Average horsepower per cfm 1

[ChrisConley]

Does anyone have a general formula for estimating horsepower (bhp) requirements per cfm?

I'm just looking for a rough number for estimating the fan motor horsepower on a large number of fan coils, and I would like to avoid selecting 150 fans at this point just to determine what the approximate bhp would be.

Any tips would be greatly appreciated.

 

[lilliput1]

bhp = (CFM x in. wg. total pressure)/(6344 x Efficiency in decimals)

For small fan coil units efficiency would probably be in the 0.40 to 0.50 range. Larger, more efficient units would be around 0.65. Check catalogs & solve for efficiency.

Total pressure would be external static + coil pressure drops + filter pressure drop.

 

[25362]

Would it be right to say the factor in the denominator isn't 6344, but 6354 ?

 

[ko99]

25362,

Good point. I think that factor is a function of air density, which can vary significantly depending on altitude and, to a lesser degree, temperature. But either value works for a rough estimate.

ko (

http://www.ecooling.biz)