Common downfalls of undersized and oversized compressors

The most common issue resulting from under-sizing compressors is insufficient airflow to production equipment. Workers may complain that their tools aren’t working properly, or that low-pressure alarms may be tripped in machining equipment. Metal stamping equipment may not be able to generate enough force to produce quality products. If piston or scroll compressors are used, under-sizing also may result in overheating of the air compressors due to exceeding their rated duty cycle.

Typical issues resulting from over-sizing air compressors are short loaded cycles and long unloaded cycles. A compressor running unloaded will waste electricity without producing any useful compressed air. However, this can be necessary in order to prevent the compressor from exceeding the recommended number of motor starts per hour.

Variable speed drive (VSD) compressors do not have a restriction on the number of motor starts per hour and are often marketed as “unlimited.” However, over-sizing a VSD compressor can cause damage to the compressor. If there is insufficient demand in the air system, the VSD will run the compressor slowly for a long period of time, and the compressor will not heat up enough to burn off the water that has condensed in the oil. If this is allowed to continue for too long, the oil’s ability to cool and lubricate the compressor’s air end will be compromised, and the air end will eventually be damaged, resulting in costly repairs and extended downtime.