Bonding a surge protector to the eletrical system ground

Discussion in 'Electrical Forum discussion & Blog' started by Ian Gills, Sep 23, 2009.

  1. Ian Gills

    Ian Gills Senior Robin Hood Guy

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    The surge protectors I have procured for my telephone lines and cable require that I bond them to my electrical equipment ground. I am thinking of running a ground wire from them, through the walls to a metal recepticle box (I have yet to put up any drywall) which is of course grounded.

    The surge protectors will be located above the walls on the wooden joists in my basement.

    Any comments?

    And do these devices mean that I can remove the "dodgy" ground wires that appear to have been attached by the telephone and cable companies on the outside of my property to my copper outdoor faucet?
    Last edited: Sep 23, 2009
  2. Thatguy

    Thatguy Homeowner

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    Thick flat straps and thick braided conductors have less inductance per foot than long skinny round wires, and so they make better grounds for surges, but I don't know how practical this would be for your situation or how much benefit you would gain over and above using regular round wires.

    http://images.google.com/imgres?img...ff&client=safari&rls=en-us&sa=N&start=20&um=1

    Don't go messin' with other people's grounds.
    Last edited: Sep 23, 2009
  3. Ian Gills

    Ian Gills Senior Robin Hood Guy

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    Thanks. If I were to screw one of these to metal studs, would that be acceptable?

    I do not feel as though it would be.
  4. Thatguy

    Thatguy Homeowner

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    Metal studs would be great if they are grounded, and will stay grounded, like if they were nailed to concrete in contact with the ground and the connection wouldn't eventually corrode.

    You can check this by hooking up a 100w incand. bulb in series with 120vac in series with the metal stud, but there shouldn't be a GFCI upstream of the outlet you use for this experiment. Full brightness = continuity to ground.
    Last edited: Sep 23, 2009
  5. Ian Gills

    Ian Gills Senior Robin Hood Guy

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    Thanks. These studs really are grounded. All of the outlet boxes connected to them are metal boxes which are grounded to the equipment service ground.
  6. toolaholic

    toolaholic General Contractor Carpenter

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    A differt way

    I put a whole house surge protector in the top slot of the service panel.
    It locks in as any other breaker. You won't fing these at Home CRAPO.

    Real Elec. supply house:)
  7. Billy_Bob

    Billy_Bob In the Trades

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    It's best to use a "central point of ground"...

    That is, if you are using a cold water pipe ground, then run large gauge ground wires from the various devices (electric, phone, cable) to that same point.

    Or if using a ground rod, then to run the wires to that point.

    The reason for this is a thing called "ground loops". You can get electricity flowing between grounds if grounded at different points. Electronic stuff does not like this - it can cause "noise" on audio/video systems.

    Ground loop...
    http://www.epanorama.net/documents/groundloop/

    Then so far as lightning goes, if a surge of this high voltage electricity is directed to the house via utility wires (electric, phone, cable), I feel it is best to keep that high voltage "outside" where it belongs. That is it would travel in the wire going to the house, then be caught by the surge protector outside, then directed via the ground wire from there along the outside wall to the ground (ground rod, cold water pipe ground).

    I would not want to "invite" a high voltage surge of electricity inside the house (by placing the surge protector there), then have the surge travel on wiring located inside the house, then go back outside.

    Like in this picture, everything is outside...
    http://www.mikeholt.com/htmlnews/grounding/figure1.gif

    Of course you can't always keep everything outside. But the idea is to not run the "path" of a potential high voltage surge through the house if you can avoid it.

    As to grounding, it used to be that a cold water pipe ground was ok. Then plastic pipe came along! These days 2 ground rods placed 6 ft. apart is the best and the cold water pipe "bonded" to the ground rods.

    The problem is that someone may have replaced the underground water pipe with plastic pipe and it is no longer a good ground! Or someone may do this in the future and not bother to move the electrical systems grounds to ground rods.

    Here are a bunch of articles on grounding vs bonding from EC&M...
    http://www.google.com/search?hl=en&...hts=&as_occt=any&cr=&as_nlo=&as_nhi=&safe=off
  8. Thatguy

    Thatguy Homeowner

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    furthermore. . .

    A good DC ground may not be a good AC ground.
    If lightning voltage takes 1 µS to rise to peak value the highest freq. contained in this waveform is 350 kHz. Lord only knows what your grounding system impedance is at this freq., and where the current will go.
    All the interconnected metal in your house becomes a very complex high frequency transmission line.

    A "single point ground" is a point of "zero" impedance, and I don't think you'll find one in a residence, but you can get close.
    In a small piece of electronic gear it is usually taken to be the negative terminal of the huge power supply filter capacitor and is practically achievable.

    The problem is there is no easy way to test and debug your system unless you rent a lightning simulator and a bunch of other test equip.
    The "standard lightning bolt" gives
    a current waveform of 8 x 20 us, the 8 is the risetime, the 20 is to half the crest value, with a 30 kA crest value.
    For voltage, it's 1.2 x 50 us, with the 50 being to half value.

    That's why the surge protectors offer insurance. They remove as much as risk as they can with the electronics and then insure the rest.
    If the cost of this policy is 10% of the price of the protector, say $10 for $5k worth of insurance, then the likelihood of your stuff getting fried over the life of the protector is a little less than 10/5000 = 0.2%.
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