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Ground rod distance from foundation?

Discussion in 'Residential Electrical Codes' started by Pcinspector1, Dec 19, 2017.

  1. ICE

    ICE Sawhorse

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    Gas pipe should never be used as an electrode. It should always be bonded. That can be accomplished by the equipment ground for a gas appliance such as a furnace or a jumper to a water pipe at the water heater. The gas pipe in the ground must be separated from the bond by a dialectic union......a twist on that is the introduction of CSST which requires a solid #6 bonding jumper between the gas hard pipe and the grounding electrode system.
     
    #41 ICE, Jan 3, 2018
    Last edited: Jan 4, 2018
  2. conarb

    conarb Sawhorse

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    How do you know the difference btween bonding and grounding? It all looks the same to a dumb builder like me.
     
  3. Pcinspector1

    Pcinspector1 Platinum Member

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    What a quandary, One forum member imply's I may be imposing my preference and the other, like me want's it safe.

    I blame this on new plastic water lines being used for water service, we've lost our water pipe ground source. When an existing home upgrades the electrical service we have altered the code by allowing an option of TWO rods, that have to be a minimum of 6-ft apart. Distance from a foundation may be difficult to achieve in some situations. In this case the contractor hit rock so he decided to go further out from the home with the ground wire less than 6-inches below grade. I suggested that the rod be installed at 45° per code, with contractor resistance. Claimed he would not be able to remove the driven rod and it would be an additional expense. The end result is the grounding wire and grounding rod is below grade.

    Conarb has mentioned additional rod requirements on some of his projects and some of us may not be aware of our soil types, that is not the case here, I have the County Soil Type Survey. There are some areas I have heard that have had problems with the rock hard caliche, the Las Vegas area I believe.

    Conarb, my avatar is a photo of the AT6 we owned when I was in HS, that paint job was the results of a whole summer of sanding after our plane partner hit a top of a telephone pole on a night landing:eek:. He walked away from the crash and said "the planes all yours!" After that we found repair parts out in CA near SF to put it back together.
     
  4. Pcinspector1

    Pcinspector1 Platinum Member

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    This is a pretty good book to have in your library: Soares book on grounding and bonding.
     
  5. steveray

    steveray Sawhorse

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    We say one rod with 25 ohms or 2 max regardless of resisitance, no resistance test...."subject to damage" is the purview of the inspector, not rod placement....
     
  6. meternerd

    meternerd Member

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  7. meternerd

    meternerd Member

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    NEC only requires that the GEC must be continuous from the electrode to the panel GEC connection, not rod to rod. You could use a grounding clamp on the first rod, then a grounding clamp to the next rod and use another clamp there. They can even be spliced if it is an irreversible splice and is rated for use as such.
     
  8. meternerd

    meternerd Member

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    There is no "max" for number of ground rods. You could put in a dozen if you wanted to....There is a "supplementary grounding electrode" requirement if ground resistance is greater than 25 ohms....but, really, how many have a ground resistance tester and know how to use it? Most just use 2 8' min. rods at least 6 ft apart and call it good. As far as utility jurisdiction, as a utility metering tech, I never got involved in grounding and bonding unless it was obvious that there was a safety hazard, such as a missing MBJ or improperly terminated GEC (such as the GEC terminating on the ground bus but not having a bus bar or jumper to the neutral bar). NEC 250.24.A.4
     
  9. Pcinspector1

    Pcinspector1 Platinum Member

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    Apparently the GEC can be 50-ft out in the middle of your backyard as long as it' covered properly and its no closer than 6-ft to another rod. Seems there should be a limitation on how far it can be from a foundation. Would't even be a discussion item if we still had a water pipe grounding source. Plastic water lines have forced us into an alternative way to ground the service.

    I have a friend in the radio tower business, He sez "wait until one of these new houses that's using the UFER ground up through the foundation wall gets hit by lighting and it blows out the foundation!" I don't know if that can happen or not? I did't have an answer for him.

    He claimed he'd rather have the two rod system!
     
  10. steveray

    steveray Sawhorse

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    We say that the 2 rods are the GE...so continuous....

    PC....If you use the metal water pipe, you have "always" needed the rod as well....
     
  11. Pcinspector1

    Pcinspector1 Platinum Member

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    steveray, yes, I agree...For years we did a water pipe ground and a ground rod. The POCO here no longer installs a grounding rod for their meter socket, the grounding is done at the pole or transformer. We however still require two grounding sources on the panel.
     
