Tingling while fiddling shower taps during shower

[Justloadit]

I have a little holiday house in Limpopo province, and ever since it was built, some 7 years now, when ever we have a shower, most times, while showering, we get a tingling feeling when we adjust the taps to get the temperature right. When there is no water we do not feel the tingling feeling in our hands, only once the water runs. At first I thought that there may be a faulty element, and I have switched the geyser circuit breaker off, but still get the sensation when adjusting the taps. Now it is not a jolt or anything like that, but have the feeling or presence that there is some small electrical current flowing.

The whole plumbing system is made of copper pipe, and I have checked, that the copper pipe at the geyser is earthed. I have not been able to check that the earth of the geyser is earthed at the DB box, my meter leads are not long enough to go from the roof to the DB box .

I have checked with an ohm meter, and there is continuity between the taps and shower head, between the shower taps and basin taps. I have tried measuring the voltage between the taps and shower when water is flowing, between the taps and the water on the floor when the shower is pouring water, and was not able to measure AC or DC voltage at all. I have noted that at the meter box on the pole, that the earth is connected to the Neutral.

Can some one shed some light for the reason that this may be happening, and what I can check. There is an earth leakage in the board, and if I press the test button, it does trip.

I am a little concern every time my family or I have a shower, that it may get progressively worse, but to date it has not.

What can I check, do or whatever to stop tingling from happening.

[ians]

Simple, make sure the pipes are bonded hot to cold close to the geyser and the bonding is earthed to the geyser, then make sure the geyser is earthed back to the DB. Then do a loop impedance test, In fact i would do a loop impedance test at the geyser just to be sure.

I would plug in my earth leakeage plug tester, verify that all 3 lights are on then test the e/l unit by turning the knob until it trips, which should be around 20 - 25 mA, if it doesnt trip you know either your earth leakage unit is fault or you have a bigger problem inadquate earth, which you might pick up doing the loop impedance test.

It could just be a bad earth connection, all speculation without being on site to see the big picture.

[AndyD]

I have noted that at the meter box on the pole, that the earth is connected to the Neutral.

This sounds like a TNCS earthing arrangement. There could also be an earth rod on your property usually at the first point of entry. The E-N connection on the council side is normal.

To receive an electric shock there is usually two completely separate problems occurring simultaneously.

Firstly there's usually an insulation fault (low IR). Insulation is what prevents current 'leaking' to earth in a healthy or compliant circuit. As the value or effectiveness of the insulation decreases the leakage current to earth increases.

The key word here is earth (ground for our US members). The current takes the path of least resistance so if the earth is good (low resistance) then the fault current flows freely away down this path instead of flowing through someone who touches the appliance with the insulation problem.

This leads to the second problem required when you get a shock or tingling in your case. If the earth wiring (cpc) is high resistance then any fault current present on a circuit or appliance will happily look for an alternative route of lower resistance to flow to earth. In most cases this is the poor soul who comes into contact with it.

Okay, I've tortured you with enough technical rubbish so I'll suggest a few things you might do to fix it.
You say you still get tingling with the HWC circuit isolated, this kinda throws a spanner in most of the usual suspects.

1. I'd certainly double check any earth bonding around the cylinder, remake the bonding connections and clean the copper under all the straps so it's shiny.
2. Visually check all the connection points at the cylinder, the isolator switch and in the DB. Test the earth impedance of the cylinder earth and preferrably use a tester such as a loop impedance tester that can put a high current pulse (40Amps) through the earthing.
3. Megger test the cylinder element at 1000v to check its insulation integrity, it should be at least 10Mohms.

All these tests so far are basic bread and butter and from what you say I doubt you'll find the problem there but rather start with the easy obvious stuff and rule it all out of the equation before you go complicated. Once you know the cylinder and its associated circuit are fine it's time to get into the DB. Visual first, check all earth and power connections for tightness, corrosion or overheating damage. Determine if you have an earth rod on the property which would indicate you have a PME system. If you do then impedance test the rod on its own and disconnected (Ra test), also visually inspect the wiring connections to the rod. Same goes for any bonding from the DB to plumbing, check the integrity of the cabling, straps and connections.

If everything checks out then it starts getting complicated I'm afraid. I'll try explain but I can't advise on how to proceed with localizing without seeing the shower and the surrounding areas. There's actually 2 directions you can get a shock. The usual direction is where you have your feet on a zero volt ground and you put your hand or fingers something that has a fault and a high touch voltage. The fault current then runs from the faulty item and through your body to ground or earth.



The other way you can get a shock is if you're standing on a floor that is at a voltage above zero and you touch a good earth. This is always a possibility with a shower becase they often leak moisture into the surrounding area and the taps are nearly always a good earth point.

