ICE MACHINES Q-Model Service Manual

Refrigeration System Section 7FREEZE CYCLEThe H.P.R. system is not used during the freeze cycle.The H.P.R. solenoid is closed (de-energized), preventingrefrigerant flow into the H.P.R. valve.HARVEST CYCLEDuring the harvest cycle, the check valve in thedischarge line prevents refrigerant in the remotecondenser and receiver from backfeeding into theevaporator and condensing to liquid.The H.P.R. solenoid is opened (energized) during theharvest cycle, allowing refrigerant gas from the top of thereceiver to flow into the H.P.R. valve. The H.P.R. valvemodulates open and closed, raising the suction pressurehigh enough to sustain heat for the harvest cycle,without allowing refrigerant to condense to liquid in theevaporator.In general, harvest cycle suction pressure rises, thenstabilizes in the range of 75-100 psig (517-758 kPA).Exact pressures vary from model to model. These canbe found in the “Operational Refrigerant Pressures”charts, beginning on Page 7-32.7-28 Part No. 80-1100-3