An opportunity to use CPR (crankcase pressure regulator)

The suction pressure regulator is also called a “hold-back” valve or a crankcase pressure regulator. It limits compressor suction pressure (regulator outlet pressure) to a maximum value. This type of regulator is installed in the suction line at the compressor. It is used on any installation where the liquid expansion valve cannot limit suction pressure. Some designs may include a flared access port on the inlet side to monitor the pressure and valve operation.

Compressor motor overload would otherwise exist because of:

• excessive starting load
• excessive suction pressure following the defrost cycle
• prolonged operation at excessive suction pressure
• low-voltage and high-suction pressure conditions

Excerpt from the Technical Institute Manual #2, available at the online store of the Refrigeration Service Engineers Society, THE HVACR TRAINING AUTHORITY.

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