where (for standard air, in inches w.g.)
The critical path is the duct run with the highest resistance, typically the longest run with the most fittings and accessories. You must calculate the total pressure drop from the fan discharge (or intake) to the furthest terminal device on this path.
To calculate External Static Pressure (ESP) in Excel, you must sum the friction losses from straight ductwork, the dynamic losses from fittings, and the pressure drops from accessories along the system's "critical path". duct esp calculation excel
= (Length/100) * VLOOKUP(Q, DuctData_Table, column_for_size, TRUE)
Open a new Excel spreadsheet and create the following columns: where (for standard air, in inches w
Example: Supply total = 0.45 in w.g. Return total = 0.28 in w.g.
You can find free templates on:
Pro tip: Create a simple hand sketch with node numbers (e.g., N1, N2, N3) to match your Excel rows.