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iansoady

Coiled Cables - An Experience

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There have been various heated (excuse the pun) discussions about the merits or otherwise of leaving the mains cable coiled up.

 

Yesterday, I had a 1 KW fan heater running in the garage. It was attached to a reel type extension cable which I foolishly left coiled on the drum.

 

After about an hour, I noticed an odd smell and found the reel too hot to touch. The insulation inside had melted in some places. I dread to think what might have happened had I left it unattended and not noticed.

 

So cables do get hot when left coiled (and 1 KW is only about 4 amps).

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I don't recall anyone disputing the fact that cables O/heat when left coiled on a drum while passing a load,what has been said is they O/heat when coiled while not loaded.

Most extension leads are marked with the max wattage when coiled this is normally 720W.

knarf

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If the reel had anything metal within the coils of cable, it would have heated up and started to melt the cable. Not sure that would happen if the reel was pure wood or plastic.

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It makes no difference what the reel is made of, it is caused by the cable overheating caused by resistance and not being able to dissipate the heat.

knarf

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Not all extension cables are 13A some are only 5A .

 

 

 

Dave

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That's exactly why in my job I refuse to fit floor coverings over electric wires. Customers think I over emphasise the fact that wires get hot and if covered with a floor covering get hotter still

Terry.

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If you have had your house fully insulated you will note that the

installers unfix the cables so they lie on top of the insulation.

I seem to remember that there are tables for cable sizes to

prevent overheating when run on cable tray. But I may be wrong.

Many cable reels have a thermal cut out and instructions to unwind

cable before use, I always put my EHU cable in loose loops to avoid

over heating

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I see it all the time on camp sites, people plugged into the EHU and the cable rolled tightly on a drum, especially in the heat of this country.

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In the home or industrial use cables have different current ratings according to their environment.

knarf


The amount of heat generated is proportional to the current being passed and the amount of time it is being passed.

knarf

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In view of the evidence I feel that all should completely unwind the cable every time regardless of how much current is being passed through. ....Peter

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I used the dyson for a quick job that actualy took 10 mins and as I hadn't pulled all the cord out I was very surprised at just how hot the cable had got in such a short time, it's easy to be fooled even after all these years.

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I used the dyson for a quick job that actualy took 10 mins and as I hadn't pulled all the cord out I was very surprised at just how hot the cable had got in such a short time, it's easy to be fooled even after all these years.

 

That was exactly my thought.

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An open coil is fine, but when on a reel or drum the heat cannot dissipate - I've seen the consequences so I always fully unreel any extension cables before use. Likewise the EHU cable is just loosely coiled never reeled.

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An open coil is fine, but when on a reel or drum the heat cannot dissipate - I've seen the consequences so I always fully unreel any extension cables before use. Likewise the EHU cable is just loosely coiled never reeled.

 

Plus one!

Edited by gravon42

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The heat is generated by the magnetic field caused by having the cable coiled which will vary with the current being drawn through it. .

That's exactly how an electromagnet works.

Having a "loose coil" if loose enough would tend to minimise this, the trouble is peoples definitions of loose will vary.

It is best to uncoil it completely and lay any slack in straight "loops" of at least a metre or so long against the caravan.

(Yes I know that technically makes it a loose coil, but it will, at least, be loose enough to avoid problems).

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I always pull the whole cable out on the odd time we are on EHU. ..................a few years ago we were on a site where a 'vanner had wound his cable tightly around his aquaroll. .....the site owner had kept it as an example as the cable had melted into the plastic. ..........

 

geoff

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It has nothing to do with magnetic fields, as the electrons are moving in opposite directions in a 2 or 3 core cable in the phase and neutral they cancel each other out. If it were the case the same thing would occur in a fully wound cable reel without it passing any current, it doesn't!

It is all to do with,as has been said before, it's inability to dissipate the heat generated by passing a voltage through a resistance.

knarf

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just like bar on a electric fire.

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I learned this lesson at a very early age when one of the mechanics in the workshop used an electric welder coupled to my extension reel which he had borrowed.

 

It was still coiled up and was completely melted. The workshop replaced it though.

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The amount of heat generated is proportional to the current being passed and the amount of time it is being passed.

knarf

The heating effect is proportional to the square of the current (W watts = I2 current X R resistance). So if you double the current the heating effect is 4 times as great.

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The heating effect is proportional to the square of the current (W watts = I2 current X R resistance). So if you double the current the heating effect is 4 times as great.

What's with the shrinking text, thought I'd had one glass too many!!!!! Leave it out will ya ?

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I always pull the whole cable out on the odd time we are on EHU. ..................a few years ago we were on a site where a 'vanner had wound his cable tightly around his aquaroll. .....the site owner had kept it as an example as the cable had melted into the plastic. ..........

 

geoff

I do wonder what planet some of our fellow tin tenter's are on. Why on earth would wrap the ehu lead round an aquaroll???

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The heating effect is proportional to the square of the current (W watts = I2 current X R resistance). So if you double the current the heating effect is 4 times as great.

It is even greater than that, as the cable heats up the resistance increases and the heat as well leading to a melt down.

knarf

I do wonder what planet some of our fellow tin tenter's are on. Why on earth would wrap the ehu lead round an aquaroll???

Perhaps to use the heat generated to keep the water warm!

I find it difficult to believe that a cable wound around an aquaroll could generate enough heat to melt it,It must have been drawing a lot of Amps!

knarf

Edited by KNARF

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It is even greater than that, as the cable heats up the resistance increases and the heat as well leading to a melt down.

knarf

 

Perhaps to use the heat generated to keep the water warm!

I find it difficult to believe that a cable wound around an aquaroll could generate enough heat to melt it,It must have been drawing a lot of Amps!

knarf

Well i guess it could stop it freezing in the winter!!!! I just dont get why anybody would win their ehu cable round an aquaroll, even if there not pulling any load of the ehu its just a strange thing to do!

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It has nothing to do with magnetic fields, as the electrons are moving in opposite directions in a 2 or 3 core cable in the phase and neutral they cancel each other out. If it were the case the same thing would occur in a fully wound cable reel without it passing any current, it doesn't!

It is all to do with,as has been said before, it's inability to dissipate the heat generated by passing a voltage through a resistance.

knarf

The magnetic field produced is directly proportional to the current being drawn through the cable.

That's why you won't get the effect on a fully wound coil without passing any current.

The fact that the electrons are reversing every fiftieth of a second is irrelevant in this context, the problem still exists with either AC or DC supplies.

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