Reasons for Measuring a Fan 

Generally, there are two reasons to measure a centrifugal fan – the user wants to retrofit the fan (or parts) or replace it with a new fan. In either case, accurate measurements are critical to replicating the system currently in place, especially if no drawing is available. If possible, separate or isolate the fan from the system to access key measurement points. If duct work on the inlet or outlet is in the way, this could impact measurement accuracy.