Stray voltage problem.

[Paul Allen]

I thank you for your responses, to add to the situation, and clarify it somewhat, i should add that this pool is a concrete pool, but has a rubber liner in it and has saltwater in it which to me maginifys the problem by creating a potential difference from the water to the equipotential grid.and a good conductor inside the pool. The only place i can see that the water in the pool and the surrounding area can be connected electrically is thru the hand rail that enters the water and the light fixture in the pool. (All of the other fittings in the pool appear to be non-metallic) I Have completely disconnected all power to the home to eliminiate the possibility of something in the home causing the problem. The only way the current flow is interrupted is by disconnecting the grid from the equipment grounding conductor to the home, which in this case is the pool motor housing and timer housing, It still seems to me that the voltage is in the ground around the pool and finding its way back to the source on the residential transformer neutral.
It was suggested that the stray voltage could be flowing from the neutral on the homes transformer network to the pool grid and flowing toward the high voltage distrbution lines neutral instead of the other way around as I think it is. If this is the case, wouldn't the greatest voltage be present between the water and the earth right around the pool? As measured, the farther I get away from the pool toward the High voltage powerlines the voltage increases,and measuring voltage from the pool in the oppisate direction the voltage decreases to near 0 V
My question is, would a ronk blocker be applicable to this situation? and could it be installed on a residential pad mount utility transformer? it sounds like it is designed for overhead installations only.. Not being familiar with this product, it sounds as if it works like a ground impedance, installed between the primary and secondary neutral on the transformer. Could this be installed somewhere on the secondary side and still comply with the NEC? Sorry for being so long with this post, thanks for everyone's input

Paul Allen
Florida Master Electrician

 

[don_resqcapt19]

John,

Why does pulling the bonding from the pump motor reduce the shock, is that the only place that the pool groundin/bonding system is attached to the POCO neutral/grounding system?

In many cases that is the only point of connection to the electrical system and the code made this issue worse when it was changed to make this connection a required connection even when the pool pump is a double insulated device.

680.26(B)(4) ... Where a double-insulated water-pump motor is installed under the provisions of this rule, a solid 8 AWG copper conductor that is of sufficient length to make a bonding connection to a replacement motor shall be extended from the bonding grid to an accessible point in the motor vicinity. Where there is no connection between the swimming pool bonding grid and the equipment grounding system for the premises, this bonding conductor shall be connected to the equipment grounding conductor of the motor circuit.

This code rule is requiring us to energize the pool bonding grid!

There seems to be a fine line as to when a transformer is used on a machine to isolate the hot and neutral from the building power and both are left floating(from the macufacturer) and when it is a seperatly derived system and therfore the neutral is bonded.

The internal wiring of a listed product is not covered by the NEC. For installations covered by the NEC, it is a very rare case where true isolation is permitted as there will be a connection via the primary and secondary EGCs.
Don

 

[Paul Allen]

The motor in question is 230 volt, and may be double insulated, however i dont think that is the case. but by requiring bonding of this motor to the pool grid and also requiring a EGC connection, we are establishing a current path thru the motor housing to the service neutral connection, where ultimately the ground wire is attached. We are not making an intentional connection to the service ground from the pool grid, but rather an unintentional one as we are required to attach a bond wire and a EGC to that motor.

 

[don_resqcapt19]

Paul,

It still seems to me that the voltage is in the ground around the pool and finding its way back to the source on the residential transformer neutral.
It was suggested that the stray voltage could be flowing from the neutral on the homes transformer network to the pool grid and flowing toward the high voltage distrbution lines neutral instead of the other way around as I think it is. If this is the case, wouldn't the greatest voltage be present between the water and the earth right around the pool?

