I'm about to get of the cable tv merry go round and am installing an antenna on my roof. The problem is that the service entrance for my coax is on the side of the house and the most direct downward line for the grounding wire ( for lightning) would be the back of the house. I need to ground both the antenna and the coax from it. Would there be any problem putting two separate ground rods in to do this,they would be separated by about 50 or 6o feet. ?? thanks for any help jk
As long as you don't short the power company's neutral to any of them except the one at the main entrance panel, you can put as many ground rods as you want. I'd make the lead for lightning ground as short as possible.
You could also install lightning rods on the peak of the roof.
Ground the mast with a short(est) lead to a good earth ground, the coax gets a grounding block also.
BTW if you have sandy soil, you can "wash" a 10 foot length of copper pipe into the ground by connecting a garden hose to it and working it in. The water pressure pushes the soil away from the tip. I use a plastic compression adapter for the pipe and solder a pigtail on before I wash it down, then a copper split bolt connector to connect the pigtail to the ground wire. Excellent ground that way - lot of surface area and well into the wet subsurface soil.
No problem - except that you are required by the National Electrical Code [article 810.21 (J)] to bond those ground rods to the building grounding electrode system with a 6 AWG or larger bonding jumper. If you do not add ground rods, you may have an easier job by connecting the antenna and lead in grounds per 810.21 (F) (1):
"The grounding conductor shall be connected as follows: (1) To the nearest accessible location on the following: a. The building or structure grounding electrode system as covered in
250.50 b. The grounded interior metal water piping systems, within 1.52 m (5 ft) from its point of entrance to the building, as covered in 250.52 c. The power service accessible means external to the building, as covered in 250.94 d. The metallic power service raceway e. The service equipment enclosure, or f. The grounding electrode conductor or the grounding electrode conductor metal enclosures; or to grounded interior metal water pipe"
I've omitted quoting two more places listed in the artice [810.21 (2) and 810.21 (3)] because they refer to buildings with no grounding means.
The connection in 810.21 (F) requires smaller wire (#10 copper or #8 aluminum) than you would need if you install ground rods.
Is that really necessary if the lightening ground merely grounds the mast and coax? Normal TVs don't use a three wire grounded line cord as a rule, and that requirement reads like they are talking about electrical safety for multi ground power distribution.
I'm not sure what you have in mind by the question, so two answers:
Any ground rod you add (for the antenna or for any other reason) must be bonded to the building grounding electrode system.
You are not required to add a ground rod, you can ground per 810.21 (F)
The way I see it, article 810 applies to antennas, regardless of the equipment the antenna is connected to, even if it is battery powered and completely isolated from the AC mains.
I make a practice of grounding any conductive mast like a flagpole or lightening arrestor on a gazebo with no power run to it, etc.. I live on the NC coast, we are second to Florida for lightening strikes
- a metal clothes line gets grounded around here - any nearby strike will induce enough voltage to zap you with just 20 feet of wire laying on the ground, but not grounded. So an absolute statement like "any" ground, makes no sense.
Makes a lot of sense for power distribution safety but not solely for lightening protection. If the article you mention was intended to mean lightening grounding, they'd first and foremost insist that the wires be as straight and direct to ground as possible. You don't put sharp bends in wire that you expect to divert the full power of a strike, or the induced voltage of a strike.
Our cable and dish installers use a ground rod at the dish or before the cable enters the building - and don't use 8 gauge wire. With cable it often comes on the same pole as the electrical service and the ground block is often cheaper to connect to the same ground as the service entrance. Dish installations however, are at the dish or at the house with their own ground rod. My own "professional" installation has what looks like insulated 14 or 16 gauge to a split bolt on the service ground (which might be 6-8 gauge).
Power distribution safety is another beast altogether. We have to meet conductor size specifications, but have to measure the resistance on industrial installations between our added grounds and service entrance ground.
With antennas you often are more concerned with electrostatic charge buildup for equipment protection. If you "listen" to the storms here you can often hear the point discharge of static build until a strike occurs then it dies out and slowly builds until the next strike. Out on the water you can often see as well as hear it. We get up to about
20" sparks from outriggers during storms - if that were coax or a high impedance radio input, the voltage would probably punch through insulation if there were no 5kv spark gaps installed.
It's not a question of what you or I think makes sense. I cited the NEC, and the NEC makes it mandatory: "250.50 Grounding Electrode System. All grounding electrodes as described in 250.52(A)(1) through (A)(6) that are present at each building or structure served shall be bonded together to form the grounding electrode system."
Your mention of gazebos and metal wire closelines and flagpoles and the discussion below do not apply to the op's situation or my post.
The National Fire Protection Agency has a standard (nfpa 780) for lightening protection systems that probably covers the appropriate ways to protect against lightening damage. That standard probably makes more sense for this application.
The scope is not related to residential TV antennas but building protection. This links to an overview:
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The link shows maps of the US with lightning frequency as well as reference to NFPA 70 for electrical power distribution grounding and a requirement to link the lightening ground to the building ground, and utilities ground - water and gas mains.
The actual document is $40 from the NFPA.
It is not a practical system for TV antennas, but it does spell out things like no sharp bends, ground location, separate ground rod for each "down comer," and size wire (huge - but then its intended to shunt 10,000 amp strikes to ground on things like smokestacks, broadcast antennas, and industrial buildings)
--
"Electricity is of two kinds, positive and negative. The difference
is, I presume, that one comes a little more expensive, but is more
durable; the other is a cheaper thing, but the moths get into it."
(Stephen Leacock)
No, 'Thomas Jettison' : "Whenever you do a thing, act as if all the world were watching."
;-)
--
"Electricity is of two kinds, positive and negative. The difference
is, I presume, that one comes a little more expensive, but is more
durable; the other is a cheaper thing, but the moths get into it."
(Stephen Leacock)
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