Elevated EMF / AC magnetic fields in home

[ffran]

Apologize in advance for the long post! We are in this particular situation and, being a novice with electrical- related issues, would greatly appreciate opinions here.

After a year long search, we found this nice home in Texas meeting all requirements my wife and I were looking for, and at the right price! We entered the option period and the home inspection went good. In the meantime, we also had a radon inspector look at the home - and since he also did EMF inspections, we added that too to our inspection list.

The radon results were good but EMF inspections revealed generally elevated AC power related magnetic fields in the home & backyard. Most of the home showed 1.2 to 1.8 mGauss (0.12-0.18 microTesla), which though a little higher than typical, is still ok. The problem is that the first floor master bedroom and the porch/ backyard, which are situated towards the west side & back of this N-S oriented house, showed EMF up to 3-4 mG levels (an overview pic is attached). I know there is debate about what the safe levels are for chronic exposure, and that there are no legal mandates, but many healthcare panels recommend residential exposure below 3mG, preferably below 2.

The magnetic fields are actually much higher at the east, south and west perimeters of the home, presumably from the power feeds running underneath the property lines (to this home and neighbors), but they fall off rapidly to <2 as we get into the property from the boundary- but it is only on the west side that the MFs persist at 3-4 mG levels well into the backyard / porch and into the west side of the MBR.

The EMF inspector told us the high EMFs in the home are most likely due to underground power feeds on 3 sides of the home- and especially the one on the west side, feeding the neighbor’s home – and there was little we can do reduce this as the utility company would typically not cooperate. That being the case, we canceled the contract a couple of days ago, despite loving this home : (

The reason I am posting this now is because we visited another home yesterday - close to this home - and that has a similar configuration (N-S oriented, power feeds on east, west & south) - but most of this home had EMFs only in the 0.2-0.8 mG range! That surprised us as we expected high EMFs in this home too, for all the reasons as in the other home! I then googled a little and discovered that internal wiring issues and grounding problems can also cause elevated AC related magnetic fields within a home.

The home inspection on the last home had actually discovered some electrical issues - grounding wire not connected to the grounding rod, a live wire in the attic, no AFCI protection, etc. I am now wondering if these electrical issue were the cause or at least a significant contributor to the EMF in that house - all issues easily fixed by an electrician! My EMF inspector however thinks that to be extremely unlikely.

Since we have canceled that contract, it is a little indelicate to go back to the seller to ask that we would like to re-test the house for EMF (with say the mains and/or circuit breakers off, to check how much the internal issues are contributing to the elevated EMF). But if there was even a small chance (say 20% or higher), I would do that, just because we liked this home so much, after having looked at 36 others!

All of your informed opinions on the possibility of an internal wiring/grounding issue causing or contributing to the elevated EMFs in the home & backyard is greatly appreciated!

 

[jim hardy]

Have you searched on "Background 60 hz field" ?

Some of the many hits are scholarly and some scaremonger-ey.

Here's just two.
http://www.ehjournal.net/content/12/1/42
http://www.calpoly.edu/~dhafemei/background2.html
From second one, which is really worth reading:

A typical U.S. home has the Earth's constant magnetic field of about 450
mG and a 60-Hz background magnetic field level (primarily not from power
lines) that ranges from 0.5 mG to 4 mG with an average value of 0.9 mG.
Five percent of the homes have fields above 2.9 mG, and 1% are above 6.6
mG. For comparison sake, one study reports that electrical powerline
workers experience an average field of 11 mG. ...
...

Walking in the Earth's magnetic field of about 400 mG produces
"electromotive force" voltages from Faraday's law. Walking in a constant
magnetic field doe not generate currents, but it is interesting to
calculate the E fields generated by walking. By moving very slowly at
the rate of 0.1 m/s, an internal E field of 4 microV/m is developed
(corresponding to 2 mG of ELF/EMF). It one runs very fast at 8 m/s (18
mph), an internal E field of 400 microV/m is developed (corresponding to
200 mG).

Rotations (or twirling) of the human body in the Earth's magnetic field
of about 400 mG creates radial electric fields, giving rise to currents
in the human body. A tilt of the head of 45 degrees in the slow time of
1.6 seconds will create an electrical field of 4 microV/m, corresponding
to a 60-Hz field of 2 mG. A fast nod in 0.16 seconds creates an electric
field of 40 mV/m, corresponding to a 60-Hz field of 40 mG.

