An operator reported a smell “like something electrical is burning” coming from the power cabinet of the equipment she operates.
An electrician investigated, but he could not smell anything. He opened the cabinet and did a temperature survey with a handheld infrared (IR) thermometer. No hot spots. The wiring all looked good. He was at a loss to explain the reported smell. After some time, he asked the operator if she could still smell that odor, and she said no. But a couple of weeks later, she reported it again.
So, another electrician investigated. As with his predecessor, he could not smell anything. How would you handle this issue at this point?
Some people have a keen sense of smell. She may have been smelling vapor that did not originate in that panel but traveled there through the raceway. It built up enough for this operator to smell it leaking from that cabinet.
Effectively, the first electrician ventilated the cabinet, thus diluting the vapor below the woman's detection threshold. The fact she again detected the odor after two weeks supports this idea.
She may be smelling the results of overheated thermoplastic, as conductor insulation degrades from being chronically overheated but not overheated enough to simply melt away.
Finding the source is probably not the needle in the haystack problem it appears to be. Start at the feeder that supplies this circuit and look for discolored conductors. This situation existed at a plant because of running differently sized parallel conductors.
