Photo Courtesy of Parker / Sporlan

There are many brands and styles of Evaporator Pressure Regulating valves (EPR), but none as common as the Parker / Sporlan SORIT and ORIT valves.

The diagram above  clearly shows some of the common applications. An EPR or “hold back” valve maintains a set suction line pressure and therefore coil temperature. This is critical in situations where multiple evaporators of different design temperatures connect back to a shared suction header as is common in grocery store refrigeration.

The EPR valve “holds back” pressure in the evaporator to a set pressure so long as there is a pressure differential between the evaporator coil and the shared suction header. The suction header must have a LOWER pressure than the lowest design pressure of any evaporator connected to it.

A SORIT valve is an EPR valve or ORIT (Open on Rise of Inlet Pressure) valve that also includes a solenoid stop.  The purpose of the solenoid stop is to
prevent the defrost gas from entering the suction line and overheating/overloading the compressors when the defrost solenoid opens and back feeds the evaporator to defrost.

For a full and detailed explanation of ORIT and SORIT valves, you can read BULLETIN 90-20 from Parker Sporlan.

— Bryan

 


I don’t do much in the way of “rack” refrigeration, but I recently had a conversation with experienced rack refrigeration tech Jeremy Smith and he got me thinking about EPR valves.

I’ve heard EPR (Evaporator pressure regulator) valves called suction regulators or hold back valves. In essence they hold back against the suction line to maintain a set evaporator evaporation or boiling temperature.

In refrigeration rack systems EPR valves play a vital role in ensuring that the product is cooled consistently and nearly constantly.

In an A/C system we have a TXV that maintains a constant superheat at the evaporator outlet. The evaporator temperature itself will fluctuate up and down depending on load.

In a refrigeration case you must first ensure you have full line of liquid using a sight glass or by checking subcooling. Then you make sure the case has proper airflow etc… then you set the EPR to maintain the proper coil evaporation temperature (by holding back pressure as needed) and then you check and / or set the TXV to the proper superheat. This ensures BOTH proper coil feeding as well as proper coil temperature.

Pretty cool right? (Pun intended)

— Bryan

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