flaming extension leads batman!

[robgil]

you know those extension leads that roll up into them selves , the kind that comes on a spool with the plug sockets in the middle ? mine just melted. :shock:
stupidly i left the thing spooled up and plugged an electric heater into it. i knew i could smell burning. so , if you have an extension lead that spools up un-spool it before you use it. apparently (i dont know the science behind it) electricity running through coils/loops creates heat and will melt the cables insulating. luckily my rcd snapped in and prevented the thing from catching fire.

 

[Flyfisher]

I believe it's less to do with the fact that the cable is formed into a loop and more to do with the insulating effect of all the coils not allowing the heat from the cable to dissipate, hence the overheating.

All cables have a small resistance, which causes some power to be dissipated within them - i.e. they heat up. The higher the current flowing through the cable (and an electric fire will be at the upper end of the cable rating), the more power is dissipated and the warmer it becomes.

The continuous current rating for any cable is generally specified in free air (also at a specified ambient temperature) and the current rating will be chosen such that any heat generated will be safely lost to the surrounding air without too much of a temperature rise in the cable insulation. If the cable becomes covered up (e.g. by coiling it on a reel or covering it with loads of loft insulation etc) then it can't lose heat as effectively and its temperature will increase. If the insulation melts then there is a real risk of fire . . . as you have just found out - though, thankfully, without any serious harm.

 

[Feltwell]

Ohh dear. My company makes cable reels, hope it wasn't one of ours!

You should never run a high wattage item such as a heater from any cable reel that is wound up, for exactly the reason that Robgil has found. Low wattage is OK, the reel should be marked up with the appropriate limits.

It must have been an older one - newer reels, sold in about the last 3 years, have to be fitted with a thermal cut-out which should have tripped before anything nasty happened. The RCD tripping was lucky, as the reel could easily have caught fire before that happened.

 

[robgil]

i bought it from wickes a few months ago. next one i buy will not be a reel cable , i cant trust myself to unspool it before using it.

 

[Flyfisher]

It must have been an older one - newer reels, sold in about the last 3 years, have to be fitted with a thermal cut-out which should have tripped before anything nasty happened. The RCD tripping was lucky, as the reel could easily have caught fire before that happened.

I've got a few old extension reels but only the one I bought last year has a thermal cut-out. I thought it was just a 'feature' rather than an actual requirement. A very good idea though because it's a classic accident-waiting-to-happen to rely on people to fully unreel the cable, which is very easy to forget when most of the time it isn't strictly necessary (e.g. when drilling a hole, or running an inspection lamp and other low-power/short-duration tasks).

Good point about the 'luck' of the RCD tripping as well. They are very useful things but they don't magically make electrical things totally safe. They can save your life in certain situations yet do nothing in others.

 

[Feltwell]

i bought it from wickes a few months ago. next one i buy will not be a reel cable , i cant trust myself to unspool it before using it.

Ahh - not one of ours then!

There's nothing wrong with cable reels, just make sure you get a decent one with a thermal cut-out. I can confidently predict that any other major chain DIY retailer will sell you one from a known source :wink:

I've got a few old extension reels but only the one I bought last year has a thermal cut-out. I thought it was just a 'feature' rather than an actual requirement. A very good idea though because it's a classic accident-waiting-to-happen to rely on people to fully unreel the cable, which is very easy to forget when most of the time it isn't strictly necessary (e.g. when drilling a hole, or running an inspection lamp and other low-power/short-duration tasks).

Good point about the 'luck' of the RCD tripping as well. They are very useful things but they don't magically make electrical things totally safe. They can save your life in certain situations yet do nothing in others.

To comply with British Standards anything manufactured after a certain date has to have a thermal cutout fitted. In truth, for short durations although not recommended you'll get away with putting a high current through a cable reel when coiled up - but if you have a sustained high load (such as a heater) then you may have a problem. There are some (no pun intended) shockingly bad quality cable reels and extension leads on the market, sold in some big name retailers, that do not comply with the British Standards and should not be on sale. I am not hinting at or including Wickes in this statement by the way, as I don't know their source (and I don't want to be sued!).

 

[Flyfisher]

My recent reel was loaded with safety goodies. Apart from the thermal cut-out there were indicator lights for power and 'good earth' and the plug had a built-in RCD.

 

[Feltwell]

My recent reel was loaded with safety goodies. Apart from the thermal cut-out there were indicator lights for power and 'good earth' and the plug had a built-in RCD.

Hmmm, who made that one I wonder????

:wink:

Robgil, please check your PM's.

 

[MdB]

Just to give you a feel for the problems, one of my extension reels has a 6 amp rating when unwound and a 4 amp rating when wound. If you were to plug in a 3kW fire, then this would draw 12.5A! and it would cause the extension lead to overheat if wound or unwound.

The rating for the reel should be marked on it but if it isn't, a quick and dirty check is that the cable diameter of the reel should the same or larger than that on the device being used.

