Objectionable Current.

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jxofaltrds

jxofaltrds

Inspector Mike®
Location
Mike P. Columbus Ohio
Occupation
ESI, PI, RBO
Given:
Outside disconnect and main 'sub' panel properly wired.
GEC from the disco to the copper water lines entering the home. Not within the 5' rule but even if it was I would still see objectionable current at the test point.

The GEC run through a chase in the house and 'may' be the reason for the high EMF readings.

Assumption on my part: I believe that this bare wire may be coming in contact with the interior water lines that are also in this overhead chase prior to it's proper termination. Giving multiple parallel paths back to the source.

409 W 65th Street 014.jpg

4.1 Amps measured at the pipe in the picture.

Now going outside, more than 10', and isolating the structure plumbing from the city plumbing should get rid of the reading.

My question is - Shouldn't there still be an objectionable current 'touch potential' present at this or any point on the plumbing system?

If so how does one solve this? Can't just not bond the interior metal water lines. Correct?
 
In a densely populated area with multiple metal water lines bonded together and to the POCO neutral, there is no way to eliminate current on the water lines while maintaining the water line as the additional electrode. From what I know this is not usually considered objectionable current, any more than current on the GEC is.

Also, there generally isn't a touch potential in this case, because you still have a solid neutral path back to the transformer. If that neutral path were broken, you might have touch potential via the plumbing system, but that's why you have to bond the water meter. Beyond repairing the neutral, there's nothing you can do about it.
 
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As Peter said, the outside metal underground water pipe and the service grounded conductor are actually connected in parallel. It is normal to have current on the GEC that is connected to the water pipe, and this current may not even originate in the building you are working on.
About the only way to get rid of this current is to break the connection via the water pipe. You could dig up the water pipe 10' from the house and install a section on non-metallic water pipe to break the connection.
 
don_resqcapt19 said:
As Peter said, the outside metal underground water pipe and the service grounded conductor are actually connected in parallel. It is normal to have current on the GEC that is connected to the water pipe, and this current may not even originate in the building you are working on.
About the only way to get rid of this current is to break the connection via the water pipe. You could dig up the water pipe 10' from the house and install a section on non-metallic water pipe to break the connection.
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And that is probably what they will do.

My question is - Is there still a shock potential on the home's water line(s) after the structure metal piping is isolated? I think that there is.

The water lines are exposed in a garage, floor level, and there are small children. Could a bare-footed child get shocked if a potential is still on these lines?
 
Chances are that the potential for the broken ground path is much less than 1 volt because of the parallel metallic neutral path. You can calculate the approximate voltage knowing the current and the wire resistance.
 
jxofaltrds said:
And that is probably what they will do.

My question is - Is there still a shock potential on the home's water line(s) after the structure metal piping is isolated? I think that there is.

The water lines are exposed in a garage, floor level, and there are small children. Could a bare-footed child get shocked if a potential is still on these lines?
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Don't forget that shock potential is relative to the amount of voltage gradient, not the amount of current. If you/they reduce current by isolating the water line past 10' underground, you are effectively increasing the resistance back to the source, and thus increasing the potential voltage gradient... especially if the service neutral conductor loses integrity.
 
I agree with Smart $, you could be making things worse by isolating the system. As long as the system is intact, there should be no more danger of shock from touching a pipe as there would be from touching any other grounded metal in the house including cover plate screws, grounded appliance housings, etc. It's only when you introduce a voltage gradient that things get dangerous - IOW, those kids would have to become a better return path for neutral current than the neutral and water pipe combined. As long as the system is intact, that ain't gonna happen.
 
You may insatall metal plates, preferably copper or brass on floor near the pipes in such a way that the kids have to stand on them before touching the pipes and bond the plates and pipes together. In this way you may ensure a degree of freedom from shock hazard to kids or any others.
 
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Sahib said:
You may insatall metal plates, preferably copper or brass on floor near the pipes in such a way that the kids have to stand on them before touching the pipes and bond the plates and pipes together. In this way you may ensure a degree of freedom from shock hazard to kids or any others.
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Oh yeah... that makes perfect sense.
 
Smart $ said:
Don't forget that shock potential is relative to the amount of voltage gradient, not the amount of current. If you/they reduce current by isolating the water line past 10' underground, you are effectively increasing the resistance back to the source, and thus increasing the potential voltage gradient... especially if the service neutral conductor loses integrity.
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PetrosA said:
I agree with Smart $, you could be making things worse by isolating the system. As long as the system is intact, there should be no more danger of shock from touching a pipe as there would be from touching any other grounded metal in the house including cover plate screws, grounded appliance housings, etc. It's only when you introduce a voltage gradient that things get dangerous - IOW, those kids would have to become a better return path for neutral current than the neutral and water pipe combined. As long as the system is intact, that ain't gonna happen.
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Exactly my concern.

POCO 'assured' her (client) that:
"Yes, they said so. They didn't call me before they came so I wasn't actually physically there to witness but they called after and said all the loads balanced and gave me attitude for why I was checking the readings if I was having no problem.

I agree I hesitate to recommend isolating the metal water electrode just to lose a reading. I'm in Ohio and she is in Indianapolis so I can't easily pop over to help with this issue.

She is getting information from electricians in her area telling her to abandon the SER running through the home to the panel in the garage and rerouting this underground around the home then back into the garage. I think that this is stupid.

I understand the grounding/bonding issues involved. Getting the objectionable current off the interior water lines is what is stumping me.
 
Stray currents flow throughout the land of North America due to multiple neutral grounding practice of POCO. By providing metal plates suitably in the garage floor if it has no reinforcement rods,and bonding the pipes properly, danger even from brolen neutral may be minimal.
 
I have this issue in two homes, have you found a solution, i may have one, not sure

I have this issue in two homes, have you found a solution, i may have one, not sure

jxofaltrds said:
Exactly my concern.

POCO 'assured' her (client) that:
"Yes, they said so. They didn't call me before they came so I wasn't actually physically there to witness but they called after and said all the loads balanced and gave me attitude for why I was checking the readings if I was having no problem.

I agree I hesitate to recommend isolating the metal water electrode just to lose a reading. I'm in Ohio and she is in Indianapolis so I can't easily pop over to help with this issue.

She is getting information from electricians in her area telling her to abandon the SER running through the home to the panel in the garage and rerouting this underground around the home then back into the garage. I think that this is stupid.

I understand the grounding/bonding issues involved. Getting the objectionable current off the interior water lines is what is stumping me.
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Check out my requests and responses on this thread

http://forums.mikeholt.com/showthread.php?t=170199&p=1655074#post1655074
 
I would be more worried about the asbestos coverings on the pipes, than the current.

Disconnect the bare cu and run a new insulated GEC.

Bury CU wire encircling house, bond water pipe to it in a manner that the wire does not enter, (or limits the length in) the living space.

Best would be to replace all the water lines with plastic. Problem solved. Unless you happen to have a gas line in there.
 
ptonsparky said:
I would be more worried about the asbestos coverings on the pipes, than the current.

Disconnect the bare cu and run a new insulated GEC.

Bury CU wire encircling house, bond water pipe to it in a manner that the wire does not enter, (or limits the length in) the living space.

Best would be to replace all the water lines with plastic. Problem solved. Unless you happen to have a gas line in there.
Click to expand...

That would not eliminate the EMF if you still had a GEC.
 
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