shocked while in the shower

[Hv&Lv]

I have been asked to troubleshoot the reason why a friend is getting shocked whenever they touch the shower head pipe. Also gets a tingle when touching the metal soffit around the house.:? I believe it to be a loose building ground. Any thoughts?

I say bad nuetral connection somewhere between the panel and the utility transformer. The return currents are going to get back to source through any available path.

 

[Hv&Lv]

A little more precision, please?

Let's start with what I measure at my house, a couple miles from hers.

The voltage difference between the metal pipe that is bonded to the neutral at my house and the earth is 2.6 to 2.8 volts no matter if the test electrode is three inches or three feet from the bonded pipe. This ground to neutral difference is a POCO thing and less than three volts is considered normal.

Now, let's say for arguement that before I bonded the pipe at my sister's house, the well pipe to drain pipe difference was 10 volts. Obviously, the drain pipe was grounded but not bonded. After the bonding of the well pipe, the difference went down to a volt or so.

So, now with the pipe properly bonded and the consumer complaint gone, what do I look for? If I disconnected all my metal water pipe from the neutral at my own home, where there never has been such a problem, what would the expected difference in voltage be? (I'm not going to do it, just wondering).

If there is voltage there, then the water pipe becomes a CCC. Is that allowed?

 

[Dennis Alwon]

So where is the OP....? :?

 

[K8MHZ]

If there is voltage there, then the water pipe becomes a CCC. Is that allowed?

It depends on a person's definition of objectionable.

 

[G._S._Ohm]

The cold resistance of a 4w, 120v incandescent lamp is pretty good at simulating the resistance of a wet human body so if this mystery source deliver >6vac or >20mA into this load it can be deadly.


Trying other loads will let you figure the source resistance and so you maybe get a clue as to the cause.

 

[kwired]

Just bonding is masking, not fixing the problem.


However the "normal" neutral to earth voltage is not high enough for a person to feel

Just bonding without checking into the source of the problem is masking. If the problem is voltage drop on POCO's MGN, you are likely not going to get the problem fixed.

That normal neutral to earth voltage does create problems sometimes, and is likely the biggest reason why we need equipotential bonding around swimming pools and in livestock buildings.


I do agree that if a voltage problem comes up that was not noticeable before that you should investigate where it is coming from before just applying bonding jumpers, but if you determine it to be coming from service, some POCO will do little or nothing to resolve the problem. Plus the bonding jumper likely should have been installed in the first place and then no one would have never noticed the problem.

 

[Coastalguy1]

troubleshooting complete

troubleshooting complete

Ok, I am thankful for all the replies.:thumbsup: They helped directing me to troubleshoot the problem. Here is what I found.
During the construction of the new siding a nail or screw hit a wire. I attached a lead from my voltmeter to the metal siding and the other to a good ground and read voltage, 103 volts to be exact! I did the same thing to the water piping prior to the metal siding and read some voltage but not nearly as much as the siding. I also found a loose neutral lug in one of the two panels in the house; tightened it. Isolated the circuit that was energizing the siding(soffit actually), turned it off re-measured soffit and water piping and all read "0".
The circuit feeds (7) duplex receptacles in two rooms.
Now, my next question is what is the best way to find the hit wire?:? I was thinking of pulling all the outlets wiring apart, finding the homerun to the first outlet, and systematically working between each one measuring the soffit at each reconnection to see what section of wiring is energizing the soffit.

 

[kwired]

Ok, I am thankful for all the replies.:thumbsup: They helped directing me to troubleshoot the problem. Here is what I found.
During the construction of the new siding a nail or screw hit a wire. I attached a lead from my voltmeter to the metal siding and the other to a good ground and read voltage, 103 volts to be exact! I did the same thing to the water piping prior to the metal siding and read some voltage but not nearly as much as the siding. I also found a loose neutral lug in one of the two panels in the house; tightened it. Isolated the circuit that was energizing the siding(soffit actually), turned it off re-measured soffit and water piping and all read "0".
The circuit feeds (7) duplex receptacles in two rooms.
Now, my next question is what is the best way to find the hit wire?:? I was thinking of pulling all the outlets wiring apart, finding the homerun to the first outlet, and systematically working between each one measuring the soffit at each reconnection to see what section of wiring is energizing the soffit.

You pretty much got it, maybe only thing to add is start about the middle of the circuit instead of at one end, then find out which way to go from there, eliminating half the circuit as the part having the problem right away.

 

[renosteinke]

"a nail or screw hit a wire"

Glad to be of help.

Now the fun begins. Maybe you got lucky and the nail only hit the 'hot' wire. If that's the case, you can use a tracer to find the route of the circuit, and follow the wire as it twists and turns through the walls. If the short won't show on your DMM, you might need to use a simple megger. You have the right idea, though: follow the circuit until you find the bad part.

