Current in water pipe
- Thread starter jerrys
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charlie
Senior Member
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- Indianapolis
Re: Current in water pipe
The return current can flow through the GEC to the water line, through the metallic water system to your neighbor's home, through his GEC, through his service drop or lateral, and back to the transformer. This will not happen to any great amount unless you have an open neutral since most of the return current will take the path of the phase conductors.
The water pipe is a higher impedance path back to the transformer but electricity will take all paths beck to the source. Therefore, current will be on the water system.
Now to address the danger. If you have an open neutral, all of the unbalanced return current will take the above path. If the water line is opened at any point between the GEC connection and the transformer, line voltage will be across the open point. That is one of the basic reason for connecting within five feet of where the water enters the building.
If this in an older home and a neutral was obtained by hitting the water pipe in a bathroom, you can get zapped by opening the pipe anywhere(I saw that done once, bad idea).
The return current can flow through the GEC to the water line, through the metallic water system to your neighbor's home, through his GEC, through his service drop or lateral, and back to the transformer. This will not happen to any great amount unless you have an open neutral since most of the return current will take the path of the phase conductors.
The water pipe is a higher impedance path back to the transformer but electricity will take all paths beck to the source. Therefore, current will be on the water system.
Now to address the danger. If you have an open neutral, all of the unbalanced return current will take the above path. If the water line is opened at any point between the GEC connection and the transformer, line voltage will be across the open point. That is one of the basic reason for connecting within five feet of where the water enters the building.
If this in an older home and a neutral was obtained by hitting the water pipe in a bathroom, you can get zapped by opening the pipe anywhere(I saw that done once, bad idea).
Re: Current in water pipe
Charlie,
Hope you had a good Thanksgiving.
I do question the " water pipe is a higher impedance path - - -.".
With-out looking-up the permit number/address info, - -,
had a house with a 2W 120V service off of a Poco pole mounted transformer with at least 8 other service drops, 2 of which were duplex(s) of a year or so old. An electrician contacted me after he seen another contractor changing the service to a 3W system after he had made trouble call to the site.
When it was a 2W system, the grounded conductor carried approximately 1/3rd the current of the ungrounded conductor and he had not yet figured-out why.
So-ooo, when I was called for the service change inspection, I took the readings on the new 3W 240/120V service which was still , temporarily, connected to the 2W service drop. The old service drop was a triplex with one conductor not connected at the pole. The grounded conductor was carrying 12A +/- and the ungrounded conductor had 42A +/-. The Water GEC was 30A +/-.
Notified Poco and the City Water Department.
Not sure what Poco actually did, but they did install a new service drop. When making a follow-up inspection, because of the above problem, the neutral service conductor was still only carrying a very low partion of the return current.
Turning off all of L1 and all of L3, L2 being the neutral, at different testing times, to simulate a 2W system, the grounded conductor was still only carry about 1/3rd of the ungrounded conductor under test. The water GEC was carrying the other 2/3rds of the current.
The City, that I worked for then, did not allow me to make further tests.
Assume it is still the same today.
The Poco transformer pole and two other secondary side poles where along an 8" cast iron water line.
Maybe a ground rod made contact with the 8" water line.
I would like to been able to check each of the other service drops.
gwz2
Charlie,
Hope you had a good Thanksgiving.
I do question the " water pipe is a higher impedance path - - -.".
With-out looking-up the permit number/address info, - -,
had a house with a 2W 120V service off of a Poco pole mounted transformer with at least 8 other service drops, 2 of which were duplex(s) of a year or so old. An electrician contacted me after he seen another contractor changing the service to a 3W system after he had made trouble call to the site.
When it was a 2W system, the grounded conductor carried approximately 1/3rd the current of the ungrounded conductor and he had not yet figured-out why.
So-ooo, when I was called for the service change inspection, I took the readings on the new 3W 240/120V service which was still , temporarily, connected to the 2W service drop. The old service drop was a triplex with one conductor not connected at the pole. The grounded conductor was carrying 12A +/- and the ungrounded conductor had 42A +/-. The Water GEC was 30A +/-.
Notified Poco and the City Water Department.
Not sure what Poco actually did, but they did install a new service drop. When making a follow-up inspection, because of the above problem, the neutral service conductor was still only carrying a very low partion of the return current.
Turning off all of L1 and all of L3, L2 being the neutral, at different testing times, to simulate a 2W system, the grounded conductor was still only carry about 1/3rd of the ungrounded conductor under test. The water GEC was carrying the other 2/3rds of the current.
The City, that I worked for then, did not allow me to make further tests.
Assume it is still the same today.
The Poco transformer pole and two other secondary side poles where along an 8" cast iron water line.
Maybe a ground rod made contact with the 8" water line.
I would like to been able to check each of the other service drops.
gwz2
Re: Current in water pipe
Charlie,
I just posted my previous post then looked at the next BB subject ' binney 's post" and see you went into a more detailed water main explanation.
Anyhow, I think the water main can be of a LOWER impedance as you indicate that that post.
Have a good day.
gwz2
Charlie,
I just posted my previous post then looked at the next BB subject ' binney 's post" and see you went into a more detailed water main explanation.
Anyhow, I think the water main can be of a LOWER impedance as you indicate that that post.
Have a good day.
gwz2
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