Random Shock From Water Heater / Geyser

[rsk11584]

Dear Friends and Senior Members ,

I am from India, Asia and we have the 240 V electrical system. We also have Geyser / Water Heater installed in our home 2 Nos. From the past 2 months I observe that sometimes, really sometimes the water heater installed in my room gives shock, I mean the shock travels from Earth / ground to water heater to tap water and tap, so when i touch tap i get tingling shock. This happens only rarest sometimes. WE called expert electrician to find out problem he checked the earthing and found it perfect and finally concluded that smoetime someone in that apartment ( its total 4 houses ) someone might be using some faulty equipment exaxctly at the same time when i m bathing and heater switched off,, which results in current coming to earthing and transferring to the heater.

so ideal condition for me receiving shcok is

my heater switched off, + I am touching tap + someone using faulty appliance,

since one neighbour is pest i don't talk with him, i feel he must be using faulty appliance like immersion heater etc, so only way out is to get a separate Earth for my apartment.
or fix a diode or cut off Earth when heater switch is off, heater switch is two pole , phase n neutral are cut off but Earth is not..


When heater is switched on nothing happens only when heater is switched off the current / shock is felt sometimes ..

I feel is there any diode which i can fix in earthing wire so that it can allow only earthing from heater to Earth / ground and not receive the Earth from faulty equipments. People mentioned about electric protector which trips as soon as it detects a leak, but also mentioned that its very sensitive and trips to almost minute changes , inductions .

Any help from fellow members ...

 

[jim hardy]

that sounds dangerous

usually it's the heater element inside a water heater.
they can crack and let water inside, and when thermostat switch connects power to the element electric current leaks into the water.

I once had the defrost heater in a refrigerator do the exact same thing.

As you point out - could be yours or the neighbors.

In my water heater you can hear the elements sizzle when they are heating.
Listen for that and see if the shock is only when your heater is on

if not, ask your neighbor if he's getting a similar shock
if you can't get the neighbors to co-operate then you'll have to work through the landlord.

The water goes everywhere and the shock comes through it so separating grounds won't help.

a GFCI on your water heater would prevent it from doing this

i'd suggest all the water heaters in your building should have them.

that really is dangerous and if it gets worse somebody could die.

 

[Mike_In_Plano]

Yes, this is a nasty situation. I've heard of it happenning when plumping is plastic or somehow isolated from the ground. Grounded, metallic plumbing should make pretty quick work of any ground faults.

There is also an odd, but just as possible situation, in which the water line is simply a path to ground, and the shock is coming from a nearby appliance that has coupled with your bath area, flooring or rug. An example was a refrigerator that had ground fault current and a leaky pan. Water would leak from the pan, moistened the floor, and shock the user at a nearby sink. To outward apperances, the sink was the source of the shock.

Best luck with resolving this quickly.

-Mike

 

[cmb]

In UK, metal sinks used to have to have a bond to ground. I believe the thinking is simply that if there is any source of electricity anywhere that a charge can build up so needs to be dissipated. This might be a full explanation of why it used to be in the regs (no longer, apparently), but I've always had the impression that a charge can build up on an isolated metallic sink simply because of the water flowing through it carrying and separating charge.

If these things are already earthed, then maybe you've bought a new pair of shoes, or synthetic underpants or whatever, and are creating a static charge that Earth's when you go for the tap. You might've just associated the new boiler with something else causing some static charge. Depends on what you mean by 'tingling shock' Is it a continuous feeling of a current when you hold the tap, or just a one-shot 'spark'?

 

[jim hardy]

"...plumping is plastic or somehow isolated from the ground. ..."

indeed i forgot most plumbing is plastic

and the water heater is probably glass lined

so if the element is cracked the electricity has to flow through water until it finds a path back to the transformer, and it'll gladly flow through Earth to get there. And as you have discovered it'll flow through you to get to earth.

your body is a better conductor than water because we contain appreciable salt.
So if you're immersed in water that's carrying current, you are the path of least resistance.

