Anyone want to take a shot at why #6 to attach antenna ground to breaker?
It was all fun and games with my off air antenna until I went to buy the #6 grounding wire. For those who aren't familiar with how big #6 is, it's 7 bare regular sized copper grounding wires stranded together. Seven!!! Anyone just want to take a guess why an antenna's grounding rod needs THAT much grounding power to connect it to the breaker panel? They want #10 grounding wire attaching the antenna to the grounding rod below, then #6 conneting the rod to the breaker panel. If they want everything to maintain the same polarity I'd think just a #14 would do it. It's not to absorb lightning, lightning does not take corners very well so it's not like the lightning will go down to the grounding rod then turn up through the #6 to my breaker panel. Anyone just want to take a guess why an outside antenna needs a huge #6 cable to connect it to the breaker panel instead of like, #14? http://www.hdtvprimer.com/ANTENNAS/grounding.gif
I'm not sure where to begin, you have so many misconceptions it would take a long time to get you on the right path. So let me say the #6 is the minimum size copper wire to a supplemental grounding rod. Usually this a bare copper wire that is solid not stranded but it can be stranded. It is ran to the main panel for good reason. This is all part of the ges (grounding electrode system). Specifically it is called a grounding electrode conductor (GEC). It's purpose is to give huge voltage events like lightning, transformer faults/surges, high voltage power lines falling on your drop if overhead etc...a path to earth. Where it can be directed away from your property and electrical appliances and equipment. Its purpose therefore is property protection. You actually should have two of these rods ( which you do according to the diagram) in the ground if the first one was tested to be over 25 ohms ground resistance. The "main" or primary electrode is almost always your metal water pipe and you will notice you probably have a #4 solid copper grounding conductor connected to it close to where it enters your home which is ran back to your panel. Without this system in place if your property was to experience any of the high voltage events mentioned it would likely explode your outlets out of the walls and ceilings and destroy most everything electrical in your home. You need all the conducting paths to earth you can get in situations like these. The NEC's requirements are the minimums. It is important to note that 500 to 600 volts or less will not push current to earth very well because of the high impedance of dirt. But get that voltage up to several thousand volts or more... like lightning.. and believe me it has no problem in doing so with thousands of amps of current. Take away the GES and all that current and voltage goes into your house electrical system and finds it's way to the egc... those itty bitty grounding wires and any metal voltage potentials like your wiring, tv's, kitchen appliances...etc and you can guess what happens. As for lightning it follows all the voltage and current laws so thats why current doesn't flow "up" to the antenna mast....why would it? It could care less if there is a corner there. But it will darn sure energize that mast with voltage..... attach a #6 grounding wire to the top of that mast and run it to an electrode in the earth ...then have a high voltage event occur at the transformer (like a lightning strike) sending several thousand volts and amps into your service panel and hold onto that grounding wire at the top of the antenna mast. If you live.... tell me if you still believe lightning will not go around corners. You gave the mast a path to ground at both ends...review your current laws ( written by a fellow named kirchoff). Believe me when these voltage events happen you need all the paths to earth you can get and the bigger the wire you use the better. so the whole idea is to give the "huge excess of current" a place to go besides your house wiring and property, thats why all this GES is married up in the main panel, to give the current laws their chance to work by sending the vast majority of current to earth. It may or may not be enough depending on the event and its magnitude but property damage will be much less with the GES properly in place.
The #10 on the antenna is sized that way for a reason I think I'll let someone else explain as this is taking a lot of explanation as it is.
Hopefully some others will jump in here and continue the discussion. I'm out of breath....:thumbsup:
If I understand the answers and If I am allowed to translate in my own words,simple answer is this Piedmont: You want to be medium rare or well done?
Wow Stubbie, great post. I think lightning is one of those things that's beyond me but after reading your post I understand it a lot more than the countless hours I've just spent getting no where. I read someone say to understanding lightning, houses, electrical equipment, etc is like asking someone how to explain mathematics... not something that can just be explained you could get a degree there's so much involved.
Sorry, the word polarity is my fault I meant potential. I understand why the connection, you want everything in the house to have the same potential otherwise someone touching 2 pieces of equipment with different potentials could get shocked (say touching something with the antenna's potential and something bonded to the regular house potential), on a roof not a good thing! By having the antenna bonded to the breaker panel everything should have the same potential and prevent shocks to both persons and equipment.
So, as my limited mind chews on this I think in summary I do it to protect the electronics from the transient lightning that does not flow through the grounding rod by the antenna. I want to give what doesn't an extremely easy path to as many grounds as possible (instead of some choosing to go through the electronics) and the breaker panel is the mother load of grounds. It's got a ground back to the pole, bonded to 2 grounding rods buried, it's also bonded to my faucet outside, bonded to the water pipes before, and after my water meter. So, am I at least in the ballpark to say that because my breaker panel has so many grounds if my antenna gets struck a tiny #14 wire is not going to handle just how much transient lightning juice will decide to travel to my monstrously grounded breaker panel I need some serious cable to handle it? I hope that's right as, it actually makes sense when you mention just how grounded my breaker panel is it should attract some major juice of the lightning so I need some serious wire to handle it.
