How to Calculate Air Compressor Power
Air compressor power is an important figure to keep in mind when purchasing an air conditioning system for your home. It is important to know both the cubic feet per minute (CFM) and the psi of output -- after all, a ceiling fan moves a lot of cubic feet per minute, but at a low psi, so you would want more power from the device cooling your entire home.
The scientific formula for a single-stage compressor's horsepower is HP = .015*P*(R^0.29-1), where P is the atmospheric pressure and R is the ratio of compressed air pressure to the existing air pressure. However, a more helpful and much easier way to calculate your compressor's power involves the true CFM, and you can measure this yourself.
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Instructions
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1
Read the specifications on the compressor to find the volume in gallons. Divide that number by 7.48 to convert from gallons to cubic feet.
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2
Turn the relief valve so that air flows out of the system, keeping an eye on the pressure gauge on the tank. Note the PSI when the compressor turns out, and then note it again when it turns off. Use a stopwatch to clock the amount of time the compressor is on.
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3
Subtract the PSI when the compressor turned on from the PSI when it is turned off. Divide that number by 14.7, which is the PSI for atmospheric pressure. The answer will tell you how much pressure the compressor generated while it was running.
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4
Multiply the volume of the compressor (from Step 1) by the pressure generated in a cycle (from Step 3). This answer will tell you the pumping rate based on the cycle length. If the cycle ran 18 seconds, then your answer would tell you how many cubic feet the compressor pumps per 18 seconds. Multiply your answer by 60/18 to get the cubic feet per minute (moving to 60 seconds instead of 18).
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References
- Photo Credit window air conditioner image by Aaron Kohr from Fotolia.com
