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Earth wire under sink



  • Registered Users Posts: 209 ✭✭Bruthal.

    I think the poster is saying that bonding a sink can introduce more risk than not bonding.

    In this particular case, it would have been less likely to receive as severe a shock with the second hand in contact with isolated metal than earthed metal.

    But the sink bonding is to mitigate against potential differences in installation fault conditions, or faults outside it (failed neutral at minipillar etc). Bonding the sink can increase the risk compared to an electrically isolated one. That risk was seen in this case also.

  • Registered Users Posts: 4,958 ✭✭✭kirk.

    Mostly there shouldn't be a hazard. There's bonded metalwork everywhere in installations.

    It's happened a fair bit with plumbers in hotpresses getting electrocuted . A spark would be more aware of the risks and take precautions

  • Registered Users Posts: 1,919 ✭✭✭Andrea B.

    We have nothing to confirm that this sink without bonding connection has a high enough resistance to prevent a fatal current. It may or may not.

    If sink, incidentally has a high enough resistance, then there is nothing to say that the floor to human contact will not be the route for the fault current in the next instance.

    Fundamentals are, a faulty machine and if it is a +30mA fault not tripping RCD, it starts to point towards something not conforming with wiring or associated protection.

    Further, the bonding that existed before the wire removal, should have been the least resistance fault route to allow equipotential state of live machine body to sink, so, something (seems) not equipotential there if a shock level current travelled through poster.

    If hand to hand is approx 2.3kohm, and the equipotential bond of sink to machine 1ohm, then for a 30mA (assuming RCD would have activated otherwise) fault current using the bonding route, the human coming in parallel would have endured 0.00001A current.....I think🤔

    I just feel that removing equipotential bond to sink is a bad patch.

  • Registered Users Posts: 4,958 ✭✭✭kirk.

    It was an unusual circumstance the exposed metal of the washer becoming live

    He only needed to investigate the issue there ,not interfere with bonding

  • Registered Users Posts: 4,958 ✭✭✭kirk.

    It could be that the sink is extraneous ie: earthy

    By fixing the washer issue and removing bonding if it were to happen again he could get a shock across the chest again next time

    The shock path through legs can happen regardless of the bonding

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  • Registered Users Posts: 209 ✭✭Bruthal.

    Floor route will never approach earthed sink to bare hand, unless floors, shoes etc now are good conductors. Anyway that's a different area. That word "assumption" has never been more used than when someone contacts 230v and the overwhelming assumption is a severe shock. It almost always requires second point of contact to earthed item of metal.

    On confirming the sink is isolated enough to remove bonding safely, I dont think that comes in anywhere. Bonding a sink CAN introduce more risk than not bonding it. "Can", being the operative word. It doesn't say "does".

    Sink earth shouldn't have been removed. We all agree there. The overlap of what it's function is compared to earth's on appliances has been blurred and/or lost.

  • Registered Users Posts: 1,919 ✭✭✭Andrea B.

    But you see, by the posts, it is not agreed that sink earth removal was a bad mitigation in this scenario.

    Further, the equipotential scenario not blurred with me.

    Fundamentally, in a correctly wired scenario, the sink and machine would have been equal potential, so should not have offered a shock-level fault current path through the human.

    Would that be a fair assumption?

  • Registered Users Posts: 4,958 ✭✭✭kirk.

    A non-extraneous sink doesn't introduce a potential ie: "usually earth" and in a fault circumstance there is no hazard

    They don't necessarily need to be same potential in a fault circumstance

    The poster won't have confirmed that either way so he may not be safer now

  • Registered Users Posts: 6,549 ✭✭✭zg3409

    Guy who got a shock from washing machine there may be a fault in the socket supplying the washing machine that was not fixed by replacing or fixing the washing machine. That fault may be still there today increasing the risk of getting a sock from new washing machine. Worst case the new machine has no earth and case could go live due to fault or old lose socket and a family member could get a serious shock some time in the future. Some shocks can kill. Trips are not guaranteed to trip as you already found out.

  • Registered Users Posts: 209 ✭✭Bruthal.

    The only person that seen it as a mitigation seems to be the one who removed the bonding. Maybe i missed others saying it was a good idea. The fact others have pointed out that metal being bonded can sometimes add risk, doesn't mean they think removing the bonding was a good idea.

    If a washing machine body becomes live near the bonded sink, that is higher risk than being beside an electrically isolated "floating" sink. Regardless if whether anyone thinks all sinks should be bonded or not, a bonded sink near another metal item at 230v is unlikely to be safer than a non bonded one.

    A faulty washing machine can present such a fault in a correctly wired installation. Saying its safe in a correctly wired setup is not really an argument in favour of bonding all sinks. Or is it?

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  • Registered Users Posts: 4,958 ✭✭✭kirk.

    I just seen poster said plastic piping so presumably a non-extraneous sink

    I've never checked but presumably the reading to MET would be high