You are measuring the voltage drop along a conductor. The longer the conductor, the higher the resistance and the larger the voltage drop. It makes sense to me that if you are measuring from the pool water along the earth in a path back to the high voltage system that you will see higher and higher voltages along this path.
Don

 

[coulter]

This one is right out of mr Mike's Grounding and Bonding Seminar. I highly suspect most everyone already knows this, but I have not seen it posted. As I recall:

1. Reference all measurements to "earth" = 0V

2. The substation where the MV comes from as a really good ground Rg = <<1 ohm

3. The MV neutral to the customer xfmr is carrying current. So there is a Voltage Drop porportional to the distance from the substation - Could be 1V, could be 4V. So, at the customer xfmr the MV neutral is offset from the earth reference.

4. As noted, the xfmr MV HO is solidly connected to the 240V XO. This puts the 240V neutral offset from the earth reference.

5. The customer neutral is bonded to all the non-current carrying metalic parts, rebar, ladders, piping, everything. So all of the NCCMP are now offset from earth reference.

Standing on earth reference with wet feet and grab a NCCMP with wet hands. Skin resistance is very low so even a few volts is enough to get a tingle.

Yes, the direct connection between the utility HO and the customer side XO is the culprit. The utility can fix this by disconnecting the xfmr jumper from XO to HO and installing an isolator (I think it is essentially back-to-back zeners ~5V.}

carl

edited to add: Well it hadn't been posted when I started this

 

[bob]

A Check of the system showed all of the grounding connections in place, neutrals and grounds proper, and the best i can tell, the pool grounding was installed properly. When the customer gets in and out of the pool, he feels a tingle. I checked the voltage between the pool deck and the water and get about .7VAC.

If you have voltage between the pool and the pool deck then the bonding
is not doing its job. There can not be a voltage if the deck and pool are properly bonded together. I have seen pools where the AL trim around the edge of the pool is not making proper contact and the bonding is lost.

The kicker to this, and where I think the problem is coming from is a High voltage power line on the opposite side of his next door neighbors house. (approx. 100' away.) Voltage measurements from the water to the ground under the power lines are 2-3 VAC., and they lessen the closer to the pool you get. I really think that is the source. I put my clamp on ground tester on the #8 bonding jumper and was reading 70 MA of current flowing on the wire.

If you are taking measurements by sticking one end of your meter lead in the
ground and the other in the pool, you will ALWAYS get a voltage reading. That can happen any where.

My estimation of this problem is that the stray voltage is coming from the high voltage lines thru the pool grid and is going thru the customers equipment ground on the pool motor .It is going thru his service panel and going back to the source thru his utility transformer connection. I removed the #8 bonding jumper from the metallic motor housing and timer housing and the current flow went to 1-2ma and the customer says he is not receiving a shock. (I realize that leaving the bonding jumper off the motor equipment is a violation of the NEC, but the equipment is not in close proximity to the pool). I am wondering if anyone has any other suggestions, something i can try to remedy this situation, or something I haven't thought of. Thanks in advance for your response.

Any time you did a hole and put in a pool, it is at some voltage potential.
This is because there is return current from the utility customers thru the dirt.
The reason for bonding everything together and then connect to the EGC
is to ensure the pool is not at a different voltage level that the electrical system. Try this. Take a long conductor and connect one end to customers ground rod with a gator clip. Connect the other end to some metal part of the pool, ladder or diving board. Now check the voltage from the water to
a metal part of the pool. If its not zero then the pool bonding is not correct.

 

[quogueelectric]

No goose zone

No goose zone

reestablish the situation where you were reading 70 ma on the ground wire. Then shut off the house main and see if you still are conducting current on the ground wire. If this stops the current on the ground then turn the ckts back on one at a time until the condition reapears. Then troubleshoot the one ckt rather than follow all the wild goose chases suggested. You are not looking for wild geese you are looking for electricity. If the current is still present when the main is off you will have to contact the power authority. as soon as they know they will be liable for any damage caused by the stray voltages they will cooperate in a hurry. My gut feeling is the current is coming from a faulty installation from within the house.

