Adding new ground rod

Discussion in 'Electrical Forum discussion & Blog' started by Smith333, Jun 24, 2008.

  1. Smith333

    Smith333 Member

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    The cable TV (broadband) and antenna lightning supressor are grounded on the copper water line of my house. The problem is that we installed a water softener with plastic connections, so the grounding no longer exists. On top of that, the grounding points are on the opposite side of the house as the softener and well service entry point.

    I think I have two options. I could drive a new grounding rod through the basement concrete floor and into the subsoil. Or, I could run about 100 ft of conductor (not sure which AWG) all the way to the service entrance and ground there. Which is the better idea?
  2. Mikey

    Mikey Aspiring Old Fart, EE, computer & networking geek

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    Generally, you want the ground path as short and straight as possible. That's a vote for the hole in the floor, but unless the basement ceiling is well over 10' it'll be tough to drive standard rod(s).

    I'm a little confused about the water softener installation. If it was just inserted into an existing copper system, it should have been jumpered with a bonding connection from one side to the other to maintain the circuit.
  3. Billy_Bob

    Billy_Bob In the Trades

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  4. Chris75

    Chris75 Electrician

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    First off, the catv must be bonded within 5' of the water entrance, so must the service disconnect if using the metal underground water pipe as an grounding electrode. with that said, I would just install a jumper around the water softner which you should have done anyways if you read the directions that came with the unit...

    If you insist on installing a ground rod you MUST bond that ground rod with the power grounding electrode with #6 AWG copper.
    Last edited: Jun 24, 2008
  5. Chris75

    Chris75 Electrician

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    A ground loop is the least of worries when it comes to bonding the grounding electrodes together...
  6. Bob NH

    Bob NH In the Trades

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    Definitions:
    Grounding Electrode - The metal device such as ground rod, or metal water service line, or other conductor in the earth that meets the code requirements.

    Grounding Electrode Connductor - The conductor that ties the ungrounded conductor (the neutral) to the Grounding Electrode.

    Service - The main disconnect point where the main power enters the house

    If the Grounding Electrode is a metal water pipe serving the house then the Grounding Electrode Conductor from the Service must be connected to the Grounding Electrode (the metal water pipe) within 5 ft of where the metal water line enters the house.

    The size of the Grounding Electrode Conductor depends on the size of the main breaker but need not be larger than 6 AWG if the Grounding Electrode is a ground rod.

    I am traveling and don't have my code with me but I recall that there is a mximum distance from the service entrance to a ground rod that is to be used as a Grounding Electrode.

    The ground of the CATV should be connected to the Grounding Electrode System or Grounding Electrode Conductor. The cable wires usually enter the house near where the power enters the house and the ground is usally attached near the Service panel. Can't cite; no code available.
  7. Chris75

    Chris75 Electrician

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    No maximum distance, but one would think shorter is better.

    Not always, but usually. At my house the electric is on the opposite side of the house from the catv drop.
  8. Bill Arden

    Bill Arden Computer Programmer

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    The more the merrier.

    But... the ground rod needs to be in conductive soil and there is no guarantee that the ground below the slab is conductive enough.

    I would suggest adding a ground just outside near where the CATV enters and run a short wire in.

    That ground then has to be connected to the main ground rod with heavy enough wire so that it does not overheat during a lighting event.

    I don't know what code requires, but I'm guessing 12ga would be good enough.

    The only problem with multiple ground rods is keeping the wires between them heavy enough to handle any currents that might occur.

    Adding more ground rods will also reduce "ground rise" during a lighting event and thus reduce the voltages that get past the protector.

    So... The more the merrier.
  9. Chris75

    Chris75 Electrician

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    Its #6 AWG.
  10. Mikey

    Mikey Aspiring Old Fart, EE, computer & networking geek

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    All the CATV grounding fittings I've seen have holes sized for #8.
  11. Bill Arden

    Bill Arden Computer Programmer

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    The wire between ground rods has to be heavier than the one going to a specific surge protector or grounding fitting.

    I am going to guess the #6 AWG requirement comes from the service current rating so that either ground rod wire could handle the fault current caused by a lost neutral wire.
  12. pudge565

    pudge565 New Member

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    Can't beleive nobody else saw this the neutral is the grounded conductor the hot is the ungrounded.
  13. Mikey

    Mikey Aspiring Old Fart, EE, computer & networking geek

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    I think Bob was just seeing if we were paying attention.
  14. Chris75

    Chris75 Electrician

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    I'm not sure I understand your statement? grounding the electrical system is for limiting voltage imposed by lightning, line surges or unintentional contact with higher voltage lines... thats it...
  15. Chris75

    Chris75 Electrician

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    Thats because all you need is #14 to ground the CATV wire, the #6 is for bonding two electrodes together if you happen to drive a rod for the CATV system...

    Clear as mud?
  16. Mikey

    Mikey Aspiring Old Fart, EE, computer & networking geek

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    About that :D. I was just musing over the voltage drop in a 10' run of 6AWG copper during an average lightning stroke of 40,000 - 300,000A... Of course, some claim the real purpose of a lightning arrestor is not to carry the full impact of a lightning stroke, but to gradually bleed off potential so that the stroke never occurs.
  17. Chris75

    Chris75 Electrician

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    What do you mean by lighting arrestor? The device you can buy, or a ground rod?

    The reason we only need #6 to a ground rod is because thats all the earth is good for anyways... any wire bigger than that would be useless.
  18. Mikey

    Mikey Aspiring Old Fart, EE, computer & networking geek

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    We must have especially good dirt here in Lightning Alley... my house came with a lightning rod system and the downleads are about 5/8" stranded aluminum.

    "Lightning arrestor" was a poor choice of terms. "Lightning protection system" is better, but still bogus, I think.
  19. Chris75

    Chris75 Electrician

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    Probably, since nothing will protect your home from a direct strike.
  20. Bob NH

    Bob NH In the Trades

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    I goofed on the grounded vs ungrounded conductor. The Neutral is the GROUNDED couductor. Brain wasn't working on that one.
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