More than a few times in the course of my travels, I have seen central vacuum power units whose electrical plugs had melted.
Often, this happens on older machines with heavy electrical consumption. My remedy in the past had been, after verifying the motors were not drawing excessive current, to simply replace the power cord. I might have plugged it into the other (non-heat damaged) side of the duplex outlet, wished my customer “happy vacuuming” and been on my way.
My more recent discovery is that the receptacle itself is most often the root of the problem. Of course, the power cord must still be replaced, but replacement of the receptacle is a critical step. Over time, older receptacles lose their grip on plugs, and a poor internal connection will cause problems when high-current appliances are used. The replacement receptacle should be heavy-duty or “spec grade”, and wiring connections should be made properly using screw terminals, NOT push-in “back stab” terminals. Also, be sure to orient the receptacle, if possible, in such a way as to minimize strain on the power cord and plug.
A good quality replacement receptacle and power cord will safely carry current right up to the rated amperage limit of the circuit, indefinitely. As a final note, it is always recommended to connect the equipment directly to a receptacle, not through an extension cord or power strip. Extra receptacles can be added by a qualified electrician.
Get in the habit of giving your built-in vacuum unit the “once over” when you empty it. If you see something that needs attention, visit www.justcentralvacs.com or call (630) 608-0175 for a free, friendly evaluation.