I've seen several similar scenarios that are a bugger to locate and usually end up with tiles removed, jackhammering and waterproofing being required. You need to think out of the box as well as in three dimensions. The trick is to find all the electrical cabling and points in the vicinity of the shower and insulation test those circuits. I've seen damp problems in sockets in adjacent bedrooms giving shocks to users of the shower in the next room. I've also seen a stove isolater that was getting damp because of a bathroom leak directly above giving shocks to people at the wash basin. I've also found one problem years ago where tree roots had grown through a drain pipe and a nearby garden light circuit connection was causing tingling at a kitchen sink through the drain water.

These kinds of faults aren't easy to find even with state of the art test equipment and the patience of Job. I wish you luck and hopefully it's something obvious. I would also advise caution if you're not electrically competent, it's easy to get a fatal shock when working on equipment, circuits and in DB's, especially when there's an underlying fault that might have unexpected results. Even earth wiring can become 220V live when it's disconnected!!! You need to know how to prove isolation as well as having the necessary testing equipment. If you're not competent or unsure of anything please seek professional assistance. You've been warned.

[Justloadit]

Hi Andy,

Thank you for your comprehensive reply. The tingling feeling is not always present, but when it does occur, it is only when the water flows. I do have a 1000v insulation tester, which I will bring with me at my next visit, and do a comprehensive insulation test.

I am no electrician, but am familiar with electrical circuits, being an electronics designer and involved in power electronics, like speed drives switch mode power supplies and other industrial controls.

I have done the usual of checking the connections as per your list. I suspect it is a TNCS earthing system with an earth rod. This was a new house in the bush, and from day one it always had this problem. It does have a french drain. I have checked the electrical earth connection between the water pipes and the DB board, and it does show continuity with a ohm meter. I currently do not own an impedance tester, and will seek to beg, borrow, steel or buy one, next time I come up to the house and do an impedance test.

I did inspect the meter box, which is shared by the stand next to mine, and noted an earth wire from my box and the adjacent box going into the ground next to the concrete pole, I suspect this has the earth rod you mentioned. The meter boxes are fed from overhead lines fed from an overhead transformer, which supplies a number of houses in the area. The adjacent box has the neutral connection to the earth wire going into the ground. My box does not have this connection earth connection, so effectively the earth, neutral connection in my house is done by the neighbors meter box. These connections have been done by ESKOM and not the local electrician.

[Justloadit]

OK, I have spoken to the neibours, it seems they are also experiencing this problem, and each one of us thought it was to do with the house wiring, and this is the first time any of us has actually discussed this problem.

I now suspect that there is either a faulty transformer, or the neutral to earth connection on the transformer secondary side may be open circuit, and hence the symptoms we are experiencing.

I will be contacting ESKOM, and hopefully they can resolve the problem. I will keep you posted, but it may take a long while, as I only pop up to the holiday house a couple of times a year.

[Justloadit]

Ignorance is bliss!.

Now that I know where the problem is originating from,
HOW dangerous is this situation?

I have noted that at times the tingling feeling is more intense, and have come to the conclusion that it depends on what loads are running on the ESKOM supply line at the time, the more loaded the more intense the tingling.

[ians]

thats what kills you, the current in the circuit not the voltage.

50 000 volts on an electric fence will not kill you, but 1 amp in a 230 volt circuit will.

[AndyD]

Is your RCD working (earth leakage breaker)? Does the RCD supply the whole house or just plug points? If the RCD is working correctly and it's supplying the whole house it should intervene if the leakage current reaches a dangerous level. Maybe just ramp test it in both half cycle directions just for peace of mind because all your eggs are in that basket if your earth is high impedance.

Good luck getting the supply authority to come out this time of year I would be tempted to whack an earth rod in close to your DB and connect it to your main DB earth bar with a 10mm wire. It's not such a daunting task, if you have access to a jack hammer for a day you can use a suitable attachment to do the hammering the easy way. I would start with 2 or 3 x 2.3meter rods coupled on top of each other, anything less will lack impedance stability. If your neighbours are fed from the same Tx it would help enormously if you could persuade them to do the same. The rods, couplings, clamp connector and wiring should come to way under R1K. I might suggest you dig by hand for the first 600mm at least to avoid hitting and services.

[ians]

what is the neutral to earth voltage at the DB or meter box?

If it is higher than 50 volts i would switch the power off, it is a dangerous installation.

[Justloadit]

There is no voltage between neutral and earth at the DB box and meter box, and the incoming supply cable is about 6 or 8 meters from the pole meter box, where there is this earth rod connected with approximate 2.5mm stranded copper wire. There is one earth leakage isolator on the incoming side, and all circuits in the house go through it. The ELB is rated at 30mA, when I push the test button it trips. I do not have any equipment which can test the 30mA, however if I connect my cell phone charger between live after the ELB and the neutral before the ELB, it trips the ELB, so it seems that it is able to pick up a low fault current.

