ICE MACHINES Q-Model Service Manual

Section 4Ice Machine Sequence of OperationRemoteQ450/Q600/Q800/Q1000/Q1300/Q1600/Q1800INITIAL START-UP OR START-UP AFTERAUTOMATIC SHUT-OFF1. Water PurgeBefore the compressor starts, the water pump and waterdump solenoid are energized for 45 seconds, tocompletely purge the ice machine of old water. Thisfeature ensures that the ice making cycle starts withfresh water.The harvest valve and harvest pressure regulating(HPR) solenoid valves also energize during water purge,although they stay on for an additional 5 seconds (50seconds total on time) during the initial refrigerationsystem start-up.2. Refrigeration System Start-UpThe compressor and liquid line solenoid valve energizeafter the 45 second water purge and remain onthroughout the entire Freeze and Harvest Sequences.The water fill valve is energized at the same time as thecompressor. It remains on until the water level sensorcloses for 3 continuous seconds, or until a six-minutetime period has expired. (See “Water Inlet Valve SafetyShutoff,” Page 6-50.). The harvest valve and HPRsolenoid valves remain on for 5 seconds during initialcompressor start-up and then shut off.The remote condenser fan motor starts at the same timethe compressor starts and remains on throughout theentire Freeze and Harvest Sequences. (The compressorand condenser fan motor are wired through thecontactor, therefore, anytime the contactor coil isenergized, the compressor and fan motor are on.)FREEZE SEQUENCE3. PrechillThe compressor is on for 30 seconds prior to water flow,to prechill the evaporator.4. FreezeThe water pump restarts after the 30 second prechill. Aneven flow of water is directed across the evaporator andinto each cube cell, where it freezes. The water fill valvewill cycle on and then off one more time to refill the watertrough. (See Page 4-1.)When sufficient ice has formed, the water flow (not theice) contacts the ice thickness probe. Afterapproximately 7 seconds of continual water contact, theharvest sequence is initiated. The ice machine cannotinitiate a harvest sequence until a 6 minute freeze lockhas been surpassed.Figure 4-4. Freeze Sequence (Typical Q450 Shown)Continued on next page …Part No. 80-1100-3 4-3