Rcbo tests

[Chrisg88]

Does it trip more-or-les 'immediately' (as you perceive it)?

You say that it is a brand new RCBO. Does that mean that it has never been tested before? Have you tried replacing the RCBO (maybe temporarily 'borrowing' one of the others, if you don't have a spare)?

Kind Regards, John

I havn't but im going back tomorrow for further investigation.

 

[Chrisg88]

Quite so - that's why it's weird, particularly given that we have been told that no current is (or should be) flowing in the kitchen ring circuit, even when it is 'on'.

Chris - do I take it that what you have observed had happened repeatedly (i.e. each time you switch on the kitchen ring RCBO, the cooker RCBO trip times go haywire, and each time you switch the kitchen ring RCBO off the cooker RCBO trip time becomes normal)?

Kind Regards, John

Yeah i tried it a few times even tried with other circuits energised only seemed to be the the kitchen

 

[JohnW2]

Yeah i tried it a few times even tried with other circuits energised only seemed to be the the kitchen

That's what I assumed. It really makes little sense but, having got to where you are, if it were me I think the next thing I'd try would be replacing the RCBO - brand new ones have been known to be faulty, even though I find it hard to imagine what sort of fault could result in what you are experiencing!

Good luck - and please let us know how things evolve!

Kind Regards, John

 

[Chrisg88]

I done a bit of digging online and seen similar problems. Some people mentioned parallel paths but i domt see how there could be with all test ok

 

[JohnW2]

I done a bit of digging online and seen similar problems. Some people mentioned parallel paths but i domt see how there could be with all test ok

Well, if there were a cross-connection between the circuits, then the test current might be shared between those circuits, thereby impairing the apparent function of the RCBO - but I thought you said that you had checked for cross-connections (presumably of either L or N), and found none?

Kind Regards, John

 

[Chrisg88]

Well, if there were a cross-connection between the circuits, then the test current might be shared between those circuits, thereby impairing the apparent function of the RCBO - but I thought you said that you had checked for cross-connections (presumably of either L or N), and found none?

Kind Regards, John

Yeah i tested betweem circuits with nothing showing. It really has me stumpped.
Tomorrow should shine a bit of light on it

 

[JohnW2]

Yeah i tested betweem circuits with nothing showing. It really has me stumpped. Tomorrow should shine a bit of light on it

Let's hope so!

I take it that the neutrals of the two circuits (2 for the ring) just go to their respective RCBOs and not to anywhere else?

Kind Regards, John

 

[EFLImpudence]

What about swapping the cooker and ring RCBOs around and see if it is the same or reversed?

 

[JohnW2]

What about swapping the cooker and ring RCBOs around and see if it is the same or reversed?

Indeed - I sort-of suggested that earlier.

Kind Regards, John

 

[EFLImpudence]

Oh ok. I thought you just suggested replacing the cooker one.

 

[JohnW2]

Oh ok. I thought you just suggested replacing the cooker one.

I didn't explicitly mention 'swapping', but I think it would be a logical extension of ...

... maybe temporarily 'borrowing' one of the others ...

When fault-finding, it's generally best to only change one thing at a time, so it would probably be desirable to first just replace the cooker RCBO. If that doesn't change anything, there would be no real point in putting the cooker one onto the ring circuit. If the replacement did cure the problem, then, as a matter of curiosity, it would be interesting to see what happened if the ring circuit RCBO were replaced with the ('probably faulty') one that had been removed from the cooker circuit. (the OP seemingly has 4 RCBOs in the CU to play with)

Kind Regards, John

 

[securespark]

Can you swap the "dodgy" RCBO for another on the board that tests OK?
Does this OK RCBO then test "dodgy" when moved?

EDIT: Sorry, John has suggested this already.

 

[JohnW2]

EDIT: Sorry, John has suggested this already.

Well, I almost suggested it, but it was EFLI who explicitly did so

However, as I've just written, I think it would be good practice to do just one thing first - i.e. just replacing the 'dodgy' RCBO with another (maybe the one currently servicing the main house ring). Depending on what then happens, one can then decide whether it would be necessary/sensible/useful to actually 'complete the swap' by temporarily replacing the kitchen ring RCBO with the removed ('dodgy') one.

Kind Regards, John