TheScullster wrote:

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 you were to check with a decent multimeter you would probably see a
small voltage difference between your neutral and earth. Especially if
you have a TN-S earth (i.e. typically provided via the sheath of the
incoming cable).

If I accidentally dab live or neutral to earth, then it knocks out the RCD.

To be expected - more so with the neutral to earth connection.

So where is the current flow being generated which will trip the RCD when
the live is isolated at the breaker?

A voltage present on the neutral can also find a route through a
connected appliance to the live when the MCB is open.

--
Cheers,

John.

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