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RE: [TCML] Main ground vs RF ground

And I've driven a car without a seat belt and suffered no ill effects, but that doesn't make it a good idea.

The hazard I was referring to wasn't the HV transients, but the possibility that there could be a hot-to-case short within the NST or thru some external wiring error, and if one grounded the NST case to RF ground rather than mains-ground, it may not trip the breaker, leaving the case (and everything else connected to it) a shock hazard.  Since we cannot provide both an independent RF ground connection to keep the RF out of our mains-wiring, and a fault-current path to mains ground without contaminating that with RF, a happy medium is that if we just don't touch the NST case going to RF ground - all is well.

OK, it may be possible to provide a fault-current path to mains-ground and keep it RF-free through the use of an isolation choke, but since no one really knows the parameters of what it is we're trying to keep out, it's just simpler to just say DON'T TOUCH IT!

Regards, Gary Lau
MA, USA

> -----Original Message-----
> From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On
> Behalf Of Dex Dexter
> Sent: Friday, November 20, 2009 1:12 PM
> To: Tesla Coil Mailing List
> Subject: RE: [TCML] Main ground vs RF ground
> 
> I have touched the case of my 5kV@20mA NST many times
> during Tesla coil operation.It doesn't hurt at all.
> My NST case is mains-grounded,and Tesla coil is grounded
> to water pipe in my house :-)
> 
> Dex
> 
> 
> --- Gary.Lau@xxxxxx wrote:
> 
> From: "Lau, Gary" <Gary.Lau@xxxxxx>
> To: Tesla Coil Mailing List <tesla@xxxxxxxxxx>
> Subject: RE: [TCML] Main ground vs RF ground
> Date: Thu, 19 Nov 2009 18:39:07 +0000
> 
> The only place for using the mains-ground is for objects that one is likely to touch
> while energized.  The purpose is in the event that there is a short between the HOT
> line and the thing that one might touch - to provide a path to ground so that the fault
> current trips the breaker or fuse and neutralizes the threat.
> 
> In a Tesla coil, there should be no objects beyond the variac case or control
> cabinet, that one might touch.  Only the variac case and control cabinet should go
> to mains ground, and the NST case must not be connected to that.  The NST case
> should be considered off-limits to touching (it will hurt the whole time...).  Unlike in a
> neon sign application in a pizza shop where a customer could reasonably make
> contact with the NST case, we and those under our supervision, should NEVER
> touch the NST case or any other part of a Tesla coil.  It is dangerous by nature and
> will never be UL-approved!
> 
> Using both an RF and mains ground for things that are RF-hot (NST case), is not
> conservative, it's just wrong and serves no purpose as far as minimizing RF
> interference.  One could argue that it may make the coil safer should there be a
> fault, but doing so destroys your effort to reduce EMI.  The Terry filter schematic is
> 100% correct.
> 
> Regards, Gary Lau
> MA, USA
> 
> > -----Original Message-----
> > From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On
> > Behalf Of chuck
> > Sent: Thursday, November 19, 2009 11:47 AM
> > To: 'Tesla Coil Mailing List'
> > Subject: RE: [TCML] Main ground vs RF ground
> >
> > "But since you are asking about NST's and the Terry filter,
> > if you are running a single low powered NST with a Terry Filter, you may
> > not have too many issues to be concerned about, but if you are running
> > multiple NST's, I would consider a separate RF ground to be safe... "
> >
> > Would I be correct to infer that using separate RF and mains grounds would
> > the more conservative way to go? That is, while I run a low risk using a
> > common ground with one or more NSTs, that risk is reduced if I use two
> > grounds: a mains ground and an RF ground? If so, I need to alter my Terry
> > Filter.
> >
> > Shouldn't somebody issue a pen and ink change to the Terry Filter schematic?
> >
> >
> >
> >
> >
> > -----Original Message-----
> > From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On
> > Behalf
> > Of BunnyKiller
> > Sent: Thursday, November 19, 2009 12:17 AM
> > To: Tesla Coil Mailing List
> > Subject: Re: [TCML] Main ground vs RF ground
> >
> >
> > Hey Chuck...
> >
> > In the majority of instances, the RF ( or secondary base wire) should
> > have its own "RF" ground rod. Hooking the secondary base to the "house"
> > ground can lead to problems with items that contain circuitry boards...
> > and thats about everything as far as appliances go... computers, ovens,
> > stoves, refridgerators, garage door openers,  touch lamps ( the kind you
> > touch to turn on) will eventually fall prey to the wrong grounding
> > techniques. But since you are asking about NST's and the Terry filter,
> > if you are running a single low powered NST with a Terry Filter, you may
> > not have too many issues to be concerned about, but if you are running
> > multiple NST's, I would consider a separate RF ground to be safe...
> > Replacing the stoves controller board isnt cheap... ask me how I know
> > about that one ;)
> >
> > There are some instances in which the NST is wired with the case ground
> > on the center tap of the unit... IIRC grounding the case and secondary
> > becomes "weird"...
> > not too sure about this situation....  see if someone else has that answer.
> >
> > Scot D
> >
> >
> > chuck wrote:
> >
> > >Some coilers say that the NST may be grounded to the mains ground and
> > >that the secondary of the TC should be grounded to RF ground and
> > >emphatically declare that the two should never meet. Others say ground
> > >is ground and it doesn't matter where the unit is grounded as long as
> > >it is grounded. The famous schematic of the Terry Filters shows the NST
> > >and the TC sharing a common ground.
> > >
> > >So which is it? Should the Terry Filter schematic be altered? Or not? I
> > >hope for first lights by Thanksgiving so I need an answer ASAP.
> > >
> > >asimov13647@xxxxxxxxxxxx
> > >Stuck in the (now infamous)
> > >23rd NY Congressional district
> > >
> > >_______________________________________________
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> > >
> > >
> > >
> >
> >
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