Adding a socket using only one junction box

[jivingjohn]

I need to add a socket onto a ring in my utility room. I have access to a run of cable in between two existing sockets, however I am unable to remove the cable from either socket as it runs behind the sink which was added after the cable was run.

I want the new socket to be on the ring, and would have no problem if it was located next to where the cable runs, but I don't have enough free cable to put the socket where I want it.

My plan is to mount a 30A junction box on the wall
I'll then cut the cable to make two ends, and run it into the junction box.

My question then is, if I run two cables from the junction box to the newly added socket, is this new socket technically part of the ring, or is the second cable redundant in this case and have I only created a spur?

If the latter is true, I can keep the socket on the ring by using a second junction box, one per leg of the cable, but this just seems pointless as this setup is performing in exactly the same way as the first, only with less load on the junction box.

Here is a diagram of what I propose to do, any help is greatly appreciated.

Untitled

• jivingjohn
• 15 Jan 2012
• 1

 

[echoes]

What you describe is a spur.

If you need this socket on the ring, then 2 junction boxes are needed to extend both cables.
Or you could use a double pattress and blanking plate with 2 sets of 30A choc-block which would be neater.

Alternatively (and practically), would an unfused spur not be acceptable? What's planned for this extra socket?

 

[jivingjohn]

What you describe is a spur.

That was my fear.

I couldn't justify it in my head until I thought about the junction box as though it were a socket.

Having thought of it that way, even if I do have two cables running to the new socket from a single junction box, it's a spur.

I'll consider the blanking plate, but the junction boxes are a little smaller and can be surface mounted as it's only the utility room!

Thanks for your help though, put my mind at rest.

 

[EFLImpudence]

There's no point nor advantage having two cables going to the new socket.

 

[echoes]

That was my fear. To confirm, I would be running two 2.5mm cables from the junction box up to the socket, not one single cable (as would be considered a standard spur).

There was a similar discussion about this on here. Nothing wrong with it electrically, but the general view was to keep things standard and recognisable.

It seems bizarre though. If there was no junction box there, just longer cables, it would be part of the ring.

Not quite - that single junction box bridges part of the 'ring' going to the extra socket. Again, nothing wrong electrically, but pity the person who has to test the ring continuity and resistances.

Also, if the junction box was another socket, it would be part of the ring as well.

Yes, same as your JB would be part of the ring, but the extra socket would be part of an unfused spur.

It seems that just because the device in the middle is a junction box, even though there are two cables leading up to the socket, it is a spur unless I use two junction boxes to separate out the joins.

OK - we can view your 2 cable proposal in 2 ways:

1) A spur with 2 cables
2) A bridged ring.

Both have same topology, and neither are a standard design. Both would require extra work to test to ensure the circuit characteristics were safe.

I totally agree with EFLI above - no point nor advantage is gained by deviationg from the standard and recognisable circuits.

 

[jivingjohn]

Sorry,

I wrote that original respone (which you quoted), then went away and thought about what I'd written.... drew a couple of diagrams, and then wrote what I edited back in!!

I'm in agreement with you, I just couldn't get it to sit right in my head!

Thanks for the help, this is now sorted in my mind!

 

[ban-all-sheds]

 

[sparkwright]

Do it so it's directly on the ring. So there's two cables at the new socket. And you use two separate 30 amp junction boxes. On junction box with one old cable and one new cable. Other junction box with remaining old cable and remaining new cable.

This will make adding new sockets much easier in the future if you need to.

 

[ryan111]

Could you not do this?

Sorry for bad paint skills

Untitled

• ryan111
• 18 Jan 2012
• 1