Spur from junction box - special setup

[henry1]

Here is my current setup:

I wanted to raise an electric socket but the cables were too short, so I replaced the socket with a junction box within the ring circuit and from the JB, I created a spur to the socket.

Now I would like to add an extra socket nearby. Since the JB already has a spur, I can't run a second spur from it. But what if I connect a second cable from the JB to the existing socket? Then the socket is no longer a spur but part of the ring circuit. The JB merely acts as a point of connection for the extension of the cables. Am I correct?

So with this new setup, the JB no longer has a spur from it, meaning I can now connect one for the extra socket nearby I want?

BTW, the JB is in an easily accessible place, so would be ideal to run all connections from it.

If what I suggested above is wrong, could you suggest another way to use the JB to add an extra electrical socket?

 

[AndrewDavie]

As long as it's wired correctly as a ring, then that is true.

 

[davelx]

As long as it's wired correctly as a ring, then that is true.

But with a single JB, it couldn't be, could it? OP - You need 6 terminals as you have to create a ring - you can't just double up the cable and call it ring.

 

[ericmark]

Would it not be easier to use a FCU instead of the JB? The problem in taking two spurs from the same point is two fold.

One is getting 4 cables into a connector in a way where there is no chance of a poor connection hence one spur from a socket although you can have a twin box with two sockets and a spur from each one but that way only three wires per hole. With JB it would depend on design.

Two is the chance of overloading a section of the ring. Where taken from the centre there is not a problem but near either end one can draw over the 20 odd amp 2.5 is rated at down one leg of the ring. This is unlikely to be a problem unless very close to the consumer unit.

Also really spurs should be limited to 3 meters from the ring but many don't worry about that rule.

Where protected with a 32A type B MCB then 1.44Ω limit to ELI also will limit length. Again since today all new sockets must be RCD protected people don't worry so much if the ELI is exceeded.

 

[AndrewDavie]

As long as it's wired correctly as a ring, then that is true.

But with a single JB, it couldn't be, could it? OP - You need 6 terminals as you have to create a ring - you can't just double up the cable and call it ring.

Yes. You'd need to crimp the wires or use some connector blocks.

 

[davelx]

As long as it's wired correctly as a ring, then that is true.

But with a single JB, it couldn't be, could it? OP - You need 6 terminals as you have to create a ring - you can't just double up the cable and call it ring.

Yes. You'd need to crimp the wires or use some connector blocks.

However you do it, you still need 6 connections though - it's not clear to me that the OP had that in mind from his initial question.

 

[henry1]

As long as it's wired correctly as a ring, then that is true.

But with a single JB, it couldn't be, could it? OP - You need 6 terminals as you have to create a ring - you can't just double up the cable and call it ring.

Yes. You'd need to crimp the wires or use some connector blocks.

However you do it, you still need 6 connections though - it's not clear to me that the OP had that in mind from his initial question.

I did have it in mind but I wanted to make sure that the design was OK first, which it seems it is.

So the problem is with the large number of connections. A large number of connections in a JB could overheat it as well I guess?

So what's the best way to go about connecting all these cables together?
Or else adding an extra socket in a different way?
I don't want to take a spur from anywhere else as there is no other socket nearby.

 

[henry1]

Would it not be easier to use a FCU instead of the JB? The problem in taking two spurs from the same point is two fold.

One is getting 4 cables into a connector in a way where there is no chance of a poor connection hence one spur from a socket although you can have a twin box with two sockets and a spur from each one but that way only three wires per hole. With JB it would depend on design.

Two is the chance of overloading a section of the ring. Where taken from the centre there is not a problem but near either end one can draw over the 20 odd amp 2.5 is rated at down one leg of the ring. This is unlikely to be a problem unless very close to the consumer unit.

Also really spurs should be limited to 3 meters from the ring but many don't worry about that rule.

Where protected with a 32A type B MCB then 1.44Ω limit to ELI also will limit length. Again since today all new sockets must be RCD protected people don't worry so much if the ELI is exceeded.

How can the FCU make the connections easier?

I don't know where in the ring circuit I will be connecting this spur but I plan to use it to power a TV. The existing socket so far is used to charge mobiles phone and power a small light.
The cabling for the new socket should not be longer than 3m I would think.

 

[davelx]

Overheating will not be an issue - you shouldn't notice any heating at all if your connections are all clean and tight. The problem is getting all the connections in the space - trying to cram connector blocks or crimps into a 4 terminal JB and not have everything too squashed together, or have too tight a bend on the cores, is not at all easy - and then you have to get the lid on!

A six terminal junction box would be better:

http://www.tlc-direct.co.uk/Products/ASJ601.html

It's rated 20A, which is the minimum needed CCC for a ring final.
Failing that, something like this with a connector strip (20A+ rating):

http://www.tlc-direct.co.uk/Products/GWBX3315.html

either way, the cables entering the box need to be clipped to joists etc to ensure no strain on the connections, as there is no strain relief in the boxes.