Adding a new spur socket

Discussion in 'Electricians' Talk' started by GeoffB, Aug 15, 2012.

  1. GeoffB

    GeoffB Member

    I need to add a new socket on the ground floor which i am planning to wall mount rather than channel in the wall. The nearest existing socket is about three metres away.Fortunately this is also wall mounted.I am assuming this is on a ring circuit as there is a single cable running into the socket and also one running from it which then is fed up to the void between the floors.I was planning to run a spur from the point above the first floor and then run it to the new socket. I am unsure if this would meet reg's etc as (a) I am not sure if i can cut into a ring circuit, and (b) whether the cable running out of the socket is already a spur or not, as i beleive you are not allowed to run a spur from a cable that is already being used as a spur.

    I would appreciate advice from people better qualified than i am.

    Geoff B
     
  2. B

    B New Member

    Make sure the new socket is also RCD protected !
     
  3. spinlondon

    spinlondon Screwfix Select

    Only required if the socket is intended for general use.
     
  4. GeoffB

    GeoffB Member

    I had a new consumer unit fitted last year so the whole house is RCD protected. If I install a spur off the existing ring main will the new socket also be RCD protected as well? If not how do I protect the new socket.
     
  5. seneca

    seneca Screwfix Select

    Yes, if you have a 17th. edition compliant c/unit your sockets circuit will already be rcd protected so will anything you add to them.
     
  6. GeoffB

    GeoffB Member

    Would the safety be improved if the new socket was fused as opposed to one that was not. Also read somewhere that a spur cable should not be too long as the longer it is the greater the fire risk, but i cannot find what an acceptable length should be. Although the shortest distance between the new socket and the spur point is about three metres,by the time the cable has run up and down two walls,plus the distance,it will probably be more like seven metres.Like i say i am not sure if this falls within reg's guidelines.
     
  7. unphased

    unphased Screwfix Select

    I don't think it really matters about the length of the spur, especially if its only 7m. The rule-of-thumb is that only one unfused spur is allowed off a ring. If you put a fused connection unit on the spur you can add as many sockets as you want. If you are going to the trouble of adding a socket and you can verify that the socket you are using to extend from is on the ring, run two cables to the new socket, join one on to one of the legs in the existing socket and put the other back in the socket terminals thus maintaining the ring. Far better and easier solution then all bases covered.
     
  8. unphased

    unphased Screwfix Select

  9. spinlondon

    spinlondon Screwfix Select

    The maximum length allowed for an unfused spur is 3m.
    The general rule of thumb, is that you can have an unfused spur at each socket, and one at the CU.
     
  10. J.P.

    J.P. New Member

    What does one at the CU mean Spin?
     
  11. GeoffB

    GeoffB Member

    there appears differing views however If the maximum length for an unfused spur is 3m,how do i get round this as i have already stated the overall length is over double this.
     
  12. spinlondon

    spinlondon Screwfix Select

    You can use a larger size of cable, provide protection by means of a fuse or use a lower rated MCB/fuse at the CU.

    J.P. as in a spur at the CU, direct off of the MCB/fuse.
     
  13. Lokkars Daisy

    Lokkars Daisy New Member

    overall length
     
  14. thelibertad

    thelibertad New Member

    fatter the better ;-)
     
  15. Mr. Handyandy

    Mr. Handyandy Screwfix Select

    Neck to bottom of ankles 'sbest.
     
  16. Lectrician

    Lectrician Screwfix Select

    Spin - Where do you get 3m from....?
     
  17. Lectrician

    Lectrician Screwfix Select

    Caveman.
     
  18. spinlondon

    spinlondon Screwfix Select

    The BGB.
     
  19. GeoffB

    GeoffB Member

    Ignoring the last 9 posts which was no help at all,the opinion seems to be that fitting a fused socket will overcome the cable length problem,is that right? Can i not run the same cable to the fused box as i would use if it was unfused, as surely the 13a fuse will stop any overload etc, i would prefer not to start making changes at the CU, as the new socket is being used for phone/broadband modem bases etc.
     
  20. spinlondon

    spinlondon Screwfix Select

    Not certain what you mean by a 'fused socket', or fused box?
    In general cables require overcurrent protection.
    With a spur off of a Ring Final Circuit, the protective device protecting the RFC has too high a rating to protect the spur cable.
    Normally the overcurrent protection is placed at the start of the cable that requires protection.
    However the Regulations allow the protection to be placed along the run of the cable, within 3m of the start of the cable being protected.
    If the cable is less than 3m, whatever it is connected to can provide the protection.
    Now you can place a Fused Connection Unit on the RFC, which would give you a fused spur, and the fuse in that FCU will protect the cable.
    Another option, is to change the RFC protective device, for one with a rating that is lower than the Current Carrying Capacity of the spur cable.
    Another option would be to place an FCU along the run of the spur cable, within 3m of where it is connected to the RFC.

    Another option would be to increase the size of the spur cable, so that it's CCC is greater than the protective device protecting the RFC.
    Your final option would be to use two cables, one connected to one of the RFC cables, and the other cable connected to the other RFC cable. This would extend the RFC.
     

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