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Grounding question

Discussion in 'DIRECTV HD DVR/Receiver Discussion' started by 420benz, Jul 28, 2010.

  1. 420benz

    420benz Member

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    Dec 19, 2006
    Georgia
    The cables from the dish are coming from the dish to a splitter and grounded to a water pipe. They ran the cables along the roof an nailed them the the roof. I am putting a new roof on NOW and i want to run the cables inside the attic. The problem is that the splitter will also wind up in the attic. I have no water pipes in the attic for a ground. They moved the splitter close to an electrical box and grounded it to the ground wire in the box.Is this a bad idea?
     
  2. mobandit

    mobandit Hall Of Fame

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    I think that is acceptable, although probably not to code. The purpose of the ground wire from your dish is to drain off static charges, nothing more.
     
  3. 420benz

    420benz Member

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    Dec 19, 2006
    Georgia
    The only pipe i have in the attic is a gas pipe. I don't feel comfortable with that.
     
  4. TomCat

    TomCat Broadcast Engineer

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    Not to mention that it may prevent lightning from killing you.

    We could debate the reason for grounding, but that will not alter the laws of physics. Grounding is a great method of using the laws of physics to minimize the possibility of the unpredictability of lightning becoming a problem for you. Code or no code, theory or no theory, lightning that can find a better path to ground than through your home theatre or through a family member will usually take that better path. Grounding properly will provide it with a better path. You really want it to have that better path.

    Waterpipes are an excellent ground, but most code does not allow that due to how easy it is to make the mistake of grounding to a gas pipe (not what anyone has in mind). Most code involves some #6 copper wire to a 8" copper-clad ground rod driven 7 1/2 feet into the ground. Try not to make sharp bends with the ground wire, as the super-high current of lightning likes to move in a straight line, and will jump out of a 90-degree bend to ground, rather than exactly where you are attempting to direct it. That means that the path it might choose might have some significant resistance in it, making that path through your home theatre more attractive to at least part of that current.
     
  5. drpjr

    drpjr Icon

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    Sakatomatoes...
    Excellent advice.

    Your house ground is designed to handle 120/240volts. It provides a path to ground for any stray voltage/current in the system. Given a short situation it should trip a breaker or GFCI receptacle within the system. It will almost always take the path of least resistance. If you do not have a proper dish ground your house ground could be used to ground grounding blocks, splitters, etc. It would only provide a ground for house type voltages and bleed off any static charges. It could also "lead" lightning into your attic.

    Also your gas pipe is probably already bonded to the cold water pipe at the water heater as well as being bonded to the home ground. Many newer homes do not continue metal pipe into the ground very far for water and sometimes gas so they are not good grounds. That's why they bond all together inside the home.

    Your dish ground is designed to provide a path of least resistance to ground in case of a lightning strike or in rare cases where house current somehow were to energize the sattelite system. Given the large voltages of lightning it does not always cooperate and take the path of least resistance. It can do strange things. That is why it is best to be as straight as possible from the dish/rooftop to the ground rod. Even better is a pole mount away from the house but that is not always practical. My jurisdiction recommends a solid #4 copper conductor in conduit for a dish ground. Having a properly grounded dish will also provide a path to ground for any static buildup on the sat system.

    So to finally answer your question. Yes you should be OK with your current ground at a recpticle but be aware of what it is capable of doing and more importantly what it will not do.
     
  6. Davenlr

    Davenlr Geek til I die

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    When I grew up, there were "lightning rods" on all our roofs connected together with THICK metal stranded wire. NO new houses use those anymore. Ours was hit at least twice that I can remember, but my house now, which doesnt have them, has never been hit. Why are they no longer used? Did they perhaps find out they attracted more lightning?
     
  7. Rich

    Rich DBSTalk Club DBSTalk Club

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    What you have to understand is that no one knows what lightning will do. The voltages are so high it's almost impossible to have any protection that is 100% effective against lightning strikes. I've seen vertical lightning and horizontal lightning and all directions in between. If you ever have a chance to sit inside the eye of a hurricane, you'll see lightning do things almost unimaginable.

    If you're ever flying above a lightning storm, you'll see lightning going up from the clouds. Obviously, nobody knew this could happen until we had planes that could go higher than storms.

    Lightning should take the course of least resistance, but that part of the theory only seems to work below 600 volts. Once you get above 600 volts it seems as if anything can happen. There are charts that show the distance that "juice" can jump from one conductor to another. For instance, 4160 volts shouldn't jump between conductors more than a quarter inch (I think that's correct, it's been a long time since I looked at the tables). But it will jump farther than that if the conditions are right.

