Oven tripping RCD

[Andy Burns]

10+ year old Neff oven, just decided to trip RCD, no previous trouble.

99% of the time it's used in fan mode (where the element used is within the fan).

Just went to use it in a different mode where top and bottom elements used, but not fan, it had been heating up for a couple of minutes then tripped the RCD in its half of the CU.

Hoped it was a one-off, so reset and tried again, tripped again, wondered if the internal light was causing it so removed bulb, still tripped.

Each time after resetting RCD have to prod the timer button to "ack" the mains failure, then the electronics are on (i.e. clock flashes) if the main selector knob is "off", it doesn't trip.

If I turn temperature knob to coldest, I can turn the selector knob to the setting where just the internal light is on, it doesn't trip (a small cooling fan also runs)

Leaving selector knob in the internal light setting (i.e. no elements or main fan) then turning up the temperature knob it trips the RCD as soon as I hear the stat click on.

To me that doesn't scream "earth leaky element" but rather "gunge has got into stat or across some wiring"

Thoughts?

[Harry Bloomfield]

Andy Burns used his keyboard to write :

Chances are, it is the element which is in use, which is failing and causing the trip. If the particular element can be seen, carefully inspect it and you might see some obvious signs of damage.

[ARW]

Screams to me knackered element.

The stat has to be switching something.

[Andy Burns]

Except it happens when no elements are in use, when the fan element is use, and when the top/bottom elements are in use, which is what leads me to think it's not element related.

Now it's cold again, I'll degunge it and see what happens

[Andy Burns]

I suppose an oven tripping normally would scream "element" to me, especially using one that hasn't been used for some time.

But what tempts me to think otherwise is that with the control knob in the "light" position it still trips; so it trips regardless of whether no element, fan element, top element, bottom element, top and bottom elements are selected ...

Do they tend to have an actual stat, or a thermocouple that operates a relay? You can certainly hear something click at the set point.

Double pole switching? then I suppose a fault from the neutral "end" of end element to earth would do it, even for an element that wasn't in use.

[Harry Bloomfield]

Andy Burns expressed precisely :

Ah, OK. Remember a neutral leakage to earth can also trip an RCD.

[ARW]

Sure that you are not turning on the grill:-)?

The oven will use a thermocouple IMHO

Ovens are complicated things and best left for women to use.

Although they are usually piss easy to fix.

Depending on your make and model it's often only about 10 minutes work to gain access to the elements terminals and do a LE resistance test or disconnect the elements one by one and see what happens.

[John Rumm]

If the element has a neutral to earth short, it can trip the RCD regardless of whether its being used or not.

It will have an actual stat of some form...

Can you isolate the cooker and do a neutral to earth resistance check?

[Andy Burns]

That's why I mostly leave the oven on "fan", same as I mostly leave the washing machine on "synthetics" :-P

From youtube videos, it seems the oven probably needs to come out of the housing to access the top and bottom elements.

[Andy Burns]

Yes, combined DP cooker switch/socket nearby ...

[James Wilkinson Sword]

Remove the RCD. Oh how simple life is with fuses....

[tabbypurr]

Probably the clicking thing feeds one end of the element and the control switch the other. It's still most likely a bad element.

There isn't any more anyone can tell you, it's time for you to either test the elements or power it up without RCD to dry them out. Proper earthing is essential for the latter of course.

[Mr Pounder Esquire]

That must be the stupidest thing you have ever come out with, Birdbrain. What a fool you really are.

[Andy Burns]

Yeah, I was thinking the thermostat would be single-pole, but I think it's reasonable to assume from the behaviour it's double-pole with the switched neutral being common to all elements.

After it cooled down completely, I tried it once again and it did switch on for several seconds before tripping, so all it needs now is to check which of the three elements it is that's f***ed, unfortunately I think that requires removing the whole oven, rather than slipping the elements out from inside the cavity, at least all spares are available.

[James Wilkinson Sword]

Everyone I know with those pesky circuit breakers gets nuisance trips. I don't.

[Brian Reay]

Check the fan.

In a previous fan oven, we had a problem with 'gunge' collecting on the fan. I'm not suggesting your oven is dirty- the fan is tucked away and not normally cleanable as part of the normal regime.

A quick clean, and all was well.

Our current oven is 'self cleaning' but I still half expect that, it time, the fan may need a clean.

[Chris J Dixon]

We occasionally had problems at work getting mineral insulated metalclad heating elements through insulation test. Running them for a while could improve matters, but sometimes it got worse. I have a vague idea that H2O became free H2O, but the details are obscured by the mists of time.

Chris

[Brian Gaff]

Could be as simple as knackered wiring on the stat. Many moons ago we had a Belling which had some kind of cracked insulation on a wire.

Nothing lasts forever I guess. Brian

[Cynic]

Beg, borrow or buy an insulation resistance tester.

[Andy Burns]

I've got one, but not (yet) the enthusiasm to drag the oven out, no turkey to incinerate here, so no rush ...