[MidwestMatthew]

I'm not paranoid over the alleged health issues surrounding EMF and so forth, but while playing around with a meter (TriField 100XE) I found that the magnetic field in my home is astronomical -- at least 100 times the national average and over 40 times what the EPA claims is safe. (The meter pegs out at 100 milligauss, so I have no way of knowing how high the measurement actually is but it's definitely over that.)

So, it looks like I have a problem to fix.

Making a long story short, I believe I've narrowed down the source to the main grounding wire for our home, which runs the entire length of the house, right down the middle, along the center beam of our basement, and is connected to the water main at the end of the house opposite our breaker box.

With that background, I'm now wondering how I can find and fix the problem. Not being an electrician, I'm not sure what my options are.

I'm wondering about turning off the power to the whole house using the main switch on our breaker box, then run the grounding wire to one of those long copper grounding bars driven into the ground on the same end of the house as the breaker box (thus eliminating the need for it to run through the house at all.)

Would that be a safe and appropriate fix for this? Or should I do something else?

 

[Oso954]

I’d get an electrician in there to measure the current on that ground wire, trouble shoot it, and recommend the appropriate fix.

 

[RAL238]

These inexpensive meters that claim to measure magnetic fields don't have a particularly good reputation for accuracy.



In order to create a magnetic field, there must be current flowing in the wire. If you put a clamp-on ammeter on the ground wire and get a significant reading, that's a sign of a problem, such as an open neutral, perhaps on your house or a neighbor's house.


If the ammeter doesn't show a current flowing in the ground wire, then the flux meter reading is bogus.



What you don't want to do is disconnect the ground wire before you understand what is going on. Doing so can be dangerous.

 

[CodeMatters]

Using those meters is a waste of time. Just something to give neurotics
something to stress over. Toss it out. Take the dog for a walk.

 

[dmxtothemax]

I would not touch the grounding system at all,
Get an electrician in to check your concerns,
Any changes or modifications to your grounding system
could have unintended changes to the safety of the electrical instalation.

 

[Bud9051]

Use your meter to check several other locations other than your neighborhood. If none show a significant reading that raises confidence in the meter.

The panel is supposed to be balanced to some extent so loads on each side of the 240v incoming cancel each other on the neutral.

Do you have a volt meter? Have you observed any lights in the house flickering or being brighter or dimmer than expected.

Have you talked to the power company? They may send out someone to look at the incoming connections. Explain to whoever comes out that you have little knowledge of electric and maybe s/he will do a bit more testing.

Bud

 

[Missouri Bound]

You need to have your neutral checked.
The ground shouldn't have anything on it.
And as you said not bing an electrician you need to have someone who is qualified to do the work.
It's more than likely you don't have a ground problem but a neutral one.

 

[joed]

I'm wondering about turning off the power to the whole house using the main switch on our breaker box, then run the grounding wire to one of those long copper grounding bars driven into the ground on the same end of the house as the breaker box (thus eliminating the need for it to run through the house at all.)

Code still requires you to have the ground wire run to the metal water line at the point of entry even if you add rods at the panel.

 

[surferdude2]

The service Grounding Electrode Conductor will be carrying a portion of the imbalance current that the neutral carries. Do not disconnect the Grounding Electrode Conductor... you could be electrocuted if there is an open neutral going back to the transformer.

That current is widely variable depending on what load are connected at any time. It is generally very low.

I think the EMF detector you are using is fibbing to you. To be sure, call your power company for a check of your neutral and any other things they normally do. It's a free service.

SD2

 

[surferdude2]

In the specs for that instrument, it gives the disclaimer:

"Remember that the TriField® meter is frequency-weighted (except Flat Version), so in most environments, it will read higher in the magnetic field setting than a more traditional meter of the type often used in epidemiological studies to set possible hazard thresholds."

SD2

 

[MidwestMatthew]

You need to have your neutral checked.
The ground shouldn't have anything on it.
And as you said not bing an electrician you need to have someone who is qualified to do the work.
It's more than likely you don't have a ground problem but a neutral one.

I checked the ground wire with a clamp meter and got a reading of 0.59 with the meter on the 20A setting (no reading at all on any other settings). I'm not sure what that means, but I couldn't get a reading on any other wiring in the house, including on the cord of a 1500-watt space heater running on high.

I guess I need to have the utility company come out sometime soon to check things out. I won't do anything to it myself in the meantime, but in the interests of being an educated homeowner I would be grateful for any insights others might have about that reading on the clamp meter.

 

[surferdude2]

There will normally be current flowing in the Service Electrode Conductor, as you have found. That's normal since it's in a parallel connection with the incoming neutral line by virtue of the bonding jumper connection in the service gear.

That current will vary depending on the conductivity of the earth that the Grounding Electrodes are embedded in and the load imbalance you are imposing on the system. No system is perfectly balanced at all times. Your reading is considered normal. It could be much higher and still be normal.

