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Thread: 277v + 0-10V dc configuration

  1. #1
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    277v + 0-10V dc configuration

    I am doing a retrofit in a conference room that originally contained 4 sp switches in a 4 gang box to control 1/2 recessed cans and 3/4 dropped fluorescent arrays. With the projector blocked by the fluorescent fixtures, it was decided to install 2x2 led flat panels using Lutron Diva switch dimmers combos on two of the circuits. Lighting voltage is 277v. I am confused by the req's of article 725 and the separation of low and hi voltage in a box. We are attempting to utilize the same location with the dimmers. How, if at all can I use the 277v terminated in the same box as the violet/grey if the dimming circuit. The low voltage wires have no id on them concerning rating for voltage or temp. I am stuck here and could use some extra input. Am I missing anything?,

  2. #2
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    Did you look at 725.136(D)? That appears to apply to your application.
    Don, Illinois
    Ego is the anesthesia that deadens the pain of stupidity. Dr. Rick Rigsby
    (All code citations are 2017 unless otherwise noted)

  3. #3
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    I have wondered the same thing, I have guