According to the refrigeration industry, a high percentage of ice machine compressors fail because of external causes. These can include flooding or starving expansion valves, dirty condensers, water loss tot the ice machine and others.
Safety limits protect the ice machine (primarily the compressor) from external failures by stopping operation before major component damage occurs. The safety limit system is similar to a high pressure cut-out control. It stops the ice machine but doesn't say what's wrong.
The service technician must analyze the system to determine what caused the high pressure cut-out, or a particular safety limit, to stop the ice machine.
Safety limits stop the ice machine prior to major component failures. Most often safety limits signal a minor problem or something external to the ice machine. This may be difficult to diagnose, as many external problems occur intermittently.
For example, an ice machine may stop intermittently on safety limit No. 1 (long freeze times). The problem could be a low-ambient temperature at night, a water pressure drop, or the water is turned off one night a week or other.
Refrigeration and electrical component failures may also trip a safety limit. Eliminate all electrical components and external causes first.
If it appears the refrigeration system is causing the problem, use the manufacturer's operational manual, along with detailed charts, checklists another references to determine the cause.
Source: Manitowoc Ice Machines Service Technician's Handbook
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