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RCBO WITH FUNCTIONAL EARTH LEAD CAUSING SMALL EARTH LEAKAGE

ietmgreen
I have read somewhere, (but I can't locate the source), that because the RCBO's electronic control operates with the neutral at a very slightly higher potential than earth, there is a very small leakage to earth through the functional earth lead.

Is this correct?

If so, what is the amount of leakage?

Regards,

Mike.
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    I have seen two variations on the use of the functional earth on RCDs and  RCBOs, one indeed to carry the current required to fire the RCD in the event of a lost neutral, and the other as an EMC earth, with small capacitors from it to the L and N incoming terminals.


    In both cases there is potential for some small current to flow in the functional earth, during the normal operation of the device. It is not clear how many such devices woudl cause a nuisence tripping probem if down stream of another  30mA device, but I'd hazard somewhere between 10 and 30.

    I am happier with designs that do not need it and can trip from an L-N voltage less than 50 without assistance.
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  • 0
    I have seen two variations on the use of the functional earth on RCDs and  RCBOs, one indeed to carry the current required to fire the RCD in the event of a lost neutral, and the other as an EMC earth, with small capacitors from it to the L and N incoming terminals.


    In both cases there is potential for some small current to flow in the functional earth, during the normal operation of the device. It is not clear how many such devices woudl cause a nuisence tripping probem if down stream of another  30mA device, but I'd hazard somewhere between 10 and 30.

    I am happier with designs that do not need it and can trip from an L-N voltage less than 50 without assistance.
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