The equipment in this month’s troubleshooting problem is a forced-air electric heating system with five resistance-type elements, and in order to ensure that this equipment can operate with maximum efficiency and prevent an electrical system overload on a call for heat, a multiple-step sequencer system employed.

When you arrive in response to the customer’s complaint that the unit “Is just blowing cool air”, you find the indoor temperature to be cool and uncomfortable and the blower motor is operating. An initial check at the return and a supply register shows a lower-than-normal temperature rise. When you check the wiring diagram shown in Figure One and access the electrical system, you proceed with the following electrical checks.

….An amp check of elements 1 through 5 (numbered from the bottom up) shows the manufacturer’s recommended current draw for element 1, and zero amps for elements 2, 3, 4, and 5.

….A voltage check directly at the L1 connection of elements 2, 3, 4, and 5 and the M1 terminals of sequencers 2, 3, 4, and 5 shows 240 VAC, and at the M2 terminals of sequencers 2, 3, 4, and 5 shows 0-volts.

As you next step in checking this electrical system, you accomplish the following tests:

….SEQ #2 control source, 0-volts.

….SEQ #1 terminals A1 and A2, 24 volts.

Your troubleshooting question: What is the next step you need to take in order to get this equipment back on line?

Compare your answer with ours HERE.

Publication date: 11/6/2017

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