Current/EMF along water heater pipes in multi-unit

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leon3536

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While inspecting a top floor unit in a 24 unit condo, I discovered the water heated baseboard pipes are slightly energized. Although the currently was relatively low, the length of the pipe gives off a very strong EMF reading throughout the unit (as much as 10mG 6 feet away from pipe with unit breakers off). The buyer insist on solving this problem during attorney review.

The 24 units in the building share same heater in the basement. Each unit has a zone valve controlled by thermostat. All baseboard pipes are laid out in a single loop of copper pipes. I also detected a current running on the water main in the basement. And there is no ground attached to water main.

There are several solutions I'm considering given a short amount of time I need to solve this problem

1. Find the source of the ground current by de-energize the entire unit. First make sure the source isn't from outside. And narrow down the source. A lot of hassle and I'm not sure if the building is willing to do this for a potential buyer.

2. Break the current going inside the heater pipe by installing a dielectric union. I'm not sure if this would break the eletric code, but technically both side of the dielectric union are still bond to the main pipes. Is there anyone with plumbing experience can tell me if a dielectric union can be used on a copper heated water pipe.

3. Another possibility is the controlled zone valves throughout the unit (which runs on 26v ac) is responsible for creating the current with induction.

Thanks in advance!
 
A couple of comments, off the cuff...

leon3536 said:
1. Find the source of the ground current by de-energize the entire unit. First make sure the source isn't from outside. And narrow down the source. A lot of hassle and I'm not sure if the building is willing to do this for a potential buyer.
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I think you have about a 50/50 chance of the problem being related to something outside the building, such as a neighbor with a marginal neutral who you share common underground pipework with.

leon3536 said:
2. Break the current going inside the heater pipe by installing a dielectric union. I'm not sure if this would break the eletric code, but technically both side of the dielectric union are still bond to the main pipes. Is there anyone with plumbing experience can tell me if a dielectric union can be used on a copper heated water pipe.
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Yes, that is within code, but may not solve your issue.

leon3536 said:
3. Another possibility is the controlled zone valves throughout the unit (which runs on 26v ac) is responsible for creating the current with induction.
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Nice theory, but I very much doubt that you're going to get the amount of EMF you're talking about over such a great amount of pipework from a 40 or 75 va 24 volt transformer.


A quick extra question... what's the brand and model number number of your gauss meter and what's the last calibration date?
 
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Why is there no GEC on the water pipes? Can one get installed? This may help some of those currents. Is there EMF's in all the units or just that unit?
 
The 24 units in the building share same heater in the basement. Each unit has a zone valve controlled by thermostat. All baseboard pipes are laid out in a single loop of copper pipes. I also detected a current running on the water main in the basement. And there is no ground attached to water main.
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Why not. If the water pipe is available it must be used.

2. Break the current going inside the heater pipe by installing a dielectric union. I'm not sure if this would break the eletric code, but technically both side of the dielectric union are still bond to the main pipes.
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If both sides of the union are still bonded you have not isolated the heater pipe. Maybe I do not understand how the union is supposed to work but I thought I did. Is the pipe feeding the building copper?
 
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Why would the dielectric union not solve the issue? If only a section of the pipe is off the cricuit, I'm sure we can proceed to put more of those in at any of the baseboard to create more isolation. The only problem I can see is the potential maintenance / leak risk.

I don't know how they pass the inspection without a ground rod. I would have recommended putting one in. There is current going through every single heater pipe in the building.

I have a toy Dr. Gauss EMF meter that has no way of calibrating. I don't use it heavily, just for comparison purpose. I have been to several condos and homes with water heating system. This is the only unit that has EMF issue.
 
1. Perform zero sequence readings on each apartment feeder.

2. Check for current on the neutral ground bond.

3. turn off the apartments one at a time watch amp meter.

4. Isolate the branch circuits in the apts, and megger neutral at 100 0r 250 VDC.

5. Megger the feeders individually with neutral isolated.

6. Fix all the neutral to ground shorts.

7. Is the service grounded with a single conductor to the H20 pipe?

8. Can you isolate the pipe.

9. If the surounding buildings share a common transformer and/or metallic water piping or common structure turn off all power in the building does current exist.
 
brian john said:
6. Fix all the neutral to ground shorts.
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:grin: :grin:

That's the impossible task in a condo building. Numerous old 3-wire ranges and dryers with the bond strap still in. Add those in with any other miswires, and that's almost monumental in scope.

