TruckSpring Times

All air compressors are built with a duty cycle rating. This rating is typically given as a percentage of the amount of time that an air compressor can be run in a full cycle, typically one hour, that includes the compressor’s run time and rest time.

Some compressors, such as Viair air compressors are built with a thermal protection that will automatically shut them down when they reach a temperature that they can be damaged. Others may not and it is up to the operator to shut them down in the correct amount of time. The compressor must be off and cooling down for the rest of the time they were run to avoid damage.

Air Compressor Duty cycle refers to the amount of time a compressor can be operated in a given time period at 100 PSI, and a standard ambient temperature of 72° F. If you are running the air compressor in the dead of winter or on a hot summer day, the amount of cool down time will vary. With duty cycle, It's all about heat dissipation and the rates will vary depending on ambient temperatures and operating conditions.

Duty Cycle is almost always expressed in percentage format: Compressor on time ÷ (on time + off time) = Duty Cycle %. The times to duty cycle in an hour is broken down in a chart below.

9% Duty Cycle      5 Minutes On / 55 Minutes Off or Cool-Down time
10% Duty Cycle     6 Minutes On / 54 Minutes Off or Cool-Down time
15% Duty Cycle     9 Minutes On / 51 Minutes Off or Cool-Down time
20% Duty Cycle     12 Minutes On / 48 Minutes Off or Cool-Down time
25% Duty Cycle     15 Minutes On / 45 Minutes Off or Cool-Down time
30% Duty Cycle     18 Minutes On / 42 Minutes Off or Cool-Down time
50% Duty Cycle     30 Minutes On / 30 Minutes Off or Cool-Down time
100% Duty Cycle   1 Hour Run Time or Constant Duty

If you want to break it down into 10 minute intervals - if an air compressor has a duty cycle of 50%, the air compressor will be running for 10 minutes, then it should run for a combined maximum of 5 minutes ON and 5 minutes OFF.  If the compressor is 60% duty cycle this means the compressor must be off for approximately 4 minutes of every 10 minutes.

If your air compressor is maintained and the duty cycle followed they will provide many years of reliable service.

Many Air Compressors are not built to be run continuously and some need time to rest between uses.

The term Duty Cycle refers to the percentage of time an Air Compressor can run before needing time to cool down. The Duty Cycle of an Air Compressor is often expressed as a percentage of a certain amount of time, usually being 10 minute periods. That is, the Duty Cycle measures the proportion of time an Air Compressor can run against the amount of time needed for it to cool.

For example, the Firestone Super Heavy Duty Air Compressor has a 30% Duty Cycle and can be run for 3 minutes, it must then rest for 7 minutes. However, the Firestone Ultimate Duty Air Compressor has a 100% Duty Cycle and can be run continuously without a cool down time. These air compressors usually cost a little more but they are a time efficient alternative to lighter duty Air Compressors.

The Duty Cycle of an Air Compressor is calculated by dividing the total run time by the amount of time the compressor can run before resting. For example:

D = R / T with ‘D’ being Duty Cycle,‘R’ being run time before resting and ‘T’ being the total time.

30% Duty Cycle = 3 minutes run time / 10 minutes total – So an Air Compressor that can run for three minutes before needing to rest for 7 minutes has a 30% Duty Cycle.

Conversely, by knowing the Duty Cycle the run time can be determined by multiplying the Duty Cycle by the total time (usually 10 minutes). For example:

R = D x T

3 minute run time = 30%(.3) Duty Cycle x 10 minutes total – So an Air Compressor that has a Duty Cycle of 30% can run for 3 minutes before needing to cool for 7 minutes.

The below table is based on a 10 minute total time.