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Thread: Understanding Earth Leakage

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    Understanding Earth Leakage

    Long story short: I had a disaster of a building experience, including shoddy electrical workmanship. In the process of arranging proper CoC but there are a few things I want to understand around earth leakage.

    On my DB I have two neutral connection bars, one comes straight from mains and other is sourced from the neutral from earth leakage (EL). Due to one of the electricians mislabeling the circuits everything was a mess, meaning that neutral was being taken from incorrect places for things like my geyser and pool pump.

    Both my geyser and pool pump's neutral was coming from the non-EL neutral bar which caused the EL to trip. After them being moved to the EL neutral bar there's been no tripping. For my own education I'd like to understand why:

    1. Did the pool pump and geyser cause EL to trip? Is it because L was coming from the EL but N was not?
    2. It seems like my light circuits are coming from non-EL neutral bar - why not just put everything on EL? Is there a good reason to not connect it via EL?
    3. For something like a pool pump, would it make more sense to have both L and N coming directly from the mains and then have a earth leakage at the pool pump's db?

    Sorry if my weak attempt at terminology is hard to follow...

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    Site Caretaker Dave A's Avatar
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    In essence the earth leakage unit ensures that the current being supplied on the live terminal is matched by the current returning via the neutral terminal.

    This means that for every circuit where the live that is supplied via the ELU, the associated neutral will have to be connected to the ELU's neutral bar.
    If a circuit has the live supplied before the ELU, but the neutral returning through the ELU, any current through the circuit will result in an imbalance at the ELU and the ELU will trip.
    Same problem when the live is supplied after the ELU but the neutral is connected to the neutral bar before the ELU.

    Quote Originally Posted by saguy View Post
    2. It seems like my light circuits are coming from non-EL neutral bar - why not just put everything on EL? Is there a good reason to not connect it via EL?
    I have everything on ELU protection at my house and it isn't a problem. The "benefit" of not putting a circuit on ELU protection is one does not get "nuisance tripping" for accumulated small current losses to earth or temporary imbalances that may occur when a load is switched on or a light point gets wet. Please note that some types of circuits must be on earth leakage protection.

    Quote Originally Posted by saguy View Post
    3. For something like a pool pump, would it make more sense to have both L and N coming directly from the mains and then have a earth leakage at the pool pump's db?
    The benefit of doing it this way is that if there is a fault at the pool pump that causes the ELU to trip, it would only affect the pool pump and not the rest of the installation.

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    Quote Originally Posted by saguy View Post
    3. For something like a pool pump, would it make more sense to have both L and N coming directly from the mains and then have a earth leakage at the pool pump's db?
    .
    Yes. It does make more sense.
    When I design the circuitry for an installation, I make sure that each sub DB has it's own earth leakage relay.
    Supply cables to sub db's not on earth leakage.

    Makes fault finding a lot easier and as Dave mentioned, should there be an earth fault then the whole installation is not affected.

    Also if possible, keep lighting off earth leakage. Should there be an earth leakage fault at night, at least you will have lights.

    Peace out ... Derek.

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    saguy (04-Jun-21)

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    Thank you both, that clears things up a lot.

    Is there any way to actually test at a plug point or light fixture that the L and N are connected correctly to L and N (either both on ELU or both not).

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    Diamond Member AndyD's Avatar
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    The cheap and cheerful socket testers you can buy at Macro or Builders Warehouse can give you an indication that the socket is connected right and whether it's on an earth leakage circuit. I don't think there's any DIY type testers that will check lighting points.
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    Quote Originally Posted by AndyD View Post
    The cheap and cheerful socket testers you can buy at Macro or Builders Warehouse can give you an indication that the socket is connected right and whether it's on an earth leakage circuit. I don't think there's any DIY type testers that will check lighting points.
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