My own opinion: Utility workers who spend lots of time in far stronger 60 hz fields don't have more cancer . I'd worry more about cancer risk from that intense Texas sun and the pesticides on the yard .
But i may be biased - I'm one of those retired utility workers.

 

[ffran]

Thanks Jim. I try my best to buy pesticide free food!

Btw, do you have an opinion on my Q, i.e., what are the odds – with the above magnetic field profile of the home- the cause is related to wiring / grounding problems within the home (versus, coming from the utility’s underground power feeds to the adjacent homes)? Thanks.

Have you searched on "Background 60 hz field" ?

Some of the many hits are scholarly and some scaremonger-ey.

Here's just two.
http://www.ehjournal.net/content/12/1/42
http://www.calpoly.edu/~dhafemei/background2.html
From second one, which is really worth reading:


My own opinion: Utility workers who spend lots of time in far stronger 60 hz fields don't have more cancer . I'd worry more about cancer risk from that intense Texas sun and the pesticides on the yard .
But i may be biased - I'm one of those retired utility workers.

 

[jim hardy]

Thanks Jim. I try my best to buy pesticide free food!

Btw, do you have an opinion on my Q, i.e., what are the odds – with the above magnetic field profile of the home- the cause is related to wiring / grounding problems within the home (versus, coming from the utility’s underground power feeds to the adjacent homes)? Thanks.

I'm hesitant to venture a guess without knowing more about the meter your inspector used.
I will say that it appears to be very sensitive. Those are weak fields.

Lamp dimmers generate a lot of electrical "noise" as do switching power supplies as in microwave ovens and TV sets and computers, but you'd expect them to be picked up strongest inside the house and your strongest readings are outside . So my guess is your inspector's assessment was accurate.

It'd be fascinating to wave the inspector's magic wand around some running appliances and see if it shows anything. I've never done that. Can you borrow or rent one?

A "Power Off" survey would tell you if the source is inside or outside the house and not a lot more, i fear. But that's what you want to know, isn't it ?

I have worked for years in magnetic fields so strong they distorted CRT oscilloscope traces
and right underneath 230 kilovolt power lines
and right next to wires carrying twenty thousand amps.
So as i said - i am hardly a neutral party.(no pun intended)

EDIT Add :
by the way - did you notice whether neighbors' airconditoners were running when you visited those two houses ?
Magnetic field(gauss) is driven by current.

For perspective

The magnetic field magnitude measured at the surface of the Earth is about half a Gauss and dips toward the Earth in the northern hemisphere. The magnitude varies over the surface of the Earth in the range 0.3 to 0.6 Gauss.

http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/magearth.html



old jim

 

[ffran]

He uses a ~$400 AC Gaussmeter. I essentially went and bought a similar one.

When I hold it close to an operative microwave, it goes up to 25mG, then drops to 2 mG about a foot away.

Yes, this home's and neighbors ACs were on at the time, but I am expecting low levels with ACs on.

The reasoning underlying my questions is this - if the cause for the > 2mG magnetic fields is something that is easily fixed by an electrician, I want to buy this home. If it cannot be easily fixed, as I assume it to be if the cause is underground power feeds, I do not want to buy the home.

I have read some of the journal articles recommending < 3mG levels for chronic residential exposure, and I am fairly convinced by them. I am aware that not everybody agrees with them.

Thanks again for your time!

I'm hesitant to venture a guess without knowing more about the meter your inspector used.
I will say that it appears to be very sensitive. Those are weak fields.

Lamp dimmers generate a lot of electrical "noise" as do switching power supplies as in microwave ovens and TV sets and computers, but you'd expect them to be picked up strongest inside the house and your strongest readings are outside . So my guess is your inspector's assessment was accurate.

It'd be fascinating to wave the inspector's magic wand around some running appliances and see if it shows anything. I've never done that. Can you borrow or rent one?

A "Power Off" survey would tell you if the source is inside or outside the house and not a lot more, i fear. But that's what you want to know, isn't it ?

