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Old 14-Jan-2015, 3:34 PM   #1
nukeman
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Antenna install on outbuilding, how to ground?

Hello,

I just completed our new house build and want to install a HD antenna. My intentions are to mount the antenna on my 40x60 shop that's about 60ft from the house and connected with buried conduit. I'm thinking about this for several reasons; it doesn't require any holes in the roof of my house, aesthetics, and it is a clearer line of sight to the TV station antennas. I bought a Channel Master 4228 antenna, and a Channel Master CM-7777 amplifier. I ran RG-6 to the proposed antenna location to test and I got the reception I expected. Now I'm ready to mount the antenna permanently and have some questions regarding grounding it.

I've been doing a little research and what I've found says I need to ground both my antenna mast and the RG-6 as close to where it enters the building as possible. I've also read it's best to ground everything to the same grounding rod that the house is connected to.

The shop does have electrical service that comes from the house via a 2-pole 100 amp breaker from my house electrical panel to another 2-pole 100 amp breaker in the shop's electrical panel. However, the shop doesn't have a separate ground rod.

What's the best strategy for this? Is my idea to mount the antenna on an outbuilding reasonable? Should I ground the signal wire before it enters the house or the shop? Should I put in a new grounding rod to ground the antenna mast? When it comes to protecting my family and my possessions it's worth taking the time to do things right, even if it means changing my plans if necessary.

I've attached picture of my layout and the shop's electrical panel.


Thanks for the help
Attached Images
File Type: jpg overview.jpg (11.4 KB, 339 views)
File Type: jpg shop panel.jpg (261.3 KB, 336 views)

Last edited by nukeman; 14-Jan-2015 at 5:00 PM.
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Old 14-Jan-2015, 7:37 PM   #2
rickbb
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I would drive a ground rod down at the out building and ground both the RG6 and mast there to the same grounding rod.

You are protecting from a spike from lighting, keeping it away from your house instead of running it into your house would be the better course to take.

And ideally your panel at the shop should also have it's own ground at the shop instead of using the one in the house, for the same reasons.

Edit, how is the RG6 being run to the house? In the same conduit as the electrical? That may create interference issues if so.
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Old 15-Jan-2015, 12:56 AM   #3
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Did you have a licensed electrician do the subpanel work? Did you tell him you'd be running a low voltage circuit with a ground back to the main structure?
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Old 15-Jan-2015, 1:53 AM   #4
nukeman
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Did you have a licensed electrician do the subpanel work? Did you tell him you'd be running a low voltage circuit with a ground back to the main structure?
Yes, a licensed electrician did the work. And no, I didn't tell him about a low voltage circuit. My plans for the antenna were not finalized at the time the electrical work was done. As the OP said, I'm not even sure if I should run the low voltage ground back to the main structure.

If you don't mind, would you please provide some background as to why those two questions are relevant? Just wondering if there's something I could have done better.

Last edited by nukeman; 15-Jan-2015 at 1:56 AM.
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Old 15-Jan-2015, 2:27 AM   #5
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Most areas of the country use the NEC as the basis of their electrical code. However, each jurisdiction can implement local variations as they see fit. In my area, each separate building on a property is required to have one or two ground rods if there is a service or sub-panel in or on the building. I have two outbuildings that are served by sub-panels. Because the soil conductivity is poor, each building is equipped with two 8' ground rods spaced 6' or more apart.

Not many years ago, the code only required that a sub-panel be connected to main service via a grounding conductor, a neutral conductor that is isolated from the ground except at the main service panel and an appropriate number of phase (hot) conductors. Back then, no rod was required at the outbuilding... My understanding is that the addition of a rod was to increase the protection of each buildings electrical system from lightning induced fault current and reduce the fault current conveyed to the main or adjacent buildings.

So currently, this usually means a total of four conductors are needed for a single phase 120/240 sub-panel feed. The only place that the neutral and ground should be bonded together is in the main service panel. Bonding the ground and neutral elsewhere, including the sub-panel can lead to unintended current flow in the ground conductors. In the worst case, mixing neutral and ground together can set up a lethal condition if the neutral conductor is broken or a splice/connection goes bad. As much as 120VAC could appear on the frame of equipment that you think is grounded.

As I look at the photo of your panel, I don't see a ground conductor and it appears that the neutral is bonded to the frame of the panel. I would add a #6 AWG ground conductor in the run from the main service and terminate it on the left 'ground' bar... leaving the bonding strap between the panel and bar connected. I would move all branch circuit ground conductors to the left 'ground' bar. I would also use the right 'neutral' bar for branch circuit neutrals only and would disconnect the bonding strap from the right hand 'neutral' bar to prevent normal neutral current from finding a secondary path to ground... All normal neutral current should return to the main service via the neutral conductor. Ground conductors should never carry normal current, they are there to carry fault current if the need arises.

