: The database catalogs round, rectangular, and flat oval fittings, including elbows, tees, transitions, dampers, and terminal units.

: Velocity, velocity pressure, and the crucial loss coefficient ( C0cap C sub 0 -factor) . Loss Coefficient Method : Pressure loss ( ΔPcap delta cap P ) is calculated using the formula

Flat oval duct behaves hydraulically differently. The database has specific divisions for flat oval. Do not use rectangular coefficients for oval systems.

In a tee or junction, the loss coefficient for the air going straight through ( C = 0.05 ) is drastically different from the air turning into the branch ( C = 1.2 ). The ASHRAE DB requires you to specify (which leg is which). Always double-check the database diagram before applying the number.

You cannot simply make up a number. To comply, you must provide a "Duct Pressure Drop Summary." The is the only approved source for fitting loss coefficients in most jurisdictions.

The raw database is not user-friendly for manual lookups. You really want to access it through a duct design software interface. Trying to navigate the raw CSV or Excel tables by hand is like drinking from a fire hose.