ESP is the measure of the pressure drop caused by components external to the fan itself. This includes: : Friction loss from straight sections. Fittings : Elbows, tees, and transitions. Terminal Devices : Grilles, diffusers, and dampers.
0.08 to 0.12 in. w.g. per 100 ft of duct (supply side). esp calculation for duct
Let's calculate the ESP for a simple Supply Air system. ESP is the measure of the pressure drop