Earth current leakage

[PeterLeest]

My gas hob has an inbuilt electronic ignition circuit; recently, it developed an earth leakage, measured 2 MΩ from live to earth. Occasionally, it tripped the main circuit breaker.

Since the resistance is high, it appears to me that the isolation is quite ok. Do you think it is a genuine trigger? or the ELCB is faulty?

What is the minimum resistance leakage (or current) that would trip the circuit breaker in a 230V system?

[Steerpike]

Usually they are set at 15mA or 20mA. That is on the high side of safe, since 20mA can kill, but too low causes false triggers.

Thats only about 12k. But several other appliances may have slights leaks too, and the breaker is sensitive to the sum of all earth leaks in your house.

I've found with electric cookers/stoves that steam from the food can get into electrical parts that otherwise measure totally fine when dry, but after 15 minutes of food in the oven - earth leak! Then it takes a day to dry out.

[Michael Chua]

Hello PeterLeest

ELCBs are very reliable. I've used the same unit for more than 20 years, no problems at all. Apart from you touching the Mains Live wire, the only other times they trip are when there are lightning strikes. Usually, the lightning is very, very near to trip the ELCB.

If your ELCB doesn't trip when your hob is off, chances are the hob is the problem. Best to have it checked. Frankly, I don't understand why they need to use the Mains for the Ignitors. Usually, they are Piezo types. Batteries can power them. After all, your hob has gas burners, so its either Butane or PUB. No electricity required.

Another solution is to simply unplug the Mains. Use one of those handheld lighters for gas stove, the ones with the long handle. Saves you the trouble and cost for repairs.

[Mooly]

Originally Posted by PeterLeest

My gas hob has an inbuilt electronic ignition circuit; recently, it developed an earth leakage, measured 2 MΩ from live to earth. Occasionally, it tripped the main circuit breaker.

The resistance may be "non linear" and measure 2 meg with a low voltage test meter, but may be much lower when subject to the 680 volts peak to peak of the mains.

[AndrewT]

I think that the UK rules for these "earth leakage" detectors is that the standing leakage must be less than 25% of the rated trip current.

i.e. <=7.5mA for a 30mA device.

You can measure this at the distribution board, but do be very careful with the mains voltages.

[multisync]

on our gas stove the oven and broiler uses a glow plug which draw a fair bit of current. When the power is out we use a match or lighter to run the top burners, but the oven will not run when the hydro is not available.

I serviced equipment that used "earth leakage" breakers in the equipment. When the breakers would trip it was almost always a nightmare to find the source of the fault, almost always it was an intermittent problem. Could be anything, a frayed wire that touches the frame when 6 different conditions are met, a faulty part that overheats expands a bit and touches something and shorts out temporarily, someone dropping a heavy item on a floor the floor shakes a bit more than usual and poof. Its almost never the breaker.