Job Specs -- Gaussmeter - Ever Seen This?

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DSamson

DSamson

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San Francisco, CA
I'm bidding a job, walk through tomorrow. Remodel of a single family residence. The following text is in the specifications. Has anyone ever seen this? Anyone know what a gaussmeter costs? Apparently the residents of the home have some kind of chemical hypersensitivity. This is labeled as a "healthy home" project.

"At the time of the final electrical closeout, and in the presence of the
general contractor, Architect or Owners, the electrician shall apply a
minimum load of 3 amps to the distal end of each electrical circuit. The
home shall be inspected under load using a gaussmeter. Any elevated
magnetic fields greater than .5 milligauss will indicate the presence of net
current."

Also in the specs, no MWBC, no fluorescent fixtures (tough with Title 24, possible), no petrochemical lubricants.

Would appreciate anyone's insight on the above quoted language.

Thanks
 
Have fun with the 3-way switch's, they have a net current on the ''travelers''.
It will not pass title 24 with the kitchen lighting , like you said.
and don't forget to mention that unless they use a special smoke detector it has a small amount of radioactive material in it.
Bid high jobs like this can be profitable, I am on the peninsula south of you , these people are going to be picky and crazy !!!
 
I had to look up the word “distal” in my dictionary; I thought it might have been a typographical error either in this post or in the specs. The word exists, and is defined as, “situated away from the point of origin or attachment; terminal.” So they mean attach a device at the far end of each circuit, such that the circuit sees a 3 amp load.

Three things strike me as “funny,” meaning that I am laughing at the engineer who approved that specification, but perhaps “tragic” is a better word. First, they don’t require you to measure the magnetic field before turning on your 3 amp load, in an effort to establish the background field. But then, the background can vary from second to second anyway, so it would be hard to establish the amount of the field that is due to background, and not due to your load current. Secondly, they say what a particular value of magnetic field will indicate, but they don’t say that it would be a bad thing, and they don’t require you to take any corrective action to bring the value of field down to a lower value. The essential error in the spec is that they did not establish an acceptance criterion. You can measure a value of 0.6, and they say "so what"? The test is of no value if it does not give an acceptance criterion and establish requirements for corrective actions. Finally, I can conceive of no meaning to the phrase “net current.” All current leaving the source will make its way back to the source. If it is not following the “normal path,” meaning for example the hot and neutral wires, and instead finds its way back to the source via the conduit (owing to a fault internal to a receptacle or other device), then the “net current” is still zero. I do not know what they are trying to prevent, or what bad thing they are trying to detect.
 
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Just out of curiosity, would the magnectic field being measured be reduced with use of a type mc or ac cable?
Rick
 
RUWired said:
Just out of curiosity, would the magnectic field being measured be reduced with use of a type mc or ac cable?
Click to expand...
Yes, but the difference is likely to be too small to measure. The closer the wires (from any given circuit) are to each other, the more nearly completely will they cancel out each other's magnetic fields.
 
A magnetic field will exist anytime there is energy being used. .2 milligauss? from what distance--- turn on a microwave and put a gaussmeter right next to it and it may open your eyes to the amout of EMF's coming from there.

There are certain technics in wiring that will cause EMF's yet they are not a violation.

Here are three common situations that will cause emf's. If the grounded and grounding conductor are touching after the load then you will get emf's.

The grounded conductors from 2 circuits are spliced all together in, say, a 2 gang switch box. Thus if 2 way switches are fed from different circuits and you tie all the grounded conductors together you will get high emf's.

The last is if the grounded conductor is run separate from the hot wire. This can happen if you have a common feed in a multigang switch box in 2 locations and you run a 2 wire traveller for the 3 way. If you feed the switch on one end and grab the neutral at the other end you will have emf's.

I would certainly ask the engineer what he is trying to do.

