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Joined: Jan 2005
Posts: 5,460
Likes: 3
Cat Servant
Sborder, the entire point of my experiment was to see if there was justification for that "rule." We have NOT established there is any hazard in leaving the cord coiled up.
Indeed, many industrial locations (and auto garages) have ceiling-mounted cord reels.

Joined: Jul 2004
Posts: 145
I think Pauluk got it when he showed the comparison between cable sizes, US commercial grade cords are *much* heavier than the UK equivalent.

A pro-grade 2.5mm cord reel (2.5mm being approximately 13 Guage) would be fine wound up even at 13 amps I would think, maybe even 16.

This cable, apparently wasn't.

I have certainly seen grossly undersized cords used coiled, for long periods, with no apparent ill effect, and then something like this comes along and makes you go 'hmm'.

I don't think 'magical' superheating is likely at all, but it may make something marginal, go just the other side of that margin.

Joined: Feb 2004
Posts: 1,438
Ahhh this is reminiscent of a garage I went into where someone was complaining a strip of plugmold had stopped working... with an air compressor and all sorts or goodies loading it up... It traced out to be running on 16/3 orange cord coiled up in the rafters 20+ feet off the floor, the coil looked about like this

Joined: Nov 2000
Posts: 2,148
I have had to repair cord on reels on fire and rescue trucks because of this type of damage. In those cases the reels were 250' of 12-3 and the load 500 to 1000 watts. Often times the outer jacket was melted together about 2/3s of the way into the reel if it had been used with only 75' to 100' unrolled. Note that part of the problem on those reels was the metal rods in the center.

Joined: Oct 2004
Posts: 806
Some time ago whilst browsing the site here I ran into a thread/post where an EC had a coil of 12/2 NM melt down when he used it as an extension cord. If I find it I'll edit this with the link....

I think with the right conditions of coil wrap it is possible for a choke or inductor-like effect to cause excessive heating, with enough build-up to cause damage. As reno pointed out, there are many cord reels in use and statistically, how many have failed in this way? Probably not a lot.

And as rescapt19 mentioned, I'm sure a metal core/rod would act to increase heating effects.

Stupid should be painful.
Joined: Dec 2001
Posts: 2,498
There must have been a significant number of failures, otherwise the Industry would never even consider putting in thermal cutouts as a standard!

Joined: Jun 2003
Posts: 1,143
A few months ago the son of a H.O. I was doing a service & panel upgrade for showed me his cord - he'd been running an air compressor via a 100' 14/3 extension cord.

Quite melty in parts... explained the theory of "electron flow" as best I could.

Joined: Mar 2005
Posts: 1,803
Errr. Is that a steel tube in that drum?....


Wood work but can't!
Joined: Oct 2004
Posts: 806
The core was cardboard tube, while the ends were plastic. I had 4 or 5 layers of cable when done.

reno, I think that was why you didn't see much of a temperature rise in your experiment. So far all the other posts seem to indicate the problem arises when there's metal of any kind in the center core. Would you be willing to try again with a metal cored reel and post the results? [Linked Image]

I'm still looking for that other thread, I'll find it eventually....

Stupid should be painful.
Joined: Oct 2004
Posts: 265
For a control, also roll out your cord so that you can see the temperature rise compared to a cord used in its "intended" state.

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