Refrigeration System | Section 7 |
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Operational Analysis (Diagnostics)
GENERAL
When analyzing the refrigeration system, it is important to understand that different refrigeration component malfunctions may cause very similar symptoms.
Also, many external factors can make good refrigeration components appear bad. These factors can include improper installation, or water system malfunctions such as hot incoming water supply or water loss.
The following two examples illustrate how similar symptoms can result in a misdiagnosis.
1.An expansion valve bulb that is not securely fastened to the suction line and/or not insulated will cause a good expansion valve to flood. If a service technician fails to check for proper expansion valve bulb mounting, he may replace the expansion valve in error.
The ice machine now functions normally. The technician erroneously thinks that the problem was properly diagnosed and corrected by replacing the expansion valve. Actually, the problem (loose bulb) was corrected when the technician properly mounted the bulb of the replacement expansion valve.
The service technician’s failure to check the expansion valve bulb for proper mounting (an external check) resulted in a misdiagnosis and the needless replacement of a good expansion valve.
2.An ice machine that is low on charge may cause a good expansion valve to starve. If a service technician fails to verify the system charge, he may replace the expansion valve in error.
During the replacement procedure, recovery, evacuation and recharging are performed correctly. The ice machine now functions normally. The technician erroneously thinks that the problem was properly diagnosed and corrected by replacing the expansion valve.
The service technician’s failure to check the ice machine for a low charge condition resulted in a misdiagnosis and the needless replacement of a good expansion valve.
When analyzing the refrigeration system, use the Refrigeration System Operational Analysis Table. This table, along with detailed checklists and references, will help prevent replacing good refrigeration components due to external problems.
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