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Re: Down to earth, off subject but safety consideration

Original poster: "Barton B. Anderson" <bartb@xxxxxxxxxxxxxxxx>

Hi Jim,
You probably read my reply to Peter so I won't bore you with the same. You described exactly the problem with not having a "real" ground. The ground is there to protect. If you lose ground, all bets are off regardless if it's netrual-ground or separate ground.
A friend I know was nearly electrocuted by his refrigerator. This is 30 years ago. The hot shorted to the fridge case (there was no ground and the case was not connected to neutral). His dad sent him in the house to get him a beer (life was different then, don't judge to harshly). Because the hot wire broke causing a "live" housing, the freezer was thawing out. This caused a pool of water next to the fridge. The water served as ground. He got a good long shock before he somehow broke loose. He was very lucky to live but was cooked a bit. He's barely 40 now and starting to have heart troubles (very fit guy).
If his fridge case had been connected to the neutral, then a fuse would have prevented this shock. (This is not the same neutral wiring which is code today). It would have taken 2 wire breaks to cause the unsafe situation.
Because of "these type" of situations, we now have GFI requirements in areas that are prone to wet conditions (pool, bathrooms, kitchen, laundry, etc..). GFI's are a very good thing.
Rewiring is a cost issue, and depending on the construction, can be pretty high. Not that to put a price on safety, of course not, but there is still the issue of what someone can and cannot afford to do. Your right in that a separate ground with GFI's is certainly the best situation with what we have available today.
But with the original question, my point is that there are different wiring configurations we deal with, and it is those configurations that will help determine a safe approach. Of course, rewiring the house would be ideal. Some cars are safer than others, but some can't afford those really safe cars and settle for second best. And in all these situations, car or electricity, safety is never guaranteed even with the best of all worlds. 

Take care,
Bart




Tesla list wrote:


Original poster: "Jim Mora" <jmora@xxxxxxxxxxx>

Hi Bart,

I'm not an electrician (but I am slowly updating my electrical), but let's
consider a modern washing machine for a moment. The neutral may not be tided
to any place for ground as the manufacture assumes a grounded GFI receptacle
and provides a plug according. Now suppose something really bad happens to
said washer like hot gets shorted to the case of the washer. There is no GFI
and no ground to blow a breaker. Furthermore, let's assume there is a metal
drain sink to drain the washer loads. I would not want to place my left hand
on the sink and open the washer door.

Bit by <300v and more:-( almost everyway but this one which could prove
fatal if not damaging to the heart.

I have plaster walls circa 1953. I can remove the 1x4" plaster base board
and run Romex(code in California) in the opening without making too big of a
mess. All our appliances and computers are on dedicated lines. I made my
wimpy service entrance into a sub panel (neutral is NOT bonded to ground
here, ground returns...audio will haunt you) and mounted a 100 amp service
outside (neutral is bonded to ground here by code) and mine is heavy duty!

If your state requires conduit then tearing out the plaster or plaster board
is how most re-habers do it. Three wire for safety! Conduit is good in
schools and industrial buildings, but home owners ought to be able to
reasonably upgrade their electrical! Especially Coilers :-)

Jim Mora

-----Original Message-----
From: Tesla list [mailto:tesla@xxxxxxxxxx]
Sent: Thursday, November 02, 2006 8:11 PM
To: tesla@xxxxxxxxxx
Subject: Re: Down to earth

Original poster: "Barton B. Anderson" <bartb@xxxxxxxxxxxxxxxx>

Hi Matt,

Your right, there are different configurations. What is preferred
depends on the coiler and the situation. For starters, some houses
(built in the 60's such as my own) do not have a mains line ground.
The 120V receptacles have only 2 prongs. The ground prong is
non-existent. I traced my neutral back to the breaker box and beyond.
Neutral is actually connected to the ground rod stake next to my fire
place about 3 feet from my breaker box. Because I've needed to plug
in my modern electronics (TV, fridge, etc..) into these outdated
outlets, I replaced the 2 prong receptacles with standard 3 prong
outlets. In the process, I tied the ground receptacle to the neutral
in order to ensure that the grounding is tied to ground (since my
neutral is tied to ground).

Ok, so now, Tesla Coils. What to do, what to do. Well, what type of
coil would I be running?

1) Pig powered coil. 240VAC with "ground" at neutral on my house. OK,
realize that Tesla Coil strikes cause transient voltages that over
volt most everything that might come in contact with it. In this
case, I felt it was "best" to run RF ground to my secondary bottom
winding, primary inner winding, and no where else. Mains ground, the
pig case, gets mains ground, as well as the power cabinet which
includes the PLC, PS, Filter, Variacs, Contactors, etc. This case
minimizes the transients felt at my TV, Microwave, PC, etc...

2) NST powered coil. 120VAC with "ground" at neutral. Hmmm, well, in
my case, to minimize transients to all my house components, it made
sense to tie everything near the coil to RF ground. This includes my
NST and Terry Filter. Thus, the only "mains ground" is at the variac
where I adjust voltage. Yes, my NST case is RF grounded, not mains
grounded. There are only 2 wires running out to the NST for Neutral
and Line voltage. This is the best configuration to minimize
transients back to the house for my particular situation.

Thus, I am a firm believer that "you" need to analyze your particular
house electrical situation, and then design your Tesla Coil
electrical accordingly to minimize transients back into your house wiring.

I have one of the worst cases to deal with. So, I look at it from a
safety stand point. And thus, the components that I'm physically
adjusting, I ensure mains ground is attached to those components I
come in contact with. But, for the rest of my components which I
don't have contact with, I revert the transients to the RF ground I
have set up for coiling.

For others who have a dedicated mains ground, there are more
opportunities to ensure safety and transient elimination to the house
components. My point here is that it is important to first determine
your particular situation and then if unsure, ask what is best in
that situation.

Take care,
Bart


Tesla list wrote:

>Original poster: Matt Gillott <mcg@xxxxxxxxxxxxx>
>
>Hi all
>Question about earthing.
>Ive seen a lot of different designes on the net for earthing
>configurations mainly the three as follows though:
>1. RF ground to the bottom of the secondary only.  Mains/line earth
>to all the other earthing points in the circuit (transformer casings etc).
>2. RF ground to all the earths, both bottom of the secondary and any
>other earthing points.  Mains/line earth connected to nothing
>3. RF ground connected to mains/line earth and all earths on the circuit.
>
> From reading I hear that the 3rd configuration is rather dangerous,
> whats the genreral oppinion about using mains/line earths and whats
> the prefered configuration?