RCD test button not working

[pc1966]

That is the first time I have seen an adjustable RCBO!

Generally if you get a 30mA tester it will show if any RCD/RCBO that is rated from 5-30mA is working OK or not. It is not as precise a test as an electrician can do with the appropriate test equipment to verify the trip-time (usual test at fixed 'fault' current at device's specification, e.g. 30mA) and the trip current (done by slowly ramping up the 'fault' current to see at what point it fires). Any external tester would confirm if it is the RCD that has failed/stuck stuck, or if it is the self-test button that has failed.

The use of 30mA is normal in the UK/Europe for most applications as that is the threshold for 'reversible effects' (i.e. it hurts but you are OK immediately afterwards):

Electrical injury - Wikipedia

en.wikipedia.org

What RCD/RCBO don't do is limit the shock current, what they do is limit the exposure time above a certain current which limits the physiological impact but it still depends on how conductive the event was (e.g. if dry skin contact or wet, etc ,etc). So RCDs are very useful in the prevention of death/injury but are always "additional protection" along with the basic protection of suitable insulation and earthing of metalwork, etc.

 

[Negrita]

That is the first time I have seen an adjustable RCBO!

Generally if you get a 30mA tester it will show if any RCD/RCBO that is rated from 5-30mA is working OK or not. It is not as precise a test as an electrician can do with the appropriate test equipment to verify the trip-time (usual test at fixed 'fault' current at device's specification, e.g. 30mA) and the trip current (done by slowly ramping up the 'fault' current to see at what point it fires). Any external tester would confirm if it is the RCD that has failed/stuck stuck, or if it is the self-test button that has failed.

The use of 30mA is normal in the UK/Europe for most applications as that is the threshold for 'reversible effects' (i.e. it hurts but you are OK immediately afterwards):

Electrical injury - Wikipedia

en.wikipedia.org

What RCD/RCBO don't do is limit the shock current, what they do is limit the exposure time above a certain current which limits the physiological impact but it still depends on how conductive the event was (e.g. if dry skin contact or wet, etc ,etc). So RCDs are very useful in the prevention of death/injury but are always "additional protection" along with the basic protection of suitable insulation and earthing of metalwork, etc.

 

[Negrita]

As promised feedack on this thread - socket tester with RCB test button fails to trip MCB on any circuit.
So I guess that means a new RCB.
Once again thanks to all those who gave me advice - and the seasons greetings.

 

[brianmoooore]

Just noticed a little switch, labelled on/off on the pic of this RCBO. Is this to switch off the RCD part, just leaving the MCB?
Before giving up on this device, I'd give it a good 'exercise', by switching it off and on again several times..

 

[Negrita]

Just noticed a little switch, labelled on/off on the pic of this RCBO. Is this to switch off the RCD part, just leaving the MCB?
Before giving up on this device, I'd give it a good 'exercise', by switching it off and on again several times..

Thank you for that - this is what happened - I switched of the little black switch and inserted the socket tester in a socket and pressed the test RCD button - One of the main switches tripped and the black button (which is labelled earth leakage indicator) came out (see pic) resetting the earth leakage black button allowed me to reset the the switch that had tripped.
Not really sure what that is telling me except that isolating the RCDO appears to provide some degree of protection (and maybe that the RCDO is Defunct).
Until I get an electrician to look at it do you think it would be better to leave the RCDO isolated?

 

[brianmoooore]

The switch that you have the red arrow pointing at IS the RCD, as far as I can make out from the pic, and tripping to the downwards position is exactly what it is supposed to do when earth leakage is detected. You introduced an imbalance between the live and neutral currents going through it, by using your socket tester, and the RCBO indicated earth leakage to be present (a feature not found on UK RCBOs) and then the big red switch turned itself off.
This is exactly what it should do, as far as I can tell from here.

 

[Negrita]

The switch that you have the red arrow pointing at IS the RCD, as far as I can make out from the pic, and tripping to the downwards position is exactly what it is supposed to do when earth leakage is detected. You introduced an imbalance between the live and neutral currents going through it, by using your socket tester, and the RCBO indicated earth leakage to be present (a feature not found on UK RCBOs) and then the big red switch turned itself off.
This is exactly what it should do, as far as I can tell from here.

Once again thank you Brian.

I must admit to being somewhat confused. The black switch that you told me to exercise was ON when the test button on the consumer unit would not work – after you told me to exercise the switch, I switched it OFF and then tried the socket tester and the trip worked!

I have now tried the test button on the consumer unit and it works correctly – this is with that little black switch set to the OFF position! So I’m unsure what that switch is switching ON and OFF.

Very confusing for me (but maybe not for you!).

Another thing I have now noticed is this: the picture I sent you was taken in May this year just before we came to the UK for 5 months (I added the arrows just before I sent it to you). In that picture you can see the little black switch is OFF and the trip value was set to the minimum 6mA.

I haven’t changed any of the settings since my return but the mA is now set to 30 and as I said above the little black switch was ON.

A Thai neighbour “took care” of the house whilst we were away and I am wondering if some “tinkering” took place for some reason.

Anyway, these are my problems and getting an admission from a Thai is impossible – I am happy that the RCBO protection is working. (not sure about the MCBs for tripping although all circuits appear to be working).

Finally, I worked in IT for 40 years (I’m 78) and I know how difficult it can be for a professional dealing with people who already have some knowledge, but limited, on a subject, so I say again I really do appreciate that you were prepared to offer your assistance with this issue.