Another extending ring main question

[Secret_Sipper]

Hi,

Currently in the process of sorting an older style house out and started in the main front bedroom. All the sockets were singles when we first moved in.

My question is:
Is it acceptable to put a separate ring within the main ring? I've drawn a crude sketch to try and explain better as pictures tell a thousand words (so they say)

The original layout of No1 and No2 looked (so far without going into the other room) to have been spurred twice which is acceptable as I understand but I'd like to put double sockets there where the singles are now which I can't do.
The proposed drawing puts No4 and No6 (which isn't there yet) into a ring within the ring so to speak and the spur off No6 to No1, would that be OK or would I have to put No1,No4 and No6 into the ring?

Looking to get some of the Hager 30A 3 way Junction boxes to do the job.


Any guidance would be appreciated

 

[Iggifer]

Why create a figure of 8 (ring within a ring) when you can simply omit the link between sockets 4 and 6 and do it properly?

The link between 4-6 isn't there on your current drawing, so just don't put it in?

 

[Secret_Sipper]

Hi Iggifer,
Socket 6 isnt there in the original drawing as its a socket I want to add (and currently isn't there at the moment)

The other thing is I've already plastered and hung wall paper around that socket which is no huge problem, just more an annoyance and a few more days waiting for things to dry etc.
(Just trying to save myself more hassle that's all!)
Thanks for your input so far

 

[eveares]

Is it acceptable to put a separate ring within the main ring?

No! The reason is because should the sub-ring from the main ring become broken, any tests done on the circuit at the DB in the future will show everything is ok when it is in fact not.

Essentially by creating a figure of 8 configuration (ring within a ring), you can't tell from the DB if one of the rings within a ring is broken.

 

[Secret_Sipper]

What's my options then eveares?

Either break into the ring and put them on it or could I use separate JBs to each socket from the ring main?

Cheers

 

[Iggifer]

Your BEST option, is to make it a proper ring with no Spurs and no JBs.

Second best is to spur off the ring - once from each point on the ring and avoid JBs.

Third and least preferable is to use JBs.

As you're aware any JBs would need to be MF.

You can extend the ring in the back of a socket if that helps you out, you don't need to use a JB

 

[ericmark]

Oh this has come up before and caused arguments. We were always told to test for a figure of eight and list it as a fault if found. However there were so many things we did without really looking as the reason why, and it has been pointed out many times that in the centre 1/3 of the ring it is unlikely to cause a problem and the is no rule that says you must not do it.

Many of the things we do are to play safe, we are also taught that over 2 kW appliance should have a dedicated supply, but again there is no fixed rule that says you must not do it, what we have is rules talking about over load situations and by following the rules of thumb it means we are less likely to run fowl of the actual rule.

So if you design according to the rule book ensuring no inspection and testing or calculations are missed then yes you can have a figure of eight. However cut any corners, for example not measuring the loop impedance/prospective short circuit current. (Both the same thing really) Then you should have no problems. But miss out any of the inspection and testing then it is very different.

In real terms the DIY guy just does not have the equipment to measure to know if what he is doing is OK or not. Step one before even starting work should be measure the loop impedance/prospective short circuit current and then armed with that info you design.

It is like building a bridge, we can all put a plank across a stream and walk across it, but when it comes to getting the tractor across it takes a little more design.

So set one are there already RCD's protecting the ring? If not then consider RCD FCU and spurs. Put reading on the diagram and we could answer the question. Other wise it is guess work.

 

[Secret_Sipper]

ericmark,

Thank you and believe me I appreciate there are limits to my knowledge hence why asking but I also understand that you need to SEE the job to comment fully how best to proceed.

The house is on old fuse wire holders so no RCD FCU.

I only set out to make the sockets doubles and it's escalated to this! Ha!

 

[ericmark]

Clearly you can break the rules, however to keep within the rules any new socket must be RCD protected but there is no requirement to up-grade those which already exist. The existing sockets only need to comply with the rules in place at the time they were done. So nothing says you must change the fuse box for a modern consumer unit, but it is nearly impossible to extend a ring without first changing the fuse box if you want to comply. However using RCD FCU you can fit fused RCD protected spurs clearly limited to 13A total.

Once the fuse box is changed for a modern consumer unit all those RCD FCU are redundant. So to add an odd one OK but to add many would get silly.

In theroy you could replace every single socket with a RCD FCU feeding a line of sockets and it would still comply. The PSC current for the 30A fuse is far higher that that required for a 13A fuse so very unlikely using RCD FCU you will not comply.