Electricity and water - a marriage made in Hell ???

[FIAT LUX]

Hi folks!

A mate of mine keeps ornamental koi, and is having some problems on the water + sparks front....

The general installation at the site is on the French 230v, radial set-up, which has at some time been converted from 3-phase to mono, and has then been progressivly bodged, patched-up and extended over the last 20 years or so. Protection is by way of 30ma RCD, and I have just installed an earth-spike (where previously there was nothing (!), or worse, where some of the old yellow-green cable in the old 3-phase multi-core had been re-utilised/cannnibalised to carry 'live' (!!!).

Tested the installation, and voltage and earth loop measurements were within norms, and RCDs tripped as they should. However, the koi pools are presenting some problems: There are four large, above-ground plastic pools, each fitted with a UV filter and submersible pump. Depending on the weather - and the thickness of the soles of your shoes - the pools willl give you anything from a slight fizz to a pretty lively jolt if you put your hand in the water. This is clearly Not Good, by any standard.

The filters and pumps are on European 3-pin sockets (labelled 'this equipment must be earthed'), and are run from an indoor socket (which measures 229.7v / 50 Hz ; Z1 - 5.07ohms ; RE - 4.1), which is run via an external extension lead to a multi-gang socket (which drops to 227v over the length of its run, and has given maximum earth loop measurements of Z1 - 22.08ohms ; RE - 21.7).

Thought I'd see how lively the water was, so dipped a piece of 2.5mm insulated copper wire into the pool, and placed another in contact with the ground. Then put crocodile clips from my tester on 'L' and 'PE' respectively, and got a reading of 230v (!!!), which dropped to 0.5-1.0 when the contact with the ground was broken (.....and the RCD didn't trip).

Am I missing something obvious here (doh!), or could it be a problem with the submersible pumps (but all 4 at the same time?????) My mate has said he's had this problem before, with other pools, and he says he's not really too bothered.... But I am! and any thoughts, ideas or suggestions would be very much appreciated - cheers!!!

 

[sparkytim]

How are the fish????

Sounds like you may have 230v in the water there!

You say its RCD protected strange that, it is not doing the job its designed to do here.

With the previous mix up in wiring is it possible that the green/ yellow conductor is still live?

A leakage from one of the Pumps or its lead would normally cause the RCD to trip but it maybe if the pools are raised and all plastic there may be no earth path for the fault current to flow.

Your Z1 reading of 5.07 at the indoors socket and then 22.8 at the extenson lead shows a higher resistance of the earthing conductor then would be expected. How long is the circuit?

It sounds like a good overhaul of the set up is required to improve the situation.

Are there any regulations relating to Domestic installations in France?

 

[ProDave]

Have you done any IR tests on the pumps? Surely that would show up any insulation breakdown.

If you are just getting a "minor fizz" then the leakage is very much below 30mA hence why the RCD is not tripping. This suggests to me perhaps a high impedance insulation breakdown in either the pumps or the UV filters, but currently the leakage current is too low to trip the RCD.

 

[SPECIAL LOCATION]

My thoughts.... :|

There are four large, above-ground plastic pools....

So if the water is not in any direct contact with earth..

e.g. plastic insulated water tight liner....

IF the water did go to 230v..

The electrics would NOT have anyway to flow to earth to trip the RCD...

Just leave the water held at the 230v potential with respect to earth..

bit like a non-bonded extraneous metalwork part becoming live with nowhere to discharge to...

Until someone sticks their hand in the pool to create a path..!

but due to higher resistance of path though water not enough current to trip RCD?

Is there something wired with incorrect polarity or some faulty pool accessory?

 

[Badger]

why just stick an earth rod in the corner :^O

 

[batty]

Probably a pump going down to earth slightly had this with my pond not enough to trip Rcd but enough to give you a little tickle.

 

[binky]

Just leave the water held at the 230v potential with respect to earth..

bit like a non-bonded extraneous metalwork part becoming live with nowhere to discharge to...

Until someone sticks their hand in the pool to create a path..!

Has been known to kill .

Would change set-up for 12v on anything immersed in the pond. or add earth strap to bypass insualted pond liners. But sounda like you have a faulty pump or 2 in ponds, and as others have pointed out a dodgy set-up in need of re-vamping anyway. Still, it should sort out any heron problems:^O

 

[FIAT LUX]

Thanks to everyone who replied to my post - much food for thought!

I was hoping to get back on site to investigate further, but my mate/the owner has become a bit pig-headed for some reason, and is resistant to any further intervention, as he says he isnt really that bothered (!!!)

What can we do to protect people from themselves ??????

 

[Doc Hudson]

my mate/the owner has become a bit pig-headed for some reason, and is resistant to any further intervention, as he says he isnt really that bothered (!!!)

That sounds like a statement from someone who knows there is a bit of inappropriate wiring practice somewhere and doesn't want the embarrassment of having it exposed?

Doc H.

 

[aptsys]

or add earth strap to bypass insualted pond liners.

Don't do that. It'll kill all the fish!