Have your say on the future of EMF guidelines

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physis

Senior Member
Re: Have your say on the future of EMF guidelines

I was wondering if any research was done to show that fields at 180? really cancel each other out when it comes to effect on a person? If you think about it they are still there just opposite phase angles?
Balanced line. You work with noise. Humbucker pickup (guitar).

I thought you knew that from direct physical experience.
 

karl riley

Senior Member
Re: Have your say on the future of EMF guidelines

Wayne, I do happen to have an instance of human response to canceling fields. I was called in to the residence of a health practitioner who is sensitive to magnetic fields over about 2 mG. She would not use the lights in the bedroom/bathroom since she was disturbed by the effect.

I found high fields, up to 30 mG in those areas. The cause of the fields was that the feed supplying the bathroom light switch box was jumped from the receptacle circuit, but only the hot was used. Why? The original feed's hot had been capped off at the breaker box. I found continuity to ground: probably shorted from a sheet rock nail or whatever. The original electrician had capped it off, but did not also cap off the neutral. Instead he used the hot from the recept circuit but not its neutral.

So he had the hot coming in around the bedroom and the neutral going back directly through the floor down to the entrance. This set up a net current loop creating the high fields.

Now to get to your question about whether balancing the fields still does not remove the effects on humans: the sensitive lady was in the room when we were working on the problem. The electrician switched on one light. She exclaimed, "that's better". The electrician grinned (he was typically skeptical) and said, "I turned it on, not off". He thought he had her. I measured with a gaussmeter and a clamp-on ammeter. His turning the light on actually reduced the field and net current since we were dealing with a 3-wire circuit and there was some balancing.

The physics of balancing of magnetic fields is that they do actually cancel. Just as in the sea with waves from two directions, if a crest and trough coincide you get no wave. Gone.

And just a note on shielding net current fields. No material shields net current fields. Only balanced fields can be shielded.

Karl
 

physis

Senior Member
Re: Have your say on the future of EMF guidelines

That's really interesting that someone could actually physically respond to stray EMF. She could be valuable in the PQ industry.

You can't blame a person for being skeptical. I think it would be foolish to not be at least a little skeptical. How often would a story like that be true? It doesn't mean you can't still be open minded.
 

karl riley

Senior Member
Re: Have your say on the future of EMF guidelines

Not a "story". I don't tell "stories".

But an open mind is all one can ask.

Karl
 

physis

Senior Member
Re: Have your say on the future of EMF guidelines

I didn't mean to imply that you're telling "a story" Karl. I would tend to believe you.

I apologize if it sounds as if I'm questioning you. That wasn't my intent. :(
 

pierre

Senior Member
Re: Have your say on the future of EMF guidelines

Hello Karl, it is good to see you post again - welcome back.
Your post on this subject interest me, is your book current with this kind of information? If not, are you planing on or have you written more info since that books printing?
thanks
Pierre
 

George Stolz

Moderator
Staff member
Location
Windsor, CO NEC: 2017
Occupation
Service Manager
Re: Have your say on the future of EMF guidelines

How large a range does EMF have with standard 2x4 construction in houses, and with a load of, say, 5 amps on a 15 amp circuit?

Trying to get a grasp on this, good to see you, Karl. :)
 

physis

Senior Member
Re: Have your say on the future of EMF guidelines

How large a range does EMF have
In one of the sacred scrolls you've dug up in the past Al Hildenbrand and I spent like 3 days and 4 pages of math to end up concurring with Karl that the field strength is reduced directly with the distance. As opposed to my initial assumption that it's reduced to the square of the distance.

The field will have 1/10 the energy at 10 ft. than it would at 1 ft.

As opposed to my initial assumption that it would have 1/100 the energy.
 

George Stolz

Moderator
Staff member
Location
Windsor, CO NEC: 2017
Occupation
Service Manager
Re: Have your say on the future of EMF guidelines

You're probably right. This is one of those subjects that won't stick in my brain for some reason, so I'll just listen again and try to absorb it. :D

Edit: Oh, yeah, I remember now... :D

[ February 14, 2005, 07:30 AM: Message edited by: georgestolz ]
 

karl riley

Senior Member
Re: Have your say on the future of EMF guidelines

George, if you are talking about 5 amps in a correctly wired circuit, the field basically cancels and so you would have to be sitting on it to get any measurable exposure.

