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#8886 - 04/08/02 11:32 AM Lightning protection for antenna mast  
rjpnj  Offline
Junior Member
Joined: Apr 2002
Posts: 2
NJ
Please give me some good info about how to propperly ground a rooftop antenna mast for lightning protesting. Here are a few specific questions I've been thinking about.

1) I assume I should use either #4 or #6 solid copper wire and copper clamps.

2) Can I run the grounding wire to a copper water pipe in the attic? It's nearby, but I'm concerned about electrifying my entire water system. Is this unsafe? My house is served by a private well, the only source of earth ground to the water pipe system is the bonding of this system to the ground rod(s) installed by the electrical utility at the point the electrical feed enters my house.
This wire is #4.

3) If I can not use the copper water pipe, and have to run the wire outside the house to the gound, can I use a burried copper propane line as the earth ground? It is burried for at least 30 feet, and seems like it would be an excellent ground. It leads to an underground metal propane tank that I know has its own grounding electrodes. Any chance of sparks/explosions here?

4) If I can not use the water pipe or the gas pipe, can I use the same grounding electrode the utility is using? THis will require about 50 feet longer ground wire. In this case, can I run the wire through my basement or must it be completely outside the house to be safe?

5) Lastly, I suppose I could install a new ground rod, but this will be very difficult to sink 8 feet into the rocky ground.

Thanks

Rich


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#8887 - 04/08/02 03:48 PM Re: Lightning protection for antenna mast  
George Corron  Offline
Member
Joined: May 2001
Posts: 717
Lorton, Va USA
RJPNJ,
Article 810-21 gives your answer, congrats, that's one of the most missed of the grounding spots.

It allows you to go to your water pipe, but the best (lowest impedance) would be directly to the service ground. The code also requires this to be as straight as possible, also for impedant reasons.

Not a good idea to drive a separate ground rod, if you do, you have to run a #6 to the system ground to be legal anyway, otherwise, a # 10 will do.

Is this just a TV? If so, put a couple 8" coils in your coax, and you also increase impedance to where lightning won't likely follow it back.

Good Luck,

George


#8888 - 04/08/02 04:08 PM Re: Lightning protection for antenna mast  
rjpnj  Offline
Junior Member
Joined: Apr 2002
Posts: 2
NJ
THanks George!

WHat does the "Article 810-21" in your post reffer to? Is it the 1999 NEC? If so, can I view this online someplace?

Will a lightning strike in this arrangement cause hazardous voltages to be present at all my plumbing fixtures? Or only if I happen to be standing outside holding the ground rod and touching a plumbing fixture while lightning strikes. (Something I rarely ever do [Linked Image])

Thanks again

Rich


#8889 - 04/08/02 11:21 PM Re: Lightning protection for antenna mast  
George Corron  Offline
Member
Joined: May 2001
Posts: 717
Lorton, Va USA
RJPNJ,
I referenced the 99 code, just checked the 2002 and no diff.

Anytime lightning strikes nearby, or even close to the distribution system, you get elevated voltages, they're just so quick you can't see them (normally), unless they take out a TV or microwave [Linked Image]

Rarely are people damaged by this, and since we control grounding a bit better these days, rarely are appliances damaged either.

As long as you ground, preferably by Code, wwe reduce the incident of problems.



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