ICE MACHINES Q-Model Service Manual

Ice Machine Sequence of Operation Section 4HARVEST SEQUENCE5. Water PurgeThe water pump continues to run, and the water dumpvalve energizes for 45 seconds to purge the water in thesump trough. The water fill valve energizes (turns on)and de-energizes (turns off) strictly by time. The water fillvalve energizes for the last 15 seconds of the 45-secondwater purge. The water purge must be at the factorysetting of 45 seconds for the fill valve to energize duringthe last 15 seconds of the Water Purge. If set at lessthan 45 seconds the water fill valve does not energizeduring the water purge.After the 45 second water purge, the water fill valve,water pump and dump valve de-energize. (Refer to“Water Purge Adjustment” on Page 3-3 for details.) Theharvest valve also opens at the beginning of the waterpurge to divert hot refrigerant gas into the evaporator.6. HarvestThe harvest valve(s) remains open and the refrigerantgas warms the evaporator causing the cubes to slide, asa sheet, off the evaporator and into the storage bin. Thesliding sheet of cubes swings the water curtain out,opening the bin switch. The momentary opening and reclosingof the bin switch terminates the harvestsequence and returns the ice machine to the freezesequence (Step 3 - 4.)AUTOMATIC SHUT-OFF7. Automatic Shut-OffWhen the storage bin is full at the end of a harvestsequence, the sheet of cubes fails to clear the watercurtain and will hold it open. After the water curtain isheld open for 7 seconds, the ice machine shuts off. Theice machine remains off for 3 minutes before it canautomatically restart.The ice machine remains off until enough ice has beenremoved from the storage bin to allow the ice to fall clearof the water curtain. As the water curtain swings back tothe operating position, the bin switch re-closes and theice machine restarts (steps 1 - 2), provided the 3 minutedelay period is complete.Figure 4-3. Automatic Shut-Off (Typical Q450Shown)Figure 4-2. Harvest Sequence (Typical Q450 Shown)4-2 Part No. 80-1100-3