ECN Forum Forums Photo Discussion Forums Photos for General Discussion Overheated Extension Cord

I'm afraid I have no more details about this mishap. I'm not sure of the source now either -- I stashed the pics and notes on my disk a while ago.

Judging by the original author's description, it sounds as though he would have no knowledge of the precise circumstances either..

As T-R suggested, I would think it's 1.5 sq mm conductors (that's between 15 and 16 AWG).

It looks like the blue version of \"Arctic flex.\"



[This message has been edited by pauluk (edited 09-24-2005).]

This might have happened because it was still on the reel; extension cables, with their paltry length, just can't wind on that many coils, bought by the drum: no limit!

So probably a company DIYer or even a qualified engineer did this!

OK, guys, here's the results of today's experiment.

I used an (nominal rating) 1800 watt space heater as my load. This heater does have temperature settings; I set it on the maximum. Since the day was rather nice (65 degrees F), the heater would not operate at full bore.

For a cord, I wound about 80 ft. of #12 SJEOW (about 2.3mm dia for stranded) around a cable reel.
The reel was 4" diameter at the smallest, and about 5" long. The core was cardboard tube, while the ends were plastic. I had 4 or 5 layers of cable when done.

I placed a thermocouple in the middle of the length, atop the first layer...approximating the location of the char in these pics.


After an hour of running, the thermocouple registered 110 degrees F; I weasured a draw of 11.4 amps. This draw did not vary for the few minutes I measured it.

I did note that one of the molded-on plugs of the cord supplying this set-up was noticeably warm to the touch. The test spool did not seem warm; I did not uncoil the cord.


I would conclude that overheating on a coil is NOT a concern. I would like to repeat this test again some time, with a load closer to 20 amps, and under conditions that would eliminate any cycling that the heater may do; I won't see those conditions until the holigay season.

" I won't see those conditions until the holigay season."


Is this a New thing for Reno
What will the marketers think of next

Wasn't the char under the top layer? Woundn't it have been better to place T/C under top layer? Even in your experiment, if you had checked again in 2 hours, What would the temperature have been? I am also curious to know why heat build up occurred in appoximately the center wraps going end to end.
Larry

I placed only one thermocouple; I had no special reason for placing it there, except that that approximates the location of the scorch in the first pic.

The temp climbed to 90 degrees pretty quickly after I started the test. After about 45 minutes, it was at 108. An hour later, 110. While I did not graph this out, it does appear that the temp had pretty well stabilised.


"Everyone has opinions...but data makes yours stand apart." This test was just an attempt to get some data. I wouldn't want to make a general concusion until I have a little more.
But...it sure looks like the theory that coiling the cord causes some magical super-heating of the cord is on it's way to the dust bin.
Can multiple layers of cord act as an insulator? Sure....we just don't know if this is a problem that needs addressing. Yet...

It does almost look as if somebody may have just bought a reel of Arctic flex and fitted a plug and trailing socket, leaving it coiled up on the original drum.

Assuming this was fitted with normal BS1363 connectors, the highest-rated appliance one would expect to have been connected would have been about 3kW, drawing around 12.5 amps on our 240V supplies.

Of course, if somebody had shoved an adapter or power strip on this extension and then connected multiple loads, the current could have been more. The 13A cartridge fuses in our plugs will carry a substantial overcurrent for quite a long time.

I see no reason to believe it was 1.5mm2 flex. Smaller 0.75mm2 blue arctic flex is readily available in the UK:
http://uk.farnell.com/jsp/endecaSearch/partDetail.jsp?SKU=152382&N=401

It looks a little large in overall diameter for 0.75mm compared to the reel, but I'll admit it's hard to judge in the photo, so it could be.

Even if it were the intermediate 1.0 sq. mm size it wouldn't be too hard to overload.

1.0 sq. mm = #17 approx.

0.75 sq. mm is between #18 and #19 AWG.


Edited to add:

The following link is to a conversion chart in the Technical reference area for those not familiar with European cable sizes:
https://www.electrical-contractor.net/ubb/Forum15/HTML/000087.html



[This message has been edited by pauluk (edited 09-26-2005).]

Pauluk

I just had a customer last week asking why it was important to unwind the cord from a reel. What a great example.

I would like to use this picture on our website as an example of what can happen.

A good example like this may just keep someone else form making a disastrous mistake.

Thanks