Thanks for that great list, Brian !
 
leon3536 said:
I have a toy Dr. Gauss EMF meter that has no way of calibrating.
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That was my gut feeling. You got a client all stirred up and an attorney involved taking measurements with a toy from eBay? :roll:
 
you could also ampprobe the pipes


off topic = I bought one of those gauss meters (xyz) about a year ago. they are fun to play with. I bought a really good little book, too explaining how to find wiring problems with it. I have yet to use it on a jobsite though - I figured I need to get a hat with a propeller or something like that to look official lol
 
leon,

IMO, the first thing that has to be done is to make sure the grounding and

bonding is installed NEC compliant. The dielectric union is an attempt at a

quick fix, like putting a roller skate under a flat tire, it will get you nowhere.

Try opening the power to the furnace real quick and see if it clears, get to

the root of the problem and then it will be fixed forever.
 
Thanks for all the advice. I think in a long term it's the goal to get all the eletrical problem in building fixed although it may or may not be a long hard battle.

Right now I just want assurance that the problem can be remedied one way or the other so it can help the buyers decision. Therefore one answer I'd really like to know is whether a dielectric coupler or union can break the grounding path. It does seem possible on paper.
 
Ground current

Ground current

I would clamp the heater pipes and see how much current is flowing, then I would clamp the water main to see if it additive. Then I would flash the mains off one at a time to see which unit is causing the ground fault and blame the power company if anyone complained.
 
leon3536 said:
Therefore one answer I'd really like to know is whether a dielectric coupler or union can break the grounding path. It does seem possible on paper.
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leon3536 said:
I'm not sure if this would break the electric code, but technically both side of the dielectric union are still bond to the main pipes.
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You seem to have made statements that contradict each other. If the unions are bonded on both sides, you have not isolated the pipe. Maybe you should explain what you mean.
 
dielectric union is a bad idea

dielectric union is a bad idea

You might electrocute someone like the plumber or wherever else becomes energized when you break the circuit. You might become liable for the death if it was your idea.
 
No, each unit has it's own incoming and return pipe piggyback off the main pipe. The main pipes are bond to the water main. The only way zone valve would work is because the pipes are not chained from unit to unit. I'm not trying to isolate the unit yet, I mainly just want to break a parallel path. I can test if I'm isolating a section with megger.

Besides, for any plumber to do work he has to disconnect the pipe. I don't think I'm liable if he gets electrocuted the instant he disconnects the pipe. I could see that happening on the water main that's not grounded at this moment. But not in a unit.
 
benaround said:
leon,

IMO, the first thing that has to be done is to make sure the grounding and

bonding is installed NEC compliant. The dielectric union is an attempt at a

quick fix, like putting a roller skate under a flat tire, it will get you nowhere.

Try opening the power to the furnace real quick and see if it clears, get to

the root of the problem and then it will be fixed forever.
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BEN A more systematic approach to locating ground current is generally a better method. With the proper tools, test equipment and time, all can be located and as Marc noted possible fixed or not.

I figured I need to get a hat with a propeller or something like that to look official lol
__________________
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I figured I need to get a hat with a propeller or something like that to look official lol
__________________
[/quote]

NAK: I do this type of work all the time for more than 30 years I normally dress like a professional, (well jeans, company shirt, maybe a hat)
 
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brian john said:
I figured I need to get a hat with a propeller or something like that to look official lol
__________________
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NAK: I do this type of work all the time for more than 30 years I normally dress like a professional, (well jeans, company shirt, maybe a hat)[/QUOTE]


you use the gaussmeter very often on the job ? (just curious - we don't do this kind of diagnostic work, don't have an infrared camera or anything like that)
 
leon3536 said:
While inspecting a top floor unit in a 24 unit condo, I discovered the water heated baseboard pipes are slightly energized. Although the currently was relatively low, the length of the pipe gives off a very strong EMF reading throughout the unit (as much as 10mG 6 feet away from pipe with unit breakers off).QUOTE]

A ballpark reverse calculation puts this current flow in the range of between 5-10 amps (subject to this "cheap" meter readings).

I agree with Brian ,a systematic approach is the best.Putting a current block in the plumbing,will only transfer this current flow to the next lowest resistance path(this could create a much larger problem)
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