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RefCalc — Duct Measurements
RefCalc step 4 — Duct Measurements. Sensible and pressure/sizing paths.
- Sensible: BTU/hr, ΔT, CFM or L/s — any path; BTU = CFM × 1.08 × ΔT (L/s converted to CFM).
- Pressure: SP and TP → VP = TP − SP; FPM = 4005 × √VP.
- Duct area in sq.in. (converted internally to sq.ft. for CFM = FPM × area).
- Enter ↵ reconciles related duct fields; multi-path CFM is harmonized when possible.
Disclaimer: Field guide for technicians — not a substitute for nameplate data or local Code.