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Re: [Phys-l] home wiring catastrophe



I've reported on the ground loop from a control room's audio board at King City *. I thought of three solutions: a separate ground wire running from the room many yards from the stage to the stage's microphones, etc.; grounding the board w/ a wire out the window and down below (about three stories) t a ground rod, and what we did, use a ground defeat plug w/ the understanding I wouldn't be sued if someone was shocked. the ground defeat has a lug intended to be screwed down by the cover plate's screw (the not a defeat). I got a call back a year later for the hum. found the lug was touching th screw. I completed the by ripping out the lug. they wanted to pay me but I explained I hadn't done the job -- still accepted the wine from the friend auditorium board member, who also runs the wines at the county fair. (Very good wine.)


* A WPA project doubles as the HS's auditorium and the community's. Seating capacity still larger than the number of HS's students. When originally built, would seat all the citizen's of King city!

Also includes a GFI post.


https://carnot.physics.buffalo.edu/archives/2005/11_2005/msg00029.html

bc, thinks many questions are answered by previous posts found by googling.

John Clement wrote:

I stayed in a house in Mexico for a month and experienced shocks from
touching the faucets in my bathroom. It seems that Mexico does not have
uniform grounding standards, and the problem was attributed to that. The
electrician came in and, as I recall, just reversed the hot and neutral
lines to fix the problem.


I've lazily done that trick also.

One thing that comes to mind is that since the neutral is supposed to be
grounded at the box, the removal of the neutral line should have been
partially alleviated by the ground connection. If the homes only had one
phase of the line coming in, the problem might have not been so severe. The
two phases and the use of a common neutral is a big difficulty when the
neutral return is removed. However, the two phases also save money because
the neutral return will on average have lower current, and transmission
losses will be reduced. So an ungrounded system would probably not have
prevented the problem, and would create other problems as JD has already
pointed out.

A minor problem caused by grounded systems is the prevalence of ground
currents which can set up ground loops. We had an experiment where the
detector was in a shack 250m away from the target. We install superb coax
cables to get the signal back with minimal deterioration. However, its
resistance was so low that we had a huge hum signal the same size as the
digital pulse. The new signal lines acted as the AC neutral. So we had to
put in a length of coax wrapped around a toroidal hunk of iron. It knocked
the hum down to manageable levels. I live near power lines and the iron
water pipes tended to carry current with measurable low frequency radiation.
But when a driven ground was installed, and pipes disconnected from the
ground some of this was fixed. An ungrounded system might have untraceable
ground loops, and might be less manageable.

Does anyone know what the European codes mandate?

John M. Clement
Houston, TX


I mentioned that the plugs [and, therefore, the outlets (sockets)] in England have three prongs -- probably more important in that they use ~ 220 V. -- in a very recent post.



Why does the USA use a grounded system in the first place? If we used
a
non-grounded system we would not have any of these problems, AND we would
not need GFI's. Thousands of lives could be saved. The entire system
would
act as if it was on an isolation transformer. Comments anyone?




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