Faulty MCB. Problem isolating ring final circuit at CU with MCB

[maxeon]

I am planning to move a socket outlet. The CU is largely unlabelled so don't know which 32 MCB to switch off. There are 2 x 32a MCB. All other mcbs are for lights (6a) and a dedicated immersion (16a).
To isolate the circuit, I tried switching off the first of the two 32a mcb which isolated some of the sockets but not the one I need to move. So I switched the 2nd 32a mcb off too (so now all/both 32a MCBs off but some of sockets still live.
So I tested RCD and main switch which tripped all sockets other circuits off.
I am assuming there is no cross over of ring circuits and that the 2nd circuit is not picking up a live from elsewhere (heavens forbid) although I then switched off all MCBs on all circuits and the 2nd 32a circuit was still live.
Can I conclude that the 2nd MCB is faulty and so not switching off and needs replacing or is there any other possible cause?
I'm an amateur so please bear with me and this is my 1st post.

 

[Pete999]

please keep at the back!

Keep what?

 

[maxeon]

Do you have a two probe voltage tester.
First thing us to ensure that the MCBs are actually disconnecting when they are switched off.

Next you'll need to go done investigating yo find out which MCBs feed which sockets.
Put coloured stickers on the sockets so you don't get lost.

That should give you a starting point. If you can't cope with that simple stuff, then an electrician is what you need.

 

[telectrix]

please keep at the back!

pass the dutchie.

 

[Pete999]

pass the dutchie.

You reckon?

 

[maxeon]

I have a multimeter basic model but works ok. I am always very careful to check and double check that a circuit is actually isolated realising that RFCs can be cross linked by someone not paying attention to detail in there working practices. My double checking with instrement and a lamp before actually working on the circuit, lead me to find this problem. I appreciate I could simply flip the main switch and isolate the whole installation but I relaise that would not address the potentially serious problem. I suppose I was just wondering if a faulty MCB is the most likely cause bearing in mind I had switched off all other mcb including lighting/immersion circuits.
I had started to map out the mcbs to the outlets so as to get the CU properly labelled but then very quickly came across the issue. I think the next task is to check each/every MCB is actually switching off which may hopefully narrow down the problem.

 

[maxeon]

it is possible the socket you are working on, is feed from one of the lighting circuits . and advise to get a local spark in.

I am going to check that but the problem arose with all MCBs off so unless I have more than one faulty MCB I am thinking it might just be the one faulty 32a MCB. I really do hope a socket circuit is not picking up a live from a lighting circuit!

 

[telectrix]

as said before, no doubting your abilities, but sometimes , maybe due to some bodger, a weird situation arises which is beyond your capabilities. might be time to call in an experienced spark with fault finding abilities to sort it.

 

[Leyland30]

Maxeon, apologise in advance if I've mis interpreted you problem ... without taking covers off consumer units or exposing live wires, can you not establish if the 32a Mcb is working by shutting every other mcb off. Identifying any electrical equipment that remains live then see what happens when you shut the final mcb off? If nothing happens then it's likely busted and it's time to call the spark. FYI, It is possible for sockets to be supplied from mcbs rated less than 32a.

 

[davesparks]

Looks to me like you could do with an Electrical Installation Condition Report (EICR) on your installation.

How's that going to help?

 

[davesparks]

I have a multimeter basic model but works ok. I am always very careful to check and double check that a circuit is actually isolated realising that RFCs can be cross linked by someone not paying attention to detail in there working practices.

You claim to be very careful in checking isolation, yet you only use a multimeter? This is contradictory, a standard multimeter is not suitable for use in safe isolation.

 

[telectrix]

You claim to be very careful in checking isolation, yet you only use a multimeter? This is contradictory, a standard multimeter is not suitable for use in safe isolation.

but better than a neon screwdriver.

 

[Specialist]

but better than a neon screwdriver.

Only Barely Tell.

Maxeon: Testing for Dead ( safe isolation ) Should only be carried out with an approved 2 pole tester, this should be tested to prove operation before testing for Dead and again afterwards. A Multimeter should Never be relied on to prove that a circuit is Safely Isolated, also it has to be said that you shouldn't be working on a circuit that has only had the single pole MCB isolated.

 

[maxeon]

Only Barely Tell.

Maxeon: Testing for Dead ( safe isolation ) Should only be carried out with an approved 2 pole tester, this should be tested to prove operation before testing for Dead and again afterwards. A Multimeter should Never be relied on to prove that a circuit is Safely Isolated, also it has to be said that you shouldn't be working on a circuit that has only had the single pole MCB isolated.

I don't intend to work on the circuit with just the MCB off especially as my initial investigations trying to label all the circuits revealed ths issue!. Also I am not relying solely on the multimeter to check for isolation. I realise the limitations of the multimeter test (wrong setting- accidently switched off etc) rather than using the correct 'prover' instrement and using it correctly before, after to check its functioning correctly etc. I also know that someone before me could have bodged the circuits (even from when house was new!) and there could be polarity issues, wrong breakers etc. hence my care in checking and double checking and also realising when an issue is beyond my knowledge, understanding and capabilities and I appreciate the general advice to get a professional in which I may well end up doing, but as with all investigations in any field, you don't know how complicated the matter is until the investigation progresses. Sometimes the answer is simple and easy & safe for a competent DIYER to at least identify if not correct but I appreciate may be not so in this case.

 

[Specialist]

Sorry but in your initial post, you said that you had turned off the 2 x 32a breakers to isolate the circuit. That would give you Single pole isolation, for correct Double pole isolation then you would have turned off the Main Switch or RCD.

Again I'd advise you, as others have. Call in a Qualified Electrician with the correct knowledge and test equipment to locate & rectify the situation safely.

 

[static zap]

Have you had kitchen fitters in recently ?

.. Some rooms are no longer DIY areas..

or a cat they say got nine lives, cos you only have one!