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

[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!

 

[Taylortwocities]

What's the issue with kitchens?

 

[DPG]

How's that going to help?

From the OPs description it seems like he may well have some suspect wiring in place - an EICR would locate this, and also confirm which MCBs control which circuits, and also prove they are isolating correctly.

Update: This is my 3000th post !

 

[Pete999]

How's that going to help?

Well for a start Dave it would prove whether the install has been interfered with or wired incorrectly, may seem expensive option, but better that than an unsafe install don't you think?

 

[telectrix]

What's the issue with kitchens?

main issue is kitchen fitters.

 

[Taylortwocities]

'Twas ever thus.

 

[static zap]

What's the issue with kitchens?

Maybe I should be asking about any recent alterations ,security lights etc ,may be responsibility of last person to install !
( or an inherited mishmash - from previous owner )

 

[Pete999]

Recommend an EICR been said before.

 

[davesparks]

Well for a start Dave it would prove whether the install has been interfered with or wired incorrectly, may seem expensive option, but better that than an unsafe install don't you think?

I think it is already quite apparent that there is a problem, an eicr won't fix the problem it will just tell you that it's there. It will also still be just as unsafe.

The fault, or at least the symptom is already known, the next step should be to find the fault surely?

 

[telectrix]

agree. and stop calling me shirley.

 

[davesparks]

agree. and stop calling me shirley.

Sorry darling