I still don't understand the spur rating !

[masona]

Sorry lads but I can't get my head round this one

I understand the UK electric have the best safely record, this is what I don't understand unless I'm missing something here.

Many household have a double socket spur running of the ring mains socket, the spur cable 2.5mm is rated at 24 amp and if you plugged in 2 x 13 amp apppliances into the double socket spur, surely it would overheat the cable and the double socket which is rated at 13 amp. If this does cause a fire then how can this be safe Shouldn't all spur have a 13 amp FCU to prevent this or why not have the double socket rated at 26 amp

 

[Damocles]

Ultimately it is quite unlikely that you could find two devices in your house which would pull 26A. It is quite hard to load a socket that much except perhaps in your kitchen. And even there it is likely the load will only last for 10 minutes while you boil a kettle. The reason it is safe is that it is quite difficult to load it that much. Experience shows that this is true.

Nice to know we have the safest electrics in the world. Shame the government is trying to stop us keeping it all up to date.

 

[andy]

Sorry lads but I can't get my head round this one

I understand the UK electric have the best safely record, this is what I don't understand unless I'm missing something here.

Many household have a double socket spur running of the ring mains socket, the spur cable 2.5mm is rated at 24 amp and if you plugged in 2 x 13 amp apppliances into the double socket spur, surely it would overheat the cable and the double socket which is rated at 13 amp. If this does cause a fire then how can this be safe Shouldn't all spur have a 13 amp FCU to prevent this or why not have the double socket rated at 26 amp

double sockets are rated 13A MAX. also, 2.5mm is rated 27A?

 

[masona]

Ultimately it is quite unlikely that you could find two devices in your house which would pull 26A. It is quite hard to load a socket that much except perhaps in your kitchen. And even there it is likely the load will only last for 10 minutes while you boil a kettle.

So it take a while to tripped instead of straight away As long as you don't use 2 plugs with a total of more than 13amp together otherwise the socket will overheat over a peroid of time

2.5mm is rated 27A?

I read the 24amp from the TLC website is the current rating.

 

[pipme]

Dual box.

2 Gang box

P

 

[Damocles]

Another way to look at it, is that this is a 32A circuit. We are only talking about one spur here. There is only 32A available for everywhere, so this socket can only ever have 32- however much is being taken elsewhere. Ask yourself, how likely is it that you have everything plugged into this spur through a daisy chain of extension leads, but nothing plugged into any of the other sockets on the same ring. Chances are some of that current is going elsewhere.

Though admittedly, part P is designed to encourage use of extension leads.

But as I said, On paper you are right, it is a bit dodgy. There is a theoretical risk. But in practice it does not happen. it is very unlikely anyone will overload the socket. If it did then people would have noticed and the regulation would have been changed years ago.

 

[ban-all-sheds]

Dual box.

Now they have knockouts between the two halves - why don't the metal ones??

 

[Damocles]

Last metal one I used had a removeable partition

 

[ban-all-sheds]

What make?

 

[Damocles]

Dunno. screwfix cheapo. But there is a picture on here on a different post of a dual box which also looks like it has a removeable centre partition. Little tab sticking up to hold it in place.

 

[mapj1]

If you ring cable is really well insulated (20 A instead of 27A for 2.5mm in lagging rather than in free air) I can see that you might be thinking if this was a spur or right at one end of the ring.

It is important to remember what happens to a cable that is over run - firstly the cable takes perhaps 15/20 mins to get hot at a modest overload (say 2 times normal rating) when it does the effect is a shortening of the cable life by the duration of the overload multiplied by an aging factor.
As I mentioned elsewhere, the aging of normal (70 degree) PVC cable at elevated temperatures, is described here.
http://www.iee.org/Publish/WireRegs/Commentary-UpdateApr04.pdf
The practical point is that if once a week, for a few hours, you take your cable to 90 degrees instead of 70, then those few hours count like 10s of hours at 70 degrees.. so your cables age at 8 or 9 days a week instead of 7.
I also said
If the rest of the time it runs cool, then it will probably still outlive you, unless you are very young !
Anyway, if the cable is in oval conduit then when it needs re-doing in 2075, then your grandchildren can pull in a new cable behind the old one...
and I believe that to be true for most of us..
regards M.

 

[Scoby_Beasley]

Wider than a 2gang box so don't think it is dual purpose !!

 

[securespark]

Wider than a 2gang box so don't think it is dual purpose !!

Mais oui, mon ami, I gang is wider than a 2 gang/2.......