AEG Oven Trips RCD when turned off only

[George Lisle]

Hi, my AEG BP3003001M wall oven, six years old, has started to trip the rcd every time it is turned off, but only when the upper element is hot. I have checked the terminal connections at the back and tightened them up, but this has not cured the problem. I am loth to replace the element on the assumption that it is faulty or to call in a service engineer in case it is the circuit board that may need replacing, in which case it might be better value to buy a new oven. It is a curious fault and difficult to understand why it is not tripping anyway when it heats up, only on turning it off, whether with the control knob or the main isolator. The rcd is shared with freezer, fridge, socket outlets, dishwasher and under cupboard lighting, but it seems to make no difference whether any of these are in use or not. Anyone have any ideas?

 

[Andy™]

almost guaranteed to be the element

 

[George Lisle]

Thanks Andy. Still don't understand how it can happen. Could turning it off cause a surge that just breaches the insulation and causes a current leakage to earth perhaps? Could there be capacitance between the element and its metal casing causing that? Anyway, I will buy an element.

 

[Geoff1946]

It is weird! I've known a few which trip intermittently on warming up but not at switch off. I can't immediately visualise how it can do that. However, if confident that its associated with that element and its temperature my next step would be to do insulation tests on the element in both hot and cold conditions.
If you were to call in a service technician its very likely they would just change the element anyway.

 

[Andy™]

no idea why. from a fault finding view, it doesnt make much sense. from experiance thats often the cause. IR test both cold and hot will show if the element is faulty or not

 

[kerching]

I had this once. The element controller was double pole. When the temp was reached the L& N in the control opened at slightly differing times. RCD saw this as a imbalance , went Moody and tripped

Just saying

 

[Andy™]

still shouldnt cause it to trip, as soon as either opens then the circuit is broken and leccy stops flowing, so no imbalance. but still, reality says otherwise

 

[Fleeting]

It is a common phenomenon for a double pole switch upon operation to trip an rcd especially if the neutral disconnects first in the off operation.

 

[DuaneMHunt1976]

Dose sound like a switch problem..

RCD, Switch, Cable to oven, & oven

RCD test ramps
Switch turn it off in the dark to see for sparks and smell it if any burnings.
IR test cable
PAT the oven

Check the switch, colours in the right place and screwed in (guy that did my sister's house screwed up with that) socket L&N wrong way, and lot lights switches terminal not screwed in (hanging in the hole)

Then look at RCD

 

[George Lisle]

Problem overcome. I changed the heating element, although the old one's insulation tested absolutely fine both hot or cold and so did all the rest of the appliance and its supply wiring. The power board, which looks as if it has enough computing power to run a space shuttle, just did not seem to like the old element. The feed only connects to the power board, as does the control switch for the oven, so the computer controls everything. What happened to ordinary on/off switches?