Defrost mode - PENN Controls - LIT-12013106 - MR534AFDN - MR534AFDV - Electronic Refrigeration, Defrost, and Multi-Purpose Controller - MR5xx Panel‐Mount Refrigeration and Defrost Controller

MR5 Series Panel Mount Case Controller Product Bulletin

PENN Controls
Product name
MR5xx Panel‐Mount Refrigeration and Defrost Controller
Document type
Product Bulletin
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Revision date
Product status

The selections you make for defrost type, defrost termination type, and evaporator fan behavior determine how the refrigeration system operates during defrost mode. To manually start or stop a defrost cycle, press the Defrost icon for several seconds.

The MR5 Controller includes the following defrost modes:

  • You commonly use off-cycle defrost on medium temperature refrigeration applications. During off-cycle defrost, refrigerant flow to the evaporator is interrupted. The evaporator fans remain on to move air over the evaporator coil and melt any accumulated frost or ice.
  • Electric defrost uses electric resistive heating elements that the defrost relay controls to melt the ice, which accumulates on the evaporator coil during normal cooling operation. Low-temperature refrigeration applications often use electric defrost.
  • Hot gas defrost systems use a bypass valve controlled by the defrost relay and extra refrigerant piping to temporarily reroute the hot gas discharge from the compressor through the evaporator coil. Low and very low temperature refrigeration applications use hot gas defrost.