The very large post above, while, impressive, does not really answer the question. Say, you got a house without a TV antenna, meaning it has just its main grounding service, connected at the panel, and not a gazillion rods all over the place, with anaconda-sized wires tying them togeather? Does it mean that should you get a lightning strike someplace, your electricals are gonna explode as if loaded with C4? I think not.
Here's the real answer: should lightning hit your antenna, all that current will go seeking ground. And it will take every possible path it can find. Two paths exist: one is directly to the ground via antenna rod, and another is through your coax, your TV, its chassis, outlet ground, breaker panel and its own ground rod. Not a good path for it to take. This is why, you want a real thick wire to short that path directly to the breaker panel rod. Some current will still travel through the TV and all - but the thicker is the wire connecting the rods, the less will go through your TV.
Piedmont, Stubbie,Scorpio et All; I know my first answer was a bit smart ass however If anyone really wants to see the answer in living color email me at CSTMCARPBYJACK@AOL.COM I have a whole bunch of pics EXACTLY related to this subject, A job I did last year.
Thanks scorrpio, and all NOW I fully understand.
Had I known how it works I'd probably opted for #4 wire instead. Maybe I'll put in 2 grounding rods bonded together below the antenna. I did choose #8 to ground the antenna & coax to the grounding rod instead of the #10 minimum the NEC spec'd.
I was fortunate enough to attend a two hour grounding and bonding seminar Monday presented by Mike Holt. As luck would have it, this very subject was broached. According to Mike, the rod at the antenna could do more harm than good. There is an issue with voltage potential when lightning is close causing voltage to flow on the wire, even though there is no lightning. Much better to just run the 6AWG wire from the antenna to the main ground. The moral of the story was to teach us that the grounds should be as close to the system bonding jumper as possible. I think that there is a code change either coming or here that is going to require us to provide easily accesible lugs so the phone company and the cable guy, etc., can bond to our ground with no fuss. Bad news when they drive their own rods.
Anyhow, the seminar was cool and I learned alot.
Actually scorpio's post is not as accurate as Stubbie's.
First off, if you think #6 is "anaconda sized" you should come work with us for a a few days. :whistling2: And we are not talking about a "gazillion" rods. We are talking about two or three.
The antenna's rod is known as a supplementary rod. It requires a #6 because that is what the code tells us it needs. A rod can only carry so much fault current so the wire connected to it is useless over a certain size. #6 in this case.
The reason it must be #6 is NOT because the antenna needs #6. The #6 is a bonding jumper between rods. It has NOTHING to do with the antenna itself.
For a reference:
Blue text is the NEC Handbook Commentary
810.21 Grounding Conductors — Receiving Stations
Grounding conductors shall comply with 810.21(A) through 810.21(K).
(A) Material The grounding conductor shall be of copper, aluminum, copper-clad steel, bronze, or similar corrosion-resistant material. Aluminum or copper-clad aluminum grounding conductors shall not be used where in direct contact with masonry or the earth or where subject to corrosive conditions. Where used outside, aluminum or copper-clad aluminum shall not be installed within 450 mm (18 in.) of the earth.
(B) Insulation Insulation on grounding conductors shall not be required.
(C) Supports The grounding conductors shall be securely fastened in place and shall be permitted to be directly attached to the surface wired over without the use of insulating supports.
Exception: Where proper support cannot be provided, the size of the grounding conductors shall be increased proportionately.
(D) Mechanical Protection The grounding conductor shall be protected where exposed to physical damage, or the size of the grounding conductors shall be increased proportionately to compensate for the lack of protection. Where the grounding conductor is run in a metal raceway, both ends of the raceway shall be bonded to the grounding conductor or to the same terminal or electrode to which the grounding conductor is connected.
(E) Run in Straight Line The grounding conductor for an antenna mast or antenna discharge unit shall be run in as straight a line as practicable from the mast or discharge unit to the grounding electrode.
(F) Electrode 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
(2) If the building or structure served has no grounding means, as described in 810.21(F)(1), to any one of the individual electrodes described in 250.52; or
(3) If the building or structure served has no grounding means, as described in 810.21(F)(1) or (F)(2), to an effectively grounded metal structure or to any of the individual electrodes described in 250.52
(G) Inside or Outside Building The grounding conductor shall be permitted to be run either inside or outside the building.
(H) Size The grounding conductor shall not be smaller than 10 AWG copper, 8 AWG aluminum, or 17 AWG copper-clad steel or bronze.
(I) Common Ground A single grounding conductor shall be permitted for both protective and operating purposes.
(J) Bonding of Electrodes A bonding jumper not smaller than 6 AWG copper or equivalent shall be connected between the radio and television equipment grounding electrode and the power grounding electrode system at the building or structure served where separate electrodes are used.
The requirements for grounding are in accordance with Article 250. Antenna masts must be grounded to the same grounding electrode used for the building's electrical system, to ensure that all exposed, non–current-carrying metal parts are at the same potential. In many cases, masts are connected incorrectly to conveniently located vent pipes, metal gutters, or downspouts. Such a connection could create potential differences between lead-in conductors and various metal parts located in or on buildings, resulting in possible shock and fire hazards. An underground gas piping system is not permitted to be used as a grounding electrode.
