A boiler-room design specifies 5,000 cfm of combustion-air supply. Two operating fans deliver 1,800 and 2,200 cfm. Ignoring interaction losses for this exercise, what additional capacity is needed?
- A0 cfm
- 1,000 cfm
- C2,000 cfm
- D4,000 cfm
Where to look it up
Explicit exercise assumptions; not a universal code requirement.
Why B is correct
Available flow is 1,800 + 2,200 = 4,000 cfm; shortfall = 5,000 − 4,000 = 1,000 cfm. Actual fan interaction must be checked in commissioning; no universal airflow-per-Btu factor is claimed.