Neff Oven Tripping RCCB

[nheather]

I have a problem with my Neff B1442N/10/GB Electric Oven. On certain oven settings, it trips the RCCB immediately.

My immediate thought was a faulty element with an earth leakage, but as I thought about it I became puzzled.

I believe that the oven has three elements - grill, fan and bottom.

The RCCB trips immediately if any of these oven settings are selected

Circotherm (fan assisted)
Grill large area
Grill small area

The RCCB does not trip if either of these oven settings are selected

Top\Bottom heat (convential)
Bottom heat (convential)


My immediate thought was that the grill element is faulty.

But what is confusing me is why is the Circotherm setting casuing the RCCB to trip as I didn't think it used the grill element.

If it were the fan element that had gone then that would explain the Circotherm tripping but not the grill tripping.

I can't imagine that two elements have failed at identical times.

Any ideas?

Many thanks,

Nigel

 

[jj4091]

If you do not have an insulation tester then you could try isolating one component at a time. It may be you have a short to earth in the neutral path which could be common for all elements. It is also feasible that you have a faulty rcd, but doubtful if it is the main one in the consumer unit.

 

[nheather]

I don't have a dedicated insulation meter but I do have a professional multi-meter.

As the RCCB trips at 30mA earth leakage, that equates to a resistance of 8k ohms or less so I should be able to pick that up with the resistance setting on my multimeter.

The RCCB is built into the consumer unit and is not being triggered other than by the oven, so I suspect it is fine. Last time it was triggered turned out to be a faulty element in the tumble dryer so it sounds like it is working fine doing its job.

Cheers,

Nigel

 

[nheather]

Solved. Took it apart which was surprisingly easy and disconnected each of the elements in turn.

All the elements share a common side (neutral I assume) which will be why I'm getting trips for different elements.

Two things still puzzle me though

(i) The failed element is the bottom oven which we have never used

(ii) With the faulty element in place, the fan oven and the grill oven trip but the bottom one doesn't.

Anyway, since we don't use the bottom oven, I've left it disconnected for now.

Will replace it in slower time.

Cheers,

Nigel

 

[jj4091]

A proper insulation tester such as a megger will show up if the insulation is breaking down under load much better than a multimeter, which will only measure a constant resistance.
"(ii) With the faulty element in place, the fan oven and the grill oven trip but the bottom one doesn't."
Don't understand what you mean by this,If the faulty element is the bottom one then with it connected it will trip with any of the others switched on because as you say they share the neutral. The bit I cannot understand is how an element that has never been used has developed a fault.

 

[nheather]

Don't understand what you mean by this

You need to read the first post. When diagnosing, selecting the bottom oven did not cause the RCCB to trip.

But selecting the Fan Assist oven or the Grill did cause it to trip.

What I was saying is odd, is that the element causing the problem is the bottom element, yet selecting the bottom oven did not cause the RCCB to trip.

I can understand why the Fan Oven and Grill caused the trip because they share a common neutral.

But why on earth selecting the bottom oven did not cause a trip is beyond me given that is the faulty element aswell.

A proper insulation tester such as a megger will show up if the insulation is breaking down under load much better than a multimeter, which will only measure a constant resistance.

I know, I have a degree in Electronic Engineering. But as I said, I don't have a Megger, nor access to one, so the point is moot.

Cheers,

Nigel

 

[jj4091]

Is the bottom element showing a short to earth on your multimeter or are you deciding it is faulty on the basis that it was ok when disconnected.Where in the circuit did you disconnect the faulty element, if it was at the element then it leaves the possibility that the short is in the controller/thermostat & when you switch it on it somehow removes the short. I'm not familiar with your product so just doing generic fault finding.

 

[captaincaveman1]

If an element isnt used it slowly absorbs moisture resulting after a time for it to become short . Ive had to call to many ex-display ovens that when eventually sold and the customer connects it then it trips and then i get called to replace all the elements!.

 

[jj4091]

If an element isnt used it slowly absorbs moisture resulting after a time for it to become short . Ive had to call to many ex-display ovens that when eventually sold and the customer connects it then it trips and then i get called to replace all the elements!.

Well that's very enlightening, not something I've come across. Thanks