Section 810.21(J) clarifies that the bonding requirement applies only to electrodes at the same building or structure. The use of separate radio/television grounding electrodes is not required.
Thanks Speedy for the detail of your post. Also for correcting some of my oversights.
I wish I had all those real answers.
If lightning strikes your house directly, all bets are off. Does anyone REALLY think lightning cares about a piece of 6AWG CU? Really?
Andy, of course lightning cares. It just hasn't called in a while.:)
Just a little about lightning so people reading this thread don't think that you can just take away all the electrodes of the GES system without consequence. I'm not talking about reference to the lightning protection system in this article on grounding and how it relates to lightning strikes. This is taken from an article by the IAEI to expound on the ges being in place to keep damage from occuring to gas lines during a lightning or high voltage event.
1.3 Lightning Impact
Lightning is one of the most destructive forces of nature. Direct and indirect strikes on or near structures can cause severe damage to the building and initiate fires that can result in the loss of property and lives. Despite this destructive power and with a few exceptions, jurisdictions throughout the United States do not require the installation of lightning protection systems. Instead, the electrical grounding system is required to address (as best it can) the issue of mitigating the lightning energy. However, the electrical grounding system is only designed to protect the building occupants from ground-faults and not from lightning strikes. It should, therefore, be no surprise that many metallic systems (such as wiring, coax cable, piping, and ducting) either fail or are damaged during electrical storms.
Lightning strikes can be direct and/or indirect. The effects from a direct strike on a structure are from resistive heating, arcing, and burning. A direct strike typically results in catastrophic damage to the structure and its contents, and is considered by most experts to be “beyond the means of man to prevent”. The National Electrical Code (NEC) specifically considers lightning protection “beyond the scope” of the Code. While installing a lightning protection system will afford a certain level of protection from direct strikes, the system is primarily designed to protect the structure and not necessarily the interior electrical and plumbing systems.
The effects from an indirect strike near a structure include capacitive, inductive, and magnetic behavior. The lightning current can branch off to a building from a nearby tree, fence, light pole, or other tall object. In addition, a lightning flash may conduct its current through the ground into a building. The current also may travel through underground power cable, telephone lines, or metallic piping. The protection of both structures and people from the dangerous effects of an indirect lightning strike requires that both the structure and all metallic systems within the structure be bonded together so as to act as a single unit. To accomplish this goal, the following steps are required:
When properly sized and installed, bonding can minimize the electrical potential difference between these parallel metallic pathways to ground. This will significantly reduce the occurrence of any physical damage to any of the affected systems when they are energized by a lightning strike.
1.4 Grounding and Bonding Considerations
Effective grounding depends on a low-resistance electrical pathway connected to the earth. The pathway to ground is affected by the resistance within the voltage system, the grounding electrode(s) and the soil conditions. The electrical resistance of the pathway to ground must be 25 ohms or less per the NEC. If not, an additional grounding electrode must be installed. Section 250.4 (A) (1) of the 2005 National Electrical Code states the following:
"Electrical System Grounding: Electrical systems that are grounded shall be connected to earth in a manner that will limit the voltage imposed by lightning, line surges, or unintentional contact with higher-voltage lines and that will stabilize the voltage to earth during normal operation.”
The surge of energy throughout the premise wiring and the other metallic systems during a lightning event can be hundreds of times greater than the normal current running through the house. These lightning surges are also occurring at much higher frequencies that normal electrical voltage. The combination of lightning current and frequency create conditions that are difficult to mitigate if the grounding and bonding systems are inadequately sized. The critical design issue involves the capability of each and every parallel metallic pathway to be energized to the same level and have that energy rise and fall at the same speed as the lightning strike completes it cycle. This capability creates an equal potential state between these pathways to ground and limits (if not eliminates) any differences in electric potential between these pathways.
I'm so glad I asked, I understand the #6 now but more importantly have achieved the next level of understanding lightning.
I have poor knowledge of what hardware is out there for certain tasks and, can anyone tell me what does one use to bond #6 to the breaker panel? I ended up using a 1/2" metal Romex connector and pinching it on the wire and screwing it into the panel but I don't feel happy using something for an intention it's not nor am I sure there's a good bond. What does one normally use to do that? Do you think I can bond it to the #6 that's already coming out of my panel to my water meter? That would be easier and certainly ensure a good connection (again, bonding it to the wire itself not to piping) but I'm not sure if it's against the rules or a bad idea... maybe they make some type of copper #6 hose clamp for doing that? Thank you
By the way after installing my roof top antenna this weekend (I previously had an indoor rabbit ears that got 3-4 stations) I now get 38 stations that come in 100%, 30 of them are Digital and many High Def & 5.1 surround sound. I figure it cost me about $450 when all was said and done but, 38 stations crystal clear and free I'm very happy.
You absolutely do not use hose clamps anywhere. The ground rod requires one of these....
In the main panel you simply connect to the bonded neutral bar like below
|All times are GMT -5. The time now is 03:28 AM.|
Copyright © 2003-2014 Escalate Media LP. All Rights Reserved