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Wiring extension into plug socket

Discussion in 'Electrics UK' started by robby71, 14 Dec 2014.

  1. robby71

    robby71

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    I've fitted an extension with 4 outlets and wired it into the plug socket from the back instead of using the plug on the end of the cable into the front of the socket - is this ok?

    The sockets are in the garage which has it's own fuse box
     
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  3. JohnW2

    JohnW2

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    No, not OK - unless there is a fuse in the extension. By doing what you have done, you have avoided the 13A fuse which would normally be in the plug and would therefore limit the total amount of current that could be drawn by what was plugged into the extension sockets. . The 4 outlets of the extension could theoretically draw a total of 52A (13A x 4), which is undoubtedly far far too much for the extension cable - hence potentially dangerous.

    Kind Regards, John
     
  4. robby71

    robby71

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    oh - is there anyway i could add an inline fuse to keep it connected from the back?
     
  5. robby71

    robby71

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  6. JohnW2

    JohnW2

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    I don't think an in-line fuse would be practical. Other than putting the plug back on, I think you have two main options - you could insert a 'fused connection unit' (FCU) into the cable (which would have to be attached to, or sunk into, the wall) - or else you could look for an extension which had a built-in 13A fuse. In my experience, 6-way extensions quite often have them, but 4-way ones seemingly not so commonly. Other people may have other ideas.

    Kind Regards, John
     
  7. robby71

    robby71

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    I didn't think about needing a fused extension when i was looking - so if i buy another with a built in 13a fuse i can wire it in like i have done with this unfused 1?

    Many thanks for the advice :D
     
  8. Taylortwocities

    Taylortwocities

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    Not without a lot of hassle.

    Better to put the plug back on the flex and plug it into the socket. Then you'll get your in-line fuse!

    MK make a 3-gang socket with a fuse built in
    http://www.tlc-direct.co.uk/Products/MKK2737.html
    you could cable that into the back of the socket, I suppose, but that is still a very flaky way of going about things.
     
  9. ban-all-sheds

    ban-all-sheds

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    Why didn't you just do it properly and add more sockets to the circuit?
     
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  11. AlanE

    AlanE

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    John are you suggesting an extension unit with a fuse built into it?

    In which case what protects the flex between wall socket and plug unit - a 30odd Amp consumer unit fuse/mcb?
     
  12. JohnW2

    JohnW2

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    Yep, although I think we're all agreed that using an 'extension unit' of any sort is not an ideal (or 'nice') way of doing things.
    Primarily the downstream 13A fuse (through which any overload current would have to pass). Provided that certain conditions are satisfied (which they almost certainly would be), the regs allow for downstream overload protection following a reduction in cable CSA. The only thing that the fuse would not protect against is a (true, 'negligible impedance') fault (not 'overload') in that length of cable itself, and the "30-odd Amp CU fuse/MCB' would almost certainly afford adequate fault protection (which is one of the conditions for downstream overload protection being allowed).

    You could have asked exactly the same question about a fused spur from a ring final circuit,if the FCU is fed by a spur cable (e.g.from a socket) rather than being part of the ring - again, this is usually allowed, for the above reasons.

    Kind Regards, John
     
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  13. AlanE

    AlanE

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    I can understand that if the extension is screwed to the wall But the majority you see would be trailing across the floor with no protection whatsoever. Just surprised it would be acceptable that's all.
     
  14. JohnW2

    JohnW2

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    It would obviously be better/safer if the cable was somewhere where it was not at risk of mechanical damage (and maybe the OP does intend to attach the extension to a wall). However, the cable itself obviously cannot create 'an overload', the only risk being that, due to damage, it would develop a 'fault' (i.e. an L-N or L-E 'short') - and, as I said the 30A/32A fuse/MCB in the CU would almost certainly provide adequate protection against such a fault. That's why it is 'allowed'.

    Kind Regards, John
     
  15. ericmark

    ericmark

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    It is clearly not allowed to fit 4 sockets to a ring final without including a fuse.

    However I can't see where robby71 says it's a ring final circuit he's added it to!

    All the advert says is current rating 13A and clearly the plug could not be more than 13A. What we don't know is what cable has been used. With 1.5mm cable when fed from a 16A MCB or fuse it could be OK.

    So instead of echoing the No's I will ask what size cable is fitted to the extension lead and what size fuse, MCB, RCBO, RCD are feeding the existing socket.

    All new sockets must be RCD protected and to say fit a FCU without first finding out if there is already a RCD in circuit is jumping the gun as we may be then saying he needs a RCD FCU after he has already bought a non RCD FCU.

    So what size cable is fitted to socket bar?, what size fuse/MCB/RCBO is the original socket fed from? and is it already RCD protected? once you have answered those questions then advice can be given.

    But the easy way is simply to leave the plug on the socket bar.
     
  16. bernardgreen

    bernardgreen

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    What size is the cable in the extension lead ? What is it's maximum safe load current ? As it was designed to be used with a plug fitted with a fuse 13 amp or less it may be that 13 amps is the maximum. If it is a cheap import it might be a lot less than 13 amps.

    It is ( as mentioned before ) possible that the load could be as much as 4 x 13 amps. Even a good quality extension lead cable will heat up with that load.

    So bottom line that to connect an extension lead to the back of a socket is bad practice and carries a high risk of accident.

    Fit an FCU with a 13 amp fuse next to the socket and feed the extension from that. Use a dual box that will take the socket and the FCU on the one back box.
     
  17. JohnW2

    JohnW2

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    No-one has suggested that it necessarily is a ring final. In fact, being a garage, it very probably isn't.
    That's theoretically all correct, but I've yet to see an extension lead which doesn't use the smallest possible cable, namely usually 1.25mm - hence not satisfactorily protected by a 16A (let alone a 20A) MCB/fuse. However, I suppose it's possible that the OP is lucky (and also has a 16A MCB).
    That's a good point (in terms of regulations), which the OP has really brought upon himself by hard-wiring the extension. It's obviously all a bit silly, since if he merely plugged in the extension, in the intended fashion, there wouldn't be any requirement for RCD protection!
    Quite so - or, in the OP's case, put it back!

    Kind Regards, John
     
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