You can get a gaussmeter for $100 and up.
 
charlie, the net current is from circuits where the whole hot and whole neutral currents do not follow the same path- I have this in my home where the neutral is actually in a different wall from the hot for some circuits. (old K&T, to be replaced...sometime). I don't think their issue is fault current. I gotta believe the spec has a "what if" in there somewhere if it is above .5 milligauss.

I don't understand why the prohibition on MWBC's from a mag. field standpoint- as long as both hots and the neutral are routed together, and then the neutral continued with each separate hot, I don't see a net current.

Isn't .5 milligauss kinda low? There was a guy here who actually wrote a book on this, I'll see if I can find the thread.
 
You could find a place to rent a gaussmeter. NIST may know of someplace.

Or you could build one, but I don't know how you'd calibrate it.

Twisting two wires together cancels out the field to some extent.
BX may also work or Romex placed on a steel plate (a ground plane) should also weaken the field, but both may increase the capacitance per foot and so trip GFIs.

These people don't need a house, they need a large test tube. Is the husband an actuary?
 
acrwc10 said:
Have fun with the 3-way switch's, they have a net current on the ''travelers''.
Click to expand...

This is not the case as long as the travelers are not run alone.

If the travelers are run along with a neutral, hot conductor, or a switch leg in the same cable the net current and / or EMF will be canceled.

Roger
 
langjahr@comcast.net said:
You could find a place to rent a gaussmeter. NIST may know of someplace.

Or you could build one, but I don't know how you'd calibrate it.

Twisting two wires together cancels out the field to some extent.
BX may also work or Romex placed on a steel plate (a ground plane) should also weaken the field, but both may increase the capacitance per foot and so trip GFIs.

These people don't need a house, they need a large test tube. Is the husband an actuary?
Click to expand...
Had to look: An actuary is a business professional who deals with the financial impact of risk and uncertainty
 
It sounds to me like the prospective customer has an issue and spent some time on the internet reading about Net Current and other Current issues....there is a ton of info, some good and some really bad.

The person who specified this is not an expert and what we have seen of his/her specifications shows that.



Before signing any paperwork, I would have some of the issues cleared up and rewritten.


I live in a fairly upscale area - which means people have discretionary time (and money as well), which puts them in front of the internet. We actually come across homeowners who have purchased Gauss meters and then complain about the EC's work.
Another hassle for the industry - people who have 1/2 the info and become "dangerous"
 
You can get Gauss meters fairly cheap and if they do not spec a meter get a cheap one, you may never need a gauss meter again. Do they spec where the measurements are to be taken. You could be .5 at the panel or at on a cable. There are easier ways.

AND WHAT HAPPENS IF YOU EXCEED .5

BETTER MEASURE PRIOR TO BUILDING AND DURING CONSTRUCTION.

And as Pierre said NOT EXPERTS this customer could end up being a PIA...

http://www.carlsenmelton.com/gm200a/gm200a_is.htm?gclid=CL-O3Zr0hZICFQEaHgod6XNQ3Q

http://www.lessemf.com/gauss.html
 
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Back to the OP, I would leave this project to someone else, like some others have said, this will be a pain from the get go and you will probably never satisfy the requirements.

Roger
 
and if a ghost walks through while you're testing your meter will spike and give you a false reading.:grin:

Come on, I figured that George would have thought of that. :)
 
actuary

actuary

I'd think he is worried about his own health risks, and probably knows all of them, from all sources, to three decimal places.

Speaking of actuaries, from a current mortality table I was able to get, I saw that nobody dies at 16 from smoking (probably they haven't smoked long enough) and nobody dies at 90 from smoking (probably they would have died sooner if this is what was going to kill them).

I live 1500 feet northeast of an AM radio tower. Fortunately we are in an area where the field is intentionally weakened to avoid interfering with some station in Rhode Island. But if I had young children I would have moved.
I also would have moved if this were a TV tower; the length of the human body is comparable to a wavelength at some TV frequencies so it is a good antenna for these freqs.
 
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