Dish grounding question

Discussion in 'DirecTV TiVo Powered PVRs & Receivers' started by sotapoppy, Sep 15, 2007.

  1. sotapoppy

    sotapoppy Member

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    Feb 7, 2004
    Minnesota
    I'm having an upgraded dish installed next week and I'm unsure as to how it should be grounded.

    My current dish is a roof mount near the middle of my house. The coax runs along the roof and down the west side of the house. It is grounded to a gounding rod on the west side before entering the house.

    The new dish will be a roof mount using a non penetrating roof mount near the east side of the house. The dish is being relocated due to neighbor's trees. With the non penetrating mount, the cables will go through the roof instead of over the roof. The cables will ultimately wind up in my utility room on the west side of the house via the basement ceiling.

    As I see it my options are as follows:

    1) Connect the cables to a new grounding block in the utility room and ground to my main water supply. (Is this a problem that the cables are not grounded before entering the house?)

    2) Run the new cables through the west exterior wall and connect to the existing grounding block on the outside. (Not my first choice since I don't really want more cables on my siding.)

    Your thoughts are appreciated!
     
  2. RS4

    RS4 New Member

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    Sep 2, 2001
    Indianapolis...
    I'm no expert on grounding, but I would think it wouldn't matter if your grounding block is inside and attached to the plumbing system which I'm assuming is also grounded. Also, if your neighbor's trees are close enough, they will become the ground because lightening strikes the tallest thing in the area, so in theory, the flash would be drawn away from your house.
     
  3. alwayscool

    alwayscool Former P3 Tester

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    May 10, 2005
    Fort...
    Don't worry about how the dish is grounded. D* installers are REQUIRED to ground your dish or the don't get paid. I got my new HD slimline dish mounted yesterday. Either a 10' copper grouning rod or a water pipe is a good ground.
     
  4. cramer

    cramer Member

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    Aug 14, 2000
    Raleigh,...
    Where's the sense in that? You're punching a hole in the roof for the cables?

    National Electric Code requires both the cable and the dish to be grounded... #10 copper or #8 aluminum wire DIRECTLY from the dish either straight to a ground block or through the coax ground lug.

    Electricity follows the path of least resistance. Metal is a far better conductor than trees. Even if the tree is the in the loop, anything within ~30ft is going to get hit as well. As a friend from Florida always says, once you've seen lightening arc out of a wall socket, you stop wasting your money on surge suppressors and just unplug your stuff. If lightening is hitting that close to your house, a wire isn't going to make a huge difference. At best, it'll keep your tivo from bursting into flame.

    (I still have a friends old S1 tivo who's modem was literally blown apart from lightening -- I never bothered to fix it. It set off the security system in his house... and it's a battery powered, free standing system -- it's not even earth grounded.)
     
  5. milominderbinder

    milominderbinder New Member

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    Dec 18, 2006
    Chicagoland
    We have heard horror story after horror story of dishes not being grounded by installers.

    Here is the document that we compiled complete with diagrams:

    Satellite Dish Antenna Grounding Requirements

    It is the same process for 1 LNB, 3 LNB, and 5 LNB dishes.

    The most common reaction when people see this is: "They didn't ground my dish..."

    - Craig
     
  6. cramer

    cramer Member

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    Aug 14, 2000
    Raleigh,...
    I've seen hundreds(?) of "professional" installations -- both DISH and DTV. None of them have ever been grounded. They don't even take 5 minutes to put a 5$ ground block in the line. Why do they skip it... a) it takes time, and b) grounding wire is expensive (and heavy.)
     
  7. desulliv

    desulliv Member

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    Aug 22, 2003
    So, does D* come out and inspect the ground before they pay the installers?
     
  8. TyroneShoes

    TyroneShoes HD evangelist

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    Sep 6, 2004
    Putting in a grounding block is only part of it. A GB is no good at all unless it is connected properly to a good ground, which usually implies ground wire run a short distance to a 8' grounding rod. The copper wire is expensive, but the rod is more expensive, is cumbersome (takes up lots of room in the truck), and is a real pain to pound into the ground and connect up, plus you have to negotiate the logistics of running the cable where it is close to where the GR can be installed.

    Every cable company and every local municipality seems to have their own particular rules, but most don't allow connection to water pipes anymore (or to any already-used ground connection). Not that it wouldn't be a good ground, but usually because installers are occasionally not that bright, and some have been known to connect them to gas co. pipes. Imagine what lightning would do to that, and imagine the liability involved when the fire marshall or insurance inspector discovers it after the fact. So they made water pipe connections a no-no to prevent that mistake.

    Grounding also protects from more than just lightning, but unless a dish is vulnerable to lightning (most are, but on a apartment patio, they're usually not) there's a lot less real need for DBS antenna grounding than there is for CATV grounding. And nothing is lightning-proof.

    They skip it because they can. Once the customer gets pictures, they normally sign off. If you are paying a fixed price for an install (even if it's free) you should hold their feet to the fire and demand proper grounding. It might not really be necessary, but it never can hurt.
     
  9. stevel

    stevel Dumb Blond TCF Club

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    Aug 23, 2000
    Nashua, NH
    Water pipes can also be a problem if there's a meter or nonconductive pipe between your grounding point and where the copper line enters the house (assuming it is copper!) Grounding jumpers over meters are often installed.

