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Installing extra appliance, electric supply advice needed

Discussion in 'Electrics UK' started by Smiffy7, 25 Nov 2014.

  1. Smiffy7

    Smiffy7

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    Hi all,

    I am wanting to install a dishwasher in a kitchen which doesn't already have one. It will go under the sink on the opposite side to the washing machine. I would ideally like to connect it up without disturbing any tiling.

    I currently have one 13A FSU above the washing machine with an unswitched socked below. The FSU I assume is on the ring main as it has 2x2.5mm feeds with 1x2.5 supply to the socket below.

    I am aware you cannot connect more than one appliance into a single socket/spur, so I was wondering if there is anything I can fit in lieu of the FSU which will act as 2 FCUs supplying 2 spurs down to 2 sockets below? The hope being it can be a straight swap!

    Apologies if there is an obvious solution to this, I'm kinda new to household electrics :oops:

    On a side note regarding plumbing, I was going to buy one of these http://www.screwfix.com/p/washing-machine-y-piece-bsp/81000 and also one of these http://www.screwfix.com/p/mcalpine-appliance-trap-40mm-white/95241. I trust they will do the job?

    Thanks :)
     
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  3. JohnW2

    JohnW2

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    It's not particularly obvious why it's been done like that - there will be a 13A (or smaller) fuse in the plug plugged into the socket, so the fuse in the SFCU is really redundant/unnecessary. Maybe it was put there just so that it could be used as a switch to isolate the washing machine.
    I can't think what - and, in any event, if you had something "which acted as 2 FCUs supplying 2 spurs to 2 sockets" you would then need a second cable (to the second socket), the installation of which presumably would disrupt your tiling!

    If you were to 'do away' with the FCU and instead just connect the spur cable to the (2 cables of) the ring within its box (i.e. turn it into an 'unfused spur' - maybe simply by moving the spur cable connections, if they will reach, from the 'load' to the 'supply'side of the FCU), then you would be allowed to change the present single socket to a double one - but many (most?) people do not regard it as a good idea to run both a washing machine and a dishwasher off the same double socket (and, daft though it may seem, whilst the regs allow a double socket on an unfused spur, they do not allow two single sockets!). Opinions about that will probably vary - so it will be interesting to hear what others think.

    Beyond that, I'm not sure there's any solution that would leave your tiling undisturbed - but others may have some thoughts!

    Kind Regards, John
     
  4. Smiffy7

    Smiffy7

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    Thanks for the quick response!

    I was hoping to pull a new cable feed through the existing conduit behind the tiling ;)
     
  5. JohnW2

    JohnW2

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    Ah - you didn't mention conduit! What type is it (metal/plastic, round/oval) and roughly what size? Does it look as if you could get two 2.5mm² cables through it (never as easy as one expects with T+E cable!)?

    If you could get two cables down the conduit, there might then be some possibilities. Although some people claim otherwise, there are not actually any regulations which prohibit two unfused spurs originating at the same point on a ring.

    Kind Regards, John
     
  6. EFLImpudence

    EFLImpudence

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    Use 4mm² and fit two single sockets.
     
  7. JohnW2

    JohnW2

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    We've discussed this before. Although, electrically speaking, it seems totally sound, I think that there will inevitably be debate as to whether it is regs-compliant - since nothing in the regs (even the 'informative' Appendix 15) explicitly allows an unfused spur to supply two sockets, no matter how large the cable (rather daft, given that two separate 2.5mm² cables would probably be compliant, give or take the discussions about concentrating load at one point on the ring).

    Kind Regards, John
     
  8. ban-all-sheds

    ban-all-sheds

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    Hard to see how there can be debate on that particular issue.
     
  9. JohnW2

    JohnW2

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    Is it? What is your view about that 'particular issue', then?

    Kind Regards, John
     
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  11. ban-all-sheds

    ban-all-sheds

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    That it does not comply.

    A15 (like all but one of the Appendices) may well be labelled "informative", but the information it is providing is what is meant by "spur" in 433.1.103.
     
  12. JohnW2

    JohnW2

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    Maybe, but the pre-amble to the Appendices says that, whilst Appendix 1 is 'normative', and "thus a requirement", all of the other Appendices are only for 'guidance'.

    I presume you will agree that, electrically speaking, there is no reason why a 4mm² unfused spur supplying two sockets should not be allowed when two 2.5mm² unfused spurs, each supplying one socket, originating at very close (or maybe even the same) points on the ring would be compliant (provided, in either case, that the designer is satisfied that consequential cable overloads for long periods are unlikely).

    Whatever, as you will have seen, I've cautioned the OP against taking the approach suggested by EFLI, since I realise that there are some who will share your view that it is non-compliant.

    Kind Regards, John
     
  13. ban-all-sheds

    ban-all-sheds

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    Indeed. Bizarrely though, A1 doesn't actually impose any "requirements" it's just a list of standards.

    Do you think that we should pay scant attention to Appendix 4 - take no note of installation methods, not use the figures for current carrying capacity in the tables?

    The information in the Appendices is provided for a reason, and Figure 15A is quite clear.


    Electrically speaking there's no reason why you couldn't have a 20A ring using 1mm² cable or a 45A one using 4mm² either, but they aren't allowed.
     
  14. JohnW2

    JohnW2

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    Indeed - very odd!
    Interesting question. The fact that it is described as 'guidance' presumably means that one is free to use other sources of information about CCCs, and the effect of installation methods thereon, (even the results of one's own experiments, I guess, if done properly enough) provided that one can justify the acceptability of that information/data?
    That's a bit different. Rings circuits with In>Iz are generally not allowed, because of the general requirement that Iz≤In. The only exception is that per the 'dispensation' of 433.1.103 (which is clearly 'a regulation') - which doesn't encompass either of the circuits you postulate. Such circuits are therefore clearly not compliant with the regs (even though 'electrically acceptable').

    Kind Regards, John ²
     
  15. EFLImpudence

    EFLImpudence

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    It is 'safe'; how can it be non-compliant?
    Reverse lollipop?


    App.15A does not state that those shown are the or only options.
    15B does depict the arrangement so it is just the connection to a ring that is disputed.
    433.1.103 does not define or describe unfused spurs but the rest of the circuit is deemed to meet 433.1.1 if CCC>20A and conditions of overload are met so it would seem that 433.1.1 is the criterion; not app.15.

    Would you still consider the arrangement to be non-compliant were it connected to the origin of the circuit?
     
  16. stillp

    stillp

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    Not bizarre at all. If the list was "informative" then it could be ignored.
     
  17. JohnW2

    JohnW2

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    The Devil's Advocate would say that there are lots of things which are 'safe', but not compliant with explicit regulations. However, in this case, as I've said, I think one can argue that what you have proposed would be compliant.
    Indeed. In fact it is clear that neither 15A or 15B are exhaustive. For example, I cannot believe that a fused spur off a 4mm² radial is not allowed if it is connected by a JB (whereas a fused spur connected via a JB is allowed with a 2.5mm² ring)
    Playing 'DA' ... It's not quite that simple. 15B just shows a 4mm² branch of a 4mm² radial. That's rather different from a 4mm² spur originating from a 2.5mm² ring.
    I essentially agree with that. As above, App 15 is clearly not exhaustive.
    No - but, again, I (or the 'DA''!) think that is 'different'. I don't think there's anything in the regs which says that one cannot have two 'circuits' (or 'sub-circuits'), in this case a 2.5mm² ring and a 4mm² radial, originating from (and protected by) the same OPD - so I think that would be compliant in most people's eyes.

    Kind Regards, John
     
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