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resolved: MCB on but no power

Discussion in 'Electrics UK' started by rp9, 9 Aug 2010.

  1. 1john

    1john

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    yeah it should but be sure to test and use safe isolation procedures, remember that the supply tails will ALWAYS be live!
     
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  3. rp9

    rp9

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    Hmm, it might be worth getting someone in to do this bit then.

    Is this likely to be the only problem? Or is it a result of a problem elsewhere?

    Do RCD's 'fail' often or is this a rarity?
     
  4. 1john

    1john

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    Well it would be best imo, get a sparky in to do some dead tests on the circuit, may turn up a reason for the fault. Any mechanical device can develop a fault though but best to get someone with the test equipment to check and replace, it shouldn't cost a massive amount, a call out charge and an RCD with peace of mind too :)
     
  5. sparkydude

    sparkydude

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    It looks to me like the right hand busbar on your faulty RCD is definiteley not installed correctly. if you look closely in the picture it is discoloured , a sure indication that it has overheated at some time. As long as you have a means of proving the supply to the rcd is dead then with the left hand RCD off the right hand one will be dead. The terminals on these RCDs are a tunnel tyoe it is my guess the terminal has been tightened up but with the busbar not in the terminal but behind it. This could be on the RCD or the MCBs themselves. To prove this , once you have isolated the power and proved its off at the rcd loosen all three terminal screws on the MCB.RCD and the busbar will drop out, Undo all the terminals fully and make sure the cage part of the clamp has backed out . Inspect all the devices for signs of overheatig and if found then replace the affected parts. Re-assemble and test. Do not even attempt any of this if you are not 100% sure you feel happy about doing this. If at all dubious then get a sparks in to sort it for you.

    Nick
     
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  6. rp9

    rp9

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    Thanks for all the replies and help, will have a think and a look at things tomorrow then probably call someone in.
     
  7. ban-all-sheds

    ban-all-sheds

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    If you end up waiting for someone to come you could temporarily move that breaker to the other bus-bar. Don't forget to move the neutrals too....
     
  8. rp9

    rp9

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    Thanks to all those who responded, I think it's all resolved now. (fingers crossed.)

    I replaced the RCD, had to clean up the busbar but all looks good now.

    Spot on. Have a look at these images:

    Does this means we've had an unsafe installation for 4 years?

    Keeping a close eye on it just to make sure.

    Thanks again.
    Rich.
     
  9. nozspark

    nozspark

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    You should really replace the busbar as it's more than likely over heated
     
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  11. 1john

    1john

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    Agreed, I would replace the RCD, bus bar and for the sake of two MCB's, those aswell if they have received any heat damage!
     
  12. rp9

    rp9

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    I will replace them, I just didn't want to hike back to screwfix once I'd removed the busbar. Will pop in on my way home tomorrow.

    It's successfully coped with a dishwasher running.

    Still wondering if people think this has been unsafe for the last 4 years?
     
  13. electronicsuk

    electronicsuk

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    Unless your installation has been worked on since then, yes, it must have been this way for at least that length of time. There is no way it could work itself loose from the terminal and then end up being lodged behind it without someone interfering with the CU.
     
  14. Adam_151

    Adam_151

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    Its always struck me as a bit of a design flaw with those rising clamp terminals, its so easy for the tab to end up on the wrong side, if you are not careful... the older wylex NS boards were better in that regard, just a screw that tightened down onto the tab, rather like a large connector block type arrangement.

    Though I do like the arrangement on some wylex boards where you have just the top profile of the DIN rail so its easy to drop breakers on and off like on a TPN board, rather than having to fight it out, or take the busbar out!
     
  15. SUNRAY

    SUNRAY

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    Am I the only one who thinks this is wired wrong?

    Is it usual to have 2 RCD's in line?

    I would have done away with the right hand RCD and replaced the 2 buss bars with one long one
     
  16. ban-all-sheds

    ban-all-sheds

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    I can't be sure, but the incomer looks like it's a 100mA one. Or it might be my eyes and a laptop size screen letting me down.

    If it is 100mA I'll bet it's a time delayed one, and yes, such an arrangement was perfectly normal for TT installations, except this one has been badly split - all the sockets should be on the 30mA RCD.
     
  17. SUNRAY

    SUNRAY

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    I was struggling to read that too but concluded they look the same. Having had another look I'm not so convinced.
     
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