When purchasing a refrigerator or freezer for clinical, research, or laboratory use, one must take into consideration the type of defrost cycle the unit offers. Storing temperature sensitive samples, especially vaccines, in the wrong defrost cycle can damage them costing time and money.
Refrigerator Defrost Cycles
Cycle Defrost: (Refrigerators)
Cycle Defrost occurs during the actual cycling of the compressor. During the regular on/off cycle of the compressor, the evaporator is in fact defrosted.
Freezer Defrost Cycles
Manual Defrost: (Value-Performance Line)
Manual Defrost freezers as the name suggest must be manually defrosted by turning the freezer off or unplugging the unit. Although, the defrosting of manual defrost freezers is inconvenient due to the necessity to empty the freezer and clean up after the melted ice, they do offer advantages. The key advantage is the absence of warm temperature spikes that are present with Auto-Defrost units.
SMART / Hot Gas Bypass Efficiency: (High Performance Freezer Line)
Hot gas defrost uses the heat of the refrigerant; it consumes less energy compared to equivalent electrical systems. Furthermore, hot gas defrosts systems heat up the entire evaporator coil, directing most of the thermal energy generated to the ice block. Consequently, only a small proportion of the heat is dispersed as additional load on freezers. The evaporator coil is heated from the inside, generating less moisture compared to electric defrost systems that have heating elements installed along the evaporator coil.
Duration of Defrost Cycles:
In hot gas defrost systems, the refrigerant vapor is already hot when the defrost cycle begins. This aspect combined with the efficiency of hot gas defrost methods translates into a shorter defrost period. This makes refrigeration systems less susceptible to significant temperature variations between refrigeration and defrost cycles.