Evaporator Pressure Regulator: Description and Operation

The evaporator pressure regulator (EPR) is a pressure control valve. The EPR is located behind the low-pressure side of the evaporator, and keeps the pressure in the evaporator constant. When the evaporator pressure drops below about 196 kPa (2.0 kg/sq.cm) [28.4 psi] the piston closes to keep the pressure in the evaporator above 196 kPa (2.0 kg/sq.cm) [28.4 psi].
Consequently, the EPR keeps the evaporator temperature and the delivery temperature constant.