High electromagnetic field from grounding wire

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  #1  
Old 01-02-14, 05:33 PM
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High electromagnetic field from grounding wire

Hello,
I found out that the grounding wire from the electric panel to the water pipe, emits high level of EMF.
Is it supposed to be like that?
Is it possible that I have some current tripping?
I would appreciate your thoughts.
Tzvi
 
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  #2  
Old 01-02-14, 05:38 PM
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I would love to know how you identified your ground wire as a high EMF source.
 
  #3  
Old 01-02-14, 05:41 PM
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With EMF meter. It emits between 50 to 100 mG.
The water pipe is 12' far from the panel so I could go with the meter along the wire.
 
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Old 01-02-14, 06:11 PM
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Maybe your neighbor closest to the water pipe has an open neutral. Or maybe he has installed a passive-type bug on the water line to monitor your activities. I would put a clamp-on ammeter on the wire and see if it's carrying any current. Do not disconnect it or get in its way.

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Old 01-02-14, 06:53 PM
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It's a little hard to explain. Although your service and panel are connected/bonded to ground..... it really isn't grounded or at 0 volts. There is always a stray voltage or difference of potential between the electrical ground and true ground.

Mike Holt has his own forum and the following link is from that forum. The video is an hour and a half long but is really interesting.

Mike Holt Stray Voltage Video
 
  #6  
Old 01-03-14, 07:45 AM
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And this stray voltage on the grounding cable emits so much emf?
 
  #7  
Old 01-03-14, 07:49 AM
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Also, is it possible that the grounding is not so good as well, so I have more current on the wire than the 'regular' stray voltage?
 
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Old 01-03-14, 08:26 AM
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How much is a lot of EMF? Are your sensitive to EMF? I can stand under overhead high voltage lines with no ill effects.
 
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Old 01-03-14, 08:55 AM
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It's between 50 to 100 mG.
The problem is that this wire runs behind a wall where we sit in the family room in the basement.
I'm not sensitive to EMF.
From my experience in life, high emf can cause cancer and other illnesses.
 
  #10  
Old 01-03-14, 08:57 AM
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There is a list on page 3 that will give you an idea as to how much EMF one can expect with everyday appliances. You will also see it decreases very rapidly with distance. A reading directly along a wire will be hundreds of times less several feet away.
http://www.xcelenergy.com/staticfile...F-Brochure.pdf

Bud
 
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Old 01-03-14, 09:01 AM
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The question is should it emit emf at all?
 
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Old 01-03-14, 09:24 AM
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Have you measured it at friends houses to get a comparison?
 
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Old 01-03-14, 09:28 AM
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Should it emit EMF.... I'd say yes. Anytime there's a difference of potential.
 
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Old 01-03-14, 09:54 AM
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Thank you all.
PJMax, does this look good (attached pictures)?
 
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  #15  
Old 01-03-14, 10:34 AM
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No expert...but everything I know/heard/read says grounds have to be solid wire...not stranded.

Mod Note: GECs and EGCs can be either solid or stranded. They can be bare or insulated.
 

Last edited by pcboss; 01-03-14 at 02:43 PM.
  #16  
Old 01-03-14, 11:01 AM
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Looks like a very professional and clean installation. Nothing inherent with the installation that would cause a high EMF reading. The stray voltage that PJMax mentioned can be very difficult if not impossible to track down. And even if you did, the power company, cable company, neighbor, or whomever may be causing it likely won't bother with it unless it's a shock hazard (which it likely is not with a proper grounding/bonding system).

EMF adheres to the inverse square law. So if you're reading 100mG at 6", double that distance (12") and you'll have 1/4 the intensity (25mG). At 2' distance, you'll measure about 5mG. As you probably know, there's a lot of research out there that states that reasonable levels of EMF are not an issue... but granted, not all research is 100% and different people have different opinions on the subject.

If it really bothers you, I would look at rerouting the bonding wire further away from your typical living space. You'll need to use the same gauge wire and it's imperative that you connect the new wire before disconnecting the old one. If there is a voltage difference, you don't want to remove the existing bond and create a shock hazard for you or anyone in the house. You'll also need to bond it before and after the water meter as yours is currently.
 
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Old 01-03-14, 12:42 PM
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No expert...but everything I know/heard/read says grounds have to be solid wire...not stranded.
Not true. Solid #4 would be almost imposable to bend/work with, and with larger services, the ground gets even larger.
 
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Old 01-03-14, 01:32 PM
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Been following, helps to keep the gray matter active, but correct me as needed. 240v power from the pole includes a ground wire which is earth grounded at the pole and then earth grounded from the main house panel AND it carries current. It is the center tap of the 240 volts. Allowing for some resistance of that return ground, there will always be some current flow through the earth path. If the ground wire at the pole is disconnected or poorly connected, then more/all of the return current will flow through the house earth ground. Note, this current is the difference between the two 120 volt loads.

So, yes there will always be a minimal current on the house ground to earth, but it may be higher if the power company side is poorly connected. A current reading would be interesting. That current would also vary as the imbalance between the 120 volt sides changes.

TIA
Bud
 
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Old 01-03-14, 02:10 PM
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250.62 Grounding Electrode Conductor Material. The grounding electrode conductor shall be of copper, aluminum, or copper-clad aluminum. The material selected shall be resistant to any corrosive condition existing at the installation or shall be protected against corrosion. The conductor shall be solid or stranded, insulated, covered, or bare.
Well..there ya go...I just always saw solid.
 
  #20  
Old 01-03-14, 03:13 PM
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You're sorta right Bud. (And to others who want to read this)

(Talking single phase here)

The other wire of the hots is not the ground, it is the grounded conductor, also call then neutral because it has equal potential (voltage) between it, and the ungrounded conductors (hots).

A ground wire, as we know it with wiring things, is never to carry current except during a fault. This is to operate the overcurrent device (fuse/breaker) and to provide a lower risk of shock hazard.

The neutral at the transformer is grounded to the earth ground via a rod in most cases. The neutral wire between the house and the pole will carry the imbalance of the load in the house between both hots. For example, if you have 10 amps on one hot and 20 amp on the other hot, your neutral current is 10 amps.

The service to the house is similarly grounded. The neutral wire from the pole is connected to the proper bus, then the bus is bonded to a ground rod outside and to the water service. These two grounding electrodes have a path to the transformer via the ground wire that is connected to the neutral through the earth. The earth is not the best conductor but it will allow some current to flow.

So now that we all know this, there could be current flowing through GEC as it is a complete circuit. Since it is only one wire, you would not have a canceling effect like you would when wires are grouped, this is why you can not run just one wire in a conduit.

The questions here are:
Why is this happening? IMO it should not.
What is causing it? I would start by shutting breakers in the house and see if it changes. Start with the water heater, well, or something else that involves water.
EMF means nothing to me, I would put a clamp on meter and see how much current, if any, is flowing.
 
  #21  
Old 01-03-14, 03:45 PM
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Thanks TI,
terminology frequently gets me in trouble. That link I posted was my attempt to get some relationship between EMF readings and what might be flowing through the wire. Not something I ever used after school. But doesn't look like much current is needed to generate those readings. Still, as you said, something to track down.

Bud
 
  #22  
Old 01-03-14, 04:25 PM
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Thanks for posting that! It was quite interesting.
 
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