This place is in the bush, so there is really no municipal services other than water which is fed by a pipeline running along the stand border line, and ESKOM electricity.
The nearest electrical wholesaler is some 55 Kms away, so it is no walk in the park to buy anything, and with all the public holidays, it just makes it almost impossible. I am also trekking back to civilization on Friday morning.
The ground here is practically rock, so not going to be an easy task knocking a rod into the ground just any where, but I feel that I must do something to set my mind at ease.

This is why I find it so strange, that the impedance from a human body is lower than the impedance of the copper pipe in the walls, common sense would say that there would be no current flow with a high impedance in a parallel circuit where the resistance of copper is almost zero ohms, and a human body is somewhere in the region of 200K ohms. I have even gone into the shower with my multimeter, and tried to measure the voltage in the same plane as my body, water and hands, and the darn meter does not show any voltage, AC or DC but yet I can feel there is something there. It could be the transformer has a primary leak to earth, which is causing this sensation.

I am thinking of connecting a piece of stripped wire, along the wall in the shower from the taps, down to the shower floor, so that there is a shorter path for the current to flow, rather than using the human body, will think about how to do this in the morning.

[AndyD]

A person in a shower has a resistance a lot lower than 200K, maybe nearer 2K, I'm not sure to be honest I've never showered with my mega tester . If anyone ever mentions this again I'll deny point blank I ever advised it because I hate the things with a passion but maybe a neon screwdriver would pick up the small leakage current if you could find a way to prevent it getting saturated.

As for earthing, if your foundations are substantial and made of concrete and there's some exposed steel somewhere this often makes a good earth, it's called an Ufer earth (sometimes referred to as a CEE in the American codes). Knocking in a rod when the ground is rocky is just pot luck. You should certainly go with the thicker rods, I remember hammering one in for hours one time, we attached the fourth or fifth 2.3m rod and shortly afterwards the far end of the rod surfaced through the driveway tarmac about 6 meters away from where we started. It can be a demoralising exercise.

[Sparks]

No fault with the answers you already have. I am also inclined to suspect high loop impedance. The only thing is that you do not mention the tingle when using the stove or light switches or touching light fittings so I would normally be leaning toward a hairline crack in the element, however, as the neightbours are experiencing the same problem, it rules that out. Having no voltage reading between N & E means they are at the same potential, no elevated voltage not no voltage and as Andy said, it is not the voltage which will kill you. As for the ELCB, I doubt your geyser circuit is connected to it. I suggest you get the local authorities out and leave it to them. You can always motivate them by calling to ask where or by whom do you submit a claim for electrocution. That will light a fire under them. Keep in mind also that the neutral at the geyser is the same as the one at the lights and stove so when either are being used the geyser neutral should have a potential difference of 220V to earth.

[AndyD]

Keep in mind also that the neutral at the geyser is the same as the one at the lights and stove so when either are being used the geyser neutral should have a potential difference of 220V to earth.

I might be misunderstanding this part but usually the neutral should have zero potential to earth.

I'm worried if your on a PME system the council is just going to tell you to get an electrician to improve your Ir (rod imdedance) which they will see as your problem, not theirs.

I'm trying out a new drawing package so here's another test I've devised for you. Have fun

[Justloadit]

The only thing is that you do not mention the tingle when using the stove or light switches or touching light fittings so I would normally be leaning toward a hairline crack in the element, however, as the neightbours are experiencing the same problem, it rules that out. Having no voltage reading between N & E means they are at the same potential, no elevated voltage not no voltage and as Andy said, it is not the voltage which will kill you. As for the ELCB, I doubt your geyser circuit is connected to it.

We have no tingling feeling on any other appliance, and this being a small house, all circuits go through the Earth Leakage Switch. Even when we wash dishes we do not get any tingling feeling, but then again it is a metal basin. Baths or basins do not behave as the shower either, which makes it even more puzzling.

Keep in mind also that the neutral at the geyser is the same as the one at the lights and stove so when either are being used the geyser neutral should have a potential difference of 220V to earth.

Not sure what you mean by this statement, if you measure the voltage between live and neutral or earth, it does show 230V.

[Justloadit]

OK, I managed to get a voltage measurement. Its a mere 6 Volts 50hZ AC, but it sure does frighten you when you do not know what the heck it is. I can not measure the current, because the cheap multimeter I currently have in my possession does not measure AC current.

It reminds me of a redesign which I did some time ago for somebody, but never came to fruition because the client ran out of money, and I never got paid.

But if you check out this video, Farm Freund, you will get a pretty good idea how good the concept is. It was originally patented by RAU university. It immobilizes farm animals allowing vets to do their thing. The voltage is variable between 1 and 12V, at a frequency lower than the mains frequency, but is very effective, and when I tested it, I recall having the same tingling feeling.