Heat at plug end of power cord higher than rest of cord

[FactChecker]

In running my vacuum cleaner, I have noticed that the plug end of the cord gets warmer than the rest of the cord. Since the wire gauge and current must be the same through the entire length, why would this happen? I have noticed this regardless of the wall socket that I use and it doesn't seem like the wall socket gets hot. Does it imply that the vacuum cleaner cord is defective at the plug end? Perhaps I should test if it still happens when a heavy gauge extension is used and see if any part warms up.

 

[CWatters]

Does the plug itself get hot?

 

[FactChecker]

Does the plug itself get hot?

Not that I can tell. It just seems to be the first foot or so of cord. But the plug plastic is thicker, so that might hide heating there. I tested it in a large capacity extension cord and it warms up at the vacuum plug end, not at the wall socket. I can only think of one possible reason: a bad cord at that end. I will see if I can notice that behavior in other high watt appliance cords.

 

[Aaron Crowl]

If there is a bad connection between the vacuum and the plug there will be some resistance there. The high resistance of the connection will heat up as the vacuum cleaner draws current. You could have something as low as a 1 Ohm connection and this would be a problem. If your vacuum cleaner draws about five amps then you would essentially have a 25 Watt heater in the cord. There would only be a 5 Volt drop so your vacuum would still operate.

This is a common enough problem that there is an entire industry dedicated to using IR cameras to find bad connections in industrial settings. The idea is to catch problems by looking for high heat in equipment. That way you can repair it before it fails.

Does the cord look like it was pinched or severely bent anywhere? Your cord should be made of braided wire. It might be hanging by a thread inside the insulation.

 

[FactChecker]

If there is a bad connection between the vacuum and the plug there will be some resistance there. The high resistance of the connection will heat up as the vacuum cleaner draws current. You could have something as low as a 1 Ohm connection and this would be a problem.

This confirms my suspicion that there must be a problem at that end of the cord. I was wondering if I might be overlooking something about heating in a good cord, but I guess not.

This is a common enough problem that there is an entire industry dedicated to using IR cameras to find bad connections in industrial settings. The idea is to catch problems by looking for high heat in equipment. That way you can repair it before it fails.

Interesting.

Does the cord look like it was pinched or severely bent anywhere? Your cord should be made of braided wire. It might be hanging by a thread inside the insulation.

No. It looks fine. But I am going to assume that there is something wrong at the plug end, cut off that end, and replace the plug.
Thanks.

 

[Averagesupernova]

It depends on how warm. Connections are never 100% perfect and will always heat depending upon how much current is passing.

 

[rbelli1]

This is something I have noticed on most high power appliances. I just assumed that it was the contact resistance between the plug and socket. Also many cords are crimped inside. They will also have an increased resistance at that point.

BoB