Service drop wire running to my house and EM fields?

[Curiousphy]

Hi, I have a case of elevated AC Magnetic field in the house, strongest nearest the electric meter and along the service drop line connecting the house to the street power lines. Should that service drop line measure no current or fields when I shut off my main circuit breaker? it seems shutting my circuit breaker has no effect on the AC magnetic field measured along that wire or the area close to my electric meter. thanks

 

[yungman]

You sure you only have one breaker box? I have two houses I have two breaker boxes after I remodeled the houses. I asked to add new plugs and the contractor put in a secondary breaker box that is totally independent to the original box. I too have hum issue in my house but mainly bad wiring, that's another story.

Theoretically, if you don't draw any current, you should not have EM field.

 

[Rive]

case of elevated AC Magnetic field

Could you please explain the details of the measurement what gave you this... measured value? What kind of equipment was it?

 

[dlgoff]

Hi, I have a case of elevated AC Magnetic field in the house, ...

If you are having health concerns from EM field exposure, this post has references/links to a couple articles you should read.

 

[jim hardy]

it seems shutting my circuit breaker has no effect on the AC magnetic field measured along that wire or the area close to my electric meter. thanks

if opening the breaker indeed drives current to zero,
then
the field is coming from something else.

 

[eeemcee]

Hi, I have a case of elevated AC Magnetic field in the house, strongest nearest the electric meter and along the service drop line connecting the house to the street power lines. Should that service drop line measure no current or fields when I shut off my main circuit breaker? it seems shutting my circuit breaker has no effect on the AC magnetic field measured along that wire or the area close to my electric meter. thanks

If there's NO current flowing, there should be NO magnetic(H) field, there will be an Electric(E) field whenever there is potential, you can minimize the fields by twisting the wires.

 

[Curiousphy]

Thank you all for your responses, for some reason I didn't get notified of them. The high AC magnetic field comes and goes, I use a 3-axis $150 meter that tells me the exact values, i measured 3-4 mG in the living room and higher as I approached the electric meter only on some days... I use the same electricity... suspect it was coming from the pipes... the field at the water shutoff valve is above 30 mG during low days..

 

[russ_watters]

The high AC magnetic field comes and goes, I use a 3-axis $150 meter that tells me the exact values, i measured 3-4 mG in the living room and higher as I approached the electric meter only on some days... I use the same electricity... suspect it was coming from the pipes... the field at the water shutoff valve is above 30 mG during low days..

That's mili-gauss? And is your meter an extremely-low-frequency (ELF) magnetic field meter?

 

[davenn]

Thank you all for your responses, for some reason I didn't get notified of them. The high AC magnetic field comes and goes, I use a 3-axis $150 meter that tells me the exact values, i measured 3-4 mG in the living room and higher as I approached the electric meter only on some days... I use the same electricity... suspect it was coming from the pipes... the field at the water shutoff valve is above 30 mG during low days..

make, model and link to the meter, please

 

[Curiousphy]

This is the meter I used: http://www.lessemf.com/gauss.html#494 Yes, it's an ELF meter measuring A/C magnetic fields tuned to 60 Hz power lines in the US. I will have to do additional testing the next time I get a high field... noticed it during cold nights (could just be coincidence). I use gas heating myself, and there's no correlation between when my furnace is on vs. not for the magnetic field.

 

[anorlunda]

Pardon us for being skeptical. Those readings sound high.

i measured 3-4 mG in the living room

I see that the meter has auto ranging with both milli gauss and micro tesla scales. It is possible that you misread the screen and it is really 3 micro tesla. That would make it seem 10 times higher. The on-screen difference might be tiny lettering or an icon.

Can you post a photo of the screen when measuring 3 milli gauss in the living room?

 

[Averagesupernova]

You likely have a neighbor that has a poor neutral connection and their neutral current is finding its way back to the transformer through the water piping system. I have covered this before here on PF. Do a search.

 

[Curiousphy]

You likely have a neighbor that has a poor neutral connection and their neutral current is finding its way back to the transformer through the water piping system. I have covered this before here on PF. Do a search.

That's what I suspect too. I will take a measurement at the water shutoff valve next time I get a high reading. Currently it reads 30 mG right next to the valve but the rest of the house is fine at around 0.2 - 0.3 mG. The field dissipates quickly along the pipes in the basement. I know this is a common issue for neighborhoods that use water pipes for grounding...

 

[Curiousphy]

Pardon us for being skeptical. Those readings sound high.

I see that the meter has auto ranging with both milli gauss and micro tesla scales. It is possible that you misread the screen and it is really 3 micro tesla. That would make it seem 10 times higher. The on-screen difference might be tiny lettering or an icon.

Can you post a photo of the screen when measuring 3 milli gauss in the living room?

I believe the ideal level is < 0.5 mG? so 3 - 4 mG should be reasonably accurate for a case of elevated A/C Mag field? I do the same test often, pretty sure it was measured correctly. It doesn't happen every day, and I only noticed it during cold winter nights, so I can't take a photo of the measurement.

