[TowerTalk] Challenging Grounding/Bonding Situation ?

[N3AE]

Jim, 

Thanks for the feedback. Really appreciated.  See my comments below. 

<There's a point of clarification needed here. Do you have one service, or two? That is, does the from the power company go first to the house and then to the garage (or vice versa), or do you have two feeds from the power company, one to each building? From your description, it sounds like you have the first option. Right?> 

Correct. Utility to the house service panel, through a breaker and then from there to the garage. 

<Here's the concern. In any SYSTEM, they must be one, AND ONLY ONE, bond between Neutral and the Green wire, and that bond must be where the system is established (usually where power enters the building). Breaker panels come with a bond between neutral and the frame (where the green wires must be connected), so if there is more than one panel in a system, that bond must be removed on sub-panels.> 

Yep, I was aware of this. Recent inspection of the current garage load panel shows that it is incorrect...the panel ground bus, panel itself and the white neutral are bonded together in the load panel ,,,,something I need to fix. Ever since I moved in I assumed it had been done correctly. Bad to make assumptions. 

< There is another way to do it, and that's what I'm doing with a similar feed. I am treating my two buildings as separate (they're about 30 ft apart). I have a single service, which comes to the house, then is fed to the garage/apartment that houses my shack. There is NO ground connection between the house and the shack -- the feed from the service is two hots and a neutral only.> 

Not sure that's an option in my case. I'm "stuck" with the bare ground wire in the feeder cable to the garage. If I disconnected it at either end, I'm afraid there would be a flash-over in the event of a lightning strike ... can't get that wire far enough away from the grounded panels in the garage and the house. 

<I have three driven rods near the service entrance. There were none when I bought the house -- a "ground" wire ran about 35 ft to a spigot for a garden hose, which was fed by PVC pipe.> 

Ditto here. When I moved in, the service panel was just bonded to the inside cold water copper water pipe. But I'm on a well. The water line going outside is PVC. Had to drive a ground rod for the service entrance. Come to think of it, the ground wire in the cable feeding the submerged well pump is grounded to the top of the galvanized steel well casing... a 300 ft deep "ground rod." Now I'm wondering if I need to take that outside bare #4 and run it around the house to the well casing too? 

There is a "mystery" ground wire coming out of the service panel which enters the cinder block wall through the same hole as the main feeder from the outside meter, but it doesn't exit on the outside. Maybe it was run down the hollow in the block to rebar in the floor (Ufer). Who knows. Not counting on it for anything. 

< Telco and CATV grounds are bonded at the service entrance.> 

Same here. 

< With respect to the tower -- coax shield should be bonded to the tower top and bottom. From each tower leg, at least one driven rod, preferably more spaced out from the tower a distance equal to at least the length of the rod. Also a bond from the tower to the structural mesh within the tower base. I do that with copper strap, using clamps for the tower legs that prevent dissimilar metal issues.> 

My tower anchor rods are bonded to the rebar cage using #4 copper and UL direct-bury copper bronze clamps with a stainless steel shim between the galvanized anchor rods and the clamps. Right or wrong, the concrete is set so that's not changing. 

I plan to ground the coax shields at the bottom of the tower, but still debating about grounding at the top as well. Since it's a crank-up tower, I doubt that the electrical continuity between the sections is that good. Plus ..., it's an older galvanized tower that I repainted with quality cold galvanizing paint. Just seems to me that bonding the coax shields at both the top and bottom make the coax the preferential lightning path for this installation. But then again, that's just a DC perspective and doesn't account for the inductance of the coax vs that of the tower. Maybe the high R and low L of the tower is still better than the low R and high L of the coax. 

Shawn - N3AE