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No ground required.

Discussion in 'DIRECTV General Discussion' started by dondude32, Apr 12, 2013.

  1. netraa

    netraa Godfather

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    In the current/upcoming NEC code the requirement to back bond an antenna has been removed. This leaves only the requirement to ground the primary drop/coax run.
     
  2. west99999

    west99999 Icon

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    Doubt it, you got a link or something to correlate that.
     
  3. studechip

    studechip Godfather

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    Sort of. You can ground the dish and that does the receiver, too. Grounding the receiver wouldn't ground the dish.
     
  4. AntAltMike

    AntAltMike Hall Of Fame

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    The NEC is a model code that states rely on when legislating their statutory code. The state can eliminate any part of the code, but at least here on the east coast, where I have read the statutes enacting the code for four different states, I have not seen any language that explicitly added to or subtracted from sections 810 and 820.

    I have read every published NEC from 1996 through 2008, which is 5 versions, since it is updated every three years, but I have gotten all ground-threaded-out over the years and so my recollections are not as reliable as they once were, but I will attempt to contribute what I can here.

    - As I recall, the restriction that cold water pipe can only be used if the connection point is within 5 feet of where it enters the building came in the 2002 revision. Even then, it says said that in a commercial building, you can use the cold water pipe anywhere provided the plumbing is professionally maintained and substantially visible from the point where the pipe enters the building to the point where the connection is made (I struck the word "says" in this sentence because when I just read a later revision of this section, it did not include the exception for commercial buildings).

    DirecTV publishes a list of acceptable grounds, and last time I saw it, they explicitly allowed connection to water sprinkler system pipe.

    - The NEC as of 2008 still said that the mast had to be grounded and that the coax outer conductor had to be grounded as near as possible to the point where it enters the building. Starting in either 2002 or 2005, they stipulated that the mast ground connection point had to be within 20 feet of the mast - which is often impossible - unless it was not practical to do so. I believe the rationalization that grounding an exterior SWM unit meets the code's coax grounding requirement is that the installler is generously assuming that that grounding connection point satisfies the definition of being as close to the point where the coax enters the building. Post #41 says that "backbonding" of the mast is not required under the "current/upcoming code", which seems to allude to either the 2011 or 2014 revisions. I have not seen either but I would not be "shocked" (heh, heh) if they did away with that requirement.

    - Starting in I think 2005, the requirement that the outer conductor had to be grounded was complicated by the additional requirement that there had to be a static discharge device used for that purpose. Unfortunately, they did not define static discharge device. Back when we used twin lead, you couldn't ground one leg or the other because doing so would cut your signal power in half, so back then they developed a do-hickey that drained off the static discharge somewhat without actually contacting the conductors. It was round, and it often went on the bottom of the mast. I bought a dozen static discharge devices designed for use with 75 ohm cable back in the mid 1990s but never used them. They basically look like bloated groundblocks that have some gas filled chamber that lets the ground be close enough to the center conductor that even a low potential static charge will jump across it. As I recall, in the next successive revision of the code, they explicitly said that the industry standard coax ground block meets that section's requirement.

    - People living on the west coast, where there is less lightning, have told me that some of their local codes do not require the mast to be grounded but still required the outer coax conductor to be grounded.

    - People living in Arizona or Colorado have told me that due to the poor conductivity of the soil, they had more stringent requirements for the sufficiency of the grounding rod, but they may have been confusing that with the sufficiency requirements for a ground rod that is used as a supplemental ground for the formation of the ground electrode, rather than for a supplemnentary ground rod used to assure a straightter, shorter ground path for one device,

    At one time the reception antenna mast requirement was in one section whereas the only coax ground requirement was inferred from the section intended for cable TV. I think that the 2008 revision now has both the reception antenna system mast and coax grounding requirements in the same section.

    At one time, an antenna rotor wire had to be grounded, and it had to be flat, and it had to have one more conductor than the rotor needed and the two outer conductors had to be grounded. Honest.

    Back in the day of 300 ohm twin lead, the downlead had to be supported by 3" standoffs, but that requirement is long gone.

