Neff Oven tripping MCB

[ukorca]

My Neff double oven is tripping the MCB on the mains.

This occurs when I switch on any function of the top oven. The model is U1744N (around 15 years old). The top oven has a double element at the top (grill and oven) with a second element under the casing at the bottom of the top oven. The bottom oven is fan and has multiple elements, but this is all working correctly and can be used without problem.

I have taken out the oven and removed the rear casing (after disconnection). The element connection points and all aspects of the wiring look undamaged with no signs of arcing. I have removed the top element and visually, it looks ok - there appears to be no physical damage. Testing the two separate circuits of this element with a multimeter shows resistance of over 40 . I tested the second element of the top oven without removing it by taking off the clips and testing resistance, this also showed over 40.

However, I'm still having the issue of the MCB tripping. It first happened a few weeks ago and having left it for a few days, I tested it again and it worked without issue. It is now happening all of the time. It's not the end of the world as we still have the bottom oven, but I'd like to try and repair it.

Can anyone please suggest other steps to try, or should I assume one or both of the elements are faulty and swap them out?

 

[telectrix]

is the circuit RCD protected?

 

[ukorca]

My Neff double oven is tripping the MCB on the mains.

This occurs when I switch on any function of the top oven. The model is U1744N (around 15 years old). The top oven has a double element at the top (grill and oven) with a second element under the casing at the bottom of the top oven. The bottom oven is fan and has multiple elements, but this is all working correctly and can be used without problem.

I have taken out the oven and removed the rear casing (after disconnection). The element connection points and all aspects of the wiring look undamaged with no signs of arcing. I have removed the top element and visually, it looks ok - there appears to be no physical damage. Testing the two separate circuits of this element with a multimeter shows resistance of over 40 . I tested the second element of the top oven without removing it by taking off the clips and testing resistance, this also showed over 40.

However, I'm still having the issue of the MCB tripping. It first happened a few weeks ago and having left it for a few days, I tested it again and it worked without issue. It is now happening all of the time. It's not the end of the world as we still have the bottom oven, but I'd like to try and repair it.

Can anyone please suggest other steps to try, or should I assume one or both of the elements are faulty and swap them out?

Update - just tried to test to see if ithe grill or the oven element tripped the MCB and on testing, the oven is working again on both. A frustrating intermittent fault!
[automerge]1588690108[/automerge]

is the circuit RCD protected?

Yes, all circuits of the house on RCD. separate MCB for lighting and mains

 

[telectrix]

Update - just tried to test to see if ithe grill or the oven element tripped the MCB and on testing, the oven is working again on both. A frustrating intermittent fault!
[automerge]1588690108[/automerge]

Yes, all circuits of the house on RCD. separate MCB for lighting and mains

assuming that the RCD is effective, that means that you don't have an earth fault. next is... what rating is the MCB that's tripping.?

at 40 ohms each element, that's only 6A each or 1440 kW. are you sure your meter is accurate, possible lead resistance?

 

[ukorca]

assuming that the RCD is effective, that means that you don't have an earth fault. next is... what rating is the MCB that's tripping.?

at 40 ohms each element, that's only 6A each or 1440 kW. are you sure your meter is accurate, possible lead resistance?

The ohm measurement was from memory. At least one of them was well over 60.

The circuit the cooker is on is completely separate and comes back to a Hager MT140 B40. I've just looked this up and its an MCB, rather than RCD. The RCD is actually the thing that's tripping!

I got it back to front! I should stick to computers

So, the RCD going signifies an earth fault, so does that mean me testing the resistance of the elements is pointless?

Is there any way I can work out which element is causing it?

 

[telectrix]

without a insulation resistance tester, the only way you can determine which element is at fault is to:
1. isolate supply
2. disconnect the leads from 1 element and insulate the ends with some tapeand dress away from any metalwork.
3. being very careful, re-energise circuit and see if it trips when you tun the oven on.

no trip... it's the element you've dissed that's faulty

trip... it's the other one. repeat test but with the good element connected and the other one dissed.

I stress ..... be careful and always isolatebefore touching anyrthing. if you're not confident with this, wait till you can get an electrician in.


whereabouts in the UK are you?

 

[ukorca]

without a insulation resistance tester, the only way you can determine which element is at fault is to:
1. isolate supply
2. disconnect the leads from 1 element and insulate the ends with some tapeand dress away from any metalwork.
3. being very careful, re-energise circuit and see if it trips when you tun the oven on.

no trip... it's the element you've dissed that's faulty

trip... it's the other one. repeat test but with the good element connected and the other one dissed.

I stress ..... be careful and always isolatebefore touching anyrthing. if you're not confident with this, wait till you can get an electrician in.


whereabouts in the UK are you?

That sounds reasonable @telectrix thank you, although reading it back, I got a little confused. Please double check my plan below.

I'm going to keep one of the elements connected, with the other one disconnected, with its supplying wires taped up and safely away from everything else. If the connected one trips, that's the problem. I will repeat the other way around to double check (I suppose there's a chance both could be faulty) and I should have identified the culprit.

 

[telectrix]

That sounds reasonable @telectrix thank you, although reading it back, I got a little confused. Please double check my plan below.

I'm going to keep one of the elements connected, with the other one disconnected, with its supplying wires taped up and safely away from everything else. If the connected one trips, that's the problem. I will repeat the other way around to double check (I suppose there's a chance both could be faulty) and I should have identified the culprit.

sounds like a plan. when you put tape on, fold over the last 1/4". then you have something to get hold of to remove it.

wordof caution, don't run 1 element for any length of time, as the stat might not react to the temperature if it's on the bottom with top element on, and vice versa. so you'd get overheating.

 

[ukorca]

sounds like a plan. when you put tape on, fold over the last 1/4". then you have something to get hold of to remove it.

wordof caution, don't run 1 element for any length of time, as the stat might not react to the temperature if it's on the bottom with top element on, and vice versa. so you'd get overheating.

Frustratingly, the oven is working correctly this morning. I guess I'll have to keep using it until it trips the RCD again, then test