TheScullster wrote:
Hi all

Quick q for the leckies out there!
I have a split load cu with upstairs and downstairs rings covered by common
RCD.
If I turn off the downstairs ring at the breaker and check Live-earth and
Neutral-earth with a crude tester, I get no indication of voltage flow.
If I accidentally dab live or neutral to earth, then it knocks out the RCD.
So where is the current flow being generated which will trip the RCD when
the live is isolated at the breaker?

TIA

Phil


Switching off the MCB will *not* isolate the neutral


If the house neutral is even at only a few mV with respect to earth -
and it usually is - then any short will cause the RCD to trip. Indeed,
this is one of the more common causes of RCD misbehaviour.