Extending a final ring circuit

Discussion in 'Electrics UK' started by howto1, 9 Feb 2012.

  1. howto1

    howto1

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    Hello,

    Just a few questions regarding the above subject. I've read the post:

    http://www.diynot.com/wiki/electrics:extend_ring

    Just want a bit of clarification/guidance. I want to install a twin socket next to an existing socket thats on a 32A ring in the living room.

    The existing socket sits 360mm from the floor (measured from floor to bottom of socket). I've read (i think) that current regulations state that floor-bottom of socket should be min. 450mm and floor to top of socket no more than 1200mm. Now this socket i presume was installed before this regulation. So my question is, now this regulation exists, does it mean if i want to place a twin socket next to this one,

    1)It has to be atleast 450mm from the floor? (Now sockets will be at different heights, won't look right)

    2)Can i install it at the same height as the existing one :frown:

    3) Or to get it to look right, is the only lawful way raise the existing socket and install the new socket to 450mm and try to patch up where the existing socket was.

    Secondly, the existing socket is in the old colours, Red (L), Black (N), Green (Earth). With the new harmonised colours introduced i guess it would be best to tape/sleeve the new harmonised colours to the old colours, if that makes sense. (Basically mark my new cable old colours)

    Lastly, with 2 flat T&E cables coming into the existing socket, if i move one of these into the new socket and run a short flat T&E between the two, connect L-L N-N, E-E, that will be sufficient to meet current standards? Seems what the above link shows. Rather than try and bung the 3 cables into the one socket. .I've read junction boxes should be used to extend these circuits, but guess this is if the install isn't as simple as mine (1 new socket next to an existing one).

    Probably easier just to put an extension lead in, not too keen on them though and like challenges :D

    Cheers guys
     
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  3. PrenticeBoyofDerry

    PrenticeBoyofDerry

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    Ques 1,2 & 3 Socket heights are for new dwellings only.
    It would be a good idea to match core colours but if you can not a notice should go up at you CU/board stating two versions of BS7671 wiring colours are present on the installation.

    If you can use one of the cables from the existing socket and keep the the cable routes within the permitted safe zones, you can indeed run a length between existing and new to extend the RFC
     
  4. RMS

    RMS

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    Simple answer,

    Install the new socket at the same height as the existing one. You are not obliged to sleeve up any colours. Just fit a "non standard colours" warning notice on your consumer unit or near the origin of the installation.

    With regards to removing one leg of the ring and running it into your new socket and fitting a new piece of cable between the sockets then that will fine as long as your existing cables are wired as a ring.
     
  5. PrenticeBoyofDerry

    PrenticeBoyofDerry

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  6. howto1

    howto1

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    Thanks for the speedy responses all!

    I shall mark the new cables with old colours, probably take just as long to fix the sticker level anyway :p

    Well as for safe zones, i was thinking leave the cable where it is at the moment and see if the tails will reach from the knock-out of the existing socket into my new socket, if they don't, what do you guys think to me in-line crimping existing cables to new length of cables, observing point about cable colours of course.

    I do believe they are wired as a ring, don't know of any radials in the house, isolate the downstairs sockets and they go dead, suppose a quick continuity check of the dead circuit, connected L/N of my existing socket with another on the downstairs circuit will confirm this?

    The CU is protected by a 30mA RCD yes.

    Cheers
     
  7. PrenticeBoyofDerry

    PrenticeBoyofDerry

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    Can you get under the floor and joint cables with MFs?
     
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  9. howto1

    howto1

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    Thanks for the reply! The floorboards have laminate flooring over the top, so not ideal really.
     
  10. PrenticeBoyofDerry

    PrenticeBoyofDerry

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    Well then I am not a big fan of them but if the RFC is complete and the feed socket is not a spur, why not just take a standard spur for your additional socket outlet?
     
  11. howto1

    howto1

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    Could you just clarify what you mean by standard spur? I'd rather ask than presume :)

    Cheers
     
  12. PrenticeBoyofDerry

    PrenticeBoyofDerry

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    If you have RFC and the socket outlet that you are extending from is part of the RFC and not a spur.
    You can take a feed from that socket, using a single leg of twin and earth without returning the leg.
    http://www.tlc-direct.co.uk/Book/6.3.2.htm

    NB * The number of unfused spurs fed from the ring circuit must not exceed the number of sockets or fixed appliances connected directly in the ring.

    * Each non-fused spur may feed no more than one single or one twin socket, or no more than one fixed appliance.
     
  13. howto1

    howto1

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    Are you suggesting i just run a T&E from existing socket too new socket? If so and don't think i'm being arrogant, afterall i'm the one asking for help here. Would this mean i'd have effectively 3 cables in my existing socket (supply from previous socket in ring, supply to next socket on ring and 1 cable going to my new socket? I think it could get quite crowded in there and would prefer to move the 'next socket cable' on the ring to the new socket and just run a feed from the existing to the new (if this is allowed).

    Without testing the whole ring, seeing where my first socket is my 'centre' and my last i guess i couldn't be sure it wasn't already a spur?


    So i guess you mean if i've got 10 sockets on my ring, i can't have more than 10 spurs (1 off each socket)? As the statement below suggests.
    Thanks
     
  14. PrenticeBoyofDerry

    PrenticeBoyofDerry

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    It's an option
    Yes
    It could but there is normally sufficient room

    It's your option, I am only making suggestions, but the cable must be in prescribed safe zones as link offered in earlier post and is allowed.

    that is something that needs to be confirmed, as it could be a spur from a spur.
    You guess correctly
     
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