[Friesen]

I am installing a duct work for a ducted aircondition (cold air only).
I am new at this work.

The supplier of the air handler equipment suggested that the return need only be 60% (measured by cross-section) of the supply, but the instruction manuel, which is very brief, says that the duct of supply and return shall not be size smaller than opening on air-handler.

can somebody answer my question or have I omitted pertinant information.

John