 

[Flyfisher]

Yes, I have a couple of those smaller 6A reels. They coil up inside the housing rather than being on an open reel. Very handy things to have for power tools and the like but no good for heavy things like electric fires. They should be fitted with a 5 amp fuse so a 3kW electric fire should cause the fuse to blow and thus protect the reel from overheating - but I wonder how many are fitted with 13A fuses, possibly after the original 5A fuse has blown due to overloading?

My recent reel was loaded with safety goodies. Apart from the thermal cut-out there were indicator lights for power and 'good earth' and the plug had a built-in RCD.

Hmmm, who made that one I wonder????

Not sure, but it came from Screwfix and has blue cable . . . one of yours?

 

[Feltwell]

Not sure, but it came from Screwfix and has blue cable . . . one of yours?

Yes.

All cable reels should be marked with a "wound" and "unwound" capacity, which is intended for "continuous" use. Personally I don't bother with the small 6amp reels - just too easy to overload. Our smallest are rated at 10amp, most at 13amp.

 

[AMc]

At an old office a colleague managed to glue one of the cassette type leads to the carpet - that was just running a couple of old powermacs off it all week. I have a lovely 50m yellow reel that allows me to get to the ends of the garden with the hedge trimmer, but I am careful to unreel it all when I'm planning on working for more than a few minutes.
I have to admit that I have my plugin RCD waiting to be returned under it's "lifetime guarantee' after the earth pin just fell out while I was mowing the lawn last year :shock:

 

[Onetap]

That is the second time I've heard of that happening, the first time could have caused a major fire, if the owner had been out.

I have to admit that I have my plugin RCD waiting to be returned under it's "lifetime guarantee' after the earth pin just fell out while I was mowing the lawn last year :shock:

Any safety device with a 'lifetime' guarantee is tempting fate.

 

[skier-hughes]

I'll give you a third then.....

Last years school fete, hired in bbq, which was electric..... they didn't uncoil extension lead, heavy smell of burning, not the food, ooops the cabel reel, all welded together.

 

[robgil]

guys , ive just had a look at this lead , its rated at 4 amps wound , 10 amps unwound however its got a 13 amp fuse , surely a 13 amp fuse is too big a fuse for a lead that's rated at 10 amps , especially a lead that has no thermal cut out? also , for some reason they dont have them advertised on wicks web site.

 

[Mo-sizely]

At least it would have been somewhere to keep your paperclips.. im sure that it had some magnetic properties...

 

[Flyfisher]

guys , ive just had a look at this lead , its rated at 4 amps wound , 10 amps unwound however its got a 13 amp fuse

Could have been worse, it could have had a bolt instead of a fuse. :lol:

Seriously though, I do agree, but 10A fuses are not exactly standard items. A 5A fuse would have been a lot better though.

It's probably better to spend a little more on a properly-rated 13A extension cable, although it would still need to be fully uncoiled to safely handle an electric fire.

Any safety device with a 'lifetime' guarantee is tempting fate.

Yes, I've often wondered what that means in practice. When it breaks, is that the end of its 'lifetime' and thus the guarantee?

Actually, the standard one year guarantee is all very well, but there's also the concept of 'fitness-for-purpose' in consumer law and durable goods can be reasonably expected to last for longer than one year anyway. I once returned a microwave oven to John Lewis for repair that was well over one year old and it was JL that told me the failure wasn't acceptable! They arranged to have it repaired at no cost to me. Same thing happened with a DVD player, except they replaced it with a brand new unit. I presume they pushed the cost back to the original manufacturers so it probably didn't cost them anything either, but it's good to know that they're on your side when anything goes wrong. That's what I call real customer service and is the sort of thing that ensures we shop there a lot.

 

[robgil]

guys , ive just had a look at this lead , its rated at 4 amps wound , 10 amps unwound however its got a 13 amp fuse

Could have been worse, it could have had a bolt instead of a fuse. :lol:

Seriously though, I do agree, but 10A fuses are not exactly standard items. A 5A fuse would have been a lot better though.

It's probably better to spend a little more on a properly-rated 13A extension cable, although it would still need to be fully uncoiled to safely handle an electric fire.

its worrisome when you think about it , they could easily have used cable rated fort 13 amps if they could not get 10 amp fuses to match 10 amp cable, i know its only 3 amps but it still sounds daft to me.

 

[Flyfisher]

Price-pressure I guess. You could have bought a 13A cable in the first place.

 

[Penners]

You should never run a high wattage item such as a heater from any cable reel that is wound up, for exactly the reason that Robgil has found. Low wattage is OK, the reel should be marked up with the appropriate limits.

Feltwell, is here any truth to the rumour* that, as well as the "trapped heat" effect of running a high wattage item from a coiled cable, the hazards of this are also exacerbated by the induction effect of the coiled cable?




*Otherwise known as Penners' inexpert, amateur and probably ridiculous theory.