How would I ground an internal ethernet surge protector?

Discussion in 'Electrical Forum discussion & Blog' started by homeoftheben, Apr 30, 2013.

  1. homeoftheben

    homeoftheben New Member

    Messages:
    2
    Location:
    Louisiana
    I have a Cat-6 cable running to an external PoE security camera that I'd like to have surge protected, but I'm unsure how to ground the protector. It has a prong coming off that I assume is the ground wire, but I don't know where to connect this. Is there an adapter to connect it to a close-by outlet and use that as ground? I feel that the location of the surge protector (indoors, about 8 feet high) is too far to try to attach it to an outdoor "to earth" pole.

    Here is the surge protector : http://www.amazon.com/Ethernet-Prot...2546&sr=8-4&keywords=ethernet surge protector

    Thanks for any help or advice!
  2. westom

    westom New Member

    Messages:
    11
    Location:
    nja
    That prong is a safety ground. Surge protection is about something completely different - earth ground. That protector must make a connection to earth that is as short as possible. A connection that has no sharp bends and is not even inside metallic conduit.

    Assuming a camera is separate from the building, then its ethernet cable must connect to earth at both ends. At the camera end. And at the building service entrance. A connection that must be low impedance (every foot shorter means better protection). IOW the cable must enter the building to be earthed within feet to the same earth ground used by telephone, TV cable, and AC electric. This short and single point ground is critically important.

    Two separate structures means a lightning strike to one can be a direct strike to earth via electronics inside the other. Damage if a cable does not connect to earth at both ends - via that protector.
  3. LLigetfa

    LLigetfa DIYer, not in the trades

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    NW Ontario, Canada
    Depending on the brand, the POE injector/power supply probably has protection already built in but it wouldn't hurt to have more protection both upstream and downstream of it.

    In most places, code requires that there be entrance protection. I generally penetrate a residential building at the service entrance where a suitable ground already exists. There, I mount an outdoor protector that ties into the service ground rod outside.

    On commercial installs, I might use a larger 66 block type protector, again bonded to the service ground. I use various products from LCom, Datalinx, and Polyphaser. Polyphaser has a very good TD (TD1007) on protecting camera systems but it is way over the top for a home DIY project on a small budget.
  4. homeoftheben

    homeoftheben New Member

    Messages:
    2
    Location:
    Louisiana
    Thanks for the great replies! I'm currently figuring out how to route the cable to the existing ground before entering the building. How would I connect the device I linked above to the ground pole? (It's just a 2 ft. metal stake I believe either the cable installers or electricians drove into the ground by the outer circuit breaker box). Also, should I just drive another metal rod where the camera is installed? Will having two ground poles within 2-300 feet of each other cause any loops or problems?

    EDIT: Also, trying to get back to the existing ground rod would be an extra 150-200 feet. Could I drive a ground rod before I get to the building and connect my surge protector ground wire to it? Then just punch into the building at that spot?
    Last edited: May 1, 2013
  5. westom

    westom New Member

    Messages:
    11
    Location:
    nja
    That rod (electrode) must first meet human safety requirements. At minimum, it must be at least 8 feet deep. Usually, electricians install multiple rods rather than buy a machine to measure ground resistance. Only to meet human safety requirements.

    You are using the same earth ground to also perform surge protection. Therefore an electrode must both meet and exceed those human safety requirements.

    To exceed code requirements, a utility's application note demonstrates good, bad, and ugly (preferred, wrong, and right) solutions at:
    http://www.duke-energy.com/indiana-business/products/power-quality/tech-tip-08.asp
    In the bad (wrong) example, a surge on AC mains can find CATV earth ground destructively via appliances. You are simply adding another incoming wire - security camera. The utility demonstrates how your camera and all other incoming utilities must be earthed.

    Its not about earth ground. All four words are significant. Its about single point earth ground - as demonstrated by good (preferred) and ugly (right) examples.

    Critical is "impedance" of that earth connection. Protector connected to earth with sharp wire bends, splices, not separated from other non-grounding wires, inside metallic conduit, or too long (ie > 10 feet) means protection is compromised.
  6. jwelectric

    jwelectric Electrical Contractor/Instructor

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    2,529
    Location:
    North Carolina
    Any and all ground rods must be bonded together no matter why they are installed
  7. LLigetfa

    LLigetfa DIYer, not in the trades

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    3,826
    Location:
    NW Ontario, Canada
    Ja, and in these parts they want #6 wire to bond them.
  8. westom

    westom New Member

    Messages:
    11
    Location:
    nja
    The point of interconnecting electrodes is to create equipotential. Accomplished by interconnecting wires that are buried. Then safety code says how deep and how much thicker that wire must be.

    Two key terms apply to earthing that must also exceed safety code requirments. Equipotential and conductivity.
  9. LLigetfa

    LLigetfa DIYer, not in the trades

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    Location:
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    You're preaching to the choir. I do this for a living.
  10. DonL

    DonL Jack of all trades

    Messages:
    3,810
    Location:
    Houston, TX
    over complicated ?

    It sounds like this project is being over complicated.

    This surge protector is not a lightning Arrestor.

    It is made to be grounded at the AC outlet at the same location as the AC Power Line surge protector, a device with a 3 prong AC plug. At the system UPS is a good place.

    The key for one of them to really work depends all on the Cable Lengths used, for the ground return path and the Ethernet cable length.

    You need to have a shorter ground return path and a longer Ethernet cable length, so that the point of true ground, (ie Electrical entrance panel ground rod) is shorter than the electrical path back thru the Device it is protecting.

    The closer the unit is to the ground rod the better.

    Since you are running power over the Ethernet cable then you can install a ground rod at the camera end with no need to bond to your electrical system, connect the protector at the ground rod. This will help with ground loop problems also.

    http://www.inscapedata.com/pdf/Outdoor Risk and Equipment Protection R01.pdf


    Good Luck.
    Last edited: May 3, 2013
  11. jwelectric

    jwelectric Electrical Contractor/Instructor

    Messages:
    2,529
    Location:
    North Carolina
    As with any surge or lightning arrestor the lower the resistance to earth the more current it will dissipate in the event of a surge caused by lightning.

    It is near impossible to achieve much more than a couple of hundred ohms with one rod but tie several rods together and the resistance drops. By burying a bare #6 in the earth to bond these rods together also helps to reduce the resistance.

    For a pole such as a parking lot light or other such items it is permissible to drive a rod just for it and be code compliant but to tie it back to the service electrode helps save the light.
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