    By the way, if you are wondering why we don't just post the model code here, the answer is, we can't. It is copyrighted. Someone owns the law that we have to follow but we can't know what that law is unless we buy a copy of it from a private seller.

    When I first moved to the Washington, DC market and began servicing TV antennas on highrise buildings, I'm sure that less than 10% were grounded to code. It is my best belief and knowledge that no one has ever forfeited his insurance coverage because of a failure to ground. DirecTV and DISH insist on grounding probably because they don't want the bad publicity that would come to them if it was reported as a news story that they didn't ground, and they might not want the customer to be able to use their failure to ground for negotiating leverage, either by blaming them for some damages or for wriggling out of a contract. Installers are motivated to ground because they don't want to be penalized by their employer for not grounding. They were paid to ground, so their employers are entitled to get out of the installer what they paid him for.
     
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  5. Diana C

    Diana C Hall Of Fame DBSTalk Club

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    Actually, if you ground any part of the coaxial network, you ground all of it. Whether that will be safe, or according code, is another issue.
     
  6. bobcamp1

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    And most of those reasons are wrong.

    You ground solely to prevent a static discharge on the dish. Which is insanely rare. But if you're on a ladder or a roof and you get an unexpected zap, you might fall off. And all it takes is one senseless death.

    The DC voltages involved with satellite are simply not dangerous and wouldn't cause a shock. And I don't think there's a failure mechanism that exists that can get line or neutral voltage on the dish. Grounding it INCREASES the chance of lightning damage, because you've increased the odds of a strike.

    Having said all of that, if your code requires it, you have to get it done. Because if some unrelated electrical disaster happens and your insurance company discovers a missing ground on your dish, they might use it to weasel out of covering the damage.
     
  7. upsss

    upsss Cool Member

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    Because the receiver has two prongs that is precisely why the Dish must be grounded! Any appliance that is not "double insulated" has to be grounded. Your refrigerator is not double insulated, it has 3 prong cord. Your electric drill is double insulated, it has only 2 prongs. This has nothing to do with opinions!

    "Too many opinions" because of too many clueless, none professional people. Professional = Electrical Engineer.
     
  8. Diana C

    Diana C Hall Of Fame DBSTalk Club

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    Precisely!!!
     
  9. trh

    trh This Space for Sale

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  10. netraa

    netraa Godfather

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    http://www.nfpa.org/Assets/files/AboutTheCodes/70/70-A2013-ROPDraft.pdf

    it's just a draft, but there is nothing in 810.21 that says the antenna still has to be backbonded, just that it must meet a common ground.
    and 820 just deals with grounding the coax network.

    unless i'm missing something, it appears that they have decided grounding the coax is all that is needed since the coax is the only thing that connects the dish on the roof which by itself is insulated from the house wiring to the wiring in the house.
     
  11. slice1900

    slice1900 Well-Known Member

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    810.1 says it only covers antennas larger than 1 meter in diameter or width, so while it would cover most larger OTA antennas, it doesn't appear it would cover Directv dishes. I don't see anything that addresses antennas smaller than 1 meter.

    From what you're saying about not requiring backbonding, would that mean that if you had a grounding block for the coax, you could run a ground wire from that block to your OTA antenna mast to cover the requirement for grounding the mast rather than running a separate grounding wire from the mast to your building ground? Or am I misunderstanding?
     
  12. Rickt1962

    Rickt1962 Legend

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    As a Home Builder and seeing what grounding does and not does ! If your home get struck by LIGHTNING ! And you dont have the Dish Grounded ! It will follow the cable into the home and could cause a house fire or death ! So people dont be F*** N lazy and GROUND IT !
     
  13. AntAltMike

    AntAltMike Hall Of Fame

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    That was a genuinely dumb comment by the inspector. There is not enough power to worry about except when there is enough power to worry about, like when the dish gets hit by lightning, or when a storm breaks an electrical power transmission line and it lands on the antenna or contacts its coax.
     
  14. bobcamp1

    bobcamp1 Icon

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    As a fellow EE, I'll comment on this post.

    You can't count on the ground from the receiver to ground your dish or vice versa. You're supposed to have a dedicated wire connected between the two for that, not just count on the RF shield in the coaxial cable.