    Simply put, lightning's scary and not well understood. We've got a good handle on anything lower than 600 volts, but you go higher and really strange things happen. Unlike Physics, there is no science of electricity. We're still learning.

    Rich
     
  8. hasan

    hasan Well-Known Member

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    Ogden, IA
    No, the purpose of the ground wire is electrical safety protecting against ground faults. For the purposes of lightning mitigation, that wire does near nothing.
     
  9. hasan

    hasan Well-Known Member

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    Ogden, IA
    Proper single point grounding is a way of using physics to protect you. A thin single wire running to an "alleged" ground is fool's gold when it comes to lightning mitigation.

    Nearly every path to ground in a sloppily implemented grounding system is available to "lightning that can find a better path to ground than through your home theatre".

    It's been said many, many times here, with appropriate references, that lack of a properly installed single point ground system provides little or no lightning mitigation, and telling people that it does is both a disservice and dangerous.

    The sole purpose of most grounding referred to in our systems is to prevent electrocution due to ground faults, and nothing, absolutely nothing more..

    That's the physics (or more specifically, the electromagnetics) of it.
     
  10. hasan

    hasan Well-Known Member

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    Ogden, IA
    No, it is a perfectly acceptable practice for an "electrical safety" ground, which prevents electrocution due to ground faults. It does near nothing to protect against lightning or lightning induced damage.

    It is important to separate these two issues, and failure to do so is very dangerous.

    It is easy to protect against electrocution, and grounding to your electrical box is fine for that purpose.

    It is very difficult and expensive to mitigate lightning damage.

    Do not assume anything you do for an electrical safety ground will help you in lightning mitigation, as it most likely will do absolutely nothing in this area!

    Lightning mitigation is a science unto itself. It has been very carefully researched, documented and published. Several companies, including Polyphasor have published "white papers" on single point grounding for lightning mitigation. If you are curious, you can google them. Suffice it to say, what it takes to install a proper single point ground (for lightning mitigation) is daunting. (and no, surge protectors are not the answer either):)

    My advice is to install your electrical safety ground as you proposed. Then, learn more about lightning mitigation. There are personal safety and equipment issues. Some of the latter can be addressed (somewhat half-baked, but better than nothing), by using a decent grade UPS (uninterruptable power supply), like those used to protect computers. APC makes very good ones, and a specific model for Home Theater systems sells for about $110 at Sam's Club. (I have 5 of them, one on each DVR, and others on computers/routers, etc.)
     
  11. TomCat

    TomCat Broadcast Engineer

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    Sounds like a nebulous statement if I ever heard one. It may contain a grain of truth, but common sense alone says that grounding properly (not a "sloppily implemented" ground using a "thin single wire") is obviously better than a poor ground or no ground. I think it is pretty hard to argue against grounding, which certainly does more good than harm.


    What is "both a disservice and dangerous" is to imply that you don't need to ground because it doesn't matter all that much. It absolutely does matter. While the jury is out on how much, the only sensible course of action (since lightning is greatly misunderstood and highly unpredictable to the point of us not really knowing what it can or will do in a certain situation) is to err on the side of caution, not to throw caution to the wind, which is what you appear to have done.

    It might make you feel above the rest of us to parrot back some totally-unsupported urban-legend tidbit you might have heard regarding grounding like you are all-knowing, but the simple fact is no one really knows what lightning will do or is capable of, which does 2 things:

    1) implies that we should have respect for it.

    2) really makes those who claim to know look pretty silly.

    And, it really doesn't matter how many times something is said if what is said is BS, regardless of "appropriate references" (which you have yet to supply). From what I have read in various grounding codes there really are no "appropriate references", because they all disagree with each other. It still sounds more like a narrowly-held opinion rather than fact (which you have yet to support).

    The facts regarding plasma behavior (which is what lightning is) are not well known; far less well-known than the physics surrounding "normal-current" electricity. One of the reasons is that there is no evidence left over after the lightning is gone other than charred remains--pretty hard to get a ruling on what happened with poor forensic evidence after the fact. The only thing that can be said with any credulity regarding the laws of physics regarding plasma behavior is that they are very probably nothing at all like the laws of physics governing normal matter, space, and time. We have yet to begin to understand it. It is as nebulous and well-understood to us as is dark matter.

    And the electrical codes of most cities (which I have browsed in a professional capacity) would disagree vehemently with you (but then as a cable plant design tech back in the day working for an MSO that had many different cities in many different states, it can also be said that the electical codes of any two cities can also disagree vehemently with each other).