 

[Paul Allen]

I agree with both of you, and we are hunting voltage, not geese. The FIRST thing we did was shut off the main to eliminate something in the home from causing the problem.(This was my first impression of what was happening.) the voltage readings and amperage in the bonding wire is the same with the main on or off. I have a 100' jumper wire with a clip on it that we use for checking bonding, voltage readings, etc. I checked the bonding grid for contunity to the ground rod and even the neighbors service, in which we measured 0 volts. Tells me that the service is bonded to the pool grid. I also agree that the purpose of pool bonding is to elliminate voltage differences around the pool. but what about a pool with a rubber liner and salt water in it? Wouldnt this be a problem since the water and the pool grid is not in contact except by the hand railing that extends from the grid into the water. I am not sure how to overcome this situation. As was suggested, there is voltage potential around the pool in the hole that I cannot remedy, what happens when I lift the #8 bond wire is the grid becomes the same voltage as the pool, and the customer cannot feel the voltage because it is at the same potential as the surrounding earth. When we ground the grid properly, we are creating the difference in potential. We have notified the Local utility and their engineer is looking into this. Hopefully they will have a solution for this issue.

Paul Allen
FL Master Electrician

 

[quogueelectric]

70 ma

70 ma

I agree with both of you, and we are hunting voltage, not geese. The FIRST thing we did was shut off the main to eliminate something in the home from causing the problem.(This was my first impression of what was happening.) the voltage readings and amperage in the bonding wire is the same with the main on or off. I have a 100' jumper wire with a clip on it that we use for checking bonding, voltage readings, etc. I checked the bonding grid for contunity to the ground rod and even the neighbors service, in which we measured 0 volts. Tells me that the service is bonded to the pool grid. I also agree that the purpose of pool bonding is to elliminate voltage differences around the pool. but what about a pool with a rubber liner and salt water in it? Wouldnt this be a problem since the water and the pool grid is not in contact except by the hand railing that extends from the grid into the water. I am not sure how to overcome this situation. As was suggested, there is voltage potential around the pool in the hole that I cannot remedy, what happens when I lift the #8 bond wire is the grid becomes the same voltage as the pool, and the customer cannot feel the voltage because it is at the same potential as the surrounding earth. When we ground the grid properly, we are creating the difference in potential. We have notified the Local utility and their engineer is looking into this. Hopefully they will have a solution for this issue.

Paul Allen
FL Master Electrician

70 ma is plenty of current to kill a human especially in a pool environment. If you have shut off the mains to the house and it is still conducting to ground then the source is coming from somewhere else unless it is an underground service with an insulation problem tracking over to the best ground it can find aka the pool. The next step would be for me to put the 2005 amprobe tracer on the ckt. First read the current where you know the problem exists then break the ckt there and read the voltage on the open ckt this will tell you more about your source voltage unless it is high voltage primary and in this event it will electrocute and kill you when you open the ckt so you might want to have a poco lineman present and have him cut the wire with suitable hv equipment. the tracer will lead you straight to the voltage source if used properly you can get the pdf user manual online. secondly was that 0 volts or 0 ohms continuity on the ground wire sometimes electricians forget to switch the scale when going from volts to ohms and amps and back again and it causes them to overlook readings that they already thought they took. Thirdly are there any underground high voltage wires in the area either underground or overhead. A little over a year ago an aprentice was driving a ground rod for a security camera install and little to his knowledge he drove it right through the oilostatic casing of a 300 kv underground feeder coming from the nuke plant in conneticut. Lucky for him he only drove it through the semiconductor and oil casing. He was getting shocks and drawing arcs when he tried to attatch the ground wire had he pierced the conductor he would have been vaporized he is a very lucky kid however I wasnt there so I cant say for certain what really happened and people will try to cover thier butt all the way up the tree. The point I am trying to make is be prepared for the worst and hope for the best when troubleshooting unknowns like this.

 

[George Stolz]

A request from the peanut gallery: try to hit the return key a couple times in your posts, it makes your posts easier to read.

This is a difficult enough problem to think about without eye strain.

Paul, keep us updated, I'll be interested to hear what the POCO says.

