Confirming a fan performance on site means measuring air velocity and static pressure and comparing them to the design duty point. Velocity is typically read with a pitot tube or anemometer across a traverse of the duct, then converted to volume flow using the duct area; static pressure is read with a manometer at tappings before and after the fan. Taking readings at a steady operating condition, away from bends, gives the most reliable result.
A measured flow well below design usually points to a fouled impeller, a blocked filter or a system resistance higher than calculated, rather than a faulty fan. Comparing field readings against the factory run-test report quickly shows whether the fan or the system is the issue. Send us your measurements and we will help interpret them against the relevant performance curve.