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Re: Steel structure - appropriate ground?

Subject:   Re: Steel structure - appropriate ground?
  Date:   Fri, 2 May 1997 06:24:57 +0000
  From:   "John H. Couture" <couturejh-at-worldnet.att-dot-net>
    To:   Tesla List <tesla-at-pupman-dot-com>


At 04:47 AM 5/1/97 +0000, you wrote:
>Subject:       Re: Steel structure - appropriate ground?
>       Date:   Wed, 30 Apr 1997 13:48:05 -0600
>       From:   Phillip Jarvis <jarvisp-at-bee.d93.k12.id.us>
>Organization:  Hillcrest High School
>         To:   Tesla List <tesla-at-pupman-dot-com>
> References: 
>            1
>
>
>Tesla List wrote:
>> 
>> Subject:  Steel structure - appropriate ground?
>>   Date:   Sat, 26 Apr 1997 16:25:35 -0400 (EDT)
>>   From:   ADatesman-at-aol-dot-com
>>     To:   tesla-at-pupman-dot-com
>> 
>> My Tesla coil is set up in a school building which has the steel girder
>> frame
>> very typical of institutional buildings.  Instead of sinking copper
>> pipes
>> into the ground, couldn't I just attach my ground wire to these steel
>> girders?  It seems the same idea to me, but possibly there is some
>> aspect of
>> this idea I don't see.  I don't want to blow up any computers in the
>> building, for instance.
>>     Thanks for the wisdom.
>> 
>>             Aaron Datesman
>
>
>Aaron,
>
>The girders may not be at ground potential - or at the same potential as
>the power company ground. There can be a significant voltage difference
>between the two. 
>
>Phil Jarvis
>
>-----------------------------------------------------

 AAron -

 The electrical service feeding the building must be connected to the
buildung steel to meet the requirements of the National Electrical Code
(NEC). There are many other NEC grounding conditions. The NEC
requirements
are the responsibility of the city wiring inspectors and the state fire
marshall, etc. The Electric Utility Company is not involved in enforcing
these codes.

 Connecting Tesla coils to the utility electrical system of any private
or
public building etc. could be considered a violation of the NEC. Do you
know
why? (Try UL). Also, if a fire or other damage is caused by a Tesla coil
the
insurance company may refuse the claim because their coverage is
normally
only for electrical systems that meet  NEC requirements. There are many
other problems of operating a Tesla coil including liability claims.

 As the above situation has not deterred coilers from operating their
coils
it is obvious that a coiler must be extremely careful when firing up a
Tesla
coil. Building and operating a small TC is a great learning experience
and
is no more dangerous than the average electrical appliance. But a coiler
should not operate a large TC unless he has a proper knowledge of
electricity and understands Tesla coils well enough to operate them
safely.
For his own welfare he should also be familiar with the NEC as these
codes
involve personal safety.

 The building steel can be used for a TC ground for systems under about
one
KW. However, it would probably be better to just use the electrical
system
ground provided it meets the NEC requirements. Larger systems should
have
both a building ground and a driven ground of several rods depending on
the
size of the TC. However, this should be checked by an electrician to
prevent
unwanted circulating ground currents. Filters should also be used for
the
hot leads. Large TC's can cause fire and liability problems in public
buildings. With a private residence a large coil outdoors can start
grass
fires, etc. etc.

 In spite of the fact that Tesla coils can be lethal I have heard of
only
one documented death caused by a Tesla coil. Let's keep it that way.

 John Couture REE