RCD's in series and how to test

[leep82]

I've always overcome this problem by testing the second RCD using the test probes across its load-side line and supply-side neutral. The tester doesn't care whether the test current returns to earth or neutral, it should still perform a valid test on that RCD provided only the line goes through it. But because the test current returns via the the first RCD's neutral, that sees the tester as a legitimate load and shouldn't trip.

Just tried this method and it still trips the RCBO in the main DB

 

[Lucien Nunes]

With no connection from tester to earth? Interesting, not sure why, anybody?

 

[Wilko]

Just tried this method and it still trips the RCBO in the main DB

If I understand correctly, it should by L and N to RCD load side as normal, but E probe to the incoming N for that RCD. So no test current in the supply earth.

 

[Karin]

If I understand correctly, it should by L and N to RCD load side as normal, but E probe to the incoming N for that RCD. So no test current in the supply earth.

that's how i do it on my kt64 with 3 probes

 

[davesparks]

It's hard to see from the picture but does that Earth leakage module not have adjustable settings?

 

[davesparks]

I've just googled the part number and it is indeed adjustable, so you can wind its settings up to stop it tripping for the duration of the test.

I'd suggest that, if it is compliant to do so, the trip should be set to something other than 30mA without time delay.