Cooker/Grill is tripping only the lighting circuit

[Shep2013]

OK - so common sense prevailed - If the main switch is off then no power flows past there in to the CU.

Indeed, although even then, to be totally safe, you should really do a test to make sure that main switch has really done its job.


True, I take this point on board for the future, thanks

I have run the suggested test and disconnected the lighting circuit completely and left the MCB on. At first it wouldnt reset from the previous test a min or before - then after a couple of minutes i tried again and it reset OK. I then started up the oven and grill and it tripped after about 30seconds.
So i am presuming this would suggest that it is thermal triggering then?

Thermal 'triggering', almost certainly, but I frankly wouldn't expect an MCB to behave like that - unless, perhaps, the one next to it was red hot or on fire - I therefore suspect that you have a 'shot' MCB.

Kind Regards, John

I can now feel a little warmth coming from the MCB but it definitely isnt really hot.

Ok great i will get a new MCB for th lighting circuit then and let you know how it goes.

Thanks

 

[securespark]

It has to be a shot MCB if it will not reset with nothing connected to it.

Unless the oven MCB next door is heating up well.

Is the warmth coming from the oven MCB or the lighting one?

 

[Lectrician]

MK ones can be finicky after a few trips.

 

[securespark]

Mmm. I've heard the new ones are made in Florida.

 

[Shep2013]

**UPDATE**

Huge thanks to everyone who has helped, I have replaced the lighting MCB and it is working fine now!!!

Huge thanks again!!

 

[JohnW2]

**UPDATE** Huge thanks to everyone who has helped, I have replaced the lighting MCB and it is working fine now!!! Huge thanks again!!

Glad to here that the problem is sorted.

Kind Regards, John

 

[sparkybird]

thanks OP for this and to everyone who contributed - you learn something new everyday (which is a good thing!)

Well done

SB

 

[scousespark]

OK - so common sense prevailed - If the main switch is off then no power flows past there in to the CU.

Indeed, although even then, to be totally safe, you should really do a test to make sure that main switch has really done its job.

Kind Regards, John

You are telling somebody, who is not showing evidence of competence, it's easy to disconnect an MCB. Proving the installtion is dead is an absolute must, not a 'should really do'.

The OP ha said he did a full rewire, but didn't work in the CU. It would be sensible to check what tests were done.

 

[JohnW2]

OK - so common sense prevailed - If the main switch is off then no power flows past there in to the CU.

Indeed, although even then, to be totally safe, you should really do a test to make sure that main switch has really done its job.

You are telling somebody, who is not showing evidence of competence, it's easy to disconnect an MCB. Proving the installtion is dead is an absolute must, not a 'should really do'.

True - but I was commenting after the event. There was no point in telling him to turn the clocks back and undo what he had already done. Perhaps my point would have been stronger (for others - it was too late for the OP) if I had written "...you should have done a test...", rather than "...you really should do a test...", but that's a bit semantic.

The OP ha said he did a full rewire, but didn't work in the CU.

As I wrote at the time, when I initially said it was easy to disconnect an MCB, I'd missed the fact that his 'rewire' didn't involve working in/on the CU, compounded by the fact that he was talking about moving the MCBs around (implying that he was used to working in CUs). However, when he put me right about his (lack of) experience of working with CUs, I told him that if he didn't feel totally competent and comfortable to do it, he should get an electrician in. He then went on and did it, without any intervening posts.

It would be sensible to check what tests were done.

It might be. We are told that, as part of the re-wire, an electrician wired the CU and commissioned the installation - so, if (s)he were a real and competent electrician (albeit, as we know, some 'electricians' are unfortunately neither), hopefully the appropriate and required testing will have been undertaken. Given that 'black sheep' obvioulsy do exist, I suppose you could argue that "it would be sensible to check what tests were done" whenever an 'electrician' installs a CU and commissions the installation.

Kind Regards, John

 

[scousespark]

John,

You posted the following (before Shep switched the MCB

Ah - my apologies. I hadn't noticed that you said that when you re-wired your house that didn't incude installing the CU or commissioning the system. I was thinking that you had done everything, and therefore were comfortable (and 'competent') working in a CU, and your talk about possibly moving MCBs rather reinforced that impression that I'd gained.

Disconnecting (and reconnecting) the lighting MCB is a very easy thing to do, but it does require that you would be comfortable, and would feel competent, doing it. If you have any doubts, it would obviously be best to get an electrician in.

I think proving dead is a bit more imortant than feeling confident. Get it wrong and you can feel dead.

 

[scousespark]

I also mentioned the testing because of the current post where the job was supervised. Shep could have gone back to his spark, to check this fault.

 

[JohnW2]

John, You posted the following (before Shep switched the MCB:

....Disconnecting (and reconnecting) the lighting MCB is a very easy thing to do, but it does require that you would be comfortable, and would feel competent, doing it. If you have any doubts, it would obviously be best to get an electrician in.

I think proving dead is a bit more imortant than feeling confident. Get it wrong and you can feel dead.

Indeed - but 'confident' (which may well be false confidence) and 'competent' (which means what it says) are hardly the same thing, are they?

Kind Regards, John

 

[scousespark]

John, You posted the following (before Shep switched the MCB:

....Disconnecting (and reconnecting) the lighting MCB is a very easy thing to do, but it does require that you would be comfortable, and would feel competent, doing it. If you have any doubts, it would obviously be best to get an electrician in.

I think proving dead is a bit more imortant than feeling confident. Get it wrong and you can feel dead.

Indeed - but 'confident' (which may well be false confidence) and 'competent' (which means what it says) are hardly the same thing, are they?

Kind Regards, John

I meant confident in relation to felling comfortable doing the job and steered away from 'competent' as that's a different bag of worms.

 

[JohnW2]

Indeed - but 'confident' (which may well be false confidence) and 'competent' (which means what it says) are hardly the same thing, are they?

I meant confident in relation to felling comfortable doing the job and steered away from 'competent' as that's a different bag of worms.

OK, but the most important part of what I wtote was 'competent' - which I meant in its everyday sense, and I feel sure the OP will have interpreted it as such - and, as below, I assumed that he did not feel competent.

With respect, you seem to be suggesting that I encouraged him to work in the CU when, in reality, I was trying to do the opposite. Given that he has already said "i have never messed around with the consumer unit, is this something easy to do and what precautions so i dont electrocute myself!", I assumed that he did not feel either comfortable or competent and therefore that he would regard my statement "...If you have any doubts, it would obviously be best to get an electrician in." to mean "get an electrician in". I guess you would have been happier if I had written "Since you have doubts, it would obviously be best to get an electrician in", but that's just a matter of words.

Kind Regards, John

 

[scousespark]

John,

I'm not playing word games. In electrical installation the term'competent' has it's particular connotation. The OP asjked if it was easy and your reply was yes (basically if he felt capable). Not mentioning the process for proving dead (before he changed the MCB) was wrong

Shep2013 wrote:
OK - so common sense prevailed - If the main switch is off then no power flows past there in to the CU.

You replied:
Indeed, although even then, to be totally safe, you should really do a test to make sure that main switch has really done its job.

Proving Dead is not an option for when you are not quite sure if the supply has been cut, it is something you should do as a matter of routine.