  12. Francis Vineyard

    Francis Vineyard Sawhorse

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    Not in the IRC that I know of but in NEC 250.30 the grounding electrode shall be near as practical to and preferably in the same area as the grounding electrode conductor connection to the system.
    The other thing that is misunderstood is the electrodes can be inches apart. The code states each electrode of "one grounding system" shall not be less than 6 feet from any other electrode of "another grounding system. "

    Would not another grounding system be prohibited to be bonded together unless it the same building or same service to another building in accordance to E3607.6 (250.58)?
     
    #52 Francis Vineyard, Jan 12, 2018 at 7:20 PM
    Last edited: Jan 12, 2018 at 8:59 PM
  13. ICE

    ICE Sawhorse

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    250.30 deals with a separately derived system.

    2560.53(D Metal Underground Water Pipe. If used as a grounding electrode, metal underground water pipe shall meet the requirements of 250.53(D)(1) and (D)(2).

    (1) Continuity. Continuity of the grounding path or the bonding connection to interior piping shall not rely on water meters or filtering devices and similar equipment.

    (2) Supplemental Electrode Required. A metal underground water pipe shall be supplemented by an additional electrode of a type specified in 250.52(A)(2) through (A)(8). If the supplemental electrode is of the rod, pipe, or plate type, it shall comply with 250.53(A). The supplemental electrode shall be bonded to one of the following:
    1. (1) Grounding electrode conductor
    2. (2) Grounded service-entrance conductor
    3. (3) Nonflexible grounded service raceway
    4. (4) Any grounded service enclosure
    5. (5) As provided by 250.32(B)
    Exception: The supplemental electrode shall be permitted to be bonded to the interior metal water piping at any convenient point as specified in 250.68(C)(1), Exception.
    (C) Grounding Electrode Connections. Grounding electrode conductors and bonding jumpers shall be permitted to be connected at the following locations and used to extend the connection to an electrode(s):
    (1)
    Interior metal water piping located not more than 1.52 m (5 ft) from the point of entrance to the building shall be permitted to be used as a conductor to interconnect electrodes that are part of the grounding electrode system.


    250.53(A)(2) Supplemental Electrode Required. A single rod, pipe, or plate electrode shall be supplemented by an additional electrode of a type specified in 250.52(A)(2) through (A)(8). The supplemental electrode shall be permitted to be bonded to one of the following:
    1. (1) Rod, pipe, or plate electrode
    2. (2) Grounding electrode conductor
    3. (3) Grounded service-entrance conductor
    4. (4) Nonflexible grounded service raceway
    5. (5) Any grounded service enclosure
      Exception: If a single rod, pipe, or plate grounding electrode has a resistance to earth of 25 ohms or less, the supplemental electrode shall not be required.
    250.54
    (3) Supplemental Electrode. If multiple rod, pipe, or plate electrodes are installed to meet the requirements of this section, they shall not be less than 1.8 m (6 ft) apart.
    Informational Note: The paralleling efficiency of rods is increased by spacing them twice the length of the longest rod.
     
    Francis Vineyard likes this.
  14. Francis Vineyard

    Francis Vineyard Sawhorse

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  15. Mark K

    Mark K Platinum Member

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    The problem with “wanting it safe” is that it is subjective. There is never total safety. One of the roles of building regulations is that the question is resolved in a way that can be understood by all.

    A basic principal of our legal system is that you cannot be compelled to comply with laws that you have no way of knowing. The problem is that the builder has no way to know of requirements that were not adopted that only exist in the mind of the building official. A building official that does not understand this is a loose cannon. You would be incensed if a police officer imposed his own personal laws on you so why not when the building official does the same thing.

    Regarding grounding, the goal is to have a ground resistance less than 5 Ohms (I have also heard 25 Ohms). Is this number or another number clearly stated in the electrical code and if so what is it.

    Because of the hassle of actually measuring the ground resistance minimum requirements or rules of thumb have been adopted. But if you have a system with low enough resistance all the rules of thumb are irrelevant. Failure to comply with the minimum spacing between ground rods just means that the grounding will be less effective. If this is a problem do not abandon the offending ground rod just add another ground rod at least the minimum distance from the first ground rod. When you do this the system will be better.

    It is my understanding the reason for introducing non conducting pipe in the water system is that this prevents grounding current from flowing in the water pipes and thus reduces the corrosion in the water distribution system.

    A ufer ground is not effective if a membrane is placed under all of the footings as is the case in some areas/sites. When this is the case you have a floating ground.
     
