Stray Voltage in crawl space

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fourteen/two

Member
Location
Richmond, VA
Having a problem on a job. Mechancial guys are getting shocked when touching the piping or boiler in a crawl space.

If they are touching the piping and the dirt at the same time, they receieve a tingle.

Multimeter reads from pipe to dirt 2 to 4 volts. I tried finding a circuit that could be causing it, but no luck.

I then turned off the main breaker and the voltage was still there, causing a tingle.

If I have no power in the house how could I still be getting the voltage on the pipes?
 

dbuckley

Senior Member
Its voltage gradient across soil, from different ground rods at different relative potentials.

the pipework (and the installation ground rod(s)) are at one potential and the soil is at another.

You can demonstrate this just about anywhere; attach one probe of a meter to the home ground, and go outside and start sticking your other probe into the ground and you'll always see voltage, sometimes so small as to be insignificant, sometimes several volts... There are several faults to do with grounding that can increase the potential gradient.

Short of a ring of bonded ground rods around the house, theres little you can do about it.
 

fourteen/two

Member
Location
Richmond, VA
Should I be worried about the tingle it is causing? If there is some fault condition causing it even though the power is off to the house, how do i go about finding it?
 

mcclary's electrical

Senior Member
Location
VA
You've probably dropped utility grounded conductor. Squirrels love sharpening their teeth on that soft exposed aluminum. If you had a good cold water ground bonded properly you probably wouldn't be having that problem
 

sparky59

Senior Member
The workers could probably take care of the problem by wearing leather gloves or putting thick plastic or cardboard on the ground to insulate them. It doesn't take much for 2 to 4 volts. I once had a homeowner that was getting a tingle from 1 volt in her pool when she touched the metal railing on the deck. I had to bond the water.
 

Sierrasparky

Senior Member
Location
USA
Occupation
Electrician ,contractor
The workers could probably take care of the problem by wearing leather gloves or putting thick plastic or cardboard on the ground to insulate them. It doesn't take much for 2 to 4 volts. I once had a homeowner that was getting a tingle from 1 volt in her pool when she touched the metal railing on the deck. I had to bond the water.
Are you serious or poking fun. This is why we bond is't it?
 

mcclary's electrical

Senior Member
Location
VA
I missed one part in the first post,,if this is happening with NO POWER on building, then it's neutral current flowing from a nearby neighbors service, Which means your utility grounded conductor HAS TO BE GOOD, What's probably happening is the neighbor probably has no cold water ground and poor ground rods, so you're the path of least resistance. I WOULD worry about the danger until you remedy the situation. Pull the meter and check for current on neutral and find where it's coming from.
 

George Stolz

Moderator
Staff member
Location
Windsor, CO NEC: 2017
Occupation
Service Manager
I missed one part in the first post,,if this is happening with NO POWER on building, then it's neutral current flowing from a nearby neighbors service, Which means your utility grounded conductor HAS TO BE GOOD, What's probably happening is the neighbor probably has ...
...an open neutral, yes, I agree!

...no cold water ground and poor ground rods...
homer-simpson-doh.jpg


The only way the neighbor is energizing our water pipe is that the neighbor is solidly connected to our water pipe.

...so you're the path of least resistance.
homer-simpson-doh.jpg
homer-simpson-doh.jpg


Electricity seeks all paths in proportion to their resistance.

Pull the meter and check for current on neutral and find where it's coming from.
Why pull the meter if the building's already shut off?

BTW, you owe me a stamp.
 

dbuckley

Senior Member
A tingle only needs a few volts, and thats easy to come by in almost any environment...

But yeah, if a neighbour (even a few doors down) has a bad neutral that would certainly make matters interesting...
 

mcclary's electrical

Senior Member
Location
VA
...an open neutral, yes, I agree!

homer-simpson-doh.jpg


HTML:
The only way the neighbor is energizing our water pipe is that the neighbor is solidly connected to our water pipe.
homer-simpson-doh.jpg
homer-simpson-doh.jpg


Electricity seeks all paths in proportion to their resistance.

Why pull the meter if the building's already shut off?

BTW, you owe me a stamp.

