Can't bond ham shack ground to service entry ground

Discussion in 'General Technical Questions and Answers' started by AE0AQ, Mar 6, 2018.

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  1. KF5LJW

    KF5LJW Ham Member QRZ Page

    Nor myself unless build your house or shack yourself. That is why the NEC 810 and 820 make for two methods. What we call Single Point is what all new construction uses and the NEC calls that INTERSYSTEM BONDING as defined in article 100. An Intersystem Bonding is a Ground Bar located on an outside wall where all services enter a building, and the bar is large enough to accommodate all services as covered in 810.21(F)(1)


    [​IMG] [​IMG]

    If a Intersystem Termination bar is not available then you have to access the Ground Electrode system by other means covered in 810.21(F)(2) aka Multi=Point Ground.

    [​IMG]
     
  2. KF5LJW

    KF5LJW Ham Member QRZ Page

    Do not get your shorts in a knot, I was making a point. Rural areas are quite unique. A house fire does not put a city neighborhood in danger .
     
  3. KF5LJW

    KF5LJW Ham Member QRZ Page

    Probable because you do not see the whole picture. The RMC is likely cad welded to the GES at ground level out of frame in the picture. The Panel will be bonded inside the shelter.

    Here is a similar picture

    [​IMG]

    On the other side of the wall is this where coaxes are bonded again. Just about any commercial instsallation will bond the coax at least 4 times, at the tower top, where it breaks off the tower at the ice bridge, just before it enters, and immediately after it enters.

    [​IMG]

    FWIW the contractor that wired the above panel was wrote up and had to fix all th ewire so they were straight.
     
    KP4SX likes this.
  4. W6KCS

    W6KCS Ham Member QRZ Page

    Dereck, if I have a ham station that includes a transmitter, and my antenna is fed with coax, am I required to have an "Antenna Discharge Unit" at the entry, or is it sufficient to ground the shield only?
     
  5. KF5LJW

    KF5LJW Ham Member QRZ Page

    Good question. You have two options per 810.57.

    1. Use an ADU
    2. Use a switch to disconnect the radio and short the coax out to ground.

    I wear suspenders and a belt, so I use both ADU's and a Switch when not operating.

    If you were to just disconnect the coax as some suggest is asking for a huge eye opening shock of an education. If lightning were to strike nearby, the open end of that coax will surge to 10,s of thousands of volts looking to flash over to anything to find earth.

    Somewhere I have video of Ball Lightning at a radio installation when a storm appeared before the installation was finished. There was un-terminated coax in the shelter and the contractors were standing in the door way when lightning stuck the tower. Ball Lightning fell off the coax and danced around the floor discharging. All the hard lines had to be replaced and new underwear purchased.
     
    Last edited: Mar 13, 2018
  6. W6KCS

    W6KCS Ham Member QRZ Page

    Thanks, the reason i asked was I see there is an exception for when the lead in conductor is "enclosed in a continuous metallic shield..." but I didn't know if that referred to coax shield, or something else.
     
  7. AF7ON

    AF7ON Ham Member QRZ Page

    Nope - Exception 1 of 810.57 applies - if you have a continuous shield (coax) all you need to do for compliance is ground the shield. An antenna discharge unit might help protect the radio but won't provide any extra safety benefits.

    Mike
     
    N0TZU likes this.
  8. KF5LJW

    KF5LJW Ham Member QRZ Page

    If you are talking TX only with no RX, that is accurate. I strongly disagree a ADU adds significant safety by limiting voltage and current. That is what Shunts do.
     
  9. W6KCS

    W6KCS Ham Member QRZ Page

    It looks like 810.20 has the same exemptions for ADU in receiving stations, unless I'm reading it wrong.
     
    N0TZU likes this.
  10. N0TZU

    N0TZU Platinum Subscriber Platinum Subscriber QRZ Page

    ADUs provide a very convenient way to both ground the outer shield and provide protection for the center conductor.

    There are grounding clamps for the shield but they must be wrapped and waterproofed unless in an enclosure. With just a shield clamp, the center conductor voltage is limited only by the breakdown voltage of the cable, which can be up to many thousands of volts depending on type, or by other items on the signal path like a tuner or radio. :eek:
     

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