Current flow in the water pipe

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mike1061

Senior Member
Location
Chicago
What happened is a plumber cut through the main water pipe to do a repair. He got the shock of his life and blew 2 garage door openers, a dish washer, and something else. The plumber said half the basement lights went brighter and half went dimmer.
It is a 3 flat residence, 200 amp, 240 volt, 1 phase, 3 meters outside, 3 - 100 amp main breaker panels inside. IMO the service is likely done without a permit. It is all in RMC conduit. The grounding conductor does not run all the way to the entrance of the incoming water service, it is connected within 10 feet of the breaker panels. Copper water pipes, no die-electric union, lead service. No driven rod.
From left to right facing the inside panels. Panel A has a #4 conductor connected to the water pipe. Panel B has a #8 conductor connected to the water pipe. Panel C has no wire connecting it to the water pipe. Panel A is connected to panel C via a 1/2 EMT pipe. Panel B is connected to panel C via a 1" EMT. All panels have the bonding screw connecting the neutral bus to the panel encloser (the back of the panel).
There is current flowing through both wires connected to the water pipe. This varies with tenet use, I think. On panel A I read .7 to 3.9 amps with a clamp on meter. The reading on the wire in panel B was less but I don't remember exactly. There is current flow on the neutral conductor in panel A, it was higher than the grounding conductor but I don't remember exactly. With the amp meter on the grounding wire in panel A, turning the main off in panel A has no affect on the reading. Turning the main off in either panel B or C changes the reading and flipping both off mains in B & C changes the reading to 0. I have indentified 5 breakers in panel B and 4 breakers in panel C that, when turned off change the reading. Some raise the amperage and some lower it.
There are no ground bushings on the service pipes. The service voltage is 113 on one phase, and 124 on the other phase, to ground (the neutral bus or the panel). I have checked the screw tightness at all neutral connections except the main service riser. The connection in the meter box was too close to the hot lug for the tools I had then. There is a hornets nest in the weather head. I did grab both wires and yank on them to see if they were loose. I'm going back with hornet spray today.

So what do I do? What tests should I run?

As I see it, I should run one #4 wire to the water service and connect it to all three neutral buss's and eliminate both of the other two. But I don't think that will fix the problem, just make a proper grounding connection.
I can't figure out why current is flowing on the grounding conductor. Shouldn't the current flow on the neutral conductor? Am I correct in thinking that installing one grounding conductor , instead of two, would increase the current flow on the one? Am I also correct in thinking that the problem is that it seems the resistance in the neutral is too high? That would allow the current flow on the grounding conductor? If that's correct how do I test that?

I typed everything I could think of to help, and I hope I didn't miss anything.
Thanks Mike
 

hurk27

Senior Member
The building has lost the neutral between the service and the transformer, it was returning through the water pipe until it was cut.

if you loose the neutral you will loose the balance between the two 240 volt hots and it will do just as you described.

You will most liklely have to get Com-Ed involved to find the neutral problem.
 

augie47

Moderator
Staff member
Location
Tennessee
Occupation
State Electrical Inspector (Retired)
seen similar a number of times and each time it has been a problem as
Wayne describes. Check your neutral connections but theres a great possibility it will be a POCO neutral problem.
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
Occupation
retired electrician
You will find the problem on the line side of the main bonding jumper. This would include the grounded conductor termination at the service equipment. As others have said this is often a utility problem.

As a side note, this issue is so common in some areas that the plumbers use a jumper around the water pipe before they cut it.
 

delfadelfa

Member
Location
Cincinnati, OH
if you loose the neutral you will loose the balance between the two 240 volt hots and it will do just as you described.

I've had this problem also and found the neutral cut at the POA. But your saying if I had checked to panel voltage from each phase to neutral I would get like 124v and 115v? That is very interesting because I was getting weird voltages but I did not know that had anything to do with the neutral loss. I was just looking at the service and noticed the missing neutral.
At another house I knew there was a neutral loss because the cable tv box was starting to melt from load going through it. That one was a center tap at the street, the neutral was burnt up at the split bolt. Next time I have unbalanced voltages I will know what to look for.
 

Cow

Senior Member
Location
Eastern Oregon
Occupation
Electrician
As a side note, this issue is so common in some areas that the plumbers use a jumper around the water pipe before they cut it.

I've often wondered, since this is such a common problem and serious hazard, I'm surprised ALL plumbers aren't trained to use a jumper wire??

Maybe not using a jumper wire for a plumber is like an electrician changing a switch out hot.....
 

sameguy

Senior Member
Location
New York
Occupation
Master Elec./JW retired
This is why the code changed to no longer allowing a ground to the cold water pipe any place. Now must be gfci or home runs. Jumper the water meter.
 

renosteinke

Senior Member
Location
NE Arkansas
It's just so hard to tell which way the electricity is travelling. Is it entering the house through the pipe, or leaving it?

Since the circuits go nuts in the house, the neutral problem is somewhere between the PoCo transformer and your main breaker. The cause can be everything from a bad PoCo splice at the transformer (experienced that once) to a cracked bussbar (found that twice).