I meant if he's in between the utility xformer and the neighbors house, and the neighbor has no cold water bond, the current could flow from utility grounded conductor to his pipe (without them being on the same pipe), and I said pull the meter because He may THINK everthing is off, but I wanted to make sure. ,,,

As for the stamp,,,Can I blame that on my wife? oh yeah! that was my handwriting! ,,,,,sorry about that, but I really appreciate it, Thanks alot

ps, I realize it will take multiple paths, but his has to be less resistant than some others around him to be getting the flow. I should have clarified not just one path. (you sure don't miss much!),,,thank you alot for the stamp(again)
 

hillbilly

Senior Member
I meant if he's in between the utility xformer and the neighbors house, and the neighbor has no cold water bond, the current could flow from utility grounded conductor to his pipe (without them being on the same pipe), and I said pull the meter because He may THINK everthing is off, but I wanted to make sure. ,,,

As for the stamp,,,Can I blame that on my wife? oh yeah! that was my handwriting! ,,,,,sorry about that, but I really appreciate it, Thanks alot

ps, I realize it will take multiple paths, but his has to be less resistant than some others around him to be getting the flow. I should have clarified not just one path. (you sure don't miss much!),,,thank you alot for the stamp(again)


I think that the neighbor's cold water bond is probably causing or adding to the problem.
If the service neutral is broken or loose at the neighbors house, and the neighbors share a common bonded (metal) water line, there will be substantial (return) current flow thru the water line, thru the first persons bonded GEC, and on to his service ground and back to the transformer.

I would expect more than a couple of volts to earth if this was the case.
Of course it's possible that the earth that the workers are laying on has a raised potential if the buried water line is close to where they are laying.
If that were so, it's possible that you are not reading the true potential between the water line and the earth....sort of like a Equi-potential grid where everything is (supposedly) at the same potential.
In that case, you could be reading the voltage drop between the pipe and the earth at that specific point.

I hope that makes sense.

If there is no metallic path between the grounds of the two buildings, and the homes are close together, it's possible that some of the return current from the neighbors house is returning thru the earth between the homes.
If that's the case, it's the earth that's energized, not the water line.

That's a lot of if's.
It all points to a nearby lost or broken service ground.

Just my opinion
steve
 

wirenut1980

Senior Member
Location
Plainfield, IN
It could be an uncleared ground fault on a neighbor's secondary branch circuit. I would suggest taking voltage measurement between water pipe and remote earth (like 50 feet away from the pipe). Also take a voltage measurement between the earth where the guys are getting shocked and remote earth.

It could also be a utility underground primary cable that is faulted or the concentric neutral is broken. The utility would need to troubleshoot this possibility themselves.

2 Volts sounds like it could be utility primary neutral return current. Odds are the voltage is coming from the water pipe and is the result of primary neutral return current taking an available parallel path.

If no problems are found indicating some other cause, I would interrupt the metal piping with a piece of PVC if the piping is the homeowner's property.

Let us know how this is resolved!:)
 

wirenut1980

Senior Member
Location
Plainfield, IN
I should also add to check whether the piping is being used as a grounding electrode. If it is, try to keep the water piping as an electrode if possible, and interrupt the piping with PVC between the GEC connection with the metal piping and the panel neutral bar.
 

stars13bars2

Senior Member
One should be extremely careful about interrupting a metal water pipe with neutral current on it as it could be fatal. It has been for others in the past who have removed a water meter from the pipe that was carrying neutral current without a continuity bond around the meter.
 

Microwatt

Senior Member
Location
North Dakota
Am I missing something? How can 2 to 4 volts AC cause a tingle. There is no way there is enough electrical pressure to cause current to flow through the body. I know the environmenal conditions can have alot to do with it but, 4 volts sounds to low.

Did you check for DC voltage?
 

hurk27

Senior Member
I would say get the utility involved with this, I had a primary neutral to a transformer go bad out on a pole a few years ago and because it was still tied across to the secondary neutral it was able to return back through the grounding of the house to it's source, over time the grounding started to dissolve away and the voltage raised to about 56 volts before the home owners child was shocked touching the outside hose bib, if this was allowed to keep going it could have eventually raised to the potential of the primary voltage, the water pipe started getting holes in it so they replaced it with plastic, then the AC freon lines started getting holes, so it was a matter of time before the ground rod was gone.

This is one you don't want to walk away from. Get the utility out ASAP!

One before this was a pad mounted transformer for a apartment building, that lost an exposed concentric neutral from the MGN.
 
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