rating , increase to the next duct size
4. Listed CFM is based on typical field results and may vary, install dampers
5. If duct run exceeds 25′, or has excessive transitions, increase to the next size
6. Design alone is inadequate, always prove design by test and balance.

The above duct sizes are based on a friction drop of 0.1 inches per 100 feet of lineal duct. This “Equal-Friction” method of duct sizing should be adequate for normal residential furnace heating and air conditioning applications. Larger volumes or higher static pressures should be dealt with on an individual job basis.

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