Drill tripping earth leakage protector

I haven't bothered to read the link but I am sure the assertion is correct.

For a period of around 6 (or 12? can't remember) months until about 6 months ago my ELCB regularly tripped at 7.30am and 10pm. Not every day, but probably 6 of the possible 14 times per week (as I write this I have a suspicion it didn't happen at the weekends, but I'm not sure). For the past 6 months it hasn't tripped at all. There is nothing in my house that would cause such an issue. If that wasn't tones on the line then I'm damned if I know what it was?

I suspect they were either doing some trials with new tones or increased the amplitude of the original ones but finally got the message they were causing problems.

Mike Harding

Have you actually measured the leakage current seen by the RCD? If so what is it? If not, then how can you know it is not too high and causing problems. Also you need to isolate the neutral at the MEN point, and megger the neutral as well.

David

No.

You think the leakage current was regularly too high at 7.30am and 10pm but OK at all other times and has now stopped being too high at those times too?

Mike Harding

Could it possibly be an off peak device like hot water heater?

Bryan

"Bazil"

** Electric water heaters usually have their own circuit, separate from the RCD protected power outlets.

Like electric stoves, heaters are known to have fairly high leakage currents.

.......... Phil

If the leakage current was marginal, then the added effect of the control tones could be sufficient to trip the RCD, especially if the leakage was partially caused by capacitance. Also, you mains voltage may have changed, which changed you leakage a bit.

David

If that were the case I would expect random nuisance tripping - there has not been any?

Any more suggestions?

Mike Harding

I suggest that you actually measure the leakage. If you can't do that, get a electrician with the right gear to measure it for you. If you don't know the standing leakage, you don't have any idea of how close the RCD is to tripping.

David

** No need to measure the standing leakage - it is far easier to measure the available margin before tripping of a protected circuit. Just add some known leakage current to earth at an AC outlet.

Eg

A 10 kohm, resistor draws 24 mA from a 240 volt outlet.

Two of them in series draws 12 mA.

Get the idea ??

BTW All appliances that are normally left on should be on for this test.

............ Phil

David if the earth leakage in my house was running close to the 30mA trip rating of my breaker then I would see nuisance tripping, especially, over a long time period. That has not happened - once! - however, as I stated, there was a contiguous time period when the breaker was routinely tripping at 7.30am and 10pm.

Mike Harding

This is not the correct way to test for leakage, and you will have no idea of what the leakage is for several reasons.

1) You don't know what current the RCD trips at. 30mA is a nominal current, and the standard says it should not trip at less than 50% of rated current, so it could trip anywhere between 15 and 30mA. 2) RCDs have a tripping time range, where the higher the current, the faster the trip. AS3190 says that 30mA RCDs should trip at rated value in less than 300mS. Lower currents will trip in longer periods. Unless you time the trip operation (as required by proper testing) you won't have much of an idea. 3) If the leakage is caused by capactitance, adding resistance will also not give a true indication of leakage, as the currents are out of phase. 4) You still have no idea of the leakage current on the neutral, and its contribution to the total leakage.

David

Oh that's just Phyllis - she's having a period or something, as usual :)

Nevertheless - Phyllis may be (is!) a total social misfit but does know a bit about electronics and what he says is correct. Although I do agree, increasing the leakage with resistors is a bit of rough method and won't tell you what the current (no pun :) leakage is to much better than 50%

But I must say you are still a very long way away from convincing me that the tripping of my breaker was not due to the tones.

Mike Harding

the

On Mon, 09 May 2005 07:44:37 +1000, David put finger to keyboard and composed:

I wonder if the following arrangement could be used to measure the leakage current in a particular appliance. The leakage would be mirrored in the single-turn secondary winding and displayed directly on the ammeter. Otherwise one could use a multiple turn secondary and a more sensitive ammeter. I suppose one could dissect an ELCB and adapt it for this purpose.

toroid _ __________ / \ | | -> Ileakage A o---/---\-----o o--|appliance |_____ N o---|---|-----o o--| | | __\___/__ |__________| | | \_/ | _|_ | | = | A ammeter E |_______| ->

Ileakage

- Franc Zabkar

--
Please remove one 's' from my address when replying by email.

Yes, that would work, assuming the torroid was OK. The recommended way to test for leakage is to use a sensitive tong ammeter. You can get ones that have 40mA FSD, and you basically clip them over the active and neutral and measure the total leakage current directly.

David

I had a drill press that was doing the same thing. I tried using the drill plugged into an ELCB built into a power board (one of the HPM ones), and it still then tripped occasionally but only the board, instead of the house one tripping. Worth a shot if you can't find a better solution.

I'd say it was luck that the power board was probably a little quicker than the house, and it only happened on switch on, I suspect some relationship to the inrush current, and the voltage phase as I hit the switch.

The drill is now out in a shed, with an ELCB, thaty doesn't trip at all.

- Rob.

Thanks for this, and all the other advice.

I had already thought of your fix, Rob and will go that way if I have to.

Cheers Glenn

snipped-for-privacy@r.r.com wrote:

Glenn Pure Canberra, Australia Web page: