grounding, neutral, and EMF situation.

Hi everyone. I am looking for some insight into some electrical problems. Sorry for the long post.
2 years ago I had my basement built out from the raw foundation into
various living spaces. One of those spaces is a little home recording studio. Ever since the build out I have not been able to record guitars and they pick up strange directional interference. No one had any idea what I was talking about.
Fast forward 2 years and I finally discover the source that my guitars are picking up: a high EMF coming from somewhere in the basement ceiling running the length of the house. So now I'm trying to figure out why this high EMF exists. Somewhere some current is leaking onto the ground or water pipe system, etc. (i think).
First of all, all of the neutrals coming into the panelboard are connected to the ground terminal (which is bonded to the neutral terminal). Is that OK? Seems like the neutral conductors should be on the neutral terminal. Maybe since they are bonded together it doesn't matter? Tell me.
There is a ground connected to the water main right where it enters the front of the house . There is another ground connected to a ground rod at the back of the house. The water pipe ground is connected to the ground terminal in the panelboard. The ground rod is connected to the neutral service conductor outside the house (before it enters).
I need to eliminate this EMF for safety reasons ans so I can get back to recording instruments with magnetic pickups.
Thanks!
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Also (been reading threads in this group), the neutral and ground are connected at the service meter (outside the house) and also at the panelboard inside the house. Is this necessary? Is it OK? I've read that they can/should only be connected once, and not again downstream.
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snipped-for-privacy@gmail.com wrote:

The rules that apply on the load side of the Service Disconnecting Means (SDM) do no apply on the supply side of the service point. The space between the service point and the SDM is a little weird. Meter enclosures are grounded by bonding them to the neutral conductor of the Supply wiring. That is normal in North American practice. The Neutral must be bonded to the SDM enclosure. That is also normal in North American practice. What seems likely to me is that some circuit in your basement ceiling is improperly wired. If all of the conductors of a circuit are not in the same raceway or cable then the conductor that is carrying current without a conductor immediately adjacent to it that is carrying the same current will set up an electro magnetic field. -- Tom Horne
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On Apr 14, 3:55 pm, snipped-for-privacy@gmail.com wrote:

