The equipment in this month’s troubleshooting problem is an electric furnace that has been in service for at least ten years, according to the customer who is reporting that the unit is running almost constantly but not keeping the building comfortable. Also, according to the customer, this unit has no service history.
When you arrive, you get additional information from the customer. They tell you that they considered calling near the end of the previous heating season because they weren’t sure that the system was performing like it should, but they put it off. Their description of the problem is that it is worse than it was last year. You also find that while this equipment could serve as an air handler for comfort cooling in the summer, it’s not being employed as such, used only as a stand-alone straight heating system. The cooling equipment for the building is a separate system.
As your first step, you confirm that the filter is clean. And when you check the wiring diagram shown in Figure One (top), you note that the indoor blower motor is wired to ORG and RED and is operating normally. After confirming that the temperature rise is insufficient, you check the electrical system, and find 240 VAC applied to terminals L and R on each of the four heating element connections. Your subsequent ammeter tests show a current draw within the manufacturer’s specifications on two of the elements, while at the top element (ORG from Circuit Breaker #1) and the bottom element (BLK from Circuit Breaker #2) show 0-Amps.
Your troubleshooting question: What is your next step in servicing this equipment?
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