Type A RCD for an old consumer unit.

That is weird. I wonder if you have an earth neutral leak somewhere other than the cooker itself?

Run all the elements a few hours. Sometimes they absorb moisture in storage.

Is that with the elements powered? If you are doing it with the appliance dead then it's possible they aren't switched into circuit (perhaps they're being switched by electronics).

Does it trip with all the rings/elements turned off, or when you turn one specific on?

Theo

It trips with everything turned off. Except of course for the electronics, and any mains filter it might have. I assume it is because of the cumulative capacitative current to earth that nearly everything in the house has nowadays. Which is why I want a type A RCD, that apparently only responds to in-phase (resistive) leakage, which my cooker, as stated in the OP, has very little of.

My sister had a similar problem some time ago when she moved her old cooker into her new house, and she called my brother who is an electrician to have a look.

What he found was that the little light that shows whether or not the oven was up to temperature was wired with one side on the live output of the thermostat switch, and the other side was wired (through a resistor) to Earth rather than neutral. Easily fixed by a quick rewire but a lot of dismantling to find it.

As you say it is a new cooker, I would suspect that being the problem rather than the Wylex unit.

Well it isn't that exact fault, because it occurs when no thermostats, elements or indicator lights are on. But I assume the electronics must be referenced to earth even if the main current path is live to neutral, and I don't what the rules are on this. I doubt it would be as simple to remedy as the situation your describe.

I've had it twice with new cookers/hobs. Both times a new RCD cured the problem. One , an induction hob, used to trip an adjacent RCD when it was turned off at the hob switch. No idea of the science behind it, but a backfeed was upsetting the adjacent RCD. A Type A RCD would not be the fix for your problem, as that is not what they are there for, but if it is a new RCD, it probably would fix it, but only because it is new, not because it is Type A. The type AC does not trip with certain DC currents, nothing to do tripping because of them. Your current RCD is the fault, fitting a new one, if available, would cure it.

First check the polarity of the cooker connection. If all is well try connecting the neutrals together at the switch and see what happens.

I don't believe a type A RCD will not help you.

Adam

It seems you're absolutely right, I misunderstood the fact that a DC component actually *reduces* sensitivity in type AC RCDs!

Ultimately I suppose I probably need a new consumer unit with RCBOs seeing I have had nuisance trips quite often since I have lived here.

I'll do the experiment you suggest.

I might, as another poster suggests, replace the RCD, but I am only going to be able to find a secondhand one.

Perhaps its time for a re-wire?

They are about....

Dave

Now if it was rewired when the RCD was fitted that would probably make the wiring only 25 to 30 years old.

I am sure we have plenty at work going spare.

Adam

I'm too old for rewiring. Nothing's broken or too old, and it would require massive redecoration. May go for a new consumer unit if I can find an understanding electrician.

But are you selling them? WSES 80 or 100A. (Current one is 80A, main fuse is

Free if I can find one

Found a 100A. Subject to it passing a bench test it's yours.

Adam

Thanks Adam, that's impressive. But sorry to put you to the trouble but it would be a waste of potentially useful spare as I'm getting the consumer unit changed in a couple of days, sick of nuisance trips every time the mains goes off for more than a few milliseconds (which is rather often). You can't use a computer without a battery or UPS round here. In the meantime, the oven is fine if I turn off a couple of socket circuits while I'm using it!

Methinks you have an earth neutral short somewhere.

No problem.

What's the new CU costing you if you don't mind me asking?