MCB Occasionally Tripping

[griffo61]

I have a separate built-in electric single oven and a built-in ceramic electric hob.
A couple of years ago, we had to replace the oven with a Neff and initially everything was fine.
After about 12 months my wife noticed that quite often when she was using all 4 heat zones on the hob as well as the oven, the MCB would trip. Recently, I had the same problem when only 2 heat zones were being used together with the oven. The MCB is a plug-in type and rated 40amp.
Could this MCB be starting to be faulty? It is approx. 6-7 years old. Nothing else has changed from the original installation.

 

[Lectrician]

What is the rating of the oven?? Look for Kw.

Ovens are getting larger and larger, and are getting to the stage when they need their own circuit seperate from the hob.

 

[griffo61]

Thanks for the reply.
I cannot find any information about the oven's rating in the instruction manual, but on visiting Neff's website their current models that are similar to mine are rated between 2.8 kW and 3.7 kW (remember that it is only a single fan-assisted oven).
The ceramic hob however, has a max. rating of 6.3 kW.

Since posting this query my wife used the oven today and the MCB tripped again and the hob wasn't even being used!

Contrary to the original information given, the 'potentially faulty MCB' is not 40 amp but 45 amp and if I remember rightly was B&Q's own brand

 

[JohnD]

If the hob is off, the oven shouldn't raise a hair on the MCB.

The hob has much greater load. If the MCB will support it then I don't believe the MCB is tripping early.

I'm thinking about a fault on the oven or its switch.

 

[RF Lighting]

Does the oven trip the MCB on every setting, or just certain ones?
If one of the elements has gone faulty then you can often still use the rest of the oven.

 

[griffo61]

Further to the suggested solutions, I have tried to replicate the problem that my wife experienced earlier in the day.
We really only use the oven on one setting (fan-assisted approx. 200 degrees). I had it turned on for 35 mins. at our usual setting then increased the temperature to 250 degrees for a further 20 mins. and the oven worked perfectly.
I suspect that it is going to be one of those infuriating intermittent faults that you never get to the bottom of.
I have a 40 amp 'Wylex' plug-in MCB for the electric shower. I will swap this with the cooker one and try it again with all the heat zones of the hob turned on together with the oven and see what happens.
I will keep you posted.
Many thanks for your input

 

[griffo61]

It must have been a faulty MCB after all.
Replaced it with the 'Wylex' MCB and I can have the oven and all 4 heat zones of the hob on all together without tripping the MCB.

Used the other MCB on the shower circuit and it tripped in under 5 mins. even when the shower was on half power.

Got a replacement on order - using original 30 amp fuse in the meantime -Works fine.