Excuse any incorrect terminology in this question (I will correct if advised).
I'm in the UK. I have a house with relatively new wiring (past 5 years) which has circuit breakers on the power and lighting circuits and two RCD devices (I think these are GFCI in the US) for the downstairs and upstairs circuits.
I have a very basic built-in electric oven with fan that runs off a standard 13A plug.
I unplugged the oven from the socket, moved the shelf in the housing that the oven sits on to make room for something else. I then plugged the oven back into its original socket (two outlet, dual pole, switched shared with microwave). When I switched on the thermostat on the oven, it tripped the "downstairs" RCD. Just switching on the lamp or the fan did not trip the RCD. I looked at the wiring in the plug and the earth wire looked to be just a few strands of copper. I stripped insulation and trimmed and refitted all three wires (E,L,N) to the plug, plugged the device in, switched on the element and thermostat and no RCD tripping. Hooray! The device has been ok for about two weeks then yesterday it tripped the RCD after running at 180C for 15 minutes.
Now, the device is probably faulty in some way but I am concerned that this is some "cumulative" effect and that there is a "baseline" current drain happening from other devices and the oven is just adding to that and causing the RCD to trip.
Is there some "plug in" tester that provides a standard UK plug and socket that can be inserted between the device and the power outlet where I can check any current drain for every device in my house? I'm trying to isolate the problem to the oven – if indeed that is the only source of the problem. I'm willing to pay £30 for such a device.
Is there any link to a systematic check I can perform on the oven if the current drain problem is isolated to that? I'm trying to decide whether there is an easy diagnosis / fix I can achieve for under £50 plus some time investment and decide whether to get the oven serviced or to junk it and buy a replacement. I chose £50 as the target expenditure as that is the charge for a call out plus half hour work around here. Also if it is possible to "residual current" test all devices that will unearth other problems and I can replace faulty devices or make me sleep better.
I don't want to replace the oven if the problem is (partly) somewhere else and replacing the oven doesn't actually fix the RCD trip.
Best Answer
Yes. Get an extension cord (I assume they are all 3-prong in the UK). Slice down the edge of the cable and remove the outer sheath for about a foot. Don't cut into any of the insulation on the individual wires (though if you nick ground's insulation, don't worry about it).
Bind the hot and neutral (brown and blue) wires tightly together with electrical tape.
Now get a clamp ammeter and clamp the hot/neutral bundle. The amp reading should be zero. If that is not zero, that is a ground fault, which explains the RCD trip. Now clamp the ground wire. The reading should be zero. If it is not zero and the same number, you have an internal ground fault that has been caught by the ground wire.
If the non-zero figure on the conductors isn't accounted for by the figure on the ground, you have current leaking in a third direction.
Either leakage implies a problem with the oven. Try giving it a good clean, especially in the wiring areas.