Cooker oven tripping MCB - how to troubleshoot?

[bickyz]

Hi, I have Kenwood CK406SL cooker with gas hob and two electric ovens. Its less than 2.5yrs old.
In main oven, when I turn-on the function knob and then as soon as I turn the temperature knob its tripping the MCB.
This doesn't happen with the smaller oven and it works fine.
Cooker has dedicated circuit to the CU and it is has cooker socket on the wall with the switch. No other appliances are connected to this circuit.

Electrician has tested the cooker circuit to the CU, Cooker Socket on the wall and the cable from the cooker to the wall socket. He said there are no issues, nor there is earth leakage problem.

I have been reading on this forum about similar issues, where some points out to the oven element or to the oven light or to the thermostat. Is there a way to troubleshoot on what is causing this?

If we take oven element out >> Can I then turn on the oven to see if MCB trips or not?
OR may be take bulb out and turn on the oven to see if MCB trips or not?

Any help on this would be much appreciated, thank you.

 

[conny]

Did your electrician disconnect the mains from the cooker and test the various elements of the cooker separately?
Did s/he use a standard multi-meter or a proper tester, Usually a much bigger piece of equipment compared to a multi-meter which is about the size of a standard iPhone.
If you are competent, you can disconnect 1 element at a time, (make sure the leads are insulated from touching anything). If it still trips, replace the leads and try the next one. If it still trips, remove the lamp and try again.
If you have no success then call out an appliance engineer rather than a general house electrician.

 

[bickyz]

Thank you, he used one of that multi function tester to test the circuit, sockets & the wire that is connected from the cooker to the socket.
Nothing tested on Cooker/its parts.

Will remove lamp/element at a time and see if it trips.

 

[jj4091]

No need to remove element, just disconnect & insulate the wires to it

 

[SimonH2]

Is it an MCB or RCD that's tripping ?
If it is tge MCB then that indicates a short and each time you test it, it's going to damage the function switch or thermostat in the cooker.
As I read it, things are OK when you switch the oven on and it only trips when you turn up the thermostat (temperature control) ? That narrows it down to the main element in the oven affected - or one of them if there's multiple elements.

A common fault is for moisture to get in. These elements are resistance wire embedded in mineral powder packed tight in a metal tube. The mineral is hygroscopic so if an end seal fails then moisture is absorbed and the insulation becomes a little conductive - so you get leakage current that trips the RCD.
As mentioned, disconnect the suspect element, insulate the wires, and you'll probably find the supply doesn't trip. Then replace the element. Don't forget to switch off at the supply before delving into the wiring.
The other possibility is a wiring fault (e.g. chafed insulation allowing an internal wire to short to earth).