 

[quogueelectric]

pulling the ground

pulling the ground

Pulling the ground on the pump is reducing the groundedness of the water I first of all believe now that the underlying problem is the neutral of the high voltage distribution sytem is leaking into the ground. Probably a wire pulled off the system caused by local excavation of some sort. I first didnt catch that you posted there was a primary distribution system nearby until I went back and reread the posts. Just as Don posted the ground apears to be conducting and using this pool as a return path to the source. The evidence of the voltages to your ground wire get increasingly stronger as you approach the high voltage lines is enough for me to say this is one side of your source voltage.
The fact that you can read any voltage at all to the water is an indication that the water itself is grounded to something giving it a reference point. In this particular case the rubber liner must have a break or designed opening givving the water a path to ground either to probably a stainless part of the impeller or through a light niche in the pool wall.
Personally I would send a registered letter to the power company explaining the situation and I would cc carbon copy a copy of the same letter to the ceo of the power company this will get thier undivided attention. They will switch gears from ho hum maybe we will get to it this month. To holy cow we better get this fixed before someone gets fired mode.
This is a life threatening situation from what I can see here and the only reason the voltages arent higher by you is that the voltage is probably dissipating in a circular gradient pattern from the ground fault location where it is using the neighborhood as the return path to the source

 

[iwire]

A request from the peanut gallery: try to hit the return key a couple times in your posts, it makes your posts easier to read.

ThatisagoodpointGeorge.

 

[russ__20000]

i had the same problem. The local utlity was nooo help...they blamed the cable company(whatever).I am convenced that it was comming from multiple high resistant neutrals and the path from the pool to the the muilty grounded netrual was just one of many.
I put the 120V pool light and recepticals on a GFI breaker, redid the motor for 115V operation and put it on a GFI, and removed the bond wire and ACEG at the pump and light.

 

[Luketrician]

redid the motor for 115V operation and put it on a GFI, and removed the bond wire and ACEG at the pump and light.

Did you have to resize the conductors after switching to 115v operation?

 

[ptonsparky]

i had the same problem. The local utlity was nooo help...they blamed the cable company(whatever).I am convenced that it was comming from multiple high resistant neutrals and the path from the pool to the the muilty grounded netrual was just one of many.
I put the 120V pool light and recepticals on a GFI breaker, redid the motor for 115V operation and put it on a GFI, and removed the bond wire and ACEG at the pump and light.

...and to think all these years I have been taught that reducing line to neutral loads and bonding everthing was the right way.

 

[quogueelectric]

shock leaving pool

shock leaving pool

Recently I was called to a service call for a customer who was recieving a shock getting in and out of his recently built inground swimming pool. A Check of the system showed all of the grounding connections in place, neutrals and grounds proper, and the best i can tell, the pool grounding was installed properly. When the customer gets in and out of the pool, he feels a tingle. I checked the voltage between the pool deck and the water and get about .7VAC. The kicker to this, and where I think the problem is coming from is a High voltage power line on the opposite side of his next door neighbors house. (approx. 100' away.) Voltage measurements from the water to the ground under the power lines are 2-3 VAC., and they lessen the closer to the pool you get. I really think that is the source. I put my clamp on ground tester on the #8 bonding jumper and was reading 70 MA of current flowing on the wire.
My estimation of this problem is that the stray voltage is coming from the high voltage lines thru the pool grid and is going thru the customers equipment ground on the pool motor.It is going thru his service panel and going back to the source thru his utility transformer connection. I removed the #8 bonding jumper from the metallic motor housing and timer housing and the current flow went to 1-2ma and the customer says he is not recieving a shock. (I realize that leaving the bonding jumper off the motor equipment is a violation of the NEC, but the equipment is not in close proximity to the pool). I am wondering if anyone has any other suggestions, something i can try to remedy this situation, or something I havent thought of. Thanks in advance for your response.

Paul Allen
Florida Master Electrician

When the customer gets out of the pool what exactly is he getting shocked to the deck? is it wooden metalic handrail? concrete deck a ladder please explain situation. If these surfaces are properly bonded together along with the pump motor this should eliminate the shock hazard by bringing everything to an equipotential plane

 

[quogueelectric]

Any updates as to the cause

Any updates as to the cause

Just wondering if any progress in solving the pool shock issue??