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The duty cycle is a measure of how long the compressor can run versus how long it should rest. In other terms, it gives you an idea about how “heavy-duty” the motor is.
If you don’t have a solid understanding of how duty cycles work, choosing a suitable air compressor might be a bit more of a difficult task.
And that’s why I created this article –to explain this particular feature and its importance on your purchasing decision.
If we set a 1-hour standard as an example, a 30% duty cycle compressor would have the ability to handle 20 minutes of use and require a 40-minute rest period.
The duty cycle is typically expressed in percentage format that’s calculated by this equation: Compressor on time ÷ (on + off time).
Before we dive into it, you should know that a duty cycle isn’t an industry definition.
While the compressed air industry has many standards that manufacturers stick to, there isn’t an exact definition of a duty cycle.
This causes a lot of confusion and may cause operators to buy expensive compressors that don’t live up to their expectations or fulfill their needs.
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Breaking Down Duty Cycle Ratings
Although there are ratings as low as 9%, 10%, 15%, and 20%, I’ll start analyzing from 25% as the others are only suitable for minimal applications as they last for less than 15 minutes.
25% Duty Cycle
A 25% duty cycle compressor would run for 15 minutes (one-fourth of the total cycle time) and require a 45-minute rest period.
So if your compressor has a cycle time of 120 seconds, the run time would be 30 seconds.
Moreover, your compressor would need a 90-second rest between every 30 seconds of operation.
With an air compressor of such a low run time, you’d only be able to take on small applications that require intermittent air power.
These include portable and domestic compressors typically used by craftspeople and DIY-ers.
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30% Duty Cycle
A 30% duty cycle compressor would run for 18 minutes (one-third of the total cycle time) and require a 42-minute rest period.
So if it has a cycle of 60 seconds, it would run for 20 seconds and require a 40-second break between every 20 seconds of activity.
This type of duty cycle would be suitable for moderate applications where you don’t use the tool continuously. This includes garages where repetitive fastening and unfastening of motor parts takes place.
50% Duty Cycle
A 50% duty cycle compressor would run for 30 minutes (half of the total cycle time) and require a 30-minute rest period.
This means that if your tool runs for 60 seconds, it would require a 60-second rest period before it draws airpower again.
With a 50% duty cycle, you can do medium-scale operations that require intermittent air power.
If you don’t want to put the money into larger compressors, a 50%-cycle compressor would be the right choice for you. You can buy multiple small ones with a 50%-capacity and run them alternatively for continuous airflow.
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75% Duty Cycle
A 75% duty cycle compressor would run for 45 minutes (three-fourth of the total cycle time) and require a 15-minute rest period.
In other words, if your compressor has a 60-second cycle time, it’ll be able to pressurize air for 45 seconds.
This suits many applications, such as in shops that use tools for brief intervals of time.
Moreover, it’s sufficient to operate pneumatic wrenches, nailers, screws, and hammers in a repair garage.
The brief rest period wouldn’t be an issue as these tools don’t need ongoing air.
100% Duty Cycle
A 100% duty cycle compressor will run for a straight hour and is referred to as a constant-duty compressor.
Those are the ones suitable for operating tools that require non-stop airflow for minutes or even hours on end. These include pneumatic sanders and spray painters.
A 100% duty cycle should come with cooling components to prevent the engine from overheating.
Important Things to Keep in Mind
1. Know that a 100% duty cycle rated compressor can keep up a constant airflow but can only do so at specific PSI and CFM rates.
A 100% duty cycle compressor is still prone to damage if you over-work it and use it with tools that require too much PSI or CFM.
2. To get the best overall performance from your compressor and to make it last the longest, you shouldn’t over-work it and let your tool rest as often as possible.
3. Remember that the standard tasks for duty cycles are performed at 100 PSI and at a 72°F temperature. So if you’re working in a colder or hotter environment, it may affect the overall rating of your compressor.
4. The heavy-duty tasks require a high-duty cycle rating, more tank capacity, and a high CFM output. Compressors with these features would be more expensive, but if you go for lower capabilities, your compressor would be at the risk of overheating and getting damaged.