Specifications

23
REVERSE CYCLE DEFROST
General Information
Master-Bilt’s patented (U.S. patent no. 7,073,344) reverse cycle defrost is a standard feature on Master Controller-
equipped refrigeration systems. A reverse cycle valve is already factory-installed on the condensing unit. The
valve’s primary function is to reverse the direction of the refrigerant flow during defrost. When the Master
Controller’s demand defrost determines that a defrost is necessary, the reverse cycle valve is activated and the high
temperature refrigerant flow is reversed.
Under the normal refrigeration cycle, the refrigerant flow is the same as traditional refrigeration modes. During the
defrost mode, the refrigerant flow is reversed back through the evaporator coil heating it from the inside-out along its
entire length and completely eliminating frost buildup (see figure 5 below).
Figure 5
Advantages
Reverse cycle technology offers several significant advantages:
• An up to 80% reduction in defrost energy usage. This savings, coupled with that from the demand
defrost feature, dramatically reduces energy consumption.
• Eliminates many mechanical parts
• Reduces cost of evaporator, installation and wiring
• Reduces defrost time
• No significant increase in freezer room temperature
• No noticeable increase in product temperature
Factory-Installed Parts
A 4-way reversing valve, operating at 24 VAC, is installed in a reverse cycle defrost unit. A transformer is also
installed in the master evaporator to supply 24VAC to the 4-way reversing valve.