Electric oven not switching off and tripping RCD

[Tykey]

Hi all,

I'm experiencing an issue with my oven which I hope someone can help with. It's an AEG B8871-4-M built-in electric oven.

I cooked a spot of lunch earlier (maple pork belly slices...very nice indeed) and after it was done turned it off as usual. 10 minutes later the RCD tripped, and I went back into the kitchen to find that the cooker was still red hot and it had been kicking smoke out into the kitchen.

I turned it off at the switch on the wall, reset the RCD and then went to investigate. As soon as I turn the over switch back on, I hear a fan kick in (although not the one at the back that I can see, so presumably it has another) and it starts heating up again. I can actually see a metal component at the back start to glow red. This is before even re-setting the clock on it, let alone turning a heating function on. The front of the oven, where the buttons are, is also too hot to touch, which usually doesn't happen even if cooking on the highest temperature setting.

Here's the strange bit, I mentioned it to my wife to keep away from it for now until I can have a look at what's causing it and she says that it happened before, a couple of months ago while I was away on business. She left it switched off overnight, and the next day ran the pyrolux cleaning cycle on it and it's worked fine since (I guess she figured it was doing it because it was dirty).

Usually if it's tripping I would presume it's just the element that's gone, but as it's heating before anything has been selected I'm concerned it's something more sinister.

Anyone have any ideas? Thanks.

 

[terryplumb]

Sounds like you have a very serious fault . I suggest you disconnect the oven ,if it has a dedicated electric circuit ,switch off the MCB at the consumer unit. And call in an electrician. When you state it tripped the RCD , do you mean the MCB ??? Do you know the difference ?

 

[Tykey]

Thanks for your reply.

Yes, the oven is on a dedicated circuit with its own MCB. It wasn't this that tripped though, it was the RCD next to it. I don't know enough about the difference between the two to know what this means though.

Here's a photo of my unit with the one that tripped shown with an arrow.

https://www.dropbox.com/s/bj7g8k99wxrhhe1/Consumer unit.jpg?dl=0

I have also just double-checked, and now that it has had a couple of hours to cool down, when I switch it on at the wall again it seems back to normal. No fan, no heating, or anything like that.

 

[terryplumb]

Yes that is the RCD. An MCB reacts to over current ,so if more current is running thru the circuit than it is designed to carry MCB trips out. RCD reacts to earth leakage ,current escaping out of a circuit that it protects , basically put in lay mans terms. Given the fact that your oven has " glowing red " parts ,and is heating when it is not supposed to ,and emitting smoke into your kitchen , I would urge you not to use it at all .isolate at the MCB ,and call in a professional . it would seem that the oven has developed a serious fault .the cause of the rcd tripping may be incidental to this fault ,but I would want to have an electrician check that out if I were you.regards terry

 

[Tykey]

Thanks for the explanation and the advice. I'll get someone in...better to be safe than sorry.

 

[terryplumb]

Your welcome ,wise thing to do. Funny enough I have just had a new oven delivered as ours packed in on Sunday .when I opened up the back to check the element resistance. ,as I thought it may need replacing. I was horrified to find the electric terminal block inside had disintegrated and was falling to bits ,several cables inside had obviously been overheating and their insulation had failed quite badly. Made by Cata ,and I would never have another .went to Curry's Sunday and bought a more expensive brand ,just gonna fit it. Mind you could easily get used to eating out everyday if it went so expensive !!! Good luck with yours.

 

[JohnD]

I'd say it needs an appliance mender rather than an electrician. There's nothing likely to be wrong with the house wiring that could cause the behaviour you describe. That said, an electrician would be able to check the connections on the oven, but is unlikely to have had experience with one like yours. I'd suspect a fault around the switch panel.

 

[terryplumb]

Not a question of the house wiring causing the oven to malfunction johnD, but rather what caused the RCD to trip. One would not expect an oven that is coming on when it shouldn't to trip an RCD . excessive heat may well cause sufficient insulation damage to allow earth leakage . so I would want a spark to do IR testing on the circuit and check the oven installation / condition, before calling in an oven repair man
Regards terry.

 

[Tykey]

Thanks for your advice chaps. I have someone coming out Monday to look over everything. If that's all ok and the oven is the issue, I'll see if it's repairable or whether I skip it and get a new one.

 

[Tykey]

Just to follow up on this, the engineer came out to look at the oven and turns out it was a relay on the PCB that had failed, which meant that the element wasn't switching off. A new PCB and hey presto, one working oven.

Thanks to all for the advice.