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He is joking isn't he - you DIY types

Discussion in 'Electrics UK' started by viewer, 16 Apr 2013.

  1. viewer

    viewer

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    http://www.voltimum.co.uk/news/1962...m=email&utm_campaign=2013_04_15_VLT_VoltiTECH

    Apart from the idea that there are ends to a ring (?), surely the first test of the circuits themselves is dead continuity. So at the MCB there would be continuity through the two legs and nothing between either of those and any other circuit.
    Circuits can be accidentally connected but this would show immediately in a normal house.
    The danger of cross connection which is hard to detect is where there are two separate sources of power feeding one piece of equipment and one is isolated by a simple switch (e.g.PIR).
    Have I missed something?
     
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  3. ban-all-sheds

    ban-all-sheds

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    There are when you break it to do tests.


    The standard test for continuity does not involve looking to see if there's continuity to other circuits.


    Depends on what testing is done. With none, it might never show.


    If you join two circuits you get all of the loads being shared by 2 devices, so your Ib ≤ In ≤ Iz breaks.

    It's even more acute with ring finals where you start with the idea that you can have a safe circuit where Iz is 20 and In is 32 because it's a ring.
     
  4. Taylortwocities

    Taylortwocities

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    Don't forget he is from Fluke and trying to sell his test equipment.

    We've all seen the results of DIY / uninformed / bad electrical work.
    Obvious examples that I come across - all too often are:
    Rings that are actually figure of 8
    Rings that have one leg in one MCB and the other leg in a different MCB
    Rings interconnected (kitchens is the best place to find this)

    All of these can be found by following proper testing procedures but (as we know) the mopst testing that is usually done is to
    "switch it on and if it works then everything is OK"

    And yet 'they' water down the one building regulation that should reduce this happening. :rolleyes:
     
  5. viewer

    viewer

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    Not quite sure what cable/circuit design loading makes to the original comments on testing, but I'd certainly agree on the dangers of overloading and cross connections which make the ring final assumptions worthless. Give me a proper radial every time.
     
  6. ban-all-sheds

    ban-all-sheds

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    Design and loading comments were in reply to what you said about the danger of cross connecting.

    And it applies to radials too.
     
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  8. viewer

    viewer

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    Ah yes; complete agreement.
     
  9. Taylortwocities

    Taylortwocities

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    An unintended ring circuit then ;)
     
  10. ban-all-sheds

    ban-all-sheds

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    If they were originally radials you'd end up with an unintended ring, two unintended unfused spurs, all supplied by 2 MCBs.

    Not good.
     
  11. OwainDIYer

    OwainDIYer

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    I could make some comment about "professional electrician types" who left an entire block of flats unearthed ... connected a ring across two 20A MCBs ... etc etc etc.
     
  12. DIYnot Local

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