Got a call the other day from the head of the water dept. There is a condo complex and there seems to be current running on the water pipe into the condo. It is causing calcium (They think) to form and clog the toilet bowls and he wants me to investigate. Wait it gets better. I was scheduled to go and meet him next week, Well today I get a call from my boss to come back to town. There was a fire in the water closet area where all these ground wires are connected. The fire dept thinks it started in an electrical heater which was used to keep this closet warm. The electrical contractor (EC) just happened to be working in this closet the day before trying to fix the current problem. Now I talk to the EC who was there and he said that there was indeed current running on the GEC's hooked to the water pipes. Not much voltage less that 1-2 volts and about 1-2 amps. He (and I )saw 1 large GEC wire, and 6 #6 ga. Al wires all attached to water pipes. He found the current coming from 1 og the #6 wires. But didn't know here it comes from. He checked the neutral connection and said that it was OK. (First think I thought of was a bad neutral and current flowing to ground.) He is going there today and check it out, and I will stop by next week to see what is up. Any thoughts about current flowing back on a GEC to the water pipe? I know this post is vague, but I didn't get into it too much because I had to get to another town for inspections. I will keep you posted as to what we find.
harold.you said he check the neutral.where in the panel????there should be no voltage on the ground.if this is an outside service the first place i check is the neutral tap.this tap is often the one that get no tape and corrosion sets in over time.
Saw info. on the problem that city water dept. workers getting hit when dealing with unhooking water pipes fairly close to where the EGC was attached.
They were typically working by roadside as is where their responsibility ends for lines.
They would kind of like the sparkies not to use the water as a ground connection.
Not to mention the corrosion it is causing, and making them repair pipes.
If the electrical system is not correctly bonded anywhere in the entire system, a current path can be created for this light current to flow. HEY-- let's take the least path of resistance, or even just a shorter one.
Even if the neutral is in good repair, the juice may feel it is easier to go to the water pipe for just a little bit of the trip.
Where is the tranformer from the PoCo located in relation to the service of the bldg./unit? If they are a bit further away, and with downsized wire as opposed to the folks closer to the transformer, then electrons will definitely go for the closer water pipe.
If it was just one #6 that seemed to carry current, and energize the pipe to the street, then definitely look in that units direction for some neutrals and grounds getting together for some bad reason.
You said aluminum wire also, Al to some copper? If so, not good. How is the Al attached? Bonded directly, or into a approved bonding device?
Lots of Al?? Lots of copper?? Lots of DIELECTRIC happening??
[This message has been edited by NonLinearLoad (edited 01-05-2003).]
Harold, More info about the service(s) please... That many GECs would indicate possibly that each panel has a main bonding jumper and a GEC connection?? Is there a Main for the building? Each unit? I recently saw an installation at a 4 story elderly housing with 6 metering closets. Each closet in the complex had it's own service conductors, main switch, breakers for apartment subpanels and GEC connection. Add one for the 'house' panel and that made 7 GECs clamped onto the incoming copper water service.
Return current on a GEC that is bonded to the neutral is not at all uncommon. 1-2 amps is quite low.
The fire may be completely unrelated except for there being someone in the closet moving 'stuff' around and blocking the heater discharge.
Know of one installation where the 2W service to the dwelling, the water Grounding Electrode Conductor (GEC) carried approximately 2/3rds of the Grounded conductor current back to the pole mounted transformer.
As I remember, the transformer supplied 8 other dwellings.
This dwelling then had a 3W system installed and when turning 'off' all of one leg CB's the GEC still carried about 50% of the grounded service conductor current in comparison with the undgrounded conductor current.
When the ungrounded service conductor had 30A the grounded service conductor had about 15A.
The city and the local utility were not concerned.
I would have liked to check each service drop to each of the dwelling's to determine if any of the other units had the same readings.
I haven't gone back to this job yet, but maybe I can explain things a little bit better. The EC checked for current at the GEC connections at the water pipe. This is 1 building, 3 floors, with 14 apt. and 1 house meter. There are 2 service drops to the building. 9 meters on the left of the building and 6 meters on the right side. In the water closet is 1 pipe coming in then 14 water meters to each apt. There is a large GEC wired up to the ater pipe. (Don't know which meter stack it comes from. There are 6 additional GEC wires. I believe they were al # 6 AL wires. The EC said that he metered each #6 wire, trying to isolate which wire was giving off the current. 1 of the #6 al GEC wires was indeed causing current to flow back to the water pipe. The EC didn't have access to the building apts. ( and neither did I) so we don't know where each # 6 comes from. The EC was suppose to be there today, but I won't see him till Wen. and I won't know what the story is until then. My main question would be has anyone seen current flowing on the GEC back to the water pipe? What caused it?
In oreder to keep these posts short I will start another. I have been called out years ago because a plumber friend of mine kept having pin hole leaks in the water pipe. Long story short, I couldn't find anything but I saw a plastic body water filter. I threw a bonding strap across the filter and the leaks stopped. I think that something inside the house was leaking current to ground and causing the pin hole leaks.
I was at that building fire again today. Long story short, the EC has to look through the whole building to see what is inducing the flow of current into the water line. people without water softners are having problems with calcium deposits in all water appliences. ( Toilets, sinks, dishwasher, etc.) Found the copper water pipe that feeds from the main water service to each apt. seems to be fed with plastic pipe. So all the pipe in each apt, would not be grounded to the electrical system. The EC still has to find out where all of the extra GEC are hooked to. The fire was caused when 110 volt heater's overload protection failed. Heater burnt up and cause fire. The flow of current in water pipe is very miniumal. The EC thinks it is a millivolt amount. There are heating elements in several water heaters that are also burnt out due to calcium build up. I will keep you informed when I find out more.