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Help Your Air Compressor Motor Beat the Heat This Summer

Help Your Air Compressor Motor Beat the Heat This Summer

Reduce the risk of failure in your centrifugal air compressor by thoroughly checking your motor this summer season. It is important to monitor your motor for these issues:

Improper Cooling 

Some common causes of an air compressor's motor overheating are improper ventilation, high ambient air temperature, low suction pressure, and excessive wear and tear.  If any of these factors prevent the motor from cooling down properly, it will become increasingly hotter over time.

Electrical Problems 

Electrical problems such as voltage imbalance and surges can happen quickly without notice and wreak havoc on your compressed system, potentially causing an overheated motor. For this reason, it is also essential to have a healthy starter for your compressor to avoid electrical issues. A well-maintained starter will ensure the proper protection of the motor, thus reducing the chances of any surge or voltage imbalance that could occur. 


All motors produce vibrations as they operate; however, motor misalignment can create excessive vibrations and cause friction between components. The friction of components will begin to wear down and place extra load on the motor, which will cause the motor to draw excessive current and overheat.

Incorrect Motor Size

When considering the size of the motor, it is important to account for the site conditions and the size of your air compressor. A motor that is too small will operate in an overload condition, and the motor will overheat.

Ambient Air Temperature

Motors rely on circulated air for the proper cooling of the motor windings and bearings. Motors have a rated ambient air temperature of 40°C (104°F). If the motor is located in an area where the surrounding air temperature is greater than 40°C (104°F), the motor will experience higher operating temperatures.  

Incorrect NEMA Insulation Class

When looking at which NEMA insulation class to choose, it is critical to select the one that is right for your compressor’s motor along with site conditions. Failing to do so can result in overheating and a shortened life expectancy for the motor, which could lead to an unexpected temporary shutdown of your business. The motor winding insulation, which protects the conductive wires wrapped around the stator, can break down at temperatures past their maximum limit (see chart below). A deteriorated point in the insulation will result in an electrical short of the windings. Knowing the temperature rise within your motor, along with the ambient temperature of your plant, will allow you to determine which insulation class is best. Most motors are equipped with Class F insulation. 

Class A:

  • Maximum Temperature Rise: 60°C
  • Hot-Spot Over Temperature Allowance: 5°C
  • Maximum Winding Temperature: 105°C

Class B:

  • Maximum Temperature Rise: 80°C
  • Hot-Spot Over Temperature Allowance: 10°C
  • Maximum Winding Temperature: 130°C

Class F:

  • Maximum Temperature Rise: 105°C
  • Hot-Spot Over Temperature Allowance: 10°C
  • Maximum Winding Temperature: 155°C

Class H:

  • Maximum Temperature Rise: 125°C
  • Hot-Spot Over Temperature Allowance: 15°C
  • Maximum Winding Temperature: 180°C

FS-Elliott’s Scheduled Maintenance Guidelines will provide the necessary instructions to follow on quarterly, semi-annually, annually, and 3-year intervals for your motor:

  • Perform driver checks annually.
  • Inspect main drive coupling annually.
  • Check lubrication of drive motor bearings quarterly.
  • Check lubrication of auxiliary oil pump motor quarterly.

Contact your authorized FS-Elliott channel partner or sales representative today for assistance with inspecting, maintaining, and help to keep your centrifugal compressors operating at peak efficiency.  

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