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Duct Fitting Loss Coefficients: wye 45 straight reduction sd5 3
branch to main
Loss coefficients (C-values) for duct fittings — elbows, tees, wyes, transitions, entries, exits, and specialty fittings per ASHRAE Fundamentals and SMACNA. dP = C * Vp where Vp is velocity pressure at the referenced duct cross-section.
| fitting type | size or range | C0 (dimensionless) | ashrae code | geometry notes | standard |
|---|---|---|---|---|---|
| wye 45 straight reduction sd5 3 | branch | 0.5 | SD5-3 | SD5-3 Wye 45-degree straight body branch with reduction transition; C branch | ASHRAE Handbook Fundamentals 2021 Ch.21 Tables 10-11 |
| wye 45 straight reduction sd5 3 | main | 0.15 | SD5-3 | SD5-3 Wye 45-degree straight body branch with reduction transition; C main | ASHRAE Handbook Fundamentals 2021 Ch.21 Tables 10-11 |
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