In many supermarket applications refrigerant gas from the discharge line or from the top of the receiver is used for defrost.This method of defrost diverts a portion of the hot gas or cool gas (from the top of the receiver) to the suction line and back through the evaporator being defrosted. The gas condenses in the evaporator and flows in reverse, through check valves, around the TEV and liquid line solenoid valve. Liquid refrigerant then flows to the liquid header where it is distributed to evaporators not in the defrost cycle. In order for this reverse flow to occur, the pressure of the defrost header must be greater than the pressure of the liquid header. The difference in pressure is known as the defrost differential.
Several methods are used to obtain the defrost differential. The (O)LDR is designed to maintain a differential pressure between the receiver and the liquid header.
Sporlan liquid line differential valves have a solenoid bypass feature that allows the valve to remain full open or modulate to maintain a differential. We supply two versions of liquid line differential valves:
The OLDR is in the full open position when the coil is de-energized, and it’s in differential operation mode when the coil is energized.
The LDR is in differential operation mode when the coil is de-energized, and it is in the full open position when the coil isenergized.
The DDR-20 is designed to create a differential pressure between its inlet (discharge) pressure and the receiver pressure.