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Thread: Use Definite Purpose Contactor To Switch Different Voltages To LED High Bay

  1. #21
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    Quote Originally Posted by rt66electric View Post
    Wouldn't be easier to add another light fixture??
    "Electricity is really just organized lightning." George Carlin


    Derek

  2. #22
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    Quote Originally Posted by rt66electric View Post
    Wouldn't be easier to add another light fixture??
    Sure would, just no space. Cheers

  3. #23
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    How about a fixture with two separate ballasts?
    Code references based on 2005 NEC
    Larry B. Fine
    Master Electrician
    Electrical Contractor
    Richmond, VA

  4. #24
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    Some clarification after some research

    Quote Originally Posted by petersonra View Post
    I think this chain of logic precludes doing this.





    However, I suspect you could buy a device that is not a whole lot more than a contactor to accomplish the same thing as long as it is listed properly.
    After researching this, I've realized that what we are actually accomplishing here is an emergency bypass, not a transfer. The actual transfer to emergency power happens way upstream. What we are doing is bypassing wall switches to make sure that the allocated emergency fixtures come on.

    This would not be an issue in most environments, as the fixtures designated as emergency lights in an area (e.g., a warehouse floor) would not go out when the wall switch is turned off at the end of the day. Our environment (a theatre), requires that all lights go out when switched. In this case, I believe that UL924 applies -- on power loss, we're simply bypassing the wall switch and returning the fixture to emergency power.

    So, then, a better question would have been:
    For a fixture that will accept both voltages, would it be acceptable to use a UL924 certified relay as an emergency bypass, with 120 volts across the NO contacts and 277 on the NC contacts?

  5. #25
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    Quote Originally Posted by dng View Post
    After researching this, I've realized that what we are actually accomplishing here is an emergency bypass, not a transfer. The actual transfer to emergency power happens way upstream. What we are doing is bypassing wall switches to make sure that the allocated emergency fixtures come on.

    This would not be an issue in most environments, as the fixtures designated as emergency lights in an area (e.g., a warehouse floor) would not go out when the wall switch is turned off at the end of the day. Our environment (a theatre), requires that all lights go out when switched. In this case, I believe that UL924 applies -- on power loss, we're simply bypassing the wall switch and returning the fixture to emergency power.

    So, then, a better question would have been:
    For a fixture that will accept both voltages, would it be acceptable to use a UL924 certified relay as an emergency bypass, with 120 volts across the NO contacts and 277 on the NC contacts?
    To me bypass would mean you have a control in parallel with the regular control - maybe a contactor contact that is in parallel with a wall switch. You are talking about bringing entirely different source to power the same load, and likely providing some sort of isolation so it can't backfeed into the circuit from the first source. If transfer occurred upstream, then you would be "bypassing" the switch in the original circuit but still supplying with same circuit - only change is in the switching arrangements.
    I live for today, I'm just a day behind.

  6. #26
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    Quote Originally Posted by dng View Post
    After researching this, I've realized that what we are actually accomplishing here is an emergency bypass, not a transfer. The actual transfer to emergency power happens way upstream. What we are doing is bypassing wall switches to make sure that the allocated emergency fixtures come on.

    This would not be an issue in most environments, as the fixtures designated as emergency lights in an area (e.g., a warehouse floor) would not go out when the wall switch is turned off at the end of the day. Our environment (a theatre), requires that all lights go out when switched. In this case, I believe that UL924 applies -- on power loss, we're simply bypassing the wall switch and returning the fixture to emergency power.

    So, then, a better question would have been:
    For a fixture that will accept both voltages, would it be acceptable to use a UL924 certified relay as an emergency bypass, with 120 volts across the NO contacts and 277 on the NC contacts?
    Answering my own question here: No. This would not be a bypass like the rest of our facility, it would be a transfer.

    Sorry to disturb.

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