You can't get a reading from clamping around a cord since you are clamping around both line conductors. You would have to split the cord open and clamp around either conductor to get a true reading. There are splitter devices that allow that type of access without cutting into the cord. Click to see line splitter

Edit: I see jbfan has explained why clamping around a cord will not normally give you any indication of current flow. That is correct under normal circumstances but if you happen to have a ground fault in the connected device and the cord doesn't have a grounding wire, you would actually get a reading. That's how the GFI receptacles detect ground faults. You are right to try to get a better understanding of how electricity works. It can be a life saver.

 

[jbfan]

To add to the post above, you will not get a reading on the cord because the hot and neutral current cancel each other out on the amp meter.

 

[CodeMatters]

I checked the ground wire with a clamp meter and got a reading of 0.59 with the meter on the 20A setting (no reading at all on any other settings). I'm not sure what that means, but I couldn't get a reading on any other wiring in the house, including on the cord of a 1500-watt space heater running on high.

I guess I need to have the utility company come out sometime soon to check things out. I won't do anything to it myself in the meantime, but in the interests of being an educated homeowner I would be grateful for any insights others might have about that reading on the clamp meter.

590mA on the system ground is nothing to be concerned about. I don't
often measure it but when I have I've seen more than 5 times that. No
big deal and others have already explained the parallel path that makes this predictable.


EDIT: It's also not unusual to see current on this conductor with
EVERYTHING in the residence turned off as it's a parallel path in
both directions for unbalanced loads.

 

[Luke M]

This is good from an electrical safety point of view, because it means you effectively have a backup neutral.


In a house with plastic water supply, a lost neutral would cause a shock and fire hazard (even with ground rods), but you wouldn't even notice.

 

[DanS26]

Code still requires you to have the ground wire run to the metal water line at the point of entry even if you add rods at the panel.

Correct.....but just stand back and think about what will happen in that house if struck by lightning.

He did say the GEC runs the entire length of the house right down the center....hmmmmm

 

[curiousB]

..."So, it looks like I have a problem to fix."...

Not really. Toss the meter in the bin and go back to living your life.

 

[tmittelstaedt]

I'm not paranoid over the alleged health issues surrounding EMF and so forth, but while playing around with a meter (TriField 100XE) I found that the magnetic field in my home is astronomical -- at least 100 times the national average and over 40 times what the EPA claims is safe. (The meter pegs out at 100 milligauss, so I have no way of knowing how high the measurement actually is but it's definitely over that.)

So, it looks like I have a problem to fix.

Making a long story short, I believe I've narrowed down the source to the main grounding wire for our home, which runs the entire length of the house, right down the middle, along the center beam of our basement, and is connected to the water main at the end of the house opposite our breaker box.

With that background, I'm now wondering how I can find and fix the problem. Not being an electrician, I'm not sure what my options are.

I'm wondering about turning off the power to the whole house using the main switch on our breaker box, then run the grounding wire to one of those long copper grounding bars driven into the ground on the same end of the house as the breaker box (thus eliminating the need for it to run through the house at all.)

Would that be a safe and appropriate fix for this? Or should I do something else?

For starters NOBODY has ever managed to show or prove a health issue with magnetic fields. Here in Oregon the BPA ran a 7 mile million volt transmission line for 20 YEARS you could go stand under it, open an umbrella and draw a 1 inch spark from a key to the metal pole of the umbrella, there was so much leakage power in the air. They ran cattle under those lines, had biologists do studies, etc. etc. etc. No ill health effects in ANYTHING.

The people claiming that MAGNETIC fields are unhealthy are the same people running around terrified about cell phone towers. They are non-scientist types and likely bible-thumpers to boot that think the world is 6000 years old.

Secondly, on power distribution systems you have a neutral from the house panel to the transformer on the pole. There is also supposed to be a ground wire running down the pole from that same transformer lug. The circuit path for the neutral return current from the panel to the transformer is either straight through the neutral wire, or through the ground wire at the pole, through the earth itself, then into your cold water pipe and into your panel. The second path though the Earth is a higher resistance connection than the actual neutral wire so it should show current flow as very low or negligible. A high resistance connection on that wire neutral from the pole will cause larger currents in the ground wire, so it won't hurt you to call the power company and have them check out the pole and transformer and drop lead to the house.

If you really are freaked about the ground current you can sometimes rebalance the loads in the panel to greatly reduce the neutral current. You need to use a clamp on ammeter and measure the amount of power each circuit is drawing in normal operation then try to equalize the load by putting half of the ones drawing on one side and half on the other side of the incoming feed. (electrically, not physically) This is an easy process if you understand it, otherwise call an electrician. With a balanced panel there will be very low neutral current and negligible ground current.

 

[surferdude2]

Currently the Odds = 1 : 280,000 of being struck by lightning. It's not something that demands immediate attention or any attention at all.

Since the current odds of dying in a automobile accident are 1:583, you'll be killed 480.274 times in car wrecks before lightning hits you! :biggrin2:

 

[DanS26]

Currently the Odds = 1 : 280,000 of being struck by lightning. It's not something that demands immediate attention or any attention at all.

Since the current odds of dying in a automobile accident are 1:583, you'll be killed 480.274 times in car wrecks before lightning hits you! :biggrin2:

The odds of your house (not your body) being hit by lightning is 1 : 200

http://lightningsafety.com/nlsi_pls/probability.html