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2 spurs and an FCU off the ring main?

Discussion in 'Electrics UK' started by Albumen, 18 Apr 2019.

  1. Albumen

    Albumen

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    Caveat - I WON'T be doing this myself. I just want to have the knowledge to talk to electricians.

    I would like an 13 amp socket on the outside wall facing the garden. The physical layout of the house means that getting a spur onto any of the downstairs mains rings will be tricky. To be precise, routing said spur to the outside wall will be tricky.

    But one place which won't be is the laundry. It's unplastered so disruption to decoration isn't an issue. What there is in there at the moment is:

    1. A double socket, which is part of (one of) the downstairs mains rings (there are two thick wires going in side of it - so it's on the ring, yes?).

    2. Coming off that socket is an FCU feeding exterior lights.

    3. Also coming off that socket is a single cable which goes to a double mains socket - washer and tumble dryer.

    Can I use that double socket for a 3rd spur? Or extend the washing machine spur?

    By "can" I mean within the regs and safely (I understand that those two things aren't always equivalent).

    The house had a rewire when we bought it in 1995. Though poorly. Since then a great deal of it has been rewired again, though not completely. The ring main in the laundry however dates from 2013 I think. The consumer unit is new and has RCBOs on each circuit.

    Thanks for any advice.
     
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  3. EFLImpudence

    EFLImpudence

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    No. From what you say, it is likely already on the limit of the regulations - depending on the size of the cables.

    If ALL the sockets and lights came from the FCU, then it would be compliant but not really useful as limited to 13A.

    You/electrician could extend the ring or make sure the cable to outside is big enough.
     
  4. Albumen

    Albumen

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    Thanks. I can't remember exactly how he put it, but your phrase "it is likely already on the limit of the regulations" was the impression I got when the electrician put this in.

    "Extend the ring" - if there is access to the cables going to the current double socket, which there is, just, is it possible to make the ring bigger then be breaking into it? Making the ring a bigger circle, figuratively speaking?

    I've never been particularly happy that two of the highest current appliances in the house, washer and dryer, which sometimes run at the same time, are fed from one spur. The room they are in is one where we can pretty much do what we want.

    My (probably inaccurate) memory of watching electricians was that they liked to run a ring main in continuous cable. Bend it at 180 degrees and fit it in the holders. But are you saying it's possible to cut it and then send one out and another back. That would make the whole thing a lot more possible.

    Otherwise I'm looking at some complicated stuff with steel trunking and/or some very uncomfortable work in a horribly confined space, and cutting traps where I don't want to.
     
  5. EFLImpudence

    EFLImpudence

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    Yes. Or replace the existing spur with larger cable - 4mm².
    Then, in either case, you can extend it with more sockets.

    Nothing wrong with them on one spur although sometimes the double socket or plugs don't like it.

    If you mean the two legs of the ring are in the same place, that's just daft; see below.

    The socket that the spur comes from will already have two parts of the ring (two cable ends) connected to it - plus the spur. You just have to add another cable to make a continuous loop.

    However, having a ring circuit where both legs are run in the same place is silly, just fit the larger cable as a spur.
     
  6. AndyPRK

    AndyPRK

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    If it were me I would connect to the incoming side of the fcu, adding another fcu for isolation to our outside socket
     
  7. Albumen

    Albumen

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    This is all very good advice, thank you for your time.

    So am I right in thinking this is the plan:

    Swap the spur cable to 4mm. Run it to the double socket for the washer/dryer. Then carry on to the outside wall. None of these distances are very long. Ring main to washer socket is probably 2 metres max. Washer socket to outside wall about 80 cm. So the heating effect of current won't be that great.

    Bearing in mind that there's already an FCU spur from the socket.

    Outside socket would obviously be whatever IP protection was needed. And probably an RCBO one too, even though there's RCBO on the Consumer Unit, I'd rather not trip the whole circuit when I slice the hedge trimmer cable (again - it was longer when I bought it!).

    Somebody somewhere said outside sockets have to be on their own circuit - not true?
     
  8. AndyPRK

    AndyPRK

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    I wouldn’t purchase an rcd socket.
    They won’t stand the weather, are expensive and it won’t stop the house one tripping at the same time.

    In your fuse box, what is written in the device that supplies the util room ? B32?
     
  9. EFLImpudence

    EFLImpudence

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    Yes.

    That's ok.

    They don't work like that. Both might trip.
    Although, a second will do no harm.

    Do you mean on their own RCBO(RCD)?
    Anyway, whatever you mean it's not true. Outside sockets don't have to be on their own anything.
     
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  11. Albumen

    Albumen

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    That sounds like it might be simpler. And an FCU means I can turn it off, so the squirrels cant's steal my electricity. I like the idea of not having 'live' electricity outside.
     
  12. Albumen

    Albumen

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    Yes, I realised that about RCBOs after I'd written it. That I can't rely on the 'first' RCBO tripping. I was trying to find an easy way to avoid tripping the whole circuit when I slice through the cable to the hedge trimmer. Again. It was quite a bit longer when I bought it.

    I thought I read that externals have to be on their own circuit, by which I mean their own 'way' at the consumer unit. Which would be a whole heap of work if true. If not, good.

    This is all sounding quite a bit easier than I'd imagined. Thanks.
     
  13. EFLImpudence

    EFLImpudence

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    Then just use a 32A switch.

    The FCU will limit your use to 13A - not enough for the washer and drier at the same time.
     
  14. EFLImpudence

    EFLImpudence

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    You might have read it but - Nope, not true.
     
  15. Albumen

    Albumen

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    Yes, I see what you mean about the weather.

    Yes, it says "B32" on the RCBO for that circuit. Which supplies 3 rooms. Well, 4 really. Laundry, utility/hall, my office and the bedroom on top of it. Actually a real lot of sockets, because I insisted on so many in the upstairs bedroom and my office (the plaster was off, so not much extra work screwing back boxes to the wall). But not much actual load. No electric fires or anything like that.
     
  16. JohnD

    JohnD

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    that's a method that used to be popular, it's a bit tricky to strip the sheath and insulation without nicking anything. The cores are not cut. Not now done AFAIK.
     
  17. EFLImpudence

    EFLImpudence

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    Ah. I see what was meant.
     
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