Emerson
PRE evaporator pressure regulators accurately maintain a predetermined minimum evaporator pressure, regardless of sudden load or suction pressure changes.
These valves operate from an inlet pressure signal, opening on rise in pressure above the valve set point and closing at any inlet pressure below the set point to prevent lower evaporating pressures than designed. Evaporator pressure regulators can also be used to avoid freezing of water in water chillers or to avoid too low evaporating temperatures in air-conditioning systems. As a further application an evaporator pressure regulator allows to a system to operate with different evaporating temperatures in a multiple evaporator system. Compressor cycling using pressure or temperature controls is not always satisfactory. Although a thermostatic expansion valve can regulate the flow of refrigerant depending on the load at the evaporator, it cannot control evaporator pressure.