    The solution by cable companies was to create their own comprehensive grounding policy and make sure it complied with all of those varying codes in the cities they had right-of-way licenses in. Their motivation in doing so (and at significant cost to them - BP should be so cautious) was specifically to minimize their legal liability; to go into every unavoidable frivolous lawsuit where someone was hurt or killed or their house burned down armed with the evidence that they had done everything in their power to prevent just such a problem. The policy that Group W/ TCI (at that time the largest cable MSO out there--even larger than Comcast)came up with is exactly what I described earlier. It worked for them. I think that is testament to how correct their policy is, and how correct we are in urging folks to heed to it.

    No one agrees on exactly what is right or exactly what to do; as I said, it is debatable. But the odds are pretty good that something with that much thought and effort devoted to it might just trump most casual internet rumors.

    Glad to see you agree. And I rode out Alicia in 1983 on Galveston island, including about 45 seconds inside the eye (it centered about 10 miles to the northwest), so I know pretty much exactly what you are saying. BTW, I don't recommend it. Scariest night of my life. 5 guys chain-smoking in a motel bathroom (and I didn't even smoke).
     
  12. n3ntj

    n3ntj Hall Of Fame

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    Actually, the NEC now requires gas pipes to be bonded. Any metal piping (water, gas, etc.) that may potentially become energized must be bonded. This essentially connects the metal gas and water pipes to the home's grounding system.

    Do you have CSST in your attic or black iron?
     
  13. Rich

    Rich DBSTalk Club DBSTalk Club

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    I thought it was always in the NEC. Working in a chemical plant environment, we had to use natural gas in some situations, but we avoided it as much as we could. A little leak, a little static electricity and Boom. And the bonding was performed as a matter of course. Makes sense when you think about it.

    Rich
     
  14. Rich

    Rich DBSTalk Club DBSTalk Club

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    I usually agree with you when it's a subject I understand. I've never been on land and in the eye of a hurricane. Always at sea. For some reason, every captain of every destroyer near a hurricane always seemed to meet the hurricane head on and we had many lunches in the eyes of those hurricanes. Perfectly calm, blue skies above and surrounded by circular walls of black clouds filled with lightning. After we ate, right back into the hurricanes again. Got to the point where we got used to it.

    You should see what a lightning storm looks like at sea. The main mast, the highest one, absorbs all the strikes. Beautiful to watch. Then there was St. Elmo's fire, but that's another tale for another time.

    Rich
     
  15. hasan

    hasan Well-Known Member

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    I'm not parroting back anything. I have over 30 years experience working with lightning protection. At no time did I suggest not using a ground. I did state clearly that lack of a single point ground does near nothing for lightning mitigation. That is indisputable. Read the research....and don't put words in my mouth.

    ...and don't confuse a careful consideration of the facts with the "better than" dodge. The facts are clear, the research is clear. Proper practices are clear. Setting this out is not an attempt at "better than", it is trying to prevent people from relying on utterly unreliable information and getting themselves or their equipment killed.

    Ignorance is not a virtue, when it comes to lightning mitigation. Pointing out the errors in "common conceptions" regarding grounding, and why they are errors is not arrogance. It is a service, and advising otherwise, is indeed, a disservice.
     
  16. n3ntj

    n3ntj Hall Of Fame

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    It may have been in the NEC for a number of years but most areas around here just started enforcing it.
     
  17. Rich

    Rich DBSTalk Club DBSTalk Club

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    Yeah, most people think the NEC somehow polices itself, but that's not how it works. The community inspectors have to do the policing. Do you even have to take a test to be a licensed electrician in PA? The test in NJ is NEC based and it's brutal.

    Rich
     
  18. codespy

    codespy Ted- Get some free agents NOW!!! DBSTalk Club

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    The NEC has for a long time required bonding of Gas piping via Table 250.122. Water piping via Table 250.66.

    What you may be thinking of is CSST. Bonding of CSST is not currently in the 2008 NEC edition but was proposed to be in the 2011 edition. The National Fuel Gas Code (NFPA 54 I believe) put language in last year requiring bonding to electrical systems in a structure where CSST is present. This was a #6 copper conductor bonding from the electrical service neutral to gas piping as near as practicable to where it enters the building.

    Us (many) inspectors in WI have been enforcing this for a while, however, violations go to the HVAC contractor as they must meet the listing and installation requirements for the product. The electrician usually gets the extra out of it for now as the HVAC contractor is usually not licensed to do the wiring from electrical panels to perform the bonding.
     
  19. n3ntj

    n3ntj Hall Of Fame

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    Yeah, with all of the problems with CSST, bonding really needs to be added in the next NEC. The insulators on new CSST do a better job than the yellow outer coverings that actually hold a charge.

    Electricians assume the plumber will bond the gas pipe and plumbers assume the electrician will bond the gas pipe... in the end, no one has bonded it. I see this all of the time, but in brand new construction it's getting better.
     

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