Voltage Leak

Bkessler

I worked at a school today where a teacher had been complaining that the emf emissions where to high and even had it down to two panels one classroom over! So I was told you could measure it buy putting all three hots and the nuetral in an amp probe and you would get a high reading. So I did that to all the branch circuits in a 2000 amp switchgear. Ten I think. They all read close to 0 mostley around .2 amps ........except 2 of them which were around 2.2 to 2.8 AND it was even the two panels the teacher had said. So I opened them up and megged out the feeders, they were ok then as I was going to do the nuetral i realized it was landed on the ground bar and then went to the nuetral bar. Probably cause it was cut to short. So I extended it with a splitbolt and taped it up. Now I tested it again and with all four wires in the feeder under my amp meter it was back down to .1 amps. So I had never even heard of this until friday afternoon, is the problam fixed and what some other people experiences with this problam?.........go wings!

CE1

You solved at least part of the problem with high EMF. What you need to do is go look for some more. More high magnetic field environments are created by electrical and grounding system problems than by power lines. This is true in both commercial and residential settings. In commercial buildings, the problem usually results from unbalanced feeders and branch circuits. In residential buildings, both single family homes and apartments, the most common problem is neutral current flow on metallic plumbing and grounding systems. Improper electrical wiring configurations are a frequent problem in all building types.

Carry on Dude, your hot on the trail of the problem.

Bkessler

How is emf measured? And besides severly unbalanced load what are some other mistakes electricians make that cause high emf? thanks bk....................go wings

ABLE1

Not to put this discussion into a different spin but, my first questions would be what tipped off the teacher and/or how did he know where it was??? Was he/she using some instruments, glow worms, the hair on the arm trick or just dousing rods???

Thanks ........................ just courious.

CE1

That was my thought too, but I just answered the question because he did find the cause of the problem and fixed it. Some people can feel EMF and it does effect electronic equipment in weird ways. There is a lot of discussion on the subject of health related problems related to electromagnetic emissions. Some experts say no and other experts say yes that there is a health problem associated with EMF. Our job is try to minimize it and let somebody else worry about the other issues.

Remember to use good wire practices and that “Someone has been there before you and he might not of done it right”.

Here is a link to a meter to measure EMF/ELF:

http://www.wallcoinc.com/Extech_4808...al3-480823.htm

Carry On

Safety-Guy

What was the ARC rating on the 2000A switchgear?

Bkessler

KNow one knows how the teacher knew, But he is a computer teacher. and sorry I do not know the arc rating on the switch gear. But it was a brand new retrofit.

Atricaudatus

I ran into a similar problem many years ago at a doctor's office.

Anytime the the overhead florescent lights were turned on, there was a weird horizontal line of static that ran across the recently installed computer CRT monitors and slowly scrolled from bottom to top. The circuits were ran in type AC cable and the computers were on dedicated circuits with an isolated ground that ran all the way back to the main panel.

We re-ran new circuits for the lighting, still no luck. Isolated the ground of the lighting, no luck. Eventually took the the grounds for the computers all the way back to the grounding electrode, which helped some but didn't fully solve the problem. Finally drove a totally separate rod for the puters, but that didn't completely eliminate it either.
Eventually the Doc choose to replace the florescents with incandesent lighting and the problem went away.

Never did figure out exactly what the cause of it was though, and felt pretty inept. But that was before I discovered Contrator Talk and all the really smart guys here that I could ask.

__________________
-Rhett
Licensed electrician and plumber