DUTY CYCLE

A compressor’s ‘duty cycle’ is rated as a percentage and indicates the number of minutes a compressor can run within a 10-minute period. Cheaper hobby units can be found around the 50-per-cent duty-cycle mark, meaning that it shouldn’t be run for more than five minutes within a 10-minute period, with the remaining five used as a cool down. Exceeding the duty cycle will cause the pump to overheat and affect life expectancy. Most industrial units are rated to a minimum 75 per cent, and can be up to 100 per cent, meaning that they can be run continuously.

This plays into the mix heavily when time is important to you — no one wants to spend double the time it could take to sand back a car, having to stop every five minutes. Likewise, for paint, having a 75- to 100-per-cent duty cycle means that you won’t end up halfway through laying down fresh licks and run out of air.

A 5hp compressor with a 100-per-cent duty cycle can actually produce more continuous air than a 7.5hp compressor with a typical 75-per-cent duty cycle — so, depending on your intended level of use, better value can be had by spending a little more coin for a higher duty cycle, even if you don’t always intend to use it at that level. And it’s not going to hurt the longevity of the unit, either.

EXPERT OPINION

Richard says: “The ‘duty cycle’ is the ratio of time the compressor spends pumping up the tank to fulfil demand versus the amount of time it spends standing while the tank is being drained by the tool. Usually, with a piston compressor, the preferred duty cycle is around 60 per cent running, with 40 per cent standing to allow for cylinder cooling. You can operate the unit on a far greater duty cycle, and, at times, up to 100 per cent, but this should be avoided for extended periods of time. Obviously, smaller machines running larger equipment have a higher temperature and produce hotter air, and increase [the] chances of having water issues in the air.”