Mk 80A Rcd

[m4tty]

Hi,

Tested an 80A Mk 30mA RCD today and it wouldnt trip when tested at the rcd but tripped when tested at sockets and lights.

think ive read about this on here before but Sandra's not finished her tutorial teaching me how to use forum search properly yet

Any thoughts cheers

 

[Andy™]

not something daft like leads on the wrong side?

apart from that, its usually that it doesnt trip at a socket but trips in isolation

 

[ProDave]

How did you connect your probes?

I think the issue with some is touching the probes to the screws does not work, but connecting them properly into the outgoing terminals does.

 

[m4tty]

Using megger 1552 'steps favourite ' I used probes onto line and neutral screws and earth croc to earth bar. Ill retry on terminals dave cheers

andy im worried now it could be something stupid lol cheers

 

[steptoe]

some RCDs RCBOs have the coils after the terminals,

F'in stoopid IMO

 

[Sidewinder]

Yes M4tty,

As Steps has said, some RCD's have the current sensing coils in the cable tunnels thus, if you test on the screws the current does not flow through the coils.

Therefore you have to connect down the outgoing cable tunnels.

Stoopid, yes, but, I suppose it makes you test the RCD in isolation, which is another anomaly, as the Regs only require the RCD testing on its own, not with any cables or loads connected.

So it can work on test, and pass OK, but fail to work in "real life" and that's OK under the regs...!

 

[sparkytim]

Ditto to above  MEM RCBOs are the same, just stick a short bit of wire into the L terminal and clip on (N not required to Test) and Earth clip onto earth bar.