I was stunned to learn that your allowed to run wires right under the surface of the wall. I've always run mine set back 1-1/2", as much as possible. The set-back/ nail plate requirement only applies to where the wires pass through the framing.

One has not lived until they've found un-fused service conductors run right under the face of a wall that has had panelling nailed up!

 

[kwired]

"a nail or screw hit a wire"

Glad to be of help.

Now the fun begins. Maybe you got lucky and the nail only hit the 'hot' wire. If that's the case, you can use a tracer to find the route of the circuit, and follow the wire as it twists and turns through the walls. If the short won't show on your DMM, you might need to use a simple megger. You have the right idea, though: follow the circuit until you find the bad part.

I was stunned to learn that your allowed to run wires right under the surface of the wall. I've always run mine set back 1-1/2", as much as possible. The set-back/ nail plate requirement only applies to where the wires pass through the framing.

One has not lived until they've found un-fused service conductors run right under the face of a wall that has had panelling nailed up!

Even if you keep your wires back the required 1-1/4" that doesn't mean the siding guys will not use nails that will pentrate farther than that. They often do, but nobody really knows why.

 

[G._S._Ohm]

A rented TDR will find it within 0.1'.

 

[Coastalguy1]

TDR?

TDR?

Can a TDR be used for 120v?

 

[north star]

* * *

"They often do, but nobody really knows why."

Mostly because of what the installers have available to them at that moment.
Also, because of laziness & very poor workmanship practices....The installer
will use 8D common nails, ...deck screws, ...staples, ...railroad spikes and yes,
occasionally, the correct sized sheathing fastener.

As we all know, ...there is never enough time to do it correctly the first
time!

$ $ $

 

[G._S._Ohm]

Can a TDR be used for 120v?

A guy used it to find the break in his cable. Somebody came along later and installed an ATM, the cable was in the way so the ATM guy just cut it.
It was on this forum, back in the days of Larry Fine and MDShunk.

 

[ptonsparky]

F

Ok, I am thankful for all the replies.:thumbsup: They helped directing me to troubleshoot the problem. Here is what I found.
During the construction of the new siding a nail or screw hit a wire. I attached a lead from my voltmeter to the metal siding and the other to a good ground and read voltage, 103 volts to be exact! I did the same thing to the water piping prior to the metal siding and read some voltage but not nearly as much as the siding. I also found a loose neutral lug in one of the two panels in the house; tightened it. Isolated the circuit that was energizing the siding(soffit actually), turned it off re-measured soffit and water piping and all read "0".
The circuit feeds (7) duplex receptacles in two rooms.
Now, my next question is what is the best way to find the hit wire?:? I was thinking of pulling all the outlets wiring apart, finding the homerun to the first outlet, and systematically working between each one measuring the soffit at each reconnection to see what section of wiring is energizing the soffit.

Good job..

 

[don_resqcapt19]

Just bonding without checking into the source of the problem is masking. If the problem is voltage drop on POCO's MGN, you are likely not going to get the problem fixed.

Yes, the neutral to ground votlage can be an issue, but most of the time this voltage it too low to be felt. Once you get to the "tingle" point and you have isolated the source as the neutral to earth votlage, you need to get the power company involved, however as you said, you may not get the problem fixed. The bonding maked the tingle go away, but in my opinon, that is still "masking" the problem as it has not be fixed. When you can't get the utility to do anything, this would be your only choice.

That normal neutral to earth voltage does create problems sometimes, and is likely the biggest reason why we need equipotential bonding around swimming pools and in livestock buildings. ...

Yes, and I have often wondered why the code rules actually make us energize the pool water to make the pool safer.

 

[kwired]

Yes, the neutral to ground votlage can be an issue, but most of the time this voltage it too low to be felt. Once you get to the "tingle" point and you have isolated the source as the neutral to earth votlage, you need to get the power company involved, however as you said, you may not get the problem fixed. The bonding maked the tingle go away, but in my opinon, that is still "masking" the problem as it has not be fixed. When you can't get the utility to do anything, this would be your only choice.

Yes, and I have often wondered why the code rules actually make us energize the pool water to make the pool safer.

Can you think of a better way? Even if the entire pool was operating at several thousand volts above earth, as long as everything in reach of users is at same potential they never know any difference and are quite safe.

Of course several thousand volts is not very likely in a pool installed in the earth, but if it were the users should still be safe.

We have had many threads before where people are shocked in and around boat hoists and other similar situations. Reason anything electrical in a natural body of water is so much more dangerous is the nearly impossible task of equipotential bonding a lake vs a much smaller swimming pool.

 

[kwired]

Actually a better way would be for the POCO to stop using a MGN. No current on a grounded conductor that is grounded at pretty much every structure it attaches to means much less possible stray currents. They would need to either connect all loads phase to phase, or run a separate equipment grounding conductor like we do, and all services would also need an equipment grounding conductor to get maximum benefits for minimizing "stray" voltages.

I don't see this happening anytime soon though.