RE: Ground - where should it stop?

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

Original poster: "G by way of Terry Fritz <twftesla-at-uswest-dot-net>" <nieporgo-at-email.uc.edu>

When I built my first coil, I tested the potential between my NST 
cases and mains ground, and it was almost 0. So, I leave them 
floating. I see no good reason to require the ground on the cases and 
my blower motor, because I never work on the equipment energized. It 
seems to me that the NST is going to have one less reason to arc to 
case if it isn't grounded. The only failure mode I see remaining is 
an NST secondary-to-primary strike, and case ground will have no 
influence on this either. While grounding will help throttle HV 
strikes from the TC secondary, my primary circuit goodies are out of 
range, so I am not concerned.


>Original poster: "Lau, Gary by way of Terry Fritz 
><twftesla-at-uswest-dot-net>" <Gary.Lau-at-compaq-dot-com>
>
>You ask a very good question, and I'm not sure there is a consensus.
>
>Most of the circuits I've seen, including my own coil, have the mains
>ground going only as far as the variac case.  The NST case is connected
>to the RF ground, as is the middle electrode of the safety gap and
>bypass caps, and secondary base. 
>
>In a thread a couple of months ago, Malcolm Watts mentioned that he
>connects his NST case to the mains ground, and for a good reason.  No RF
>ground is perfect.  There will be some very high voltage noise present
>between the RF ground and the mains ground.  If your NST case is at RF
>ground and your NST primary is ar mains ground (ons side is neutral,
>same as ground), then this high voltage noise will be trying to break
>down your NST primary-to-core insulation.  I can't say though that I've
>ever heard of this taking out an NST.  I'm not sure how such a failure
>would manifest itself. 
>
>If the NST case is connected to the RF ground, then it's very important
>to use an EMI filter between the NST primary and variac.  I added a page
>to my web site explaining the importance of hooking up an EMI filter in
>the correct direction.  See
>http://people.ne.mediaone-dot-net/lau/tesla/emifilter.htm
>
>One problem with a mains-grounded NST case is that should a streamer
>strike the primary circuit, it would be directly coupled to the mains
>ground.  Malcolm pointed out that he's taken precautions to prevent
>primary strikes.
>
>I'm not sure the issue is settled.
>
>Gary Lau
>MA, USA
>
>
>Original poster: "Matt S. by way of Terry Fritz <twftesla-at-uswest-dot-net>"
><matt777777-at-hotmail-dot-com>
>
>I have another question that I was hoping for some help with... (thanks
>to
>all who responded to my lest one).
>I have seen conflicting (to me) information on where to stop the house
>ground.
>I am planning on running it (the house ground) up to my
>variac/controller
>cabinet, and then I am unsure of whether to run it through the
>(relatively
>long) cord to my NST(s) or not.  I will be grounding my secondary and
>the
>center of my safety gap (and strike rail) to a (separate) RF ground
>(buried
>Cu pipes)
>---------so, my question is.... should the house ground be run to the
>NST
>ground terminal on the input side or should it stop at the controller
>cab.
>with the RF ground hooked up to the NST ground terminal?
>(I am hoping to have my NSTs right under the primary  - i.e. in harm's
>way
>sort of).
>Thanks in advance - I have no doubt that this has been asked before, but
>
>there are so many occurances of "ground" in the archives, it could take
>days
>to find..(!)
>Matt

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