Power Lost on Restriction in Ductwork

In summary, the formula for calculating power wasted on air filters in a residential central air ductwork is CFM*dP/6356/eff=hp, where CFM is the flow in cubic feet per minute, dP is the pressure drop in inches of water gauge, and efficiency is the efficiency of the fan. An average HVAC fan has an efficiency of about 65%.
  • #1
gm10
2
0
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:
 
Last edited:
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  • #2
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
 
  • #3
russ,

Awesome. Thanks a lot.
 

1. What is "Power Lost on Restriction in Ductwork"?

"Power Lost on Restriction in Ductwork" refers to the energy that is lost when air is forced through a restricted or obstructed duct system. This can occur due to factors such as bends, kinks, or buildup of debris or dust in the ducts.

2. How does restriction in ductwork lead to power loss?

Restriction in ductwork creates resistance to the flow of air, which requires the HVAC system to work harder to push the air through. This leads to a decrease in air flow and an increase in pressure, resulting in a loss of energy (power) in the system.

3. What are the consequences of power loss on restriction in ductwork?

The consequences of power loss on restriction in ductwork include decreased energy efficiency and increased energy costs for the HVAC system. It can also lead to uneven heating or cooling in different areas of a building, as well as reduced air quality due to poor ventilation.

4. How can power loss on restriction in ductwork be prevented?

To prevent power loss on restriction in ductwork, it is important to regularly maintain and clean the ducts. This includes removing any obstructions or buildup of debris, as well as ensuring that the ducts are properly sealed and insulated to minimize resistance and maintain efficient airflow.

5. What are some signs that indicate power loss on restriction in ductwork?

Some signs that may indicate power loss on restriction in ductwork include uneven heating or cooling in different areas of a building, increased energy bills, and excessive noise or vibration from the HVAC system. Visual inspection of the ductwork may also reveal any obvious obstructions or damage that could be causing power loss.

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