Antenna grounding questions

dprljackson · 12-Jul-2011, 11:53 AM

I'm a newbie who just installed an outdoor antenna (HBU33), which is currently not grounded. So the first question is how dangerous is it to have an ungrounded antenna? I'm planning on grounding it soon but is it absolutely essential that I do this as soon as possible, or is it fine to do it sometime in the next few weeks?

I think I understand the basics of grounding this antenna, but perhaps someone can correct me if I'm wrong. Connect a ground wire (#6 copper) to the mast, run this to a coax grounding block as close as possible to where the coax enters the house. Then run the ground wire in a straight-as-possible line to the house ground.

While this sounds reasonable, running the ground wire all the way to the house ground is not going to be the easiest job in the world. It won't be all that tough, but I had a thought that would really simplify things. I have solar panels attached to the roof of the house. Presumably, these are grounded to house ground. So my second question is, assuming the solar panels are properly grounded, can I simply run the ground wire from the antenna to the chassis of the solar panels? This would be incredibly easy.

Are there any dangers associated with such an approach? It seems like it accomplishes the same thing as running the ground wire all the way to house ground.

ADTech · 12-Jul-2011, 2:40 PM

Per 2008 NEC Art 810, a #10 copper wire (or permissible alternative) should be run from the mast in as straight a run as practical to the home's ground electrode system (GES). A separate permissible ground wire should be run from a coaxial mounting block (located at or near the cable's point of entry) to the same GES. Connecting to your solar array does not satisfy code requirements.

That said, I'd have to guess that 95+% of our customers never ground their outdoor antennas despite our recommendation that they do so....

GroundUrMast · 12-Jul-2011, 4:08 PM

Agreeing with ADTech...

Ideally the mast ground would run from the mast to the electrical service ground, not connected to, or combined with, any other ground along the way. As ADTech has said, #10 copper is the minimum size wire mentioned in the code.

Ideally the coax ground block will be connected to the electrical service ground via a separate wire, again, not connected to, or combined with, any other ground along the way.

If you decide that you are going to add a ground rod, it needs to be bonded to the existing electrical service ground system. In most residential situations, a #6 copper wire is the minimum size for the bonding conductor.

Even if your solar system is grounded properly, it's not a suitable alternative for a direct connection to the electrical service ground. Combining or interconnecting the grounds of the antenna and solar systems impairs the effective protection for both systems.

(Emphasizing that best practice is to treat the mast ground and coax ground as separate and distinct from one another.)

ADTech · 12-Jul-2011, 4:22 PM

Art 820 (CATV systems) permits #14 for the grounding block ground wire. However, Art 820 doesn't apply (810 does) to antenna receiving systems. Art 810 uses the same requirement for the grounding conductor for both the mast and the grounding block. See 810.20(A) and 810.21(H).

GroundUrMast · 12-Jul-2011, 4:25 PM

Quote:

Originally Posted by ADTech

Art 820 (CATV systems) permits #14 for the grounding block ground wire. However, Art 820 doesn't apply (810 does) to antenna receiving systems. Art 810 uses the same requirement for the grounding conductor for both the mast and the grounding block. See 810.20(A) and 810.21(H).

Thanks ...

ADTech · 12-Jul-2011, 6:21 PM

..just one of those inconsistencies in the NEC!

dprljackson · 13-Jul-2011, 1:11 PM

OK - so if I use two grounds for the mast and the coax and keep them separated, how far should these two wires remain from each other as they travel to ground? The mast and the coax entry point into the house are pretty close to each other (a few feet) and so these two ground wires will take very similar paths to ground.

Second question - exactly where do I connect these two ground wires? I found what looks like a ground wire where the electrical enters the house. There is a copper wire that runs from the house directly into the ground. The telephone line ground is connected to this wire via a grounding block. Can I connect my two ground wires to this grounding block or should I connect them to a different grounding block connected to this wire or something else all together?

I appreciate the assistance.

ADTech · 13-Jul-2011, 2:47 PM

Quote:

how far should these two wires remain from each other as they travel to ground?

It doesn't matter. You can run them under the same staples if you want to.

Quote:

There is a copper wire that runs from the house directly into the ground.

This is the perfect location. Use a split nut (like the phone installer used) for each new ground wire to be attached to the main ground wire (probably a #4 or #6 copper) unless you can find a split nut that is manufacturer-rated for multiple wires. Simple split nuts should be available in the electrical section of any home center. Here's an example from Home Depot's site:

nrpardee · 13-Jul-2011, 9:04 PM

This has been really helpful!
How careful does one need to be about bends in the grounding wire. For my application, I can't see any way to avoid a couple of basically 90 degree bends (rounded, of course!) and one 60 degree bend. I could definitely avoid two bends by putting in a grounding rod but what I read says I would have to bond that to my existing rod, which would require running a #6 copper probably 50'. or more.

GroundUrMast · 14-Jul-2011, 12:57 AM

Sharp bends result in higher values of inductive reactance (the opposition to the flow of alternating current), therefor the advice to avoid sharp bends. An effective ground connection will have low resistance and reactance.

This simply means that a large, short, straight wire will offer an easier path for current than a thin, long bent or coiled wire.

Don't worry too much, just make bends as gradual as you can tolerate cosmetically.

GroundUrMast · 15-Jul-2011, 1:19 AM

Here is a synopsis of the NEC Article 810.

dprljackson · 15-Jul-2011, 12:19 PM

Great - thank you very much for the assistance.

John Candle · 17-Jul-2011, 9:18 PM

dprljackson also made another separate post with more questions and answers. Go there.

dprljackson · 27-Jul-2011, 5:24 PM

One last question. Is it OK to attach the grounding wire directly to the house or does it need to be held some distance away from the house?

ADTech · 27-Jul-2011, 5:34 PM

It may be affixed to the surface of the building.