Saturday, Jan 18, 2014 at 15:04
Mate I know exactly how an
RCD works.
RDC..ELCB no matter what you call it and no matter the difference.
Without an earth conductor bonded to the neutral there is nowhere for the current to go but out the active and back into the neutral.
there fore there will be NO imbanance, there will be no difference.
If you have an object that is not connected to the earth the
RCD is connected to.....like a metal table connected to the active.
and another object that is not connected to the same earth that the
RCD is connected to connected to the neutral such as a tent pole.
One hundred percent of the current that flows up the active into the table thru a human body and back thru the tent pole will flow back to the neutral......the earth that the
RCD is connected to is not involved...thus there IS no imbalance and the
RCD will not trip.
In fact the only time an
RCD not connected to a universal earth is any damn good at all is within the cabling leading to and withn an earthed appliance with a three core power lead.
in a floating portable power supply device, If there is no earth conductor in the power cord and there is no universal earth or bond to the greater mass of earth ..the existance of an
RCD on the circuit is completely irrelivent.
for example.
If I have a "typical " metal cassed toaster, supplied from a floating portable supply WITH and earth neutral bond, but not connected to an earthing system.
If I throw said toaster into a bath, assuming all is correct the
RCD will trip and in less than the blink of an eye.
IF however the earth conductor of that toaster is disconnected at the plug.
Throw that toaster in the bath now and it will sit there sizzling & generally being deadly indefinitely.....because all the current that flows out of the active has nowhere else to flow but back up the neutral.
In a permanent installation or where the earth is bonded to the greater mass of earth.
RDC/ELCBs provide protection against fauts involving not only the item and the cabling but faults with alternate paths to earth...that is the whole point of them....without this they are pretty well pointless.
If said toaster with the earth lead disconnected was thrown into a metal bath...that realy should be earthed in a building with a permenent electrical system ( another argument), the
RCD will trip.
A gen set that is not bonded to the greater mass of earth or to a constructed universal earth situation provides very little protection via the
RCD.....with a double insulated device it provides none.
Remember multiple faults ARE common.
cheers
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