EPR valves 101
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)