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Metal Halide light fitting

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  • 29-06-2009 8:15pm
    #1
    fjh79
    Closed Accounts Posts: 31 ✭


    Hi guys just 2 quick questions for ye.
    First of all I recently went to change a bulb in a metal halide fitting, the fitting is facing up the front of a building and was 3/4 full with water. That was only part of the problem. The main problem is nothing tripped. Its on a circuit with 2 other lights which have been working fine while the one I'm changing is full of water. The water is covering everything including incoming connections and all switchgear. Can anyone tell me why this has not tripped the MCB feeding them? Is it down to a bad earth or what?

    Also how much bonding is required on a gas boiler? Its piped in copper so I assume I still have to bond all pipes back to the earth bar?


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    #2
    Dardania
    Registered Users Posts: 3,612 ✭✭✭Dardania


    i'm not an electrician, only an electrical engineer, so I may be wrong, but I think an MCB only protect against overcurrent, and that you would need an ELCB (AKA an RCD) to detect the earth leakage. That is presuming that the fitting is earthed correctly in the first place?


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    #3
    2011
    Moderators, Home & Garden Moderators, Technology & Internet Moderators, Regional East Moderators Posts: 12,591 Mod ✭✭✭✭2011


    An MCB should protect against over current and short circuit conditions.

    Good earthing can result in a large earth current flowing which can cause the MCB to operate quickly.

    TBH I dont know why your MCB did not operate the water should have caused a current large enough to flow between live and neutral or live and earth. What rating is the MCB???

    Perhpas the MCB is faulty.
    Also how much bonding is required on a gas boiler?
    A 10mm sq. earth should be connected (with a bonding strap) to the incomming gas pipe on the customer side of the meter. The other end of this cable should go directly to the main earth terminal in the distribution board.


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    #4
    fjh79
    Closed Accounts Posts: 31 ✭fjh79


    Its on a 10A MCB. Can't understand it. Even with a faulty MCB the main fuse should have blown as the water had to have caused a dead short. Very strange.
    Cheers for the bonding tip. So its only the mains gas pipe needs bonding? Its been a while since Ive done some housewiring.


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    #5
    Stoner
    Registered Users Posts: 10,952 ✭✭✭✭Stoner


    the hotpress will need a 10sq too. Some electricians link the incoming and outgoing popes on a boiler too, but the incoming pipe is the important must connection (as is the 10sq to the hotpress and bonding the Kitchen sink)

    Maybe the light fitting had its own fuse that has blown ?


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    #6
    fjh79
    Closed Accounts Posts: 31 ✭fjh79


    No fuse in the fitting and the incoming feed was completely submerged.


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