Can You Solve the Service Ticket?
Winner to Receive Fieldpiece LT-17A Digital Multimeter
There’s still time to get in on the June drawing for a Fieldpiece LT-1A digital meter. Submit your diagnosis to the troubleshooting situation — featured in the Dec. 15 issue of The NEWS — involving an electric furnace and a customer’s complaint of not enough heat.
To recap, a check of the airflow system showed the volume was normal, but the discharge air temperature was far below the manufacturer’s specifications. And, a current draw check showed 0 A on two of the elements (review the wiring diagram) connected via the YEL wiring to their sequencer.
When submitting your diagnosis to the two-part troubleshooting question we asked:
1. What did your check of the M1/M2 and M3/M4 connections tell you about the condition of the elements and the limit switches and fusible links wired in series with the elements?
2. What is the next step to take in servicing this equipment?
And, recall that your voltage tests yielded the following information;
….240 VAC across connections M1 and M2 of the sequencer;
….240 VAC across connections M3 and M4 of the sequencer; and
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….24 VAC at H1 and H2 of the sequencer.
Consider this fundamental concept of understanding and troubleshooting an electrical circuit. When switches (control or safety) are wired in series with the load they control, the two simple rules apply to their operation are, first, that voltage will be read across an open switch, and, second, that no voltage will be read across a closed switch.
If you believe you have the answer to this troubleshooting problem, please submit your diagnosis by email to Jim Johnson at thenewstroubleshooting@techtrainassoc.com. In the subject line, please print “Service Ticket Answer” and indicate which issue of The NEWS the problem you are responding to was published. You can also submit your answer by regular mail to Technical Training Associates, PO Box 2259, Green Valley, AZ 85622-2259.
All correct answers will be entered into a drawing, the winner of which will receive a Fieldpiece LT-17A digital multimeter.
Publication date: 3/9/2015
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