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#142488 - 01/20/05 04:04 PM Live Bath  
PaulCornwall  Offline
Member
Joined: Jun 2003
Posts: 112
England
how about this, i wont bore you with all the small talk..

i have a customer who bath becomes live when they pull the plug out???

tested the house all ok.. bath is bonded.. house on rcd,, the current is only small like a tingle,,

when you put the plug in it stops..

any ideas i have none at all


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#142489 - 01/20/05 06:36 PM Re: Live Bath  
Trumpy  Offline


Member
Joined: Jul 2002
Posts: 8,211
SI,New Zealand
Gidday there Paul,
Long time no see!. [Linked Image]
Well here's one for the books, I can't say I've heard of anything like this before.
Only advice I can offer however, is, it may pay to check the Neutral connections at the Main switchboard, as I have a feeling one of them may be loose.
Just a wild guess.
Only other thing I would suspect, which is even more remote, would be RF currents getting into the pipe-work.
BTW, is the bath body bonded to the drain?.
I'd get a voltmeter and test to a known Earth point, something sounds a bit wierd here. [Linked Image]


Let's face it, these days if you're not young, you're old - Red Green grin

#142490 - 01/20/05 09:00 PM Re: Live Bath  
uksparky  Offline
Member
Joined: Jul 2004
Posts: 200
UK
Like something out of Hammer House...

Have you checked the drain run? Is it in copper ( like mine ) or cast iron? Where is it discharging? And exactly what is bonded?

And yes - check the neut terminal, main earth bond and PME. Look for no-volt on the PME path ( needs a temp rod unless there is already one in ).

Bizarre!! [Linked Image]


If hindsight were foresight, we'd all be millionaires!

#142491 - 01/21/05 03:44 AM Re: Live Bath  
C-H  Offline
Member
Joined: Sep 2002
Posts: 1,497
Stockholm, Sweden
Maybe it is not the bath that is at fault but whatever is around it. I know what follows is a long shot, but it's the only I can come up with at the moment:

On the circuit, there is some equipment (towel rail or washing machine, maybe?) with capacitive coupling to earth or poor insulation leading to a slight current trying to find its way back via the circuit protective conductor. However, the cpc of the circuit has somehow been broken. This means that the equipment and possible the surrounding area are live with respect to properly bonded objects, like the bath. Thus the tingle.

When the bath is plugged into the circuit, the circuit becomes bonded/earthed through the cord to the bath. This eliminates the potential between the bath and whatever is connected on the circuit.

{Edit for lack of grammar}

[This message has been edited by C-H (edited 01-21-2005).]


#142492 - 01/21/05 12:59 PM Re: Live Bath  
PaulCornwall  Offline
Member
Joined: Jun 2003
Posts: 112
England
the waste is plastic,, it discharges into a normal grid and doesnt even touch it.
all neutrals are tight,

the only soultion i could think of is there is a supply company pole a few yards from the house which has an earth stake,(pme) i have asked them to check it out just in case there is current flowing down here into the ground, then when you empty the bath you will get a connection to earth via the person pulling the plug and the water running into the drain.. the bath is enammeld so probably no earth connection through that,

it is very worrying,


#142493 - 01/22/05 02:03 PM Re: Live Bath  
pauluk  Offline
Member
Joined: Aug 2001
Posts: 7,520
Norfolk, England
Certainly a head-scratcher!

You mentioned a PME ground rods on a nearby pole, but is the house actually connected as PME or is it TN-S or TT ?


#142494 - 01/22/05 04:25 PM Re: Live Bath  
PaulCornwall  Offline
Member
Joined: Jun 2003
Posts: 112
England
hi Paul
yep its TNC-S (pme) and connected in the house as that..

something i forgot to mention which as a long shot.. there is a 2.5 swa going to the stables over 100mtrs away. i have the problem that the cable full of capacitance, something i am waiting for the ECA to come back to me with regard to getting it discharged. never thought about that.. C+H mentioned capacitance in a machine, now would or could this have a bearing on things... ie the path via the bath having the least resistance?? when it discharges.. the cold main enters the house under the bath, solid floor, so effectivley the ground around the pipe would be live, and when the water leaves the bath as you pull the plug you get a small current flowing through you???

Long shot???? thoughts..


#142495 - 01/23/05 01:11 AM Re: Live Bath  
Trumpy  Offline


Member
Joined: Jul 2002
Posts: 8,211
SI,New Zealand
PaulC,
Shouldn't the Armouring in the SWA cable be at Earth potential?.
I would have thought that this would tend to drain away any Capacitive effects from within the cable.
Is the Cold water main actually buried before it enters the house, if it is, that should also be at Earth potential.
Are the hot and cold water systems bonded together?, I have seen Elements leak current into the pipework, before today and it is usually the sign of an imminent element failure, however the current is too low to trip any RCD protection.
Only other thing I can come up with is:
Is the house on one single RCD or a couple of them?.
One thing I have come across before is where an "RCD neutral" was connected to the wrong Neutral busbar in the switchboard, referencing it back to the Mains earth, this in turn, causes tingles at poorly earthed fittings.
Other than that, I'm empty!. [Linked Image]


Let's face it, these days if you're not young, you're old - Red Green grin

#142496 - 01/23/05 09:13 AM Re: Live Bath  
pauluk  Offline
Member
Joined: Aug 2001
Posts: 7,520
Norfolk, England
I can't see the capacitance in the SWA feeder being the culprit so long as everything is securely bonded.

If the feeder insulation was damaged and you had a leak in the drainage system, you might get some leakage into the water. Or maybe if just the outer sheath was damaged and the armor wasn't grounded (I see that a lot) then the capacitance could be enough to give some leakage current into the water. Either way, that could be checked easily by cutting power to the feeder.

Are there any other feeds underground near the drain which could have gone faulty, such as the main to the house? Just a thought.

Just one other point to clarify: When somebody gets a tingle as the water is running away, is this while still sitting in the tub, or while standing on the bathroom floor and touching it?


#142497 - 01/23/05 09:24 AM Re: Live Bath  
lyledunn  Offline
Member
Joined: Jun 2002
Posts: 159
N.Ireland
pme is probably the problem. this is the result of small diverted neutral currents causing perceived shock. It is a relatively well documented phenomenon that people showering in leisure complexes connected to pme earths often feel a tingling sensation. It is often cured by ensuring that a metal floor grid is installed which is connected to the local supplementary bonding arrangements. Many designers will ensure that such facilities are not connected to a pme terminal but are TN-S or TT.
I take it that Paul is right when he assumes the water is flowing and the client is touching the bath while standing on the floor.
I should also say dont discount other possibilities. Remember a spark a few years ago got six months for negligence in just such a situation. A girl was electrocuted at a kitchen sink after reporting shocks as she used the kitchen sink. Poor old sparky investigated but was beat and put it down to static. It turned out that there was an intermittent earth fault om central heating timer. So I give my diagnosis only by way of technical chat and suggest that you dont let the matter go unresolved! Good luck!

[This message has been edited by lyledunn (edited 01-23-2005).]

[This message has been edited by lyledunn (edited 01-23-2005).]


regards

lyle dunn

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