Be especially careful with children in that bathtub until this is fixed.

old jim

 

[rsk11584]

Thank you seniors very much for your reply, actually as mentioned earlier this occurance only occurs sometimes and rarely, i.e as suggested by electrician as mixture of

me using water tap with heater switched off + someone using faulty appliance

we even got the water heater checked by the company and found it working well water heater is just 6 months old.

And please note the shock happens only when heater is swithced off and not when its ON or in use. So now since this is a rare occcurance neither could electrician or anyone solve it, to solve it something has to malfunction when electrian comes to check but when he comes all is well also this happens only during morning hours 06:30 to 07:00 somewhere between this time, so my guess is some pest neighbour is using faulty applicance so my option now remains to use a three pole swithc so that when heater is swithced off all phase neutral and Earth r disconnected also my house has plastic pumping with metal taps, but one thing to note earthing is very strong as checked by electrician, I am not a technical person but the electrician explained that it shows diff of 210 volts which is very good,,

Now my query how to solve a problem which occurs rarely, i.e which does not occur always, then only trouble shooting is possible, hope you understand my problem.
Also want to ask is there any device which allows earthing to flow from heater to ground but prevent current flow back to heater like a DIODE

 

[cmb]

It is meaningless to talk about a 'diode' which only allows grounding on one direction. This is showing some misunderstanding, suggesting you should attempt nothing electrically. Just ask an electrician to bond both the sink/taps and the boiler to a real ground, if you are still concerned.

But, again I ask, is the 'shock' you refer to a single spark-type stab in your finger, or do you get a soft continuous pulsating in your hand when you hold it, or does your hand cramp up and stay cramped up without any 'rippling' sensation?

 

[jim hardy]

might even be a neighbor's water heater.

""And please note the shock happens only when heater is swithced off and not when its ON or in use.""
Now THERE's a clue ---

I do not know how houses are wired in India.
Is indeed there a "phase" that's 210 to earth, a "neutral" that's zero to earth, and a third safety ground also eaqrthed?

Here in USA our 115 volt has that arrangement - hot wire is black, neutral is white and connected to earth, safety is green or bare and also earthed but carries current only if insulation inside something has failed.
Our 230 has two black wires and often no neutral, each black being 115 away from Earth (and from neutral too).

SOMETIMES in this country somebody will miswire a fixture so that the switch interrupts the white wire not the black one. Usually it's by accident. Sometimes ignorance.

IF your water heater were miswired that way , AND your 210 has a neutral that's earthed , AND your water heater has an element that's cracked near the neutral end of element, that would match with your symptom.
So would a neighbor's heater with same trouble.
But look at your switch and try to verify it interrupts the hot wire not neutral.
Probably it's okay since you had an electrician look at it. I would have to see for myself, being a bit obsessive-compulsive.

If you have an inexpensive meter or test light you could check at the heater that neither terminal is "hot" when switch is open. If both are hot, the hot wire is not being interrupted.

Lastly and i hesitate to suggest this because it's a band-aid on a serious problem...

If you got into your plumbing and at the faucet(s) causing this trouble,
replaced about four feet of that plastic pipe with copper,
and tied that copper pipe to earth,
you should be able to intercept that electric current and drain it away to Earth before it gets to your hands.
That would protect you from your neighbor's trouble.
Probably have to do both hot and cold pipes since both are connected to everybody's water heaters by water.

old jim

 

[dlgoff]

might even be a neighbor's water heater.

""And please note the shock happens only when heater is swithced off and not when its ON or in use.""
Now THERE's a clue ---

I do not know how houses are wired in India.
Is indeed there a "phase" that's 210 to earth, a "neutral" that's zero to earth, and a third safety ground also eaqrthed?

That's the big question I had. Evidently in India they use a neutral according to http://en.wikipedia.org/wiki/Electrical_wiring" .
red,blue,yellow for the phases, black for the neutral and green for the safety ground.

 

[jim hardy]

from original post:

""When heater is switched on nothing happens only when heater is switched off the current / shock is felt sometimes .. "

AHA!

my logic says this:::
thermostat correctly interrupts hot lead
your power switch wired improperly interrupts neutral lead
and an element is cracked near its neutral end

so it only shocks you when switch is OFF <<AND>> thermostat calls for heat.

fix switch and replace element.

