Britannia S1-E10T Main Oven Tripping RCD

[LeighSawczyn]

A customer has a Britannia range cooker which trips the RCD everytime the main oven is switched on. At first the problem was intermittent and progressively worsened until now it happens every time the oven is switched on. The RCD trips even with the oven temperature setting on minimum before the audible click of the thermostat, so even before a signal is sent to the heating elements the RCD is tripped. I'm inclined to think that the switch is at fault as the RCD trips when the top or bottom oven element is switched on. Should I move it to a non RCD side as it is on a 40A MCB? There is no socket next to the isolation switch so RCD isn't an issue. Any advice is most welcome.

 

[Marvo]

Don't move it to the non-RCD side, rather fix the fault. Disconnect the oven element and IR test it at 500v with your mega tester. If it's less than 1Mohm then replace it. If it's more than 1Mohm the repeat the test with the element hot.

 

[LeighSawczyn]

Thanks Marvo. Would you test at the rear of the cooker or the whole cable length back to the MCB?

 

[Marvo]

Nope, I'd disconnect both wires from the oven element and IR test just the element itself. The element is the most likely cause of the RCD tripping problem as you've described it.

 

[overskilled]

I'll agree entirely with Marvo, sounds very much like the element has gone.
If the element tests ok hot and cold....then it could be a damaged cable inside the cooker touching the earthed body of the cooker. Which would mean disassembling it to find the damage and repair it.
However my money is on a faulty element.

 

[LeighSawczyn]

Thanks Marvo and Overskilled. I did an insulation test on the bottom element and it showed 0.08 ohms pretty much a dead short. I disconnected it and all functions on the control knob worked without tripping the RCD. New element on order, customer happy!

 

[telectrix]

0.08 ohms, or 0.08 M ohms???

 

[topquark]

If you just tested the element resistance and didn't IR test it as suggested, it should read around 25 Ohms for a 2.4KW element.

 

[telectrix]

yeah. hope he tested to E and not L-N.!