How do I properly Ground an antenna?

[nogard1126]

First I would like to say if I'm not posting this in the right spot, then feel free to move it. I've read through the NEC with some confusion, and also read many things online. In NEC 810 is says that you must ground an antenna, and it needs surge protection which must be grounded, I get that part. I thought the ground would be for lightning, but there is no way a small wire could carry lightning and survive. I've heard these points and they all make sense. That it is done to: prevent static build up, make the antenna the same potential as the rest of the terrain, if lightning does hit it to have only one common path to ground (try to keep energy from grounding through equipment).

I received a grounding kit with one of the antennas I purchased. It consisted of #10 solid coated wire and a simple grounding block that the coax goes into then out of, and there is a place to attach the ground wire to it. This didn't see fully correct.

The way I understand it, if the antenna is installed at a commercial/industrial building with a ground system, then the antenna ground can be attached to this. In 810 it says minimum of #10, but wouldn't you have to use a minimum of #6 per 250 if it is exposed to physical damage? Or a smaller gauge armored ground wire (#10) could be used, but which would be better? Then can this ground enter the building through the roof and make its way to a water pipe, or does it need to go right to a ground wire of the grounding system?

In a residential antenna installation I've heard of pounding a separate ground rod for the antenna, running #6 stranded from the antenna to the ground rod and then also bonding this new rod to the existing electrical rods, if this is the case what size wire is required for the bonding between the rods?

If an antenna was installed on a metal mast anchored in the ground, couldn't this be used as the ground if everything was bonded together?

Could someone please give an example of the proper way to ground an antenna in a residential and commercial/industrial environment? Thank you.

 

[nakulak]

what kind of antenna are you installing and what is it being used for ?

 

[tom baker]

First
In 810 it says minimum of #10, but wouldn't you have to use a minimum of #6 per 250 if it is exposed to physical damage? .

Article 810 is not subject to the rules in Chapter 1-4 unless a reference is made in 810, see 90.3

The very important method for grounding and bonding is to create a single point ground.
Bond the antenna to your grounding electrode system following the rules in Art 810.

 

[StephenSDH]

If lighting hits in your neighborhood it creates an emp wave that metal objects like your antennia pick up and direct into your house on the coax cable. Your tvs, revievers, computer equipment are both plugged into your house power and connected to the antenna. If there is a surge to create a voltage between the two ground systems your equipment serves as a high impedance bond between the two ground systems. Grounding the mast and coax shield to the grounding electrode system will create a low impedance bond and hopefully your equipment will survive. Nothing survives a direct lightning hit.

 

[crazyboy]

Question, if your GEC is on one side of the house and the antenna is on the other side of the house, how are you supposed to keep a common low impedance ground? Going all the way around the house with rods and wire doesn't seem practical.

 

[erickench]

The 2008 NEC has something new. It's called an intersystem bonding terminal. This ties all the grounds for communications, lighting and power together. And if you don't have this intersystem bonding terminal then NEC 800.100(B)(2)(5) clearly states that the ground wire for the communications system must be bonded to the service equipment enclosure which already has the minimum #6 AWG wire for the ground.

 

[Smart $]

Article 810 is not subject to the rules in Chapter 1-4 unless a reference is made in 810, see 90.3

The very important method for grounding and bonding is to create a single point ground.
Bond the antenna to your grounding electrode system following the rules in Art 810.

...and don't forget, both the lead-in coaxial cable and the mast need grounded.

 

[iMuse97]

[QUOTE

I received a grounding kit with one of the antennas I purchased. It consisted of #10 solid coated wire and a simple grounding block that the coax goes into then out of, and there is a place to attach the ground wire to it. This didn't see fully correct.

[/QUOTE]

This sounds like a lightning arrestor, which is for the coaxial cable only. The other ground issues discussed in previous posts still apply to the whole antenna.

 

[Smart $]

...apply to the whole antenna.

Hmmm... you might kill transmission and reception if you go to that degree

 

[JohnJ0906]

Question, if your GEC is on one side of the house and the antenna is on the other side of the house, how are you supposed to keep a common low impedance ground? Going all the way around the house with rods and wire doesn't seem practical.

Impractical, or not, that is what needs to be done.

Going by memory, I think in that situation, you can drive a seperate rod for the antenna, but it still must be bonded to the main GES. (Sorry, I am on jury duty, and my NEC is at home :roll

 

[mcclary's electrical]

I alwaly drive a ground rod at the antenna mast,,,,,then run a #6 solid to the service GEC and bond there,,,,,then run a # 10 from coax splitters to panel. That's about all that needs to be done

 

[nogard1126]

One instance is a cell phone antenna (booster) on a metal mast about 3' attached to a pvc vent pipe, so it is isolated, with the exception of the coax being the only thing metal bonding it to the electronics it is connected to indoors where it terminates.

The other would be an antenna I plan on putting up on the side of a wood chimney. Which would basically have the same isolation problem.

I understand if the antenna was on metal mast that was pounded into the ground and a ground wire was ran down the mast from the antenna in to the ground, attached to a ground rod pounded just for the antenna, and then ran around to the main ground at the service entrance (ground rods)

The cell phone antenna is at a job site. It is in the middle of a large roof. I would have to run ground wire along the roof and then over the edge and down the side of the building to be able to pound a ground rod, and then still get the ground back through the wall and attach to the grounding system. I don't mind doing the work, I just want to make sure I know what is required before I tell the customer this is what you have to do. If they don't then I look stupid and I just made them pay a lot of money for something they didn't need. If I had to run the ground wire like I mentioned, what size does it need to be? If #10 then it would need to be in a raceway to be protected, correct? Or can I run the ground wire into the building with the coax and then take it to a point of the grounding grid, which is about 50 feet away. There is a spot with bare wire that I could split bolt to. If I did it this way what size wire would the ground need to be from the antenna to the grounding grid?

Then back to the residential antenna I want to put up. So if the antenna is on the roof. I would run a ground from it along the roof then over the edge down the side of the building to a new ground rod. Then run a ground wire underground to the main ground (rods) at the service entrance. Again what size would the ground wire have to be from the antenna to the new rod? What size would the ground wire have to be from the new ground rod to the existing rods?

Thanks.

 

[LarryFine]

The other would be an antenna I plan on putting up on the side of a wood chimney.

I can't inagine a wood chimney would last very long.

 

[Smart $]

One instance is a cell phone antenna...

The other would be... residential antenna...

#10 Cu, or its code equivalent, to any point on the service GES is all that is necessary to be code compliant. However, if you install a new ground rod, it will need to be connected to the service GES, and become a part thereof. with a #6 Cu, making the installation compliant with Article 250 requirements. As stated earlier, it is not required to "protect" these grounding conductors... but that should not stop you from doing so even if only a small section truly needs be protected.