Overloaded extension lead

[Lower]

This was a 40m extension lead partially uncoiled and left running a dehumidifier and a fan heater overnight. It ran for about 14 hours before tripping the RCD.



The extension lead was rated to 13a when fully extended by only 3a when coiled.

The extended section of cable was cold to the touch. But the centre of the coil got rather hot.

It all stopped working when the smoke was let out.....

A very good example of why its important to pay attention to cable ratings and consider de-rating when the cable is in an insulated or confined space.

 

[ericmark]

It is so easy to include an over temperature device in the centre of a cable reel to auto switch it off before it over heats, with a enclosed type of extension it is so easy to think it's all out where in fact it has jammed, it is hard to add an over temperature device as an extra but so easy during the design and manufacture.

What it shows is poor design.

 

[ericmark]

It is so easy to include an over temperature device in the centre of a cable reel to auto switch it off before it over heats, with a enclosed type of extension it is so easy to think it's all out where in fact it has jammed, it is hard to add an over temperature device as an extra but so easy during the design and manufacture.

What it shows is poor design.

 

[JohnW2]

It is so easy to include an over temperature device in the centre of a cable reel to auto switch it off before it over heats, with a enclosed type of extension it is so easy to think it's all out where in fact it has jammed, it is hard to add an over temperature device as an extra but so easy during the design and manufacture.

Indeed. Some of the ones I have do have some sort of 'cutout' (with a 'reset' button) - but I'm not sure whether it is current-operated or temperature-operated.

Kind Regards, John

 

[securespark]

Thermal, I believe.

Lower, what was the CSA of that lead out of interest?

 

[JohnW2]

Thermal, I believe.

I'm not certain. I need to have a look when I have a moment because, on reflection, I think that ones I have with cut-offs/resets are probably low current (i.e. <13A) ones - for example, 6A ones - and I don't think that any of my 13A ones do have anything like that. If that's the case, then it might increase the chances that it's an over-current cut-off. Watch this space.

Kind Regards, John

 

[Lower]

Thermal, I believe.

Lower, what was the CSA of that lead out of interest?

1.5mm by the look of it.

 

[securespark]

According to the IEE code of practice, that does not compute!

1.25mm² csa max length 12m
1.5mm² csa max length 15m
2.5mm² csa max length 25m

Although there are loads of factory-produced extension leads out there that far exceed these figures. Even ones with 1 milli flex that is not even on the IEE's chart!

 

[Echo the husky]

Isn't it a (British standard?) requirement that all extension reels be fitted with thermal cutouts?

 

[securespark]

Not familiar with the standard...

AFAIK, all Masterplug reels have a cut out, and they operate thermally. But I don't know if this is a standard.

 

[JohnW2]

Isn't it a (British standard?) requirement that all extension reels be fitted with thermal cutouts?

Don't know. If that is the case, then most must have auto-resetting cutouts, since very few (and, as I said, probably no 13A ones I've seen) have any sort of 'reset' button.

Kind Regards, John

 

[Echo the husky]

Neither am I but I seem to remember reading something about it in the pat testing book. Edit: I have several reels here, all have reset buttons on them.

 

[securespark]

The standard Masterplug manufactures to is BS EN 61242 and all their reels have a thermal cut out.

 

[JohnW2]

Neither am I but I seem to remember reading something about it in the pat testing book. Edit: I have several reels here, all have reset buttons on them.

Maybe mine are just old (which I'm sure most of them are!), then! If they have a reset button, then they obviously must have some sort of cut-out - be it thermal or current-operated.

Edit: I think the age of mine must be the issue (I doubt that any of them are less than 20 years old). Screwfix offer 15 extension reels, varying in make and spec - and all of them say that they have a thermal cutout.

Kind Regards, John

 

[Lower]

The extension lead was around 10 years old and had no thermal cutout.

Rated loads were cast into the reel moulding.