Here we have a graphic demonstration from the U.K. of the damage which can result from running a heavy load on a coiled extension cord.
I came across this extension lead in work, I was borrowing it from another department. They kept it coiled on a cable reel. When I collected the extension cable it looked fine, when I began to uncoil it; it still looked fine, until I had removed the first set of turns, the whole outer coil, then I noticed a problem. The inner coils wouldn't unwind, they had melted into an amorphous blob of plastic and copper. Clearly someone had run this extension lead at close to full load when it was coiled. The cable heated up but as the cable was coiled the heat couldn't dissipate fast enough and the cable just kept getting hotter, until it melted.
I forced off some of the second layer of coils so that I could see exactly the extent of the damage.
This is a cardboard drum of cable, as supplied by the manufacturer, and adapted to make up an extension reel!!? - Unless the Chinese re-exported this from The New Guinea Rain Forest Economic Electric Co Inc. The mind boggles at what crass idiocies businesses will get up to to save a few pounds!
Help! Guess that's why all real extension cord reels here now have a thermal cutout!
Mine is bit hefty though... sometimes it trips on the load of a standard 18W flourescent wand the second you plug it in, out in cold weather... a hefty kick on the reel or stomping it onto the ground usually helps...
Re: Overheated Extension Cord#122083 09/23/0509:17 AM09/23/0509:17 AM
My son learned a valuable lesson after he plugged in a heatgun into the outlet on my retractable trouble light drop cord while working in the garage. I discovered it the next time that I tried to extend it to work on the car. That may be why most retractable trouble lights (if not all) sold today don't have outlets on them today. It's one of those thngs you forget about and them after it happens "dah" I should have known better.
Re: Overheated Extension Cord#122084 09/23/0510:37 AM09/23/0510:37 AM
I have an extension cord mounted on a reel, with receptacles in the end cap. I find it very useful, and a great way to transport and store the cord. While mine is home-built, it anticipated the commercial manufacture and sale of a similar product- though theirs' is a lighter-duty version.
The commercial product is, I believe, UL listed. My cord does not show any signs of heat damage.
I would be very interested in learning the details of this melt-down. What wire size? How many amps? Over how long a time?
With the neutral accompanying the hot wire within the cord, I have trouble thinking "induction heating" occurred. Rather, I think that heat built up as if the wire was within thermal insulation.....and only reached melt-down because of overloading.
Anyone willing to set up a test?
Re: Overheated Extension Cord#122086 09/24/0509:16 AM09/24/0509:16 AM
I assume 1,5 sq mm wire and a significant overload. Commercially manufactured ones for 230V usually have a label "1500W max. when rolled up, 3500W completely unwound", that means 6.5 and 16A. So a 16A load might already be able to do that.