behaviour differential switches (ELCB)

[Robert]

I have 2 differential switches (ELCB's) in my electrical system. One is rated at 0.03 Amps; the other at 0.30 Amps.

When plugged into a 20 Amp fused circuit, protected by the 0.03 Amp switch, my new 1600 Watt electric grass verticutter causes the switch to trip at the slightest (physical) resistance. When plugged into a circuit using the 0.30 Amp switch, after a short test, I have had no problems.

This does not sound normal to me; should I be worried? The fuse does not go, so does this mean there is a short to earth somewhere?

Robert

[Andrew Gabriel]

Sounds like the verticutter(?) has an earth fault. (Never heard of one before, but I would have expected it to be double insulated, so must be leak to the ground under it). There are other possibilities such as incorrect wiring of the

20A circuit. Try a different high current load on it like a kettle or 2kW heater, and see if the same happens. Since we are suspecting there could be a wiring fault, it would be a good precaution during such a test to assume the earthing could be faulty, so avoid touching the test appliance(s) when they are switched on.

[bigcat]

I dont know what a verticutter is, but presumably when this physical resistance occurs, it is pressing against whatever its cutting, thus making better connection with it, thus the earth leakage goes up.

so the leakage is apx between 30mA and 300mA.

No, just dont use your verticutter again, remove the cable etc so no-one else does, otherwise it might fry you.

yup. It wont be a wiring fault, the motor currents are too high. With a wiring fault it would trip the instant it was switched on.

NT

[Robert]

[bigcat]

yep, can be pertty sure about that

Im not saying that, no

Ideally you need a megger, but you could likiely find it using a multimeter. If its on a 2 core mains wire, the fault current is going to the blades most likely. If its a 3 core mains wire, the fault current is more likely to flow back down the earth wire. Either way, divide and conquer: disconnect bits so you can find out which bit has lowest R to earth. This will generally identify the culprit part.

Of course it needs to be unplugged when working on.

NT