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Ductwork Sizer
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Ductwork Sizer
Equal-friction circular duct sizing per CIBSE Guide C 2007 — EN 1506 standard sizes
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Active Regulation
CIBSE Guide C — Reference Data (2007)
Equal-friction method, CIBSE Eq. C4.3 + Colebrook-White friction factor · Verified 2026-06-15
CURRENT
⚙️ Design Parameters
Design Pressure Drop
(Pa/m)
Typical: 1.0 Pa/m (CIBSE C4.5 recommend 0.8–1.5)
Application
Sets velocity acceptability range (CIBSE Table C4.3)
Residential — 3–5 m/s main
Commercial — 5–8 m/s main
Industrial — 8–12 m/s main
Fan Motor Power (optional)
(W)
If entered, SFP [W/(l/s)] will be calculated
🔵 Duct Sections
+ Add Section
#
Label
Flow (l/s)
Length (m)
1
×
2
×
3
×
🔵 Size Ductwork
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📋 Velocity Limits — CIBSE Guide C, Table C4.3
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