 

[Curiousphy]

While we are on this topic, I also noticed there's a single receptacle that's in the middle of a series of connected receptacles in the same circuit that always gives a high A/C Mag field reading... (4 - 5 mG close to it compared to 0.4 - 0.5 for the others before and after it). I checked the wiring, it's correctly wired (i.e., standard black line/load on the right side, white line/load on the left side, with ground connected; ground does not touch neutral). Is there any reason why a particular receptacle would exhibit a higher mag field but not the one before or after it in the same circuit?

 

[Curiousphy]

Call me old fashioned, but stick an amp clamp on your water pipe. Also take an amp draw on your grounding electrode conductor at the first point of disconnect. This (likely) be a #6 copper uninsulated wire going directly to the Earth bond. It will be at your main panel OR at your meter can where the service drop comes in. If your metal pipe gives you no reading in that amp clamp, and your Earth wire gives you no current, then you aren't having anything backfeed from a nearby residence.

I held a pen style voltage detector next to the pipe and got nothing while the A/C mag field was showing a high 30 mG... I don't have an amp clamp though (multimeter shows 0 volts between the grounding copper wire and the pipe, which is expected...not sure how to read amps on a pipe without a clamp). the Earth's B field isn't A/C though, I believe the concern is the 60 Hz AC field inducing a biological effect after long term exposure... or so I've read.

The voltage on the water pipe is probably much lower than 120VAC so the pen detector doesn't detect it and why it dissipates quickly through the water pipe's resistance. (or perhaps most of the incoming current runs along the copper grounding wire back to the service neutral through my panel?) how do you calculate the voltage from a 30 mG mag field?

 

[sophiecentaur]

I don't have an amp clamp though

The voltmeter would probably show nothing / very little. If you try disconnecting the water pipe (drain-down needed), you might find some high volts appear there. But be careful because you could be getting your only return path via that pipe and it could be dangerous.
To come to any valid conclusion about your problem, you really do need to measure current. Can you borrow an Amp Clamp from somewhere? I bought one (AC/DC version) a long time ago and it is really worth having for car / boat applications as well as home electrics. Not many tens of GBP, as it happened.

 

[Rive]

Currently it reads 30 mG right next to the valve but the rest of the house is fine at around 0.2 - 0.3 mG. The field dissipates quickly along the pipes in the basement.

Really sounds like some problem around neutral/grounding. Maybe you could try follow the water pipes with your instrument till the source? Actual current measurement feels like overkill at this point and disconnecting the pipe is a bit dangerous in this situation.

 

[sophiecentaur]

Really sounds like some problem around neutral/grounding. Maybe you could try follow the water pipes with your instrument till the source? Actual current measurement feels like overkill at this point and disconnecting the pipe is a bit dangerous in this situation.

The 'source' of a magnetic field would be current round the whole loop. E field could be higher in some places but it would probably be low if there is reasonable continuity. Current measurement is much lower tech than magnetic field measurement. Clamp meters are pretty common in the contents of your average DIYer's kit.
+1 for mentioning the dangers of opening a circuit though.

 

[Rive]

The remark about the disappearing field in wet (?) environment might indicate that the current ends (sinks into ground) there: and if it has endpoint then there will be an entry point somewhere too. Maybe it can be tracked.

 

[sophiecentaur]

The remark about the disappearing field in wet (?) environment might indicate that the current ends (sinks into ground) there: and if it has endpoint then there will be an entry point somewhere too. Maybe it can be tracked.

That's worthwhile considering - that would be equivalent to a number of loops / paths, all going to a node. But seriously, the system is basically broken and needs some significant re-wiring. I would guess that the installation is not in the UK (?). The regs are quite tough here and the company would send someone out PDQ if a situation like this one existed in the UK. Of course, the vast majority of supplies are underground and they do not usually get damaged or disturbed for decades. It's an environment with fairly dense housing and without domestic transformers etc. that you get in the US - and only one voltage for home equipment. Perhaps my view is a bit biassed due to the practical / DIY profiles of PF members in the US; their knowledge of their installations is way above what your average consumer has in the UK.

 

[Rive]

I would guess that the installation is not in the UK (?).

Yes, too many possible rules, systems, environments, so we can have only limited opinion.

Based on the another mentioned fact - disconnected breakers has no effect - I think there is a high chance that it'll be about some neighborhood business, not about local wiring. If so, then at this point the goal is no longer to find the wrong wire but to gather enough evidence what can be provided to the utility staff. Locating the point on the piping where the current comes in would spare a lot of explanation and push.

 

[sparkie]

Back to the OP's original post. If you do not have current on your ground, then you do not have an open neutral, and likely have a normally functioning electrical service. Yes, you will get a higher B-field reading there, as you are closer to a larger amount of oscillating current. I'm not quite sure why you are concerned about the magnetic fields of your electrical system, however if you are using AC electricity, you should expect that there will be all of the associated fields as a result of using that form of power.

As a side note, and forgive me for being a bit direct here, but if you can afford an instrument to measure a magnetic field, you can surely afford a clamp meter. I'm very happy with both Fluke and Klein as far as clamp meters go, and you can get one for less than $100.

 

[berkeman]

Lordy. Thread closed for Moderation and deletions/cleanup...

 

[anorlunda]

This thread will remain closed. It is far too speculative. I see nothing in the thread to hint that we are on the right track.