I have worked for years in magnetic fields so strong they distorted CRT oscilloscope traces
and right underneath 230 kilovolt power lines
and right next to wires carrying twenty thousand amps.
So as i said - i am hardly a neutral party.(no pun intended)

EDIT Add :
by the way - did you notice whether neighbors' airconditoners were running when you visited those two houses ?
Magnetic field(gauss) is driven by current.

For perspective

http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/magearth.html



old jim

 

[jim hardy]

... if the cause for the > 2mG magnetic fields is something that is easily fixed by an electrician, I want to buy this home.

Understand.. sorry if i appeared to be dismissive your concern; au acontraire i was making a genuine effort to not do that yet felt so self conscious about it i perceived a need to explain why...

I will be surprised if the fields he measured are due to something inside the home, for the reason his biggest numbers are outside it.

I find it admirable that you are interested enough to investigate and educate yourself, let alone buy an instrument. Your measurements aren't out of line with this utility sponsored information
http://www-ehs.ucsd.edu/LBCI/LIPA_Magnetic_Field_Levels_Around_Homes.pdf

If you'll post the brand and model of that gaussmeter i'll read its instruction manual.
I have a small handheld one for DC fields, Earth's magnetic field is about the limit of its resolution.. In the power plant i measured AC fields with a coil of wire and a voltmeter but was dealing with quite a bit stronger ones.

Thanks. No offense was intended.

old jim

 

[ffran]

I bought this one:
http://www.davis.com/Product/FW_Bel...KHyTtDTLmrVKIFsMUqOhgMQhD6e3M4Np96SYxJ_nw_wcB

His was a different one, but similar specs I think.

No, I didn't find your comments dismissive in any way..

Understand.. sorry if i appeared to be dismissive your concern; au acontraire i was making a genuine effort to not do that yet felt so self conscious about it i perceived a need to explain why...

I will be surprised if the fields he measured are due to something inside the home, for the reason his biggest numbers are outside it.

I find it admirable that you are interested enough to investigate and educate yourself, let alone buy an instrument. Your measurements aren't out of line with this utility sponsored information
http://www-ehs.ucsd.edu/LBCI/LIPA_Magnetic_Field_Levels_Around_Homes.pdf

If you'll post the brand and model of that gaussmeter i'll read its instruction manual.
I have a small handheld one for DC fields, Earth's magnetic field is about the limit of its resolution.. In the power plant i measured AC fields with a coil of wire and a voltmeter but was dealing with quite a bit stronger ones.

Thanks. No offense was intended.

old jim

 

[jim hardy]

If you do pursue this house here are two articles written by a very practical electrician whose physics is pretty good too.

He describes using a clamp-on ammeter in combination with gaussmeter to flush out wiring errors that cause magnetic fields inside a building.
Basically you clamp around both wires going out to a branch circuit, nonzero indication indicates a problem with that circuit. I used to do that a lot in the power plant so can vouch for the technique.
He also discusses incoming power to the building. But it'd be a hard sell to get a neighbor to fix his service.
I'd suggest you print the articles and discuss them with whoever does your next inspection of the house. It'll require substantial poking around in the electrical panel so warn both the realtor and homeowner.

http://www.mikeholt.com/technical.p...ed/EMIKarl&type=u&title=Power Quality Article
http://www.mikeholt.com/technical.p...mf&type=u&title=Electro Magnetic Fields (EMF)Good luck !

old jim

 

[jim hardy]

Good choice on that gaussmeter. FWBell was making quality equipment in early 1970's when i used some.

I note Mike Holt recommends a triaxial, which yours is.

You didn't say what is your background. Search on Ampere's Law and Right Hand Rule will take you to the magnetic fundamentals.

And thanks for the kind words.

 

[ffran]

Thanks - those links, esp. the first one, is something I was looking for.
It is a little long, will look in more detail later.

I am an MD. I am generally aware of many things outside my field, but electricity and related is one of those things I am completely clueless about.

 

[jim hardy]

I am an MD. I am generally aware of many things outside my field, but electricity and related is one of those things I am completely clueless about.

Well - I'm sure glad you're here.

I hope you find the site interesting and join in often.

 

[dlgoff]

I am an MD. I am generally aware of many things outside my field, but electricity and related is one of those things I am completely clueless about.

Welcome to Physics Forums ffran.

Here's a good site on http://www.emfs.info/Sources%20of%20EMFs and a lot more.