Master-Bilt has announced patent approval for its reverse-cycle process. The proprietary technology involves a reverse-cycle valve that is added to the condensing unit which reverses the direction of refrigerant flow during defrosts. The reverse cycle is automatically activated by the Master Controller electronic control system, saving the user energy, according to the company.

When the demand defrost feature determines defrost is necessary, the reverse-cycle valve is automatically activated and the high temperature refrigerant flow is reversed through a multistep process. Once triggered, the refrigerant flows back through the evaporator coil, heating it along its entire length and eliminating frost buildup, said the company.

"While other reverse-cycle methods exist, ours is unique because it is controlled by the electric expansion valve found within the Master Controller system. Other systems rely on mechanical components, such as check valves and extra thermostatic expansion valves, to control the reverse cycle valve," said Pat Melvin, engineering manager.

There are several advantages to reverse-cycle technology, he said. First, the process uses less energy than electric defrost heaters, resulting in an 80 percent reduction in defrost energy usage. This savings, coupled with that from the demand defrost, is designed to reduce electrical bills.

Reverse-cycle technology was also created to eliminate the need for defrost heaters, head pressure control valves, check valves, and thermostatic expansion valves.

Melvin said defrost time is lessened. Reverse cycle performs a completely "clean" defrost in 3-5 minutes, he said. "And because defrost is so rapid, there is no noticeable increase in freezer temperature and the product temperature rise is also significantly less."

For more information, call Mary Lowstuter at 800-647-1284, ext. 4203 or e-mail

Publication date: 11/06/2006