RCD tripping (even with MCB off) when main cooker/hob switch turned on?

[hztm2008]

Hi, last night the RCD started tripping and I found that it was due to the main cooker switch (the big red switch with the mains socket on the side). If I leave the cooker switch off then the RCD resets and is happy. Even with the MCB turned off, the RCD still trips when the big red switch switch is turned to on.

Today I have changed the cooker switch for a new one and the same thing is still happening. Am I correct in thinking it will be a problem with the hob or cooker that is connected to the circuit even thought MCB is switch off?

Thanks for your help.

 

[Iggifer]

Yup. Will likely be a neutral to earth fault.

If the hob and oven are separate and both connected to the same circuit try disconnecting one at a time to see which is causing the issue and then you can take it from there

 

[hztm2008]

Thanks Iggifer.

 

[hztm2008]

Yup. Will likely be a neutral to earth fault.

If the hob and oven are separate and both connected to the same circuit try disconnecting one at a time to see which is causing the issue and then you can take it from there

Found the hob to be causing the problem. The live connection looked a little black on the copper so disconnected all wires, cleaned them up and reconnected. Turned everything on and all working fine. Is it possible that a bad connection could have been causing the RCD to trip? Or maybe it is just where I have been knocking the unit around a bit getting it out that has temporarily fixed something. Guess I will have to see if it fails again over the next few days. Thanks for the advice.

 

[ban-all-sheds]

Found the hob to be causing the problem.

Hope your new switch wasn't too expensive

The live connection looked a little black on the copper so disconnected all wires, cleaned them up and reconnected. Turned everything on and all working fine. Is it possible that a bad connection could have been causing the RCD to trip?

It's possible that carbon deposits because of a bad connection could cause tracking between N and E.

When you say "cleaned up", did you literally only clean off any black deposits?

If bad connections have resulted in overheating then the conductors and/or the insulation could have been damaged, so it could be that you need to cut them back to clean bright copper and soft insulation, not just clean the black off.