ICE MACHINES Q-Model Service Manual

Section 4Ice Machine Sequence of OperationSelf-Contained Air- and Water-CooledQ200/Q280/Q320/Q370/Q420/Q450/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(s) is also energized during waterpurge, although it stays on for an additional 5 seconds(50 seconds total on time) during the initial refrigerationsystem start-up.2. Refrigeration System Start-UpThe compressor starts after the 45 second water purge,and it remains on throughout the entire Freeze andHarvest Sequences. The water fill valve is energized atthe same time as the compressor. It remains on until thewater level sensor closes for 3 continuous seconds, oruntil a six-minute time period has expired. (See “WaterInlet Valve Safety Shutoff,” Page 6-50.) The harvestvalve(s) remains on for 5 seconds during initialcompressor start-up and then shuts off.At the same time the compressor starts, the condenserfan motor (air-cooled models) is supplied with powerthroughout the entire Freeze and Harvest Sequences.The fan motor is wired through a fan cycle pressurecontrol, therefore it may cycle on and off. (Thecompressor and condenser fan motor are wired throughthe contactor. As a result, anytime the contactor coil isenergized, the compressor and fan motor are suppliedwith power.)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.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 4-1. Freeze Sequence(Typical Q450 Shown)Continued on next page …Part No. 80-1100-3 4-1