what causes earth leakage?

[ExArmy]

testing a house today before I put RCD protection on it and i got 300mA earth leakage. appox 100mA from the sockets, 180mA on the downstairs lighting circuit, then 20 odd mA accross the rest of the circuits.

I had a poke around the downstairs lighting circuit, couldn't see anything obvious, did R2 tests at all points (OK), did IR test and it was in the region of 650MΩ L-N, L-E and N-E.

as for the sockets, 2 chest freezers that are older then me are the cause of 50mA between them, rest is unnacounted for?

what causes this?

 

[kung]

Arr but it wont be long now they got christopher lloyd on their side !

 

[chrisreid186]

i reckon that you should do a zs test then check for broken/loose cpc's, i don't know why but i've seen weird voltages on incorrectly installed earth's and beleive its something to do with induced voltage, maybe not the answer but worth a try

 

[ExArmy]

And how many meters go that high? I suspected it was 650Ohms not MegOhms.

my Metrel goes to 999 MegOhms actually!

 

[topquark]

my Metrel goes to 999 MegOhms actually!

Ah well we live and learn

 

[tony mc]

Hi Ex Army

Are you saying all your IR tests are clear with 650 Meg and the leakage is when appliances are plugged in when tested with the earth leakage clamp meter ?

 

[telectrix]

my Metrel goes to 999 MegOhms actually!

typical army, everything by numbres.

 

[topquark]

Hi Ex Army

Are you saying all your IR tests are clear with 650 Meg and the leakage is when appliances are plugged in when tested with the earth leakage clamp meter ?

Not just appliances though, he's got 180mA on a lighting circuit, so unless there are some dodgy transformers on there then there's a problem lurking somewhere.

 

[topquark]

typical army, everything by numbres.

Fair play, he meant exactly what he said. Can't say fairer than that.

@ExArmy, sorry if that caused any offence

Have you made any progress with this?

 

[ExArmy]

Not just appliances though, he's got 180mA on a lighting circuit, so unless there are some dodgy transformers on there then there's a problem lurking somewhere.

thats right. i only did IR test on the lighting circuit, was in a rush and never got time to have a look at the sockets.
I also missed a few points from the circuit when i was there last, owner of the house was out and i didn't realise that a seperate part of the house(outside workshop) was fed from the downstairs lights, hopefully i will find it fairly easily next time , could be a light connected L-E as somebody suggested earlier.
although I am a bit puzzled as to what it is, can't be a light left on as i would have seen it, and whatever it is 500V IR test didn't kill it!

 

[topquark]

I'd be tempted to get a differential reading from the lighting circuit (clamp around line/neutral feed). If there are a few dodgy wiring connections then there's a chance that what you're seeing leaking on the earth from the lighting circuit may not actually originate from the lighting circuit.

 

[pushrod]

Hi Pushrod

Well as Tel has already stated, becuae of the PME link the neutral current has a several paths, now dependent upon the CNE/PME impedance and the impedance of the protective conductors to earth, then you will find that some diverted neutral current will flow through the protective conductors.

The diverted neutral currents may be from your installation or even a neighboring installation.

Place a amp clamp around the live conductors at the origin on a TNC-S and see what leakage is present,and what the RCD will see.

Now dependent upon current, place a clamp/leakage clamp around the Earthing conductor and then other protective conductors.

See what you find

Cheers Chr!s - was thinking i might have been missing something else

 

[Chr!s]

Hi Pushrod

Cheers Chr!s - was thinking i might have been missing something else

No, just an example where as measured protective conductor currents may not be all down to installation leakage.

 

[FatBob]

Tel has discovered a new quantum effect: Indecisive electrons

An electron can be found at any distance at any time and in any direction from the nucleus due to the Heisenberg uncertainty principle. Isn't that indecisive?

Although being a topquark, you might consider the uncertainty principle rather convenient

 

[topquark]

An electron can be found at any distance at any time and in any direction from the nucleus due to the Heisenberg uncertainty principle. Isn't that indecisive?

Although being a topquark, you might consider the uncertainty principle rather convenient

Ohh, distance and direction, you sure

If you take a peek at New Scientist this month, you'll notice that he ain't so uncertain anymore though ;-)

 

[FatBob]

Ohh, distance and direction, you sure

Going to have to dig out some old books and come back to you on that, but say 90%. We cannot know both the exact position and momentum of a particle, we can only find an approximation of each. The better the approximation of one, the worse the approximation of the other.

Can you expand on the NS article, I will get it at the weekend. I know its stationary in the whsmiths frame of reference, but I don't know which shelf it's on.