    The purpose of grounding a dish is not to conduct a lightning strike, as far as I know, but to reduce the voltage differential. The typical 8GA aluminum wire used for grounding isn't going to last long in a lightning strike.
     
  10. HiDefGator

    HiDefGator New Member

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    Oct 12, 2004

    Apparently none of my installers were ever told that.
     
  11. HiDefGator

    HiDefGator New Member

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    Oct 12, 2004
    If you are going to have multiple grounding rods at your house they all need to be connected to each other. You can't just drive one at the dish and not connected it to the existing house ground.
     
  12. dougfetter

    dougfetter New Member

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    May 14, 2006
    They didn't ground my dish!
     
  13. Danflip

    Danflip New Member

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    Sep 18, 2007
    As a Directv Installer, the cable will have to be grounded on the outside of the house. If you ground on the inside of the house, if the dish gets struck by lighting it can send the current through your house tell it hits the ground. This is electricity it can set anything in the house on fire, not a good idea. Make sure they ground it on the outside. :) :)


     
  14. TyroneShoes

    TyroneShoes HD evangelist

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    Sep 6, 2004
    You are right about that, but the training I've had indicates that it (proper grounding) may shed some of the current away from the house and equipment during a lightning strike, so that is also one reason.

    One of the reasons that there is no definitive answer is that gounding practice is largely theoretical, even though it is widely adopted. Lightning implies mega-amps of current, plasma issues, and laws of physics that are operating on the boundaries. There isn't much evidence left after a lightning strike to really judge accurately what happened, or predict what will happen next time, so we don't really have a handle on what the best thing is to do. Some regulations suggest not making sharp bends in the ground wire because the current will just ignore the bend and shoot out in whatever direction it is traveling. Is there a lot of evidence of this? Probably not. A lot of it is just an educated guess.

    But one other reason to ground CATV, at least, is to prevent problems if the power ground lifts. I've seen issues where the power ground had lifted, and cutting the RG-6 cable actually shut the lights off (try explaining that to the biker that emerges from his now-dark house and waits for you at the bottom of the pole - true story). I've also seen issues where the potential is 7-8 volts different, and the cable melts at the GB overnight, which protects the CATV equipment.

    Yes you can, and yes some companies do that. If each ground is proper (IOW "fully" grounded, meaning miniscule voltage potential difference between each other), there's technically no reason to do that and actually some reasons not to (re: my "biker" story above). Connecting grounds to one another is verbotten for the two cable TV companies I worked for as a sweep tech/headend tech. Each CATV ground had to be on its own isolated ground rod, period.
     
  15. Matt L

    Matt L New Member

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    Aug 13, 2000
    Flushing, MI
    I have all my grounds tied together and that is the way it should be. With unbonded ground the potential for a voltage difference increases with each ground rod added to the system. If you have a very small house the difference in ground potential may be small but if you have a home with a large footprint what are the odds the the earth all around the home is of the same composition? In that case you are begging for different potentials.
     
  16. Phantom Gremlin

    Phantom Gremlin Active Member

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    Jun 20, 2002
    Tualatin,...
    Be careful about this. Here's a quote from a page of excerpts of the National Electrical Code:

    NEC Article 250.58 instructs us to use "the same electrode for grounding conductor enclosures and equipment in or on that same building." The concept of "separate ground" is nonsense. Two good sources for more information on this are Soares Book on Grounding and IEEE-142.

    But I don't personally know enough about the topic to have my own opinion.
     
  17. cramer

    cramer Member

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    Aug 14, 2000
    Raleigh,...
    There's plenty of evidence for this. You should've learned this in high school science class. Sharp points lead to charge concentrations. The best example is metal in a microwave oven. You can put metal in a microwave. If there are no points, it won't arc. For example, a perfect sphere would have a uniform charge over its entire surface. It can spark, but most ovens aren't powerful enough to charge a sphere faster than the charge can dissipate into the air. Put something with a sharp point in there, say a needle, and it will spark vigorously, but now there's a place for the charge to concentrate.

    Don't think of it like fiber optics where sharp bends allows the light to "escape." (it's no longer being reflected down the cable.)
     
  18. tucsonbill

    tucsonbill Member formerly known as cranky

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    Aug 11, 2004
    Tucson
    Thanks Stevel, It's always bugged me how people fail to understand the amount of energy in a lightning strike. There is absolutely nothing that protects against a direct strike.
     
  19. newsposter

    newsposter Poster of News

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    Aug 18, 2002
    SE PA
    2 on topic questions

    1. my 3lnb dish is on the back porch roof. For myself install, i did put in 2 grounding blocks and tied them to my outside water line. There are very tall trees immediately adjacent to the dish (yes had some LOS issues). Can I assume that since i do have it grounded and the trees are right there that i'm 'ok'

    2. the new 5lnb dish is on the other side of the house, at the lowest point on the roof, and wasnt grounded by the installer the other week. however, there are trees right next to the roof and of course the roof itself along with my UHF antenna are much higher than the slimline. This leads me to believe the slimline itself should be ok but i would have more issues with my much higher uhf antenna. Sound reasonable? I guess i should demand they come back and ground though...
     
  20. rminsk

    rminsk TiVoted TiVo User

    5,612
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    Jun 4, 2002
    Marina del...
    The National Electrical Code requires it to be grounded...
     

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