RCD test button not working

[brianmoooore]

If a RCD isn't tested regularly, the hair trip mechanism can become stuck in place and the contacts of the test button can tarnish. If you can get it to trip, and then 'exercise' the mechanism, by tripping and resetting it several times, they can usually be brought back to life.
Note that anon working test button is a fail when an electrical condition report (EICR) is undertaken, and will result in the installation being declared 'unsatisfactory'.

 

[Negrita]

Thanks for all your advice I really appreciate it - so trying to trip the MCB via a socket tester would show if the problem was with the test button and if the RCD was working or not?
Now I will explain the three years - The Consumer unit is in Thailand! and was installed by a "professional" electrician (at least as professional as you will get in Thailand when we built the house - EICR in Thailand -non existent) 8 years ago.
I tested the RCD at least twice a year until - Covid struck and I was in the UK and my Thai partner was in Thailand we were apart for just over 2 years and asking her to check it would have been a useless exercise and I must admit when I got back in January I forgot to check it until now!

 

[brianmoooore]

Your socket tester is better than nothing, in that it will confirm that the RCD is kaput, if it is, but a full test involves checking that it trips within a certain range of leakage current, and measuring the time it takes to disconnect the power, which has an upper limit.

 

[Negrita]

Your socket tester is better than nothing, in that it will confirm that the RCD is kaput, if it is, but a full test involves checking that it trips within a certain range of leakage current, and measuring the time it takes to disconnect the power, which has an upper limit.

I understand what you are telling me and of course if I find I need to replace it I will get a "professional" to do that.
This is the tester I am buying - I'll let you know and thanks again

 

[Negrita]

Your socket tester is better than nothing, in that it will confirm that the RCD is kaput, if it is, but a full test involves checking that it trips within a certain range of leakage current, and measuring the time it takes to disconnect the power, which has an upper limit.

 

[Negrita]

Sorry to bother you again but I have just noticed that the RCD in my consumer unit has a variable trip can be set to 5, 10, 20, 30 (currently 20) and the socket tester is available in 30 Ma or 5 Ma RCD tester should I buy the 5 Ma socket tester not the 30 Ma tester as being more sensitive?

 

[westward10]

Can you show a picture of the RCD.

 

[Negrita]

Can you show a picture of the RCD.

Sorry for the delay - it's dinner time over here

Can you show a picture of the RCD.

 

[westward10]

The 30ma tester should trip it. Being set at 20ma anything above this which 30ma is should cause it to trip.

 

[Negrita]

The 30ma tester should trip it. Being set at 20ma anything above this which 30ma is should cause it to trip.

Thank you

 

[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?