Rules Re Junction Box on Ring Final unfused spur?

levstar · 2 Aug 2010

Hi, I was going to add an unfused spur in my bedroom from a double socket to supply another double socket, I am aware that I can do this only once. However on further investigation I have found:

The socket I was going to spur off has 4 way 30 amp Junction box connected.

The Junction box has 3 of the four taken up consistiing of:
1.The feed in for the socket
2.The feed out for the ring
3. And a feed for Central Heating electrics.

My question is, should this be therefore treated as an unfused spur off of that socket i.e the feed for Central Heating electrics. Or is this different because its connected via junction box an not out of the back of the sockets.

Ideally I would like to use the last outlet on the junction box to supply the new socket as this will be the most straight forward option.

Many Thanks

LoveRocket · 2 Aug 2010

levstar said:
The Junction box has 3 of the four taken up consistiing of:
1.The feed in for the socket
2.The feed out for the ring
3. And a feed for Central Heating electrics.

That don't make no sense boy!

Do you mean:
1. A feed IN from the final circuit
2. A supply OUT to the socket
3. A supply OUT to the CH

If so, this is already a spur, and it already feeds two accessories (socket and CH) and is thus non-compliant before you do anything.

Are you sure the final circuit is a ring? If it was a radial (like in most civilised countries!) this would never be an issue. Oh the joys of the Great British Ring Final!

levstar · 2 Aug 2010

The circuit is a Ring Final.

It looks as though:
The double socket previously was just part of the ring.
When the central heating has been installed they have used a junction box to break into the circuit. I take it this counts as an unfused / fused spur (TBC), which I thought was allowed.

I take it from your previous post that the rules are not different when using a JB?

LoveRocket · 2 Aug 2010

There is only one supply in to the JB. This is therefore a spur from the RFC

The JB then supplies TWO accessories, which is NOT allowed.

You can use a JB within the ring to create a spur (it doesn't have to be from the back of a socket), but the spur can still only feed ONE accessory.

What you have is a spur TO the JB, and the JB splitting the spur in two. NOT ALLOWED!

levstar · 3 Aug 2010

Hi
Thanks for this, however I think the JB is a spur from what I can see, maybe I have not articulated this too good

One leg from the ring final feeds a socket in the bedroom.
The other leg from the socket is then broken by the JB.
One feed goes off to the Central Heating feed.
The other contiues it original path to the ring final.

Bearing mind the previous post is this a legite Spur.

LoveRocket · 3 Aug 2010

levstar said:
Hi
Thanks for this, however I think the JB is a spur from what I can see, maybe I have not articulated this too good

One leg from the ring final feeds a socket in the bedroom.
The other leg from the socket is then broken by the JB.
One feed goes off to the Central Heating feed.
The other contiues it original path to the ring final.

Bearing mind the previous post is this a legite Spur.

So in the JB you have
Leg A of the ring
Leg B of the ring
A feed off to the CH (which I imagine would be an FCU at the other end?)

Right.
That is a compliant spur.

By the book, no, you can't spur again from the JB, as you're only allowed one spur from a single point on a ring final.

However, common sense must apply. The regs say you could spur from the socket, even though this is right next to the JB. Assuming you're not planning on running a 3kw heater and electric kettle from your new socket, and the CH electrics take only a couple of amps - it wouldn't be the worst contravention to take another spur from this JB.

levstar · 3 Aug 2010

Great stuff, the new double socket is intended for TV and DVD, maybe the occassional use of a Hair dryer (not for me I might add).

However I am now wondering would it be better / more compliant to break into the other leg (i.e the leg that goes straight to the back of the socket) with a newr JB that has not been broken by the original JB. Thus creating an unfused spur on a socket that has no spur.

ban-all-sheds · 3 Aug 2010

What would be much better still would be to extend the ring rather than f*rt about with JBs and spurs.

levstar · 3 Aug 2010

Cheers guys, all useful stuff.

Not sure how easy it will be to pull the cable through to acheive this.

Also I only have one channel chased with 20mm conduit for the cable, is it permittable to run the two legs of T+E in one peice of conduit to supply the new socket or do I need to chase another channel out?

ban-all-sheds · 3 Aug 2010

Both legs in one conduit is OK, but you'll need to take care as you feed it in to avoid twists, or it will jam.

levstar · 3 Aug 2010

Thanks for all the information on this guys, this gives me a few options.

Just as a parting query I have a copy of the regs as I am doing the 2330 as we speak, but I couldnt seem to see too much info re Junctiuon Boxes.

Can you point me in the right direction re:

The regs say you could spur from the socket, even though this is right next to the JB.

Thanks once again for the advice.

1john · 3 Aug 2010

if it's hidden it cant be a screwed terminal jb, someone will reel off the reg numbers for you to check out soon enough, they are here on other junction box related threads though

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Rules Re Junction Box on Ring Final unfused spur?

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