Grounding question

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Daniel Hess by way of Terry Fritz <twftesla-at-qwest-dot-net>" <dhess1-at-us.ibm-dot-com>


I second Jim's comments regarding general household electrical safety but
with coiling, the concerns are magnified by several orders. I've been
reading this list long enough to hear of many horror stories of wall
outlets, wall switches and lamp sockets shorting, arcing. I've read of
washing machine motors, garage door openers burning up, shorting out and so
on from coiling activities. Then there's vulnerable, sensitive electronic
equipment such as PC's, microwave ovens and audio/video gear.

Yet thanks to the information on this list I've never had a coiling related
incident as described above. (knock, knock, knock!) But I've learned to
employ both types of grounding systems which I feel are necessary to safe
coiling. (Safe to me, the operator and/or visitors, safe to the coiling
equipment and safe to the electrical system in the house and all that's
plugged into it.)

The first type of ground is the 'house ground.' In my last shop, my garage,
I had the hot water heater nearby in a closet. I attached a water pipe
clamp to the cold water pipe and from there ran an 8 gauge solid bare
copper wire to the ground buss in the breaker box I'd installed
specifically for powering Tesla projects. This breaker box had 240 run from
the main breaker box where my electrical service entered the house. This
ground was used ONLY for equipment that I, as the operator, would be in
contact with; The variacs, control box/panel, equipment rack and so on. The
house ground is for my protection.

The second ground is the 'RF' ground. (Sometimes referred to as a dedicated
ground.) Basically, I buried a series of 10' lengths of 1/2" copper water
pipe vertically into the ground just outside my garage in the yard. (I read
somewhere that these ground rods should be at least 8-10 feet away from the
house or any other structure.) Then I connected the rods with more 8 gauge
copper, with solder, and from there ran a 4 gauge stranded cable into my
shop. I tested the integrity of the RF ground by connecting an ohm meter
between the house ground and the RF ground. My understanding is that you
want to read less than 1 ohm. (Mine was.) The methods of how to install an
RF ground vary as there are many. The RF ground attaches to the NST case,
(that's the GND terminal you mentioned) the center electrode of the safety
gap and the base of my secondary coil. The idea here is to provide a low
impedance, high current path to ground but keep those nasty, noisy spikes
and RF currents out of the house ground.

BTW, I always unplug my PC, microwave and stereo before a coil run. It's
grief to do so but I justify it by considering how many hours I'd have to
work to earn the cash to replace my PC, microwave, etc. For me there's no
argument.

Daniel

"Tesla list" <tesla-at-pupman-dot-com> on 02/15/2002 06:06:56 PM

To:    tesla-at-pupman-dot-com
cc:
Subject:    Re: *****Grounding question



Original poster: "Jim Lux by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<jimlux-at-earthlink-dot-net>



Tesla list wrote:
>
> Original poster: "by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<dbanse-at-comcast-dot-net>
>
> I have a 15kV60mA NST....
>
> I have an older house where none of the sockets are grounded....(they
were all
> 2 prongers....I just 'put in' three prong outlets....(but no wire to
ground
> with)
>
> I want to test my NST with just the spark gap, and the capacitor.

This is hard on the NST... Why not just run the NST with the gap alone...

>
> What will happen if I just plug it in with no variac or anything else?
> Will I get the shit shocked out of me?

Well.. probably not that bad, but it very well might hurt a lot, and you
might start a fire inside the wall..

The risk is that one of the HV terminals will short to the case or to the
low voltage primary (the short might be a spark breakdown inside the
transformer, and be invisible, and not present when transformer's not on).
Then you've got several bad scenarios:

1) Case at HV
2)  case at HV shorted to power line, putting HV back into the line, where
it will hopefully be shorted to ground by something along the way (loose
screw, corona discharge, the power companies transformer).  Depending on
all the impedances along the way, the voltage might be fairly high (several
hundred volts).. enough to breakdown the feeble insulation designed for
300V (when it was newly installed).  If your house is wired with "knob and
tube"... words fail me...