Hello,

For ESP calculations, generally I've seen Engineers selecting the longest duct run, which has most pressure drop. It is said, this selection is enough to over come pressure drop in other ducts.

I have my doubts here. Lets consider the longest duct run has 500Pa ESP with its sound attenuators, dampers all misc accessories. Assume there is a branch duct connected to it having a pressure drop of 200Pa.
Will 500Pa ESP be enough, or should 700Pa be considered?

If its just 500Pa, I don't understand the logic of how this air can over come this additional 200Pa, when it has already burned out its energy to overcome 500Pa static??