Power Lost on Restriction in Ductwork

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To calculate power loss due to air filters in residential ductwork, the formula CFM*dP/6356/eff=hp is used, where CFM is the airflow in cubic feet per minute, dP is the pressure drop in inches of water gauge, and eff is the fan efficiency. Typical pressure drops range from 0.1 to 0.2 inches wg, with airflow volumes between 700 and 2000 CFM. A standard HVAC fan efficiency is around 65%. For example, using 2000 CFM at a 0.2" pressure drop results in approximately 0.097 horsepower loss. Understanding this calculation helps assess energy efficiency in HVAC systems.
gm10
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Hello,

I need a formula to calculate how much power is wasted on different types of air filters. A typical application is a residential central air ductwork. A typical pressure drop is 0.1-0.2 inch wg. Typical volume passing through filters is 700-2000 cfm. A typical filter size is 2-3 sq. ft.

Your help is much appreciated in advance.

gm

This is not a homework. :smile:
 
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Welcome to PF. The equation is:

CFM*dP/6356/eff=hp

That's flow in CFM, dP in inches w.g. and efficiency of the fan. A typical good HVAC fan is about 65% efficient, so for example, 2000 CFM at 0.2" is 2000*.2/6356/.65=0.097hp
 
russ,

Awesome. Thanks a lot.
 

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