For a duct-design calculation, the pressure available for duct friction is 0.30 inch of water column after all other component losses have been deducted. The controlling supply-and-return path has a total equivalent length of 200 feet, including fittings. Using friction rate = available pressure × 100 / total equivalent length, what rate results?
- A0.10 inch of water column per 100 feet
- 0.15 inch of water column per 100 feet
- C0.30 inch of water column per 100 feet
- D0.60 inch of water column per 100 feet
Where to look it up
Explicit exercise assumptions; not a universal code requirement.
Why B is correct
Apply the supplied relation: 0.30 × 100/200 = 0.15 inch of water column per 100 feet. Use the stated complete path and remaining pressure, not just the straight supply-run length. This exercise does not establish a universal code maximum.