Ask the Expert: Is it ok for my shop compressor to run all day?

Q: Is it ok for my shop compressor to run all day?

A: This is really a question about duty cycle. Duty cycle is the percentage of time a compressor can operate without the risk of overheating and causing excessive wear and tear. So it depends on the type you have. 

Most compressors below 15 hp are piston compressors with a 60-70 percent duty cycle. This means it needs to shut down and cool off periodically. You cannot run a piston compressor all day without excessive wear

Rotary screw and vane compressors are specifically designed for 100 percent duty cycle.  If your operation needs it, they can run 24/7, but like a piston unit they run when a pressure signal turns them on. 

Unlike most piston compressors, most rotary compressors idle before they shut down completely.  When the demand for compressed air stops, the pressure sensor will send a signal to close the inlet valve, but the motor and pump keep turning for a few minutes. For example, on a 10 hp compressor the idle timer might be set for just three minutes (it’s adjustable). After the three minutes of idling, the unit completely stops (unless air is needed again before the three minute timeframe ends).  This keeps the motor from starting and stopping too often. Think of it like a car at a stop light. Better to idle a few moments than shut the engine off and restart when the light turns green. And like a car, it uses far less energy at idle.

You may also want to consider why your compressor is running all day. Keep in mind that to a compressor, leaks are just another demand for air, so even when no one is purposely using air the compressor will run to feed leaks. The bigger the leaks, the more it will run. 

Information provided by: Kaeser Compressors