Your role in this troubleshooting situation is a follow-up to visits by other technicians who responded to this customer’s complaint about the cost of operating their heat pump in the winter. Opinions offered so far range from a possibly failing reversing valve to improper use by the customer, who has been comparing electric bills from several previous years, as the source of the increased utility costs.

When your initial evaluation doesn’t indicate any apparent refrigeration or airflow problems, you decide to do an in-depth evaluation of the electrical system. The diagram in Figure 1 shows a schematic representation of this equipment, and Figure 2 shows the legend.

After operating the equipment for an appropriate amount of time, you initiate the defrost mode, and note that the outdoor fan motor continues to run. Testing with a voltmeter at the appropriate test points, you get the following results:

1. At the coil of the DFR, 240 volts.

2. At contacts 1 and 2 of the DFR, 240 volts.

3. At contacts 4 and 5 of the DFR, 0 volts.

Your troubleshooting question: What is the specific failure that is causing the higher-than-normal operating cost of this equipment?

Compare your answer with ours here.

Publication date: 9/7/2015

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