    Also, the dish is not an appliance. It sees no hazardous voltages during normal operation (all voltages < 50 V), nor does it directly connect to the electrical outlet. Even if you considered the dish and receiver to be a system, a single failure in the receiver cannot generate a hazardous voltage at the dish. And the receiver can easily be a two-pronged IEC Class II device by using a plastic chassis.

    You generally bond to ground any large metal structure attached to your house. To protect against overhead transmission lines, maybe your neighbor four houses down gets hit by lightning, etc. from putting 600 V or more on the dish. You don't have to bond small metal objects, such as the nails holding your siding up, house decorations, doorbells, etc. How big is the dish? Pretty small, actually. As someone else said, only antennas larger than three feet need to be bonded to ground, so the dish is technically excluded. It doesn't hurt to bond it to ground if you do it correctly (but it is NOT done correctly half the time), and it prevents lawsuits from greedy lawyers, so D* made it their policy to bond the dish to ground.
     
  15. n3ntj

    n3ntj Hall Of Fame

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    I am also an EE.

    Grounding the dish is to dissipate static that can accumulate on the dish simply by air movement past it. It should be grounded per NEC part 820. It should be grounded to the home's main electrical service electrode (where your electrical service is also grounded to) but must have it's own clamp on the grounding electrode. If the dish is a good distance (6m or more) from the service electrode, a secondary electrode should be used at the dish location and then the two electrodes must be bonded to each other to prevent possible differences in potential (voltage). My original dish (1998) was bonded to a nearby water spigot.. the installer never asked if my plumbing was plastic or metal. It is plastic (PEX) so I had a floating ground when it was initially installed. I called D* to have the installer come right back out and properly ground the system. I had to come out and show the installer the NEC book and diagrams to show him how to properly ground my system... too bad D* doesn't train their installers properly.

    I rarely see satellite systems (D* or E*) properly grounded while out on inspections.
     
  16. west99999

    west99999 Icon

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    You must be out on old installs cause I can tell you at least with D* quality control has gotten way better and I would say that at least 85% attempt to ground the dish properly although maybe only 60-70% actually do it right.
     
  17. bobcamp1

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    Yes, I mentioned ESD build up in my first post (where I talk about an unexpected zap and falling off the ladder or roof) but forgot it in my last post. I'm getting more forgetful the older I get. :(

    Since my dish is on a 4' metal pole in the ground, I had to make sure it was properly bonded to the ground rod at my service entrance on the other side of the house. My installer did it right by accident -- he bonded it to my cold water pipe. It's clearly all copper plumbing. But I know he didn't check to see if the copper pipe was bonded to the ground rod, because that connection is hidden very well behind insulation. It took me an hour just to find it.

    But I'd argue that according to the NEC, it doesn't HAVE to be grounded in certain cases. If it's just the dish bolted to the side of the house, and it's low enough to the ground so that a fall won't cause an injury, it probably doesn't need it. But I also don't want installers making that determination, and even if it's not required it's always a good idea, so if I were D* I'd make it company policy to bond all installations to ground.
     
  18. peds48

    peds48 Genius. DBSTalk Club

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    and this statistics are on what? Is it just in your market on nationwide? Links? documents stating these facts?
     
  19. west99999

    west99999 Icon

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    Check your PM.
     
  20. Rich

    Rich DBSTalk Club DBSTalk Club

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    And yet, D* tells me the same thing. I recently had the CMG send out a Tech and a supervisor to do something and the supervisor and I got into it about grounding the system. He stated it did not need to be done. I know it was in the NEC at one time, but I really didn't want to wade thru that confusing book that says one thing in one place and then contradicts itself in another place. Don't even know if the NEC book is still like that, I had enough of trying to wade thru that book and always went to the Electrician's Handbook which is much easier to read and doesn't contradict itself.

    As of this moment my system has been ungrounded since I joined D* in 2002 and it works quite well. I do know how to ground it, but I'd rather have D* do it the correct way (if they ever send someone to my home who knows the correct way, so far that hasn't happened).

    I did call the CMG agent back and told him what the supervisor told me and he told me the supervisor was wrong. Still, they haven't sent anyone out to do anything about it.

    Rich
     

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