  16. ICE

    ICE Sawhorse

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    "The problem with “wanting it safe” is that it is subjective."
    Code is clear, easy to understand with subjectivity removed.

    "There is never total safety."

    But there is. In collaboration with Southern California Edison I have rendered many electrical installations totally safe.

    "One of the roles of building regulations is that the question is resolved in a way that can be understood by all."
    Following code and understanding code are sometimes divergent concepts harbored within a particular mass of brain matter. A great many practitioners of construction trades follow codes with no inkling of why.

    "A basic principal of our legal system is that you cannot be compelled to comply with laws that you have no way of knowing."
    Wrong as wrong can be. Break some arcane law and observe the result with your nose in a corner. "But teacher, I didn't know"

    "The problem is that the builder has no way to know of requirements that were not adopted that only exist in the mind of the building official."
    Well then, that's usually only a problem once. But yes, there are some dimwitted......well Shirley you get where I'm going with this.

    "A building official that does not understand this is a loose cannon."
    A loose cannon is a deadly hazard.....slamming around on the deck of a warship smashing conscripts to bits. The building official you are referencing is more of a sniper in a crows nest. He sees the cannon and it's random destruction while delivering pinpoint correction.

    "You would be incensed if a police officer imposed his own personal laws on you so why not when the building official does the same thing."
    With most folks, that is absolutely correct. Incensed? Such a mild term applies to a few. Pissed off applies to the many. But as Tommy, the oldest Henderson boy said, "Here's the thing about that" The correction could have come from a code book or perhaps my ass. Seldom does anyone know the difference.

    "Regarding grounding, the goal is to have a ground resistance less than 5 Ohms (I have also heard 25 Ohms)."
    Logically the usual goal is zero.

    "Is this number or another number clearly stated in the electrical code and if so what is it."
    25 to 6,100,000,000 can be found in the NEC. Clearly stated? That depends on the level of electrical engineering acumen one has achieved. PHD maybe.

    "Because of the hassle of actually measuring the ground resistance minimum requirements or rules of thumb have been adopted."
    Rules of thumb vary region to region. Here and there it's a thumb on the scale.....with others it's a thumb and a nose.....and yet others have a thumb up their ass. In my experience it is a thumb and a forefinger parroting code for all comers.

    "But if you have a system with low enough resistance all the rules of thumb are irrelevant."
    I do believe that you don't understand the rules that govern the rule of thumb. The relevance of the rule of thumb forces the outcome.

    "Failure to comply with the minimum spacing between ground rods just means that the grounding will be less effective."
    Duh! It's a "just" as in trifling??? This is the subjectivity that was left out of the code.

    "If this is a problem do not abandon the offending ground rod just add another ground rod at least the minimum distance from the first ground rod."
    "If"? Ther's no ifing in baseball. Toss in a rod you say....six feet from the first rod says you. It sounds like advice but is hardly sound advice.

    "When you do this the system will be better."
    Better than what exactly? Is better the best that can be accomplished? Follow the code rather than half baked internet musings and best is your companion.

    "It is my understanding the reason for introducing non conducting pipe in the water system is that this prevents grounding current from flowing in the water pipes and thus reduces the corrosion in the water distribution system."
    Could it be that plastic pipe is so much cheaper and easier to work with.

    "A ufer ground is not effective if a membrane is placed under all of the footings as is the case in some areas/sites. When this is the case you have a floating ground."
    That single sentence lends credence to the rest of what you have written. Shouldn't be that way...do I have permission to remove it?
     
    steveray likes this.
  17. Mark K

    Mark K Platinum Member

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    Ice

    Your reaction suggests that I hit a nerve. Your responses indicate that you did not understand what I was saying.

    I think my posting was a positive informative posting.
     
  18. ICE

    ICE Sawhorse

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    I just didn't have anything to do while I waited for my wife to walk out of a mall. Naturally you like your post....and I suppose that I would not...
     
  19. tmurray

    tmurray Sawhorse

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    What Mark is saying is to ensure we differentiate "rules of thumb" from what is written in the code. As a building official, I cannot enforce a rule of thumb anymore than I can enforce best construction practice. All I can enforce is the code.
     
  20. ICE

    ICE Sawhorse

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    That’s not an uncommon refrain from Mark K. Peppered with loose cannons and big bad wolf building officials threatening to blow the house down.
     
    #60 ICE, Jan 15, 2018 at 3:52 PM
    Last edited: Jan 15, 2018 at 8:21 PM

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