Ask the Expert: What’s the difference between displaced CFM, actual CFM and standard CFM?
Q: What’s the difference between displaced CFM, actual CFM and standard CFM?
A: Displaced CFM (DCFM) is simply a mathematical calculation of a reciprocating piston compressor’s bore, stroke and rpm. It does not take into account many important variables like temperature, atmospheric pressure, humidity, friction or heat dissipation. Therefore, it does not provide an accurate picture of a compressor’s actual performance.
Actual CFM (ACFM) represents the compressor’s true output according to actual working conditions. However, ACFM is difficult to determine because it’s calculated from a complex equation that involves gathering site-specific data, including temperature, altitude, humidity and other variables.
Standard CFM (SCFM) is determined from a set of standard conditions, such as 14.5 psi atmospheric pressure (the pressure at sea level), 68 degrees F and 0 percent humidity.
When comparing one compressor with another, it is generally recommended to judge them based on SCFM. That’s because SCFM is a standardized metric, which levels the playing field for an even comparison among various compressor manufacturers.
Information provided by: Daniel Leiss, president, Jenny Products, Inc.
