1. If you add a spur to astandard 2.5mm ring you basically take a supply to a socket outlet using a single piece of 2.5mm t&e from the nearest point on the ring. Now if i wanted to extend the ring to include this spur why cant i just run another cable back to the socket that supplied the spur.
You can. Obviously though you can't just connect it to the socket terminals, you'd need to join it to one of the circuit legs using choc-block or crimps.
BAS obviuosly i did not explain my question and note it was a question clearly enough. Your response means it should be wired how i thought but other than that it doesnt answer why it cant be done how you show in your diagram lower down. Thats what i am interested in knowing.
The only reason i could come up with not to do this was that potentially one of the conductors on what was the spur could come off and if doing checks with a meter continuity would still show as in tact. Am i correct are there other reasons not to.
No - you're not correct, you are worryingly wrong, because if you'd extended the ring you'd no longer have a spur.
My question was can i extend the ring as asked. Absolutely agree if i have extended the ring then i dont have a spur. But again i was trying to obtain clarity as to why it couldnt be done the way i asked. So yes if it could be done in the way i asked you would have a ring connected to a ring, whats wrong with that other than it doesnt conform to the normal description of a ring. The current would still flow around two cables(4 at one point if it could be done the way i asked) just like a ring. I then went on to ask that can this not be done because if the conductor breaks at the extended socket then it effectively reverts to being a spur but any continuity measurements would still show a ring exists on the circuit.
I'm starting to worry that you really don't understand the fundamental topology of a ring.
I do i just like to explore other ideas
2. When i look at the diagrams in the regs book and on site guide for adding a FCU to feed a spur so more than one outlet can be attached they all show the FCU as wired into the ring. Why is this, why cant you just run a single cable to the FCU then add your outlets. I would have thought the fuse in the FCU would prevent the supply cable to it from being overloaded.
You can and it would.
Why, when you looked at the diagram on p362 of the regs did you not see the spur at 9 o'clock?
Got me on that one i missed it i looked at the diagram in the electricians guide to building regs page 54 and my notes.
Chris5 Thanks for the reply. To make sure i have not misunderstood, are you saying that to add to a ring you just run two cables back to the nearest socket.In other words how i asked if it could be done in my first question. I thought you had to break into the ring ie disconnect one cable from the existing socket, extend this to the new socket then run another cable from the new socket back to the one where you disconnected the cable from.
Of course you do
I am assuming sarcasm here. I still like to explore other ideas and will continue to do so. Its not a sign of incompetence just interest.
I understand the loading principles of sockets on the spur but that doesnt explain (or at least i cant see it yet
) why a FCU needs to be on the ring. Surely if this is fused at 13a then it will trip once the current goes above that point whether it is attached to the ring or just on a single piece of 2.5mm spurred from the ring.
OMG.
What ? given my initial question was based upon the diagram on page 54, my notes and i am sure but cant currently find it there is another diagram showing an FCU as part of the ring why the eye roll, My thoughts are correct it doesnt need to be on the ring. Thank you its been clarified no need for the eye roll.
Hi PBD, Yes i thought the space might be an issue as well as getting 4 conductors into each terminal.
But what do you mean by connecting the cables correctly other than p-p n-n and e-e?. what about the issue of a lost contact at the new socket not showing up as a break as the ring would still effectively run through the old socket.
So you have no idea how an FCU is wired, and how it works.
Yes I do this reply from PBD was nothing to do with the FCU it was back to my original question on adding a socket to the ring.
You think this is a ring:
And you're working as an electrician.
No my question was why couldnt that be a ring
God help us all.