Manitowoc

ANALYZING WHY SAFETY LIMITS MAY STOP THEICE MACHINEAccording to the refrigeration industry, a highpercentage of compressor failure is a result of externalcauses. These can include flooding or starvingexpansion valves, dirty condensers, water loss to theice machine, etc. The safety limits protect the icemachine (primarily the compressor) from externalfailures by stopping ice machine operation beforemajor component damage occurs.The safety limit system is similar to a high-pressurecutout control. It stops the ice machine, but does nottell what is wrong. The service technician mustanalyze the system to determine what caused thehigh-pressure cutout, or a particular safety limit, tostop the ice machine.The safety limits are designed to stop the ice machineprior to major component failures, most often a minorproblem or something external to the ice machine.This may be difficult to diagnose, as many externalproblems occur intermittently.Example: An ice machine stops intermittently onsafety limit #1 (long freeze times). The problem couldbe a low ambient temperature at night, a waterpressure drop; the water is turned off one night aweek, etc.When a high-pressure cutout or a safety limit stops theice machine, they are doing what they are supposed todo. That is, stopping the ice machine before a majorcomponent failure occurs.Refrigeration and electrical component failures mayalso trip a safety limit. Eliminate all electricalcomponents and external causes first. If it appearsthat the refrigeration system is causing the problem,use Manitowoc’s Refrigeration System OperationalAnalysis Table, along with detailed charts, checklists,and other references to determine the cause.Part Number 80-01111-9 7/10 111