Dig's link shows wire color is not a good guide to what's what
do you know where it was made and for what market? Blue is hot some places, neutral others... same for black.

that's my best guess.

old jim

 

[rsk11584]

Thank you all seniors for your guidance and suggestions will surely do something and see this problem is solved.

 

[kvsankar]

Hello, Jim:

I came across this thread through a search - I have a very similar problem being described by rsk11584. I didn't quite clearly understand what you mean by below. Can you please explain?

> my logic says this:::
> thermostat correctly interrupts hot lead
> your power switch wired improperly interrupts neutral lead

What do you mean by the above?

> and an element is cracked near its neutral end
>
> so it only shocks you when switch is OFF <<AND>> thermostat calls for heat.
>
> fix switch and replace element.

Is a stray neutral voltage required for the tingling shock?

Thanks
Sankar

 

[sophiecentaur]

If you get your friendly electrician to connect ALL exposed metal plumbing bits and metal house fabric together (bonding) with an Earth cable and connect the lot to a good local Earth (spike in the ground) then there is no way that any of the metal bits can acquire a significant voltage above anything else you could be touching (including the floor).

If any faulty equipment provides a conducting path to any of these metal bits (which it shouldn't) then the current will be routed to Earth and you should not get a shock. What can happen is that a fuse may blow (and rightly so!), to reveal the faulty item or someone may find they are paying a small bit extra for their supplied electricity. Either way, you should be safe.

 

[kvsankar]

Thank you, sophiecentaur.

 

[sophiecentaur]

It's just standard practice in the UK. Maximum safety - maximum cost.

 

[jim hardy]

Hello, Jim:

I came across this thread through a search - I have a very similar problem being described by rsk11584. I didn't quite clearly understand what you mean by below. Can you please explain?

> my logic says this:::
> thermostat correctly interrupts hot lead
> your power switch wired improperly interrupts neutral lead

What do you mean by the above?

I mean i believe the wiring is not as i would have done it.
Let us think for a moment -
one wire brings "live" power to the heater from the 240 volt side of your source
and the other wire carries "spent" power back to the zero volt side of your source.
Live wire is called "Hot" and is at ~240 volts
Spent wire is called "Neutral" and is at ~zero volts.
Interrupting either wire with a contact, either switch or thermostat, turns off the heat element by blocking current flow.
Hot and Neutral should be diffferent color wires and the colors vary between countries.
The "Hot" wire should be the one interrupted. That's for safety, see your next question.


> and an element is cracked near its neutral end

Heating elements are a central wire which gets hot surrounded by ceramic or mineral electrical insulation that's waterproof.
It is not uncommon for a heating element to develop a small pinhole or crack in the insulation which let's water get in and make contact to the central wire. That let's electric current get into the water and from there it gets into your pipes. It can get into any pipe connected to that water, but will be most noticeable on the ones physically close to faulted heating element. Same can happen to the element on your stove, but it's not immeresed in water so there's no ill effect until failure results in sparks&flame.
>
> so it only shocks you when switch is OFF <<AND>> thermostat calls for heat.
If switch is in the neutral wire instead of the hot wire, it cannot interrupt the connection from live side of your source to the failed part of your element. So power will leak into water whenever thermostat calls for heat.
>>> BUT --- SINCE the failed part of element is near neutral end of element , closing power switch places that end of element near zero volts making amount of current leakage un-noticeable. Opening that switch makes leakage current go up to however much the element will allow into the water which is very noticeable to you.
>
> fix switch and replace element.

Does that help ?

Is a stray neutral voltage required for the tingling shock?

No.
The conduction path is from hot side of power to failure in element and into water.
Let's just guess failure is 90% of the distance from hot end of element and 10% from neutral end. When switch is closed the voltage at failed point is only 24 volts, 10% of supply, which might not be noticeable. But when switch is open the voltage at failed point is almost the full 240 volts - because there's near zero drop along element at near zero current.

Thanks
Sankar

Hope you find the trouble.
I could be wrong but this kind of thinking should help you track it down.

