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Thread: EPO button

  1. #1
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    EPO button

    We have an IT room, all receptacles and UPS were fed out of a 208/120V panel with main shunt trip CB.

    The CRAC unit serves the room is 480V/3PH, we have ran 480V circuit to a shunt trip - enclosed CB mounted in the room and feeds the CRAC unit.

    Per, NEC we have to install an EPO at the room entrance, this EPO will shuts down power to both the panel and CRAC unit through shunt trip feature once EPO is activated by someone.

    Question:

    - Do we need to run 120V circuit to EPO to operate it or it can be operate at 24V DC? If it operates at 24V, should we need a step down xfmr to 24V or it comes as integral part of EPO?

    - Do we tie fire alarm signal wiring to the EPO output too? (24V)

    - What is the wiring connection between EPO and panel as well as between EPO and enclosed CB? Will this 120V or 24V or 277V?



    * Note:

    * The shunt trip coil for panel is 120V.
    * The shunt trip coil for enclosed CB is 277V.

  2. #2
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    anbm, Per code, you do not have to do any of this for an IT Rm.
    Frank Arizona,USA

  3. #3
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    There is no requirement to install an EPO unless you want the wiring leniencies allowed in article 645.

  4. #4
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    Quote Originally Posted by anbm View Post
    We have an IT room, all receptacles and UPS were fed out of a 208/120V panel with main shunt trip CB.

    The CRAC unit serves the room is 480V/3PH, we have ran 480V circuit to a shunt trip - enclosed CB mounted in the room and feeds the CRAC unit.

    Per, NEC we have to install an EPO at the room entrance, this EPO will shuts down power to both the panel and CRAC unit through shunt trip feature once EPO is activated by someone.

    Question:

    - Do we need to run 120V circuit to EPO to operate it or it can be operate at 24V DC? If it operates at 24V, should we need a step down xfmr to 24V or it comes as integral part of EPO?

    - Do we tie fire alarm signal wiring to the EPO output too? (24V)

    - What is the wiring connection between EPO and panel as well as between EPO and enclosed CB? Will this 120V or 24V or 277V?



    * Note:

    * The shunt trip coil for panel is 120V.
    * The shunt trip coil for enclosed CB is 277V.
    A bit of circular logic in that 645.4 says~ . . . article shall apply provided all the following . . .(1) Disconnect complying with 645.10 is provided.
    So if you will meet the 5 conditions, call it an IT equip. room.

    You can use separate buttons, or integrate the hvac and electronic into one. Just be sure they are grouped at the main exit. Voltage shouldn't matter. You only need to disconnect power to the hvac, closing required dampers, and shut down "electronic equipment" in the room (or secial zones), so a 24 volt supply to the buttons could remain on, incandescant lights, resistance loads, etc, but of course you wouldn't want to do that if not needed.

    Don't forget to provide a means for removing the UPS batteries from their loads with the disconnect too. Not always easy.

    Don't know much FA, but might be smart to send a signal

  5. #5
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    Quote Originally Posted by Volta View Post
    A bit of circular logic in that 645.4 says~ . . . article shall apply provided all the following . . .(1) Disconnect complying with 645.10 is provided.
    So if you will meet the 5 conditions, call it an IT equip. room.
    Not exactly, if you choose to use 645 then you need a EPO.

    Here is a great article co-written by one of the forum members

    NEC 645 Might Not be for You

  6. #6
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    There is only one manufacturer that has tried to make a pre-packaged EPO system. Otherwise, it is designers choice.

    You could do it all at 24V, 120V, or whatever you choose to design it at, as long as it will work.

    The fire alarm does not need to be tied into the EPO, unless you need it to for operation of dampers or you just want to design it that way. You can always go above the minimum code if you like.

    I agree with Bob's point about needing it or not.

    BTW, thanks for the "shout out" Bob. I understand that is new slang I overheard from my kids.
    Ron

  7. #7
    Join Date
    Jul 2006
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    If you choose to put up an EPO, get one of the nice pre-made plexiglass covers for it. Prevents (most) nuisance tripping. Regarding the FA tie-in, sgtate/local codes will probably cover that.

  8. #8
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    Quote Originally Posted by iwire View Post
    Not exactly, if you choose to use 645 then you need a EPO. . .
    I think we agree, but trying to be sure.
    Agreed that the room does not need to comply with the 5 conditions spelled out in 645.4.
    Thus, would not be called an IT Equipment Room per NEC.

    But I feel that if the five conditions have been met, that compliance with 645 is then mandatory per 645.4, "This article shall apply, provided all of the following conditions are met: . . . ".
    At that point it has become an IT room, and things like 645.11 should be followed.

    That said, I am aware of the exception to 645.10. It is not an exception to 645.4, however, and seems to simply change the list of 5 conditions, (1) essentially becomes "Disconnecting means complying with 645.10 are provided or compliance with Article 685 is shown". The remaining 4 conditions stand.

    Quote Originally Posted by ron View Post
    . . .BTW, thanks for the "shout out" Bob. I understand that is new slang I overheard from my kids.
    Nice article.:smile:

  9. #9
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    It is very difficult to get the exception for 645.10 because you need to show that an orderly shutdown is required to minimize personnel hazard and equipment damage. The equipment damage part isn't a problem, but the personnel hazard is tough.
    Ron

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