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New CU question.

Discussion in 'Electrics UK' started by conny, 8 Jun 2021.

  1. conny

    conny

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    I had a new CU fitted today and it has a 40A circuit marked up as 'Surge Processor'.
    Can someone shed some light on what it may be 'protecting'?

    IMG_0390.JPG
     
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  3. AndyPRK

    AndyPRK

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    Protecting the yellow thing.
    Which is protecting your electric gadgets
     
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  4. conny

    conny

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    So it's not an actual circuit somewhere in the house?
     
  5. AndyPRK

    AndyPRK

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    Nope
     
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  6. conny

    conny

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    Thanks Andy.
     
  7. JohnW2

    JohnW2

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    Is it not the labelling that is confusing the OP? The 'yellow thing' (the SPD) is not labelled, but the adjacent B40 MCB is labelled 'Surge Suppressor". Despite that, the B40 must be protecting some circuit - which I might guess could (despite the absence of appropriate labelling) be a shower circuit, perhaps?

    @conny : do you have an electric shower?

    Kind Regards, John
     
  8. AndyPRK

    AndyPRK

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    Some manufactures use an Mcb to protect the spd, rather than rely on the main fuse!

    so what I said stands

     
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  9. sparkwright

    sparkwright

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    Re: Conny's consumer unit.

    Never actually fitted a surge suppressor on an RCD side of a dual RCD board...
     
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  11. conny

    conny

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    No John. It runs off an oil fired boiler. I hate that it just says sockets without stating which floor or room.
    I'll have to go round flicking the MCB's off one at a time and tracing which circuit they control.
     
  12. JohnW2

    JohnW2

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    Oh, I didn't realise that.

    However, does not "protecting the SPD" with an MCB actually impair its intended function?

    Also, as per sparkwright's comment, do you think that SPD is just protecting one half of the board, or do you think the busbar is cut at that end?

    Kind Regards, John
     
  13. JohnW2

    JohnW2

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    Fair enough. However, in view of what Andy has said, maybe it is as 'simple' as he suggested (and correct in terms of the labelling) - i.e. that the 40A MCB is merely 'protecting' the surge protection device (the yellow thing on the right), rather than protecti9ng any circuit.

    Kind Regards, John
     
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  14. plugwash

    plugwash

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    I've always been skeptical about the idea of parallel connected SPDs. If a surge comes in that is too big for the SPD to shunt then the SPD has to be disconnected (either by internal protection or an external breaker) to stop it going up in smoke, but that leaves the connected load with no protection.
     
  15. AndyPRK

    AndyPRK

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    Isnt that why they have replaceable plug in modules (the dual width ones) and indicator windows.

    You don’t often see these on dual rcd boards. And yes i suspect it is connected to one rcd b/bar.
    The length of the cable must be kept to a minimum, but it’s still protecting the whole install.
     
    Last edited: 9 Jun 2021
  16. JohnW2

    JohnW2

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    Exactly my point. However, in reality is it likely that any spike/surge short of a 'direct lightning strike' (in which case all bets would be off!) would/could result in enough current for an SPD to 'go up in smoke'?

    In any event, I think the jury is still very much out as regards my personal view as to whether I should remain an "SPD sceptic" :)

    Kind Regards, John
     
  17. JohnW2

    JohnW2

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    If it's downstream of an RCD, it will only protect anything (let alone 'the whole install') if the RCD has not operated (or been manually 'switched off').

    Kind Regards, John
     
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