[TowerTalk] WHOLE HOUSE SURGE/LIGHTNING PROTECTION -resp. DAVIS RF Co.

[jimlux]

On 1/4/11 8:45 AM, Stephen Davis wrote:

> I get calls for quotes to replace wire, cable, SPOE's, insufficient
> protectors, etc  etc  and I find that often when a single point
> ground was used, close to the station, what was missing was the
> return from that back to the entrance panel ground.  This is such a
> simple undertaking....usually a # 6 or # 4 THHN (check your code),


The size rules are in Art 250.66.  It basically depends on the size of 
the power feeder... bigger feeder needs bigger grounding conductor, 
since the idea is to deal with a fault.

If the service is AWG2 copper or 1/0 Aluminum, then you need #8 copper 
for the ground bond.  If the service is 1 or 1/0 copper or 2/0 or 3/0 
aluminum, you need AWG #6, etc.

In general, as far as mounting it goes, if it's #6, it has to be 
attached to the side of the building and protected.  If it's smaller 
than #6, it has to be in conduit (which can be plastic.. the mechanical 
protection is what the code is looking for).  If it's away from the 
building, it has to be #4 AND protected "where exposed to damage".

One thing to not overlook is that the bonding wire has to be one 
continuous length.  No cobbling together 20 pieces 5 feet long that you 
found in the scrap bin.  (irreversible compression splices and 
exothermic welding are the same as continuous, but no split bolts, 
soldering, wire nuts, etc.)


For antenna grounds, you can also look to Art 810.21 (for receiving) 
which requires AWG10 copper or AWG17 copper clad steel (clearly, they're 
looking for mechanical strength, more than resistance), but that's for 
the "RF ground"..

the "bonding jumper" between your antenna ground and the rest of the 
building's grounding system has to be AWG 6  (Art 810.21(J))

Art 810.58 has some stuff about sizes for transmitter grounding (AWG10 
for protective ground, AWG14 for operating)

So the take home appears to be that a continuous run of AWG6 would 
probably suit the vast majority of applications.


> which is a std. Home Depot item (DAVIS RF always tells you to get it
> at Home Depot, the best price and no shipping cost).   And you can
> simply run it on the ground, next to your foundation.

it needs to be attached to the foundation or the side of the building, 
or it has to be in conduit.  In practice this is easy, and it's what 
you'd do anyway.


>
> ALso, you never know when you can have a hit, somewhere down the
> utility line, away from your station, and a killer to your equipment
> even if no lighting attraction at your QTH.
>