Hot Spurs!!

[ian413]

I'd like to run two spurs off two existing sockets i have. Both Spurs are to be Double sockets.What size cable do I use? I have bought 10amp 1mm 3 core cable , is that ok??

 

[toasty]

No good i'm afraid.

You need 2.5mm Twin and Earth cable.

 

[ian413]

Live, Neutral and Earth then??
Bugger!!

 

[JohnD]

No, the cable is too small. Remember that someone might plug in two 13Amp appliances to the double socket, so 10Amp cable is not enough. You must use 2.5mm T&E.

Remember to put rubber grommetts in the knock-out holes in the metal back boxes, so that the sharp metal edge cannot cut into the cable covers, and to slide green-and-yellow sleeving over the exposed parts of the earth conductors.

Edited: I type too slow. Also, Twin-and-earth means the cable has a brown-insulated phase, a blue-insulated neutral, and a bare copper earth wire, all inside a flattish PVC sheathing. On your old sockets you will find the old cable is red (not brown) and black (not blue) as the standard colours changed recently.

 

[ian413]

My new double sockets have a terminal for earth, shall i just use that instead of sheaving the earths?

 

[RF Lighting]

No. The earths need to be covered in green and yellow sleeving and then connected to the earth terminal on the socket. From your posts so far I suggest you get an electrician in to do the job for you as you do not appear to possess the knowledge to carry out the task safely.

Rob

 

[sparky40]

The earthing conductors should be sleeved and connected to the outlet itself, if using metal knockout boxes you must use grommets and fit an earth lead (1.5mm if using 2.5mm t&e) from the back of the box to the outlet.

 

[ian413]

Got the cable now, so i connect earth cable to the earth terminal on the socket and sheave it? ok I'll do that, grommets too!

 

[JohnD]

I thought there would be some pictures of spurred sockets on Read Here First - FAQ - For reference but I was wrong.

 

[sparky40]

No chance of making it into a complete 'ring-main' ?

 

[securespark]

No, the cable is too small. Remember that someone might plug in two 13Amp appliances to the double socket,

I can feel that "maximum of 13A per outlet limit" debate welling up again.....

 

[RF Lighting]

Just because you shouldn't doesn't mean that some muppet won't come along with a couple of 3kW heaters. At least if the cable is rated properly then it should just be a case of replacing the socket front and giving said muppet a good talking to.

 

[JohnD]

Anyway, he started out with 1mm cable which is a bit weedy for even a single 3kw heater; never mind a washing machine and a tumble drier, which are the two big loads most likely to be next to each other

 

[ninebob]

No, the cable is too small. Remember that someone might plug in two 13Amp appliances to the double socket,

I can feel that "maximum of 13A per outlet limit" debate welling up again.....

No debate - the definitive answer was here:

Here is a quote from the Technical Section of MK's catalogue:

All MK socket-outlets are manufactured to comply with BS1363 part 2: 1995 and are rated at 13A per unit. Double socket-outlets have been manufactured and tested to exceed this rating by margin that allows electrical safety and reduces the risk of heat and mechanical damage to components due to overloading. It should be noted that BS1363 part 2: 1995 does not allow double sockets to operate at twice the permissable maximum loading and it should be remembered that double socket-outlets are not manufactured to be able to withstand a 26A load for sustained periods of time.

Research by ourselves and third party organisations has shown that all MK double sockets can safely withstand a continuous load of 19.5A for an indefinite period. Increasing the load slightly will begin to cause heat and mechanical stresses on the components in a relatively short period. Testing showed that a load of 22.3A was sufficient to cause heat stress that would cause a browning of the faceplates and sufficient heat to cause insulation damage to cable cores. A load of 24A for 43 hours was sufficient to cause significant heat damage to the material in which the socket-oulet was situated and within 75 hours sufficient to cause significant damage that would lead to the very real potential of fire.

MK recommend that users of their sockets consult professional design Engineers when designing installations to avoid the possibility of heat and mechanical stress to components and installations caused by overloading of MK socket-outlets.

 

[JohnD]

very informative, 9b, thanks. I've heard that double were safe for 20A, but not seen anything official. I know that when the 13A socket was designed there was no expectation that there would be 2 x 13A loads plugged into it.

Coincidentally, when I extended the ring in my utility room some years ago (where both the washing machine and tumbledrier live) I installed a socketwall with ridiculously large numbers of single sockets, because I happened to have them and they wanted using up. Looks like a good unintended consequence.