what causes earth leakage?

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ExArmy

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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?
 
There are a number of devices that may cause leakage. For example anything that involves a power supply, transformer, heating element. First step should be IR test on the circuit (all devices disconnected and protect any vulnerable equipment) to elimate any faults with the wiring (often the cause of relatively high leakage, like you appear to have).
 
I should add that some of this can be considered (arguably) valid leakage, although it's undesireable. A typical personal computer for instance would leak less than 5mA in healthy condition.
 
how have you measured this 300mA leakage? that's a hell of a leak, worse than my local plumber!!!
 
Suspect something is a bit wrong somewhere. A few mA here and there is ok with some devices but 300mA ???

Filters are devices in electronic systems often made from resistors, inductors and capacitors that control the form of input waves and as a result will of leak very small currents to earth but this is usually < a few mA.

A resistance of approx 766Ω between a Line and earth would give you 300mA of current in the cpc. I would be looking at dodgy appliances and low IR readings :)
 
pity we can't harness the power. would beat sunshine panels hands down.
 
suppy is TN-S, and it was measured using an earth leakage clamp meter.
since looking at the lights i've been told theres more lights and sockets that have been spurred off the downstairs lighting circuit in another part of the house, so when i go back i'm fairly confident I'll find the problem.
 
think it's electron confusion as the E and N are connected together at the head, the poor little buggers don't know which route to take.
 
they were fine when they were using a map and compass, but now they've been supplied with a sat.nav. that's what's buggered the poor little sods. they want to take the neutral path, but the sat.nav. directs them down the earth path, even though it's clearly marked as " no through road for electrons".
 
the really confusing issue is when the positrons decide to intervene. a traffic jam at the junction would ensue, causing road rage and the release of megajoules of energy, this could result in a massive meltdown of the supply cable and so we could all have the rest of the day in the pub
 
ah but thats where the sub atomic particle police turn up and arrest all the rowdy particles and throw them in a capacity for the night until they find a use for them...
 
use to be called a cell block, but now it's a custody suite with CCTV cameras in the bogs. wonder what the new name for a cess-pit is now. excrement suite? , poo parlour?
 
pushrod said:
hi chr!s, care to expand on this?
Click to expand...


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:)
 
Oooh, now that's a tease. Are you suggesting that the imbalance in the live/neutral won't be reflected in the main earth for the instalation? That's nothing surprising because of the other extraneous paths, why is this more prevalent with PME? I feel like I'm missing something now ;)
 
i think the answer lies in a piece of toast. have you noticed, every time you drop a piece of toast, it always lands butter side down.
 
and here was i thinking we'd got nicely off topic.
 
all meters will go that high if you've got a tall pair of steps.
 
topquark said:
Nurse, don't let that man ever do any design work! :p
Click to expand...
now then. kung has just come up with a design idea for simultaneous IR testing of 3 phase installations, he's just got to get the probes at the right angle. 120deg. apart.
 
He was that Mike Tysons promoter with the steel wool hair ! ear come to think of it his hair was at 120deg mabe thats the answer to the probe spacing design problem ! just employ him as an apprentice and glue the probes to his hair and wala ! he can hold the Meggers and just walk foward for the 3ph test !
 
i remember him. thought it was christopher lloyd in back to the furniture
 
if you look at the plan view of the starship enterprise, you can see that the whole ship is a giant flux capacitor. no wonder the romulans never caught up with them.
 
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
 
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 ?
 
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