Cooker/Grill is tripping only the lighting circuit

[Shep2013]

I have just tested it again and it has tripped out after 3 1/2 minutes - There is no noticable heat coming from either of the MCBs!!!

Im stumped!

 

[Shep2013]

There's a simple way in which you could eliminate (or not) all 'electrical' explanations, hence (as far as I can make out) leaving only flameport's 'thermal' one. .... temporarily disconnect the lighting circuit from the MCB, so that there is nothing connected to the load side of that MCB, but leaving the lighting MCB 'on'. Then try your oven+grill. If flameport is right, the lighting MCB should trip even though there is nothing connected to it.

Kind Regards, John[/quote]

Hi John,

Thanks for all your thinking - It is hugely appreciated!

With regards to disconnecting the lighting circuit this would make perfect sense. However i have never messed around with the consumer unit, is this something easy to do and what precautions so i dont electrocute myself!

Thanks again

 

[securespark]

If it helps the cooker MCB says B40, does this mean 40Amp? And the lighting is B6

Do you still have the old fusebox without RCD protection?

 

[JohnW2]

Do you still have the old fusebox without RCD protection?

Do you mean the 'previous fusebox' (tucked away in some box in the garage, not in service)? If so, I'll be intrigued to know what you have in mind!

The OP has indicated that he's currently got a dual-RCD CU.

Kind Regards, John

 

[securespark]

Ah. Missed that.

 

[JohnW2]

Thanks for all your thinking - It is hugely appreciated! With regards to disconnecting the lighting circuit this would make perfect sense. However i have never messed around with the consumer unit, is this something easy to do and what precautions so i dont electrocute myself!

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.

Is there any chance that you could provide us with a photo of your CU?

Kind Regards, John

 

[Shep2013]

I feel happy to disconnect the mcb if it is easy to do but need to confirm how and if I can isolate it first. It I flip the rcd will this mean it is no longer live?

I have tried uploading a pic but it doesn't like the format

Thanks

 

[ban-all-sheds]

What kind of camera do you have that doesn't store images as either JPG, GIF, PNG or BMP files?

 

[Lectrician]

Try resizing them first too!

There isn't an under cabinet light, light switch or something running too close to the cooker? No cable run behind the cooker which is squished, and failing when the cooker is hot?

Does the MCB go with a pop when you try to reset it?

 

[Shep2013]

What kind of camera do you have that doesn't store images as either JPG, GIF, PNG or BMP files?

Using the camera on my phone - directly uploading from phone...

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

Firstly the Earth from the lighting circuit had come loose - Im not sure if this was me taking the front off?I tested it after reconnecting this and it still tripped

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 interference then?

Thanks

 

[Shep2013]

Try resizing them first too!

There isn't an under cabinet light, light switch or something running too close to the cooker? No cable run behind the cooker which is squished, and failing when the cooker is hot?

Does the MCB go with a pop when you try to reset it?

No other cables run behind the cooker - The closest is the kitchen ring which runs above the worktop and is unaffected.

When you say with "a pop" im not sure exactly what you mean but it generally wont reset immediatly

Thanks

 

[Lectrician]

If it was reseting onto a fault, it would make a pretty lound bang/pop noise.

It certainly sounds like the MCB is shot - I expect it feels 'loose' when you try to turn it on, there being no resistance or click?

Change the MCB for new, and perhaps the cooker one too (it could be getting too hot).

I can't remember now, but did you say it was a wylex? They had some B6 and B16's recalled two years ago as they were failing quite spectacularly. Perhaps you should see if you can get the batch number off the side of the MCB (it needs removing to see it) and post it here.

 

[Shep2013]

If it was reseting onto a fault, it would make a pretty lound bang/pop noise.

It certainly sounds like the MCB is shot - I expect it feels 'loose' when you try to turn it on, there being no resistance or click?

Change the MCB for new, and perhaps the cooker one too (it could be getting too hot).

I can't remember now, but did you say it was a wylex? They had some B6 and B16's recalled two years ago as they were failing quite spectacularly. Perhaps you should see if you can get the batch number off the side of the MCB (it needs removing to see it) and post it here.

When it trips it makes a relatively loud click, i can hear it from the next room (there's no door) and when resetting it it doesnt feel floppy or anything it just pushes up smoothly and either stays or clicks back.

The CU is MK less than a year old - Would it go that quick?

Thanks

 

[Shep2013]

UPDATE!!

It has now just tripped out with just the oven on???

 

[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.

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 interference 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