Refrigeration systems are closed loop operations, and maintain the colder temperatures since they are within a closed, insulated box. Low temp refrigerants are used for freezers and medium temp refrigerants are used for coolers. They contain at least (and usually many more) components: a compressor, a metering device, a hot (condenser) coil, a cold (evaporator) coil, fans (for the condenser and evaporator coils) and a control unit (thermostat). The cycle is as follows:

  1. The compressor receives refrigerant from the evaporator. It compresses the refrigerant, which cause it to become a hot, high pressure (a couple hundred pounds per square inch) gas.
  2. The liquid refrigerant then passes through a metering device where it evaporates, resulting in a low pressure, cold gas.
  3. This low pressure gas circulates through the evaporator coils, absorbing the heat and cooling the box.
  4. The gas returns to the compressor, starting the cycle again.

Some suggestions if your refrigeration unit is not functioning correctly