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Two Spurs off one ring mains socket

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Looking for help...


Existing 32A ring mains in 2.5mm2 cable. I want to add in two double sockets. I know that option 1 and 2 are allowed. But it's not clear to me if option 3 is allowed?


Option 1 is adding the two sockets into the ring creating a bigger ring

Option 2 is a single spur for each socket using a JB from the ring mains

Option 3 is a a double spur off the back of a ring main double


Hopefully the attached image can explain what I'm trying to do.


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  • Nickfromwales changed the title to Two Spurs off one ring mains socket
43 minutes ago, Jinglish said:

Thanks do you happen to know where in the regulation it says it's ok?

Historic regs will say you can have as many radials spurs as you like, whereas more modern (but still historic) regs (applicable here as it is not new works) state a max of 2 radials off a ring main; taken from wherever is practical / possible. Any time you can limit this then you should do so.

Cable entry points on the rear of the socket will accommodate 3x4mm2 cables, or 4x2.5mm cables, but that is the least desirable.


Not sure if / where this is stated in previous (16th & 17th) editions, but I've been doing this for 30 years and know what you can and cannot do.


Option 1 is preferable.

Option 2 is the worst possible solution, avoid!

Option 3 is doable.

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Thanks I've got the 17th edition "green book".


Option 3 is harder to get 4 x 2.5mm cables in I agree but I don't understand why option 2 is worst? Could you elaborate why?

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I'm not an electrician or anything so I can't comment other than to say that with option two you need two additional junction boxes so more places for things to go wrong. Easier if the cabling comes off the sockets so you can access it more easily to check for problems in future. 

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Not an electrician, but my recollection is that you can only have one spur from any 'one point' on a ring main, unless the spur is fused - though maybe 2 connections still count if they're not connected in series (if you can jam in all the wires). But otherwise option 3 would need to be modified to have 1st a FCU, then the 2 new sockets - it would at least be another way of doing it. But I agree that option 1 is best, and option 2 to be avoided.


Edited by Mike
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Thanks for everyone's input, I'm going to go with option 1, however I must say I can't technically get my head around the difference between option 2 & 3 and why option 2 is suggested the worst option?

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Option 2 shows the spurs connected mid way between sockets.  The junction boxes required would need to be easily accessible.  It would involve stripping and terminating 8 cables.  Option 3 only involves 4 cables.

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You can’t take more than 1 spur from a single point on the ring. 

You can’t create a ‘ring within a ring’. 

It’s  always best to take a spur from an accessible point on the ring. Ie a socket. Buried joints are a nightmare sometimes when fault finding etc. 


Take 2 twin and earth cables from a socket. One to each socket and then another twin and earth between the 2 new sockets. 

Connect one old and one new twin and earth in the back of the existing socket and one old and one new into the socket front. It’s the easiest way of keeping it a true ring and what we do all the time. 

After, of course, verifying the existing ring is in good condition. Ring continuity, insulation resistance at a minimum. Also making sure there is RCD protection 

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