RCBO Query...

[TopDog73]

Thanks kindly for all your responses.
It's looking like DaveSparks is spot on with my problem and the way I'm doing it. You explained it better than me Dave! lol.
Just some more info for you to look at so as to clarify at bit more.
- Yes, I'm testing in the workshop
- Yes, testing continuity L1 from the inlet plug to the L1 outlet socket (same for N and E and other lines if testing on 3 phase)
- outlet sockets vary in sizes. For example if it were a 16A socket, my RCBO would be a type C16.
and for a 32A socket, it would be a C32 RCBO. We don't tend to use type A's and very rarely use type B's.
- The tester I'm using is a Mettrel.
- 30mA operating current is the norm for these particular RCBO's
- The tests I have to carry out are continuity, Insulation Resistance, RCD operating times and obviously the general visual checks.

When doing the RCD operating times the Mettrel tester shows it a 'pass' with a green light and a 'tick' therefor giving me assurance that it's capable of doing what it's supposed to.

So it's baffling to see that it passes the RCBO's that trip out during my continuity test.
Even my IR readings are good.

Maybe you're right Dave - my tester is just giving out a bit too much 'umpf' to a slightly sensitive RCBO....

 

[davesparks]

Your tester isn't giving out too much, it is required to test with a nominal current of 200mA and the RCD is required to trip at a nominal 30mA imbalance so the RCD should operate in this situation.

You should be doing more than watching for a green light on the tester. You need to be keeping a record of all test results and comparing them everytime it is tested to see if anything has changed.

 

[Richard Burns]

Just to be clear about my post the tripping curve of an MCB e.g. B, C or D is a different thing from the sensitivity of an RCD to DC currents with the type A, AC, B.
This is a picture of two type A RCBOs but one is a C32 and the other is a B6 MCB.