Finally, I'd add at least one 8' ground rod near the sub-panel and connect it using #6 AWG to the 'ground' bar in the sub-panel. I would then ground my antenna mast and coax via a connection to the ground bar outside the building.

http://forum.tvfool.com/showthread.php?t=901 (post #20 is a general antenna system grounding summary)
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Last edited by GroundUrMast; 15-Jan-2015 at 2:38 AM. Reason: sp
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Old 15-Jan-2015, 2:32 AM   #6
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Quote:
Originally Posted by nukeman View Post
Yes, a licensed electrician did the work. And no, I didn't tell him about a low voltage circuit. My plans for the antenna were not finalized at the time the electrical work was done. As the OP said, I'm not even sure if I should run the low voltage ground back to the main structure.

If you don't mind, would you please provide some background as to why those two questions are relevant? Just wondering if there's something I could have done better.
Was a permit issued and was the work inspected by the permitting agency? I ask because I think it's unlikely that that sub-panel would meet code in very many jurisdictions. I won't go so far as to say it's wrong in your area... but I'm quite sure it would be rejected for lack of ground and improper bonding in my area.
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Old 15-Jan-2015, 11:51 AM   #7
nukeman
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A building permit was issued, but there's no electrical permit. I'm in a relatively rural part of the area and in the country, not in a city. We don't even have a building inspector in the county. I guess work like that at my sub-panel is a consequence of that! Sounds like I need to get another electrician out here and get the situation fixed.
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Old 15-Jan-2015, 1:11 PM   #8
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If you don't mind, would you please provide some background as to why those two questions are relevant?
Tom may have covered this in his comprehensive reply above which I don't have time ATM to go through.

It's been 10 years since I studied this, but I do recall that there was an NEC provision that if there was a circuit that included any grounded path between the outbuilding and the main building, then there were specific things that had to be done. Don't recall the exact particulars, but I seem to remember that a proper current carrying neutral and ground had to be run between the structures, the bonding jumpers had to be set correctly in the subpanel, and grounding rod may or may not have been required. Like I said, it's been too long so someone feel free to refresh my memory as to NEC requirements.
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Old 15-Jan-2015, 2:39 PM   #9
rickbb
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One thing to remember about building codes, including electrical, is that they are MINIMUM codes. That is they are the bare minimum that you can legally get away with.

Your panel may well be up to "code" for you locale, but I'd still put in the ground rods at the outbuilding and separate that "real" ground from the neutral running back to the house.

With something that can burn your house down or electrocute you I'd go better than code, by a couple of steps.
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Old 17-Jan-2015, 5:34 PM   #10
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I have probably linked to a similar comment already, but I think it's important to mention it in this thread...

If you choose to drive a ground rod it needs to be bonded (*) to the existing grounding system of your electrical service. Isolated ground rods leave you with the illusion of safety but due to the resistance of the soil, very high voltage differences can occur during fault conditions such as short circuits or lightning events. This is a recipe for property damage and personnel injury.

I have to advise against 'grounding' the antenna, mast or coax to an isolated ground rod. If you add a ground rod, you must bond it to the existing ground system with #6 AWG (or heavier) copper.

I would be inclined to contact the electrician that performed the sub-panel install, unless you are already sure they are not a 'stand-up' kinda person.

Here's a moderately technical discussion of the concepts of grounding and bonding as it applies to electrical systems in general: http://ecmweb.com/bonding-amp-ground...ding-part-1-12 (Parts 2 through 12 should be easy to locate if you're interested.)

(*) NEC Art. 100 Defines: Bonding (bonded). The permanent joining of metallic parts together to form an electrically conductive path. This path must have the capacity to safely conduct any fault current likely to be imposed on it

Last edited by GroundUrMast; 17-Jan-2015 at 6:00 PM. Reason: Added ECM link
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Old 17-Jan-2015, 11:35 PM   #11
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Here's a crude drawing that outlines the way I have approached similar situations.

Attached Files
File Type: pdf Out-Building Grounding of Antenna System.pdf (21.4 KB, 1062 views)
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Old 19-Jan-2015, 12:12 AM   #12
nukeman
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That drawing's helpful, thanks. I will run it by the electrician
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Old 19-Jan-2015, 4:46 PM   #13
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It's vital that your existing electrical system be properly bonded and grounded before you attempt to bond and ground an antenna system to it. Here is a slide presentation that briefly covers the basics of grounding and bonding of electrical service and load side equipment.
https://www.nachi.org/documents/GroundingandBonding.pps

Here's a summary of antenna system bonding and grounding based on the NEC article 810. The assumption is that the existing electrical system is bonded and grounded correctly.

http://ecmweb.com/code-basics/articl...sion-equipment

(I'm probably well past 'beating this to death'... Cheers)
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