Head pressure control is key to proper refrigeration. Here is a common problem and a solution for it.
Problem: As the outdoor ambient gets lower, head pressure also will drop. This will result in poor refrigeration and component damage can occur.
For example, when the ambient drops to 0 ° F, head pressure actually will be lower than the back pressure for medium- and high-pressure applications. The TXV will not be able to feed refrigerant to the evaporator and the space temperature will not be able to be achieved.
Solution: Install a head-pressure control system. These systems will cause the head pressure to remain up during low-ambient conditions. There are various methods of head-pressure control systems: dual valve/valve-and-check-valve method, dual valve/two-valve method, and single-valve method.
This is one solution. There are other methods for controlling head pressure.
Source: Supermarket Refrigeration Seminar by Arthur Miller, CMS.
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