 

[sophiecentaur]

What is the meaning of "spent Power"? No power "returns to the source" and even the current, in an AC supply, flows in both directions, alternately. The power is carried by both conductors and it makes no difference which one happens to have a potential near the local Earth. terminology needs to be used correctly or explanations can get very confusing and don't help people who are trying to 'get it right'. All one can say is that the potential at the Neutral end is nearer Earth potential than it is at the Live end.

In a decent installation, the resistance path from the metal case of any appliance should be low enough to maintain a safely low voltage whatever fault occurs. This may involve a blown fuse - if there is enough current flowing to Earth or just a continuous, sustained low value of Earth current which can give a noticeable 'tingle' (this is where am RCD breaker comes in handy).

If the device is switched in the 'wrong' leg of the supply then more current will flow to Earth through any fault if the neutral connection is opened - but aren't all major appliances double-pole switched?

 

[jim hardy]

What is the meaning of "spent Power"?

mea culpa indeed i may have abused the language in attempt to paint a picture for somebody who's not versed in physics.
By "spent power" i meant coulombs that have given up their joules as heat inside the heating element and are en route back to the transformer to replenish their energy. They are at low potential wrt earth.

In a decent installation, the resistance path from the metal case of any appliance should be low enough to maintain a safely low voltage whatever fault occurs.

Imagine a water heater, glass lined, with plastic pipe connections. To get away from a faulted heater element any leakage current must flow through the water, which judging from his symptoms it appears to be doing.
A conductor outside the glass lined tank that's between heater's input terminals and the heating element, should it develop a fault, would indeed conduct to appliance frame and act as you describe.
But the water inside the heater tank is a mildly conductive medium that's not electrically tied to the metal frame. So there's a path for leakage current out of the appliance if the water pipes are not conductive.

- but aren't all major appliances double-pole switched?

My water heater has single pole thermostats, as does my 230 volt window mount airconditioner. Water heater has no on-off switch but the panel breaker is two pole of course.

Here in US the disconnect for water heater is allowed to be the wall plug.
It would be unusual to see a switch for a water heater.
I don't know what is standard in India, but from his symptoms I'm guessing it's wired as i described.

If there's better words to help this fellow out, please improve on mine !

old jim

 

[kvsankar]

Thank you Jim and sophiecentaur for follow-up responses. Additional information below:

I checked whether the wall wiring is correct: The heater is connected through a 3-pin 15A wall socket. There is an on-off switch through which the power to the socket can be turned on or off. The socket is correctly wired as indicated by an electric tester - no socket hole is hot unless the the switch is in the ON position. And when the switch is in the ON position, the "correct" socket hole - the one on your right - is hot - as per the Indian standards.

Given this I am not sure whether a hot wire + broken element combination is causing the issue.

What I have seen is that the shock (though just tingling) appears to get stronger (but still remains within tingling limits) when additional electrical equipment in neighboring rooms is powered on. My wiring has been checked by an electrician and found to be fine.

Another observation which I found out accidentally is that if the house neutral isn't secured properly the shock gets more severe. An inverter/UPS neutral connection was found out to be a bit loose and in this situation the shocks were more tangible. (That problem has been fixed since then.)

The strange fact is that the tingling shock is felt only during night or early morning hours. (The original initiator of this thread too had observed something similar.) And the tingling is not felt by many. It is very evident only when you are wet. But when the electrician tries he is never able to feel it!

 

[jim hardy]

The strange fact is that the tingling shock is felt only during night or early morning hours. (The original initiator of this thread too had observed something similar.) And the tingling is not felt by many. It is very evident only when you are wet. But when the electrician tries he is never able to feel it!

well that's a good one. I don't know what to think.

At the edge of perceptibility it's hard to troubleshoot. I guess i'd try placing my voltmeter probe in the stream of water and writing down the AC volts and AC milliamps that flow from water stream to Earth at various times of day.

