Advice wanted on neutral to earth

[karv1]

Hi Just wondering if anyone can help me out. Is it possible to get 0.03 to 0.09 m amps on a clamp meter on copper water pipes when an appliance is plugged in and the unit attaches to hot water copper pipes via a metal braided hose? On 2 x units the first unit had external damage with messed up electronics. This was replaced. Then a second unit shows the same fault with electronics which runs off low voltage 12v (main unit runs on 230v). When you unplug the unit from the socket the m amp go to 0 on copper pipes and it is a intermittent fault.
Is it possible that maybe its from the neutral side of a socket leaking to earth somehow and when the unit is plugged in and feeds the neutral it rubs on to the earth some where? I can't prove it and it does not trip the rcd.
The earth pin of plug to chassis gives continuity under 0.1 ohm.
The copper pipes to socket screw gives continuity 0.39 to 0.98 ohm on cold and hot pipes.
The socket and see loop tester gives under 1 ohm; 3 green dots.
Insulation test 999 on live and neutral to earth on unit.
Tried using volt meter; neutral to pipes 0 volts and on 0.0 to 0.00 setting reading got few low numbers but got them before I even touched the copper pipe and no way to reset to 0 on volt meter. Therefore inconclusive if any volts on pipework. Going back with a third unit as client says electrician has checked electrics and believes it is the units. I can't see two units having the exact same fault. Would appreciate any advice / thoughts. Thanks.

 

[Wilko]

Hi K - what units are these and what are the symptoms?

 

[littlespark]

Are any of your testers calibrated?
There may be nothing "wrong" with the equipment

 

[ferg]

0.09mA is not a lot.

 

[shaun1]

Are yiu measuring N to E insulation with a multimeter? You need to carry out a proper insulation test at 500v to get a true reading. Sounds like you also need to carry out proper earth loop tests to get ZE and ZS for the circuits. This will show most faults on the instalation.

 

[karv1]

yes its a 500 v insulation tester socket and see test meter and tryed with an old with megger insulation tester as well did live to earth and neutral to earth and both together the earth loop was a socket and see meter as well. is it possible for the neutral to be leaking to earth from the socket when the unit is plugged in by a tiny amount

 

[PEG]

Hi bud,you to state what the test meter is...Socket-n-see,is not a standard test instrument.
Please do not be offended,but i recommend,a bag of commas,also.

 

[shaun1]

Thinking about it, equipment damage coupled with current flowing in bonded pipework, could indicate a TNCS supply with a high resistance PEN conductor.

In any case it's probably worth getting someone in with a calibrated loop impedance tester to establish the supply type and if there is a good earth at the supply. The circuits can then also be tested.

 

[ferg]

Everything will leak by a tiny amount. Some amounts will be less tiny than others.

At .03 mA you would need 1000 of these to trip the RCD.

In all honesty I imagine your readings are well within the margin of error for your test equipment.

 

[shaun1]

I forgot we were only talking about 0.03mA. I don't think many meters would even measure in that range. You memtion 12v equipment connected by hoses? Is this some kind of electronic tap? Or other device to control a water valve. I would have thought this would have to be SELV and so completely electrically seperate from the mains side. Is the transformer mounted to the pipework?

 

[Deleted member 26818]

Ok, so you have measured current on the water pipes.
Have you measured any voltage?

 

[cliffed]

Why would you measure current in copper pipes,that’s not in the remit...surely.Approx 7,666 ohms,7.6 m ohm.

 

[Baddegg]

As others have said 0.03ma is not a lot at all, what made you clamp the copper pipes in the first place anyway? For curiosity sake try changing the metal braided hose for a plastic one and see what you get?

 

[karv1]

Yes it’s a 12v tap and when laying on floor just connected to usb lead and not the copper pipe it works fine when you touch the copper pipes with the braided hose the tap lights cuts out when you removed from copper pipes it then lights back up , customer used his new clamp meter and was picking up the tiny m amps in pipe when unit is plugged in and turned on , I believe this is interfering with the 12 v tap but you only get this when you plug in unit , he says electrician is saying socket is fine .
my meter say everything is fine on socket and unit.
I suspect that the neutral is leaking on the socket or wire leading to socket to the earth by a tiny amount when unit is plugged in and drawing power 1930/40 house on rcd is this a possibility?

 

[Wilko]

Hi K- can you tell us about the 12V tap please? (make, model, pic)