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RCD tripping without ground fault

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    #32
    Cycling Dumbasses
    Registered Users Posts: 417 ✭✭Cycling Dumbasses


    Bruthal wrote: »
    Any arcing would be balanced if there is no earth fault on the appliance. Often seen arcing at sockets from worn sockets, without RCD trips.

    Shower pull chords frequently reported burning out. No RCD trips occur with them.
    I be of the opinion arcing may not be balanced, this is my only explanation really, i see your point on the shower pull cord switches.


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    #33
    Bruthal
    Closed Accounts Posts: 13,422 ✭✭✭✭Bruthal


    The Glass Key wrote: »
    The current on both the live and neutral has to be the same (within ~ 30mA) or the RCD will trip. You seem to be getting this mixed up with earth leakage trip.
    Very good. Except when an imbalance occurs, its due to reduced current return on neutral. Where do you think that residual current goes?
    The most obvious way for the current on the live and neutral to have an imbalance is for the current coming down the live wire to be shorted to earth often via the earth cable but that's not the only way. If we have no earth and you were to touch the live wire you'd be sending current to earth through you and there'd be an imbalance between the live an neutral and the trip would go off.
    Great. But read the op. Item plugged in, isolated from earth.

    Also, a person touching a live terminal will also need to touch something earthed to trip an RCD. I've done it myself a couple of times by accident. Its a fairly nasty shock before it trips. It won't trip by a person simply contacting a live item alone.
    Now if you have say some damp in the walls and some damaged cable in that area that could also create an imbalance but if it creates an imbalance of say 25mA then the trip won't go off. Now if you switch on an appliance that draws a lot of current then the conductivity of the damp patch may change or if the appliance itself might create a small imbalance of 6mA, normally this 6mA wouldn't trip the trip but with an existing wiring problem it can make it look like the problem is the appliance when it might not be.

    If I have that all wrong I'm sure some will be along soon to put me right :o

    I'm sure its all perfect


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    #34
    Bruthal
    Closed Accounts Posts: 13,422 ✭✭✭✭Bruthal


    Cycling Dumbasses wrote: »
    I be of the opinion arcing may not be balanced

    Arcing on a circuit will be balanced. If not, then every time we plug any item in and switch on, the RCD would trip.

    Some arcing always occurs at switching on and off of items. And where is the arcing current flowing, only on L & N.


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