Figure 1. (Click on the image for an enlarged view.)

Your role in this month’s troubleshooting situation is as the follow-up technician on a problem that was made worse by the technician who preceded you. When the restaurant manager originally called for service, the complaint was that their small walk-in cooler “wasn’t keeping as cool as usual.” After the initial visit by another technician, who advised you before you went on the follow-up call that he added a significant amount of refrigerant, the customer’s description of the problem is that the unit is “hardly cooling at all.”

When you arrive, you confirm the customer’s description of the equipment’s performance and find initially that the refrigeration system pressures are far beyond what you would expect them to be, indicating that the system is obviously overcharged. Based on the information from the original technician, you decide to make two temperature tests (see the illustration in Figure 1), and when you do, you note a temperature drop of 8°F between Test A and Test B.

Your troubleshooting question: What is the specific failure that caused the original performance problem, and what do you have to do to get this unit back on line?

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Publication date:07/05/2010