[TowerTalk] Fwd: Grounding of tower

[Jim Lux]

On 5/9/13 10:05 PM, Grant Saviers wrote:
> Brazing works to steel as well as Cu,  with the use of flux on the
> steel.  On Cu, Ag/ P (Harris Stay-Silv 15) containing brazing alloys are
> self fluxing and are pretty much the standard for HVAC and refrigeration
> piping.  Georgia Copper sells it specifically for ground system
> brazing.  http://www.gacopper.com/BrazingRod.html
> Cadweld probably gets the nod for few-off rods and for many joints or no
> Cadweld form,  brazing.
>
> Silicon Bronze can be used for steel to Cu MIG welding.
>
> Interesting link re corrosion of Cu underground and how to protect it.
> http://www.copper.org/resources/properties/protection/underground.html
>
> Grant KZ1W
>



 From a NEC standpoint, brazing is allowed only in the case where you 
are using piping or structural materials as the "grounding electrode 
conductor" (GEC).  The NEC requires that the run from the "grounding 
electrode" to the service entrance neutral be "uninterrupted", and 
brazing is an acceptable way to "splice" the wires, for instance.

It's not allowed for the actual connection to the "grounding electrode": 
listed compression clamp or exothermic welds are all that are allowed.

Interestingly, conventional welding, brazing, etc. is allowed when 
connecting a AWG4 or larger wire to structural steel in a concrete 
foundation (e.g. as part of a concrete encased grounding electrode).


For antennas and RF counterpoises, radial farms, etc. you can use 
whatever connection means works for your application.  There's no "life 
safety" aspect to it.  So if you're driving 30 rods as part of your 
antenna farm, brazing is fine, as long as at least a couple of the rods 
have exothermic welds or listed clamps (assuming you need a ground for 
code compliance).


If you're putting up an antenna next to your house with no concrete pad 
(e.g. it's just sitting on the dirt, or maybe you're burying a section 
in dirt as a base, then you have a bit of a grounding problem, at least 
from a NEC safety standpoint.  Article 800 says that antennas need to 
have a conductor bonding them to the building's ground system, so you're 
going to be running a wire there anyway.

WOuld that be a good lightning ground?  probably not, but that's not 
what NEC cares about.. what they are worried about is a power line 
hitting your antenna, or more likely, your antenna hitting a power line 
(a few people die every year from this.. many fewer these days since 
cable TV has become popular.. not so many folks putting up a big LPDA on 
a 50 foot pushup mast on their roof with funky guy wires)