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#122077 - 09/21/05 09:37 PM Overheated Extension Cord  
pauluk  Offline
Member
Joined: Aug 2001
Posts: 7,520
Norfolk, England
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.

Quote
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.


[Linked Image]

[Linked Image]


Tools for Electricians:

#122078 - 09/21/05 11:58 PM Re: Overheated Extension Cord  
Alan Belson  Offline
Member
Joined: Mar 2005
Posts: 1,803
Mayenne N. France
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!

Alan


Wood work but can't!

#122079 - 09/22/05 07:52 PM Re: Overheated Extension Cord  
ShockMe77  Offline
Member
Joined: Jun 2005
Posts: 821
Rahway, New Jersey
^^
Not mention the money the company wasted! LOL.

I have never seen anything like this before, thats for sure...


#122080 - 09/22/05 08:42 PM Re: Overheated Extension Cord  
Jim M  Offline
Member
Joined: Aug 2001
Posts: 457
Chestertown, MD, USA
Of course it is a cardboard roll. If they used a metal reel everything steel would have been flying thru the air and landing on the magnetized coil.


#122081 - 09/22/05 10:48 PM Re: Overheated Extension Cord  
NJwirenut  Offline
Member
Joined: Sep 2001
Posts: 806
Bergen County, NJ
I've replaced a few of those overhead retractable cord reels used in garages, etc. Exactly the same failure mode when someone plugs in a heavy load without unreeling the entire length of cable.


#122082 - 09/23/05 10:06 AM Re: Overheated Extension Cord  
Texas_Ranger  Offline
Member
Joined: Dec 2001
Posts: 2,399
Vienna, Austria
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...


#122083 - 09/23/05 10:17 AM Re: Overheated Extension Cord  
Dave T  Offline
Member
Joined: Jan 2005
Posts: 155
Waukesha, WI, USA
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.


#122084 - 09/23/05 11:37 AM Re: Overheated Extension Cord  
pauluk  Offline
Member
Joined: Aug 2001
Posts: 7,520
Norfolk, England
Quote
If they used a metal reel everything steel would have been flying thru the air and landing on the magnetized coil.


With opposing AC currents in adjacent conductors? [Linked Image]

The center of this is actually metal. As Alan pointed out, this reel is the type that our equivalent of Romex comes on -- A central metal cylinder with cardboard disks fitted each end.


#122085 - 09/23/05 08:21 PM Re: Overheated Extension Cord  
renosteinke  Offline
Cat Servant
Member
Joined: Jan 2005
Posts: 5,316
Blue Collar Country
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?


#122086 - 09/24/05 10:16 AM Re: Overheated Extension Cord  
Texas_Ranger  Offline
Member
Joined: Dec 2001
Posts: 2,399
Vienna, Austria
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.


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