Yes, others are finding problems with EMF energy being attracted to their underground water, sewer, drain pipes. Especially hydraulic sewer systems. Seems if the sewer systems are having problems with sewer breaks, the hydraulic systems negative hydrogen ions are attracted to the EMF sources. The answer is still alusive to others having this problem.
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On 14 Apr 2007 15:55:41 -0700 snipped-for-privacy@gmail.com wrote:
| Hi everyone. I am looking for some insight into some electrical | problems. Sorry for the long post. | | 2 years ago I had my basement built out from the raw foundation into | various living spaces. One of those spaces is a little home recording | studio. Ever since the build out I have not been able to record | guitars and they pick up strange directional interference. No one had | any idea what I was talking about.
What does this inteference sound like coming out? A hum? Some other kind of sound? Could you make an MP3 file of it and upload it? Don't actually play any real music in that recording ... just go through a sampling of strings much like you would tune the guitar. If you have no place to upload to, you could email it to me as an attachment and I could put it online.
| Fast forward 2 years and I finally discover the source that my guitars | are picking up: a high EMF coming from somewhere in the basement | ceiling running the length of the house. So now I'm trying to figure | out why this high EMF exists. Somewhere some current is leaking onto | the ground or water pipe system, etc. (i think).
You might want to buy one of those clamp-around amp meters to use to see if some wire or pipe is carrying current. If you clamp it around a whole cable, it should show a total current if zero if all of the current going in one direction is also coming back over another wire in that cable. If you get a current reading on any cable, something is wrong. You should only get a current reading if you clamp around one individual wire where the return current goes back over another wire that you are not clamping around. And, of course, none of the pipes should be showing a current reading when you clamp around them. Be sure to also check clamping around the wires going to the ground connections, as well as anything and everything you can see in and around the studio area.
| First of all, all of the neutrals coming into the panelboard are | connected to the ground terminal (which is bonded to the neutral | terminal). Is that OK? Seems like the neutral conductors should be | on the neutral terminal. Maybe since they are bonded together it | doesn't matter? Tell me.
In the service entrance panel, the neutral and ground must be bonded. A better practice in building out such a panel would be to have two separate bus bars in that panel with all the neutrals going to one of them (each in a separate hole) and all the grounds to another (where they may share holes, though with a bus bar the same size as the neutral bar, that won't be needed). Then a grounding strap would go between the two bars. If you later decide to change things electrically adding another panel ahead of this one, then this one would be a subpanel and the only change needed is to remove the bonding strap.
However, it is legal, and electrically equivalent, to have them all mixed in the service entrance panel. It's just less convenient.
| There is a ground connected to the water main right where it enters | the front of the house . There is another ground connected to a | ground rod at the back of the house. The water pipe ground is | connected to the ground terminal in the panelboard. The ground rod is | connected to the neutral service conductor outside the house (before | it enters).
I'm always suspicious of these grounds, especially if the water mains are involved, and more especially if they are older pipes.
How far from the entrance panel does the ground wire that goes to the ground rod (grounding electrode) run? It should be a close to the panel as possible. If the panel is on an outside wall (it would have to be to meet various requirements for minimal runs of unprotected power), the ground rod, or at least the first if there is more than one, should be directly on the other side (outside).
| I need to eliminate this EMF for safety reasons ans so I can get back | to recording instruments with magnetic pickups.
Shut off all power except for powering the outlets needed to run the studio. Is the EMF still there?
Did the above shut off the lights in the studio? If not, shut those off at the panel, and turn on some other circuit elsewhere in the house and run a heavy duty extension cord to power the studio equipment.
You might need to explore the ceiling to see what all is in there, if you have determined the EMF source is there.
Can you temporarily test the studio equipment, or some subset of it that can show the problem, in other locations in the house?
Is _all_ (or just _some_) of the studio equipment equipped with grounded 3-prong plugs? Are the circuits it uses correctly wired with not only the real ground wires, but also have the hot and neutrals wired right?
Many studios do have a hum problem that can get into the audio, and a cure for this is known. But it also costs some money, so I don't want to suggest this unless and until we know that this is your only real problem.
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| Phil Howard KA9WGN (ka9wgn.ham.org) / Do not send to the address below |
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Thanks everyone.
There is no hum in my audio gear. Only my guitars, which have magnetic pickups, pick up this interference.
Still digesting your repsonses....
BUT it sounds like my grounds are OK. The ground rod is very close to the service panel. Right outside, basically. The other ground (on the water pipe) is connected to that water pipe at the other end of the house, then runs allllllll the way back to the back of the house and into the panel.
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On 15 Apr 2007 12:28:13 -0700 snipped-for-privacy@gmail.com wrote: | Thanks everyone. | | There is no hum in my audio gear. Only my guitars, which have | magnetic pickups, pick up this interference.
it could still help to hear it. I'd like to know if it is more like a sine wave or more like a square wave. I'd like to know if it sounds more like 60 Hz or 120 Hz.
| BUT it sounds like my grounds are OK. The ground rod is very close to | the service panel. Right outside, basically. The other ground (on the | water pipe) is connected to that water pipe at the other end of the | house, then runs allllllll the way back to the back of the house and | into the panel.
I'd like to know if there is current on that ground to the water pipe.
If something is creating an EMF field the guitar picks up, this is what needs to be narrowed down.
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| Phil Howard KA9WGN (ka9wgn.ham.org) / Do not send to the address below |
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You might want to do some "detective" work with a cheap digital voltmeter.
If you panel is properly wired, you should not detect more than a small fraction of a volt difference between neutral and ground in an "unloaded" circuit. This voltage should be VERY close to zero as both conductors are in the same cable. While "ground loops" exist, currents tend to return via the same cable.
Likewise, you should not detect more than a fraction of a voltage between the grounds of different circuits. These separate groups with y your voltmeter are a "loop" which will pick up magnetic fields in the area. If you have time on your hands, you can construct a good sized sensing coil to hunt out any significant AC magnetic fields. At power frequencies, AC electric fields usually don't "couple" into electronics.
These are simple measurements than can be done with a meter costing less that $10.
Make these measurements and report back.

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remove the X to answer ----------------------------
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| Likewise, you should not detect more than a fraction of a voltage between | the grounds of different circuits. These separate groups with y your | voltmeter are a "loop" which will pick up magnetic fields in the area. If | you have time on your hands, you can construct a good sized sensing coil to | hunt out any significant AC magnetic fields. At power frequencies, AC | electric fields usually don't "couple" into electronics.
However, nonlinear current waveforms can produce harmonics that can more easily couple into other wiring and electronics.
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| Phil Howard KA9WGN (ka9wgn.ham.org) / Do not send to the address below |
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