Manitowoc Marine Q 1800 Service Manual

Also see for Marine Q 1000: Use and care manual Installation instructions Service technician's handbook

Contents

29Refrigeration SystemOperational Analysis (Diagnostics)GENERALWhen analyzing the refrigeration system, it isimportant to understand that different refrigerationcomponent malfunctions may cause very similarsymptoms.Also, many external factors can make goodrefrigeration components appear bad. These factorscan include improper installation, or water systemmalfunctions such as hot incoming water supply orwater loss.The following two examples illustrate how similarsymptoms can result in a misdiagnosis.1. An expansion valve bulb that is not securelyfastened to the suction line and/or not insulatedwill cause a good expansion valve to flood. If aservice technician fails to check for properexpansion valve bulb mounting, he may replacethe expansion valve in error.The ice machine now functions normally. Thetechnician erroneously thinks that the problemwas properly diagnosed and corrected byreplacing the expansion valve. Actually, theproblem (loose bulb) was corrected when thetechnician properly mounted the bulb of thereplacement expansion valve.The service technician’s failure to check theexpansion valve bulb for proper mounting (anexternal check) resulted in a misdiagnosis andthe needless replacement of a good expansionvalve.3. An ice machine that is low on charge may causea good expansion valve to starve. If a servicetechnician fails to verify the system charge, hemay replace the expansion valve in error.During the replacement procedure, recovery,evacuation and recharging are performedcorrectly. The ice machine now functionsnormally. The technician erroneously thinks thatthe problem was properly diagnosed andcorrected by replacing the expansion valve.The service technician’s failure to check the icemachine for a low charge condition resulted in amisdiagnosis and the needless replacement of agood expansion valve.When analyzing the refrigeration system, use theRefrigeration System Operational Analysis Table.This table, along with detailed checklists andreferences, will help prevent replacing goodrefrigeration components due to external problems.