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Crankcase Heaters

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Summary

  • Crankcase heaters provide some protection to liquid refrigerant entering the compressor.
  • Properly operating Crankcase heaters become even more important when using blends.

Background

Crankcase heaters (CCH) are used to boil off excess refrigerant in the oil sump to prevent liquid refrigerant, particularly liquid refrigerant without any associated oil, from entering the compressor.

During system off-cycles, refrigerant migrates to the coldest part of the system which tends to be the condenser and/or compressor(s) in cold ambient conditions. Due to the nature of Blends, which all contain components that boil at a higher temperatures than R-22, this issue can be exacerbated during the off-cycle.

NOTE: Even with properly operating crankcase heaters, liquid refrigerant can still migrate into the suction line during off cycles. Proper refrigerant control is still important for larger systems with significant refrigerant charge available to migrate.

Best Practices

  • Always¬†ensure existing CCHs are operational.
  • CCH are recommended on passive oil compressors that operate in cold ambient conditions.
  • In some systems, such as 3D scrolls, CCHs may not ensure adequate protection.

Additional Tips

  • Refer to OEM recommendations for minimum CCH operation times prior to startup.
  • Never¬†operate a CCH when evacuating a system.
  • When installing or inspecting a CCH, ensure good contact with compressor surface area.

Video

Figure 1. Crankcase heater.