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New socket from spur

Discussion in 'Electrics UK' started by JohnNox, 17 Jun 2018.

  1. JohnW2

    JohnW2

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    That depends upon the cable size and the rating of the MCB/fuse. If it's 2.5mm² cable with an 'appropriate' MCB (20A, possibly 25A), then you could have as many sockets as you wanted (a 'real radial'). However, if it were 2.5mm² cable protected by a 32A MCB (as it probably would be if it was sharing an MCB with a ring circuit), you would be limited to one (single or double) socket.

    Kind Regards, John
     
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  3. winston1

    winston1

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    No. A radial circuit on a 20a MCB in 2.5mm cable or a 32a MCB with 4mm cable can both have unlimited sockets. But not a radial in 2.5mm cable on a 32a MCB which is the case with a spur on a ring final.

    John2 beat me to it.
     
  4. Yorkshirebloke

    Yorkshirebloke

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    Ah, I see, so it's the fact the MCB isn't protecting the cable that's the problem, not that there is an fcu somewhere in the line.
     
  5. sparkwright

    sparkwright

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    The question is - is a fused connection unit the same as a single socket?

    The major difference is that a fused connection unit will have a fixed load connected to it, and single socket could have god knows what plugged into it.

    That said, if an adapter is used in the socket for multiple appliances, the adapter (at least the modern ones) will have a 13amp fuse in it.

    If a 32amp ring has a so-called radial with two or more accessories spurred off it at the origin, then this could be a radial wired in 2.5mm2 protected by a 32amp protective device, which is not considered good, and not a recognised circuit arrangement.

    Technically, it may well be permissible to spur from a ring in 2.5mm2 cable and feed 4 FCUs fused at 3amp. Or even 8 FCUs fused at 3amp. Then again, even more than that if the load of each FCU is actually a lot less than that of the fuse in the FCU.

    It was allowed once for a spur from a ring to serve two single sockets, but not now.

    Which takes us back to the question - is a FCU the same as a single socket?

    It also takes us back to the possible need for an accessory to be designed which comprises of one single socket and one FCU. This would need one set of terminals to supply the socket outlet and the supply side of the FCU, and another set of terminals for the load side of the FCU.
     
  6. EFLImpudence

    EFLImpudence

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    Right as long as the CCC of the cable is more than the OPD rating.

    That is correct - but what relevance has the floor area?
    Sometimes I wonder about the authors of such "rules".

    Not really.
    It is just because Appendix 15 - only informative - says you can only have one socket on such a spur - but it can be a single or double.
    (You can have as many sockets as you like on the load side of an FCU but obviously the current is limited to 13A.)

    If john had connected his new socket to the load side of the FCU no one would have complained, but a fault would disable both his alarm and thermostat.
     
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  7. EFLImpudence

    EFLImpudence

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    So - an FCU and single socket with 13A fuses would be LESS hazardous.

    I presume you mean 13A appliances rather than just fuses.
    I wonder if the OP has two 13A appliances.

    I believe you know that the fuses are to protect the cable; not the appliances.
    Would that be the case in this example? Clue: yes it would.
     
  8. EFLImpudence

    EFLImpudence

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    The cable is being protected against overload by the fuses.
    It will also be protected against fault current by the MCB.

    The only problem is a lack of a picture showing your arrangement.
     
  9. ban-all-sheds

    ban-all-sheds

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    A 2.5mm² 32A radial with 2 single sockets would have (subject, of course, to installation method) IbIz, downstream overload protection and adequate fault protection.

    You can't disallow something which is OK on the basis that at a later date someone might change it to be not OK. You wouldn't disallow the 20A radial because someone might come along and change the MCB to a 32A, would you.
     
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  11. ban-all-sheds

    ban-all-sheds

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    I don't think EFLI was saying that you do.

    But if you think that you are not required to answer questions which arise from your posts then this site is not for you.
     
  12. securespark

    securespark

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    No. He's just saying the situation is not dire as you seem to be implying.
     
  13. ban-all-sheds

    ban-all-sheds

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    I really can't work out who "he" and "you" are in that...
     
  14. securespark

    securespark

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    "He": the person that comment was aimed at.
    "You": the person commenting.
     
  15. ban-all-sheds

    ban-all-sheds

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    I may go back to bed and start again.
     
  16. EFLImpudence

    EFLImpudence

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    "He": Me.
    "You": Someone else. :)
     
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  17. securespark

    securespark

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    We all get days like that.:sneaky:
     
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