Here's an anecdote that's true:

A friend of mine's wife complained of "tingling" from the water in her shower. He didnt feel it. But he did measure a few volts between showerhead and a nearby wall outlet ground screw.
Their house was adjacent utility right-of-way for a 138kv line, perhaps a hundred fifty feet away from the power lines.
The house was built with modern methods using metal studs in the walls not wood ones.
My friend went into the walls adjacent shower from the opposite side, fortunately he had access through closets so the repairs afterward were not prominent.
He tied all the metal studs and the shower head together with a green wire which he snaked down through a wall and earthed at power panel. I think he got the metal shower drain too, can't quite remember, and often they are plastic.
Basically that's a real life example of Sophie's suggestion, which is my point.

Problem solved. But we never knew exactly why.



old jim

 

[sophiecentaur]

I have come across this effect and it's usually been associated with a bad earth. The most sensitive test seems to be to brush the item lightly with the back of your finger and you can feel more of a trembling than an actual shock. The sensation goes when you grip tightly. Aamof, I have some touch operated lamps which exhibit the same effect (by design, though). Have you tried a multimeter on it? Check both AC Volts and (μA) current.

 

[sophiecentaur]

mea culpa indeed i may have abused the language in attempt to paint a picture for somebody who's not versed in physics.
By "spent power" i meant coulombs that have given up their joules as heat inside the heating element and are en route back to the transformer to replenish their energy. They are at low potential wrt earth.

old jim

Which way would those Coulombs be travelling? They change their minds 100 (120) times every second and don't actually go anywhere. Each leg of the circuit is of equal importance in the carrying of energy. The Potential relative to the 'user' is not relevant to the energy transfer situation.
I am picky about this because I really want to educate people to forget about electrons whizzing all over the place. It only serves to confuse (as all the posts we get about it go to prove).

 

[Studiot]

A comment for the science advisors to consider.

The UK wiring regulations require a double pole isolating switch (line and neutral) for fixed water heaters - not just a single pole switching only the line. This has been the case since at least 1960.
Further if the switch is within a bathroom it must be of the pull cord type, not a normal wall plate type.

This is an additional requirement to that for other switched fixed outlets that may be double or single pole and may or may not incorporate fusing and be wall plate mounted.

The regulations further point out that (instantaneous) water heaters with an uninsulated element are unsuitable where a salt regenerative water softener is in use because the increased conductivity of the water is likely to lead to excessive Earth leakage current.

The regs specify ( my comments in brackets)

It is essential that all (metal) parts of this type of heater are solidly connected to the metal water pipe which is in turn solidly earthed independently of the circuit protective conductor (earth wire). The heater must be controlled by a double pole linked switch. If that switch is not built into the apparatus a separate pull switch must be provided adjacent to the shower, with the switch itself being out of reach of a person using the shower. If the neutral supply to a heater with an uninsulated element is lost, current from the phase will return via the water and the earthed metal. A careful check must be made to ensure that there is no fuse, circuit breaker or non linked switch in the neutral circuit.

The above is different from 'electrode type water heaters' which heat water in tanks. I am guessing that the instantaneous uninsulated type is being referred to here.

 

[jim hardy]

The above is different from 'electrode type water heaters' which heat water in tanks. I am guessing that the instantaneous uninsulated type is being referred to here.

instantaneous uninsulated ? i was unware of such a device.

Thanks for all that information, Studiot. Much food for thought ..

It is essential that all (metal) parts of this type of heater are solidly connected to the metal water pipe which is in turn solidly earthed

combine that with possible plastic plumbing...

 

[thebeaverwhis]

As being an electrician for 31+ years,I would recommend grounding your water pipe system if it is copper or galvanized,also the water heater itself should be grounded,( I would check my main ground also,because some contractors use cheap clamps that corrode and fall apart because they really weren`t intended for outdoor or direct burial use) what happens is the heating element can burn in two, or can warp and touch inside wall of tank,as current takes least resistance to ground,poor grounding can resulting shock when you touch a better ground source and are in contact with water that more than likely has plenty of minerals- that posses free electrons for conducting!

 

[kvsankar]

Thank you for the response! I think I have to look into grounding the water pipe system better. The main ground is good - I had it replaced as part of this investigation.