If you are talking about 5 amps net current (like 10A on hot, 5 amps on grounded conductor) then you will have 32.8mG one foot out, or 2.2mG 3 feet out. Or in meters, 10mG one meter out.

About my book, I expect to get it in print by the end of the month. I don't include more than some basic info and sources on the health aspect, since it is basically a trouble-shooting guide for tracing and correcting wiring errors that cause the high fields.

Karl
 

greenlight

New member
Re: Have your say on the future of EMF guidelines

So if i have it right or not? Wiring 3 way switches will be safe if we run a 12/3 or even metal conduit/mc cable with the two travellers and one common (hot) between the two 3 way switches. Then run the switch leg back up to the fixture with the common (or in the case that the power was brought into the switch box first with the neutral)? Please correct me if I am wrong, but is it not necessary to run the neutral between the two 3 way switches as long as the common is there (as long as there is equal current returning)? Simlilarly no net inductive current effect would be generated in a switch leg with the hot coming down from a light to the switch, and the switched leg run back up to the same light even if inside the same conduit or cable sheath. With or without a neutral, there would be no difference in that situation. What am I missing?

Could someone address a similar situation with a bunch of 4 way switches instead? I can see how any net current would balance out between the two end switches (3 ways) by wiring them together by a 12/2 directly. But running a 12/2 between the "4 way" switches cause an inductive field because only one conductor would be carrying current at any given time, so there would be no cancelling effect? Sorry if I have this confused. Any help or clarifications appreciated.

BTW. Karl, your book has been extremely helpful. Tahnkyou. How much different will the new book be? Gosh 10 year anniversary! Congratulations!

Don
 

George Stolz

Moderator
Staff member
Location
Windsor, CO NEC: 2017
Occupation
Service Manager
Re: Have your say on the future of EMF guidelines

Originally posted by greenlight:
Please correct me if I am wrong, but is it not necessary to run the neutral between the two 3 way switches as long as the common is there (as long as there is equal current returning)? ...What am I missing?
Nothing, that's correct. A return "hot" or a neutral will cancel the EMF.

Could someone address a similar situation with a bunch of 4 way switches instead? I can see how any net current would balance out between the two end switches (3 ways) by wiring them together by a 12/2 directly.
No, with two travellers run with 2-wire, there is no return conductor cancelling the EMF.

4-ways are irrelevant to this discussion. If a 4-way is installed in a dead-end or regular threeway system, which use three-wire, that third, cancelling, conductor runs anytwhere the travellers do. 4-ways or not.
 

karl riley

Senior Member
Re: Have your say on the future of EMF guidelines

Sounds right. As long as you have equal and opposite currents, no field.

The new version of the book has more on grounding as well as miscellaneous updates. A big improvement is the 8 1/2 X 11 page size, spiral bound so it lies flat.

Karl
 

brian john

Senior Member
Location
Leesburg, VA
Re: Have your say on the future of EMF guidelines

I have been involved with numerous EMF investigations, where PQ was the issue (I avoid investigations where health is a concern for legal reasons), Almost all the investigations were related to wiring errors. Too long a screw cuts into a neutral (grounded conductor) in a metal box grounding the neutral, nicked neutral in a fitting grounding the neutral, neutral termination block grounded in a sub panel.

In all cases the problem could have been avoided very easily, with a simple continuity test or better yet meggering the conductors to ground prior to final connection. Instead the management companies had to pick up the bill of two men on straight time looking for obvious neutral ground wiring errors and then 10 men 12 hours each on double time isolating feeders and branch circuit locating the source of the downstream neutral grounds.

Any standards/codes that would make electricians think about what they are doing and perform a better quality installation would be a plus. And IMO would minimize EMFs. Training and understanding are necessary.

Proper testing methods during installation can avoid many EMF issues and for that matter many electical faults, thermal issues..ect.

[ April 15, 2005, 04:15 PM: Message edited by: brian john ]
 

karl riley

Senior Member
Re: Have your say on the future of EMF guidelines

Txt2: This website carries the book.

Brian, that's way too much time to locate the errors. I don't want to seem to be plugging my book, but it might cut their time way down. 120 man hours!

Brian, why would a client's health concern scare you when you are just looking to correct some wiring errors? I've never had a legal problem no matter what my client's concern.

Karl
 

tx2step

Senior Member
Re: Have your say on the future of EMF guidelines

Karl -- I finally found your book listed under the 2005 NEC books on this site. It was hard to find.

I'll buy a copy! I look forward to reading it!

Thanks!
 
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