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Thread: generator tap box

  1. #1

    generator tap box

    Can someone help me. A generator tap box is located for the purpose of bringing a Food Store to life again after a storm. So rather than renting a portable gen and runing cables all over the floor back to the main board disconnecting the mains and connecting the generator cables. This box is already connected to the main board via taps and all the genrator company have to do is plug into the tap box near the loading doc with camlocks and open the main brker and away she blows.
    The question is can you connect the conductor via conduit say 100' right to the main board without a disconnect means?
    The main board is rated 2500A the conductors for the generator tap box is 800A. The tap box is kirk key with the MCB at the board.
    This feeder is only used when their is a power failure the rest of the time is connectd hot to the tap box.

  2. #2
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    Quote Originally Posted by jrvazzer View Post
    The question is can you connect the conductor via conduit say 100' right to the main board without a disconnect means?
    No, you would not be able to connect the conductors directly to the main switchboard without an OC protection device. You will have to follow the rules for tap conductors in 240.21(B)(1) or (2).

    Rick
    If I can't fix it, it's not broke.

  3. #3
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    Generator Tap Box Conection

    As stated you cannot run from the generator to the switchboard without overcurrent protection. From what you stated, you have the tap box connected to the switchboard via the 800amp breaker and the Kirk Key interock only allowes either the MCB or the 800 Amp breaker to be closed, but not both. Typically the generator will have a main breaker to protect the conductors from the generator to the tap box and the switchboard.

  4. #4

    generator tap box

    Quote Originally Posted by grant View Post
    As stated you cannot run from the generator to the switchboard without overcurrent protection. From what you stated, you have the tap box connected to the switchboard via the 800amp breaker and the Kirk Key interock only allowes either the MCB or the 800 Amp breaker to be closed, but not both. Typically the generator will have a main breaker to protect the conductors from the generator to the tap box and the switchboard.
    Why does it need ocp at the main board? These conductors are only backfeeding the Main board. The Generator tap box can only be activated when the main ckt. beakers is off. The generator is only 600 Amps.

  5. #5

    Generator Tap box

    Quote Originally Posted by RUWired View Post
    No, you would not be able to connect the conductors directly to the main switchboard without an OC protection device. You will have to follow the rules for tap conductors in 240.21(B)(1) or (2).

    Rick
    Why does it need ocp at the main board? These conductors are only backfeeding the Main board. The Generator tap box can only be activated when the main ckt. beakers is off. The generator is only 600 Amps

  6. #6
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    Quote Originally Posted by jrvazzer View Post
    Why does it need ocp at the main board? These conductors are only backfeeding the Main board. The Generator tap box can only be activated when the main ckt. beakers is off. The generator is only 600 Amps
    I don't see that it does need OCP at the main board. Just a switch with no OCP should be sufficient. The conductors need OCP at the supply end.

  7. #7
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    Considering you often have little control over the size of the overcurrent device on the generator that you rent in an emergency I think it is more than prudent to install overcurent protection at the gear that has a setting less than the rating of the conductors to and the tap box itself.

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    Quote Originally Posted by jrvazzer View Post
    Why does it need ocp at the main board? These conductors are only backfeeding the Main board. The Generator tap box can only be activated when the main ckt. beakers is off. The generator is only 600 Amps
    The way i see it is the conductors are tapped at the switch board, and are energized from the bus bar untill interlocked out. There would'nt be any short circuit protection on the conductors while in the normal condition.

    Rick
    If I can't fix it, it's not broke.

  9. #9
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    Quote Originally Posted by RUWired View Post
    The way i see it is the conductors are tapped at the switch board, and are energized from the bus bar untill interlocked out. There would'nt be any short circuit protection on the conductors while in the normal condition.

    Rick
    Because of the kirk key set up it should be impossible to feed the tap box from the utility.

  10. #10
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    Quote Originally Posted by iwire View Post
    Because of the kirk key set up it should be impossible to feed the tap box from the utility.
    Unless i'm missing something in the OP,the tapped conductors are still energized up to the tap box located 100' plus away. The kirk key opens the main breaker on the switch board, then allows the closing of the tap box breaker/ enclosure from the generator source.

    Rick
    If I can't fix it, it's not broke.

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