Normal requirement is + /- 10% of design CFM at the terminals if a safety factor of minimum 10% was built in the load calculations. If not, use +15%/-0%. The CFM traverse at the fan will be greater than the sum of the CFM measured at the terminals because of leakage. Leakage of more than 10% is not allowable. Fan bhp equal or greater than motor hp or fan FLA more than design are not acceptable. Check for duct blockage.
