Ring Main - OK to Spur?

[Munzz]

Hi,

Attached is how my socket circuit is mapped in our master bedroom.

I need to add another socket but access to the existing sockets is a challenge.

Is it acceptable by today’s standards to run a spur (2.5mm single cable) from one of the existing junction boxes to a new socket?

 

[davelx]

The existing wiring, if correctly described by your drawing, appears to show a figure of 8 topology, which is not compliant with the regs. There should be a single in, on one JB only, and a single out on the other JB. Where do those "ins" and "outs" go?

Photos of the wiring inside the JBs will help inform our comments.

 

[ericmark]

The ring final it not so cut and dried, the idea is to stop 2.5 mm cable which is rated around 20 amp from getting a load over its rating, there is a picture in the BS7671 which shows the options which if used will reduce the likelihood of an overload to acceptable limits, two sockets can deliver 26 amp (2x13) but in the main it will not supply over 20 amp average over an hour so a double socket on a spur is permitted, with a 100 meters of cable in a ring final, sockets need the consumer unit can overload one leg, so there are rules like fixed appliances over 2 kW should have a dedicated supply, as portable items will be unlikely to overload the system for long.

So a kettle will likely only be used for 5 minutes, where a tumble drier is used for maybe 1½ hours, so kettle does not need a dedicated supply, and a tumble drier would need a dedicated supply if otherwise it would load one end of the ring final, but if at centre of ring final not really a problem. But an immersion heater which could run for 3 hours clearly needs a dedicated supply.

There has been some discussion on figure of 8, I was told when doing my C&G2391 to test to see if there was a figure of 8 and list it as a fault, however I can't find a regulations to say it must not be used, however the ring final is a bit of an odd one out, and the appendix shows most options and does not show fig of 8, as to if the appendix is part of regulations is also in debate, however to get the C&G certificate one is tested with questions from the appendix, so it seems it is part of regulations.

I don't have the circle to hand, I am sure some one will post the page, which shows what it permitted, to be frank can't quite work out what you are trying to do.

 

[davelx]

Perhaps the OP could update his drawing with his proposed additions in a different colour?

 

[Munzz]

Thanks for the feedback, and I completely agree that testing needs to be carried out before any amendments are made.

For clarity, here is what I’m trying to achieve.

 

[ericmark]

In the main we only have three wires in any terminal, over three and you can't be sure every wire securely clamped, but can't work out why the JB has three wires anyway, so can't really answer question.

 

[davelx]

Figure of 8 topology regs compliance issues aside, wired in 2.5mm² (min) cable that's fine.

https://www.diynot.com/wiki/Electrics:socket_circuits:A1-Ring-final-Circuit

Note that the regs require that junctions boxes are of the maintenance free variety if they are not accessible for inspection.

 

[Munzz]

Figure of 8 topology regs compliance issues aside, wired in 2.5mm² (min) cable that's fine.

https://www.diynot.com/wiki/Electrics:socket_circuits:A1-Ring-final-Circuit

Note that the regs require that junctions boxes are of the maintenance free variety if they are not accessible for inspection.

Thanks for the response Dave.

In this particular instance then, where would you spur from? I would have thought a socket ideally, however, would going from one of the junction boxes cause a problem?

 

[davelx]

Thanks for the response Dave.

In this particular instance then, where would you spur from? I would have thought a socket ideally, however, would going from one of the junction boxes cause a problem?

Whatever is most convenient - though you might find the terminals in the junction boxes are too full to take another wire as they already have 3, so back of a socket would be easier.

 

[Munzz]

Whatever is most convenient - though you might find the terminals in the junction boxes are too full to take another wire as they already have 3, so back of a socket would be easier.

Thanks Dave. Typically the room has been plastered so the junction boxes are my best bet. I’ll redo all the cables and throw them in a Wago XL box with 222’s?!

 

[JohnW2]

Attached is how my socket circuit is mapped in our master bedroom. I need to add another socket but access to the existing sockets is a challenge. Is it acceptable by today’s standards to run a spur (2.5mm single cable) from one of the existing junction boxes to a new socket?

As has been asked, could you explain where the "In"s and "Out"s from the two JBs go?

Kind Regards, John

 

[EFLImpudence]

...and how you determined which was 'in' and which was 'out'.

If in fact they are the ring circuit then aren't they both 'ins'?