Power of Motor

For fans and blowers:

HP = Volume (cfm) x Head (inches of water)

6356 x Mechanical Efficiency of Fan

Or

HP = Volume (cfm) x Pressure (lb. Per sq. ft.)

3300 x Mechanical Efficiency of Fan

Or

HP = Volume (cfm) x Pressure (lb. Per sq. in.)

229 x Mechanical Efficiency of Fan

For purpose of estimating, the eff. of a fan or blower may be assumed to be 0.65.

Note: Air Capacity (cfm) varies directly with fan speed. Developed Pressure varies with square of fan speed. Hp varies with cube of fan speed.