BUT ... for future caution ... remember when the plumber gets that spark that the power can be coming IN as well. This will happen when the neighbor has a bad neutral connection, and his nutral current is returning to the PoCo transformer through your grounding network.
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
Occupation
retired electrician
Also just because there is current on the water pipe or a spark is observed when the pipe is disconnected does not mean that there is a shock hazard. The only time there is a shock hazard is if the grounded conductor has some type of problem. The metal underground water piping system will be in parallel with the grounded conductor and there will be current flowing on it. It would not be unusual to find 20% of more of the grounded conductor current on the water pipe in areas where there is a common underground metallic water pipe system. Where the pipe is in parallel with a grounded conductor that is in good condition, the only voltage that will be between the disconnected pipes is equal to the voltage drop on the grounded conductor. This voltage will not be a shock hazard.

When the grounded conductor is open, the water pipe becomes the grounded conductor and opening will result in line to netural voltage between the ends of the pipe and is a serious shock hazard. There is no easy way to tell if the grounded conductor is in good condition before cutting the pipe, so it would be a good practice for the plumber to always provide a jumper around the pipe before he cuts it.
 

mike1061

Senior Member
Location
Chicago
It's not really a number for the change. It's just that the code was changed. The newer code says the ground has to go to the street side of the water meter. The older code allowed you to connect to the nearest cold water pipe.
Thanks Mike

What is the number for that code change? Thanks
 

mike1061

Senior Member
Location
Chicago
This occured to me. I thought if I disconnect the grounding conductor at the neutral buss to check for voltage, I'd blow more appliances. I called Edison today, we'll see what they say.
Thanks Mike

It's just so hard to tell which way the electricity is travelling. Is it entering the house through the pipe, or leaving it?

Since the circuits go nuts in the house, the neutral problem is somewhere between the PoCo transformer and your main breaker. The cause can be everything from a bad PoCo splice at the transformer (experienced that once) to a cracked bussbar (found that twice).

BUT ... for future caution ... remember when the plumber gets that spark that the power can be coming IN as well. This will happen when the neighbor has a bad neutral connection, and his nutral current is returning to the PoCo transformer through your grounding network.
 

mike1061

Senior Member
Location
Chicago
I don't have the code in front of me, but that's what there making us do here. One or two inspectors told me that would allow them to change the water meter and still be grounded the whole time. Also the inspectors use the words "street side of the meter"
I did a job in one of the west suberbs with a finish basement where the inspector would not accept a connection anywhere else. We had to cut holes in the ceiling or surface mount the pipe. The ceiling finish could not be matched.
I've got too much to do this week to look. What does the NEC say?
Thanks Mike
 

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
I don't have the code in front of me, but that's what there making us do here. One or two inspectors told me that would allow them to change the water meter and still be grounded the whole time. Also the inspectors use the words "street side of the meter"
I did a job in one of the west suberbs with a finish basement where the inspector would not accept a connection anywhere else. We had to cut holes in the ceiling or surface mount the pipe. The ceiling finish could not be matched.
I've got too much to do this week to look. What does the NEC say?
Thanks Mike

The NEC says attached to the water pipe, within 5' of entrance into the building and that you need a jumper across the water meter. Nothing about being on the street side of the meter.
 

delfadelfa

Member
Location
Cincinnati, OH
I had a whole house inspector put in his report that the second floor receptacles were grounded to a cold water copper line and that was not to code. I like to prove whole house inspector wrong so I searched for about 3 hours for anything about this in the NEC. I was hoping somebody else found it.
 

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
I had a whole house inspector put in his report that the second floor receptacles were grounded to a cold water copper line and that was not to code. I like to prove whole house inspector wrong so I searched for about 3 hours for anything about this in the NEC. I was hoping somebody else found it.


Here are your choices:

VII. Methods of Equipment Grounding
250.130 Equipment Grounding Conductor Connections.
Equipment grounding conductor connections at the source of separately derived systems shall be made in accordance with 250.30(A)(1). Equipment grounding conductor connections at service equipment shall be made as indicated in 250.130(A) or (B). For replacement of non?grounding-type receptacles with grounding-type receptacles and for branch-circuit extensions only in existing installations that do not have an equipment grounding conductor in the branch circuit, connections shall be permitted as indicated in 250.130(C).
(A) For Grounded Systems. The connection shall be made by bonding the equipment grounding conductor to the grounded service conductor and the grounding electrode conductor.
(B) For Ungrounded Systems. The connection shall be made by bonding the equipment grounding conductor to the grounding electrode conductor.
(C) Nongrounding Receptacle Replacement or Branch Circuit Extensions. The equipment grounding conductor of a grounding-type receptacle or a branch-circuit extension shall be permitted to be connected to any of the following:
(1) Any accessible point on the grounding electrode system as described in 250.50
(2) Any accessible point on the grounding electrode conductor
(3) The equipment grounding terminal bar within the enclosure where the branch circuit for the receptacle or branch circuit originates
(4) For grounded systems, the grounded service conductor within the service equipment enclosure
(5) For ungrounded systems, the grounding terminal bar within the service equipment enclosure
FPN: See 406.3(D) for the use of a ground-fault circuit-interrupting type of receptacle.
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
Occupation
retired electrician
I had a whole house inspector put in his report that the second floor receptacles were grounded to a cold water copper line and that was not to code. I like to prove whole house inspector wrong so I searched for about 3 hours for anything about this in the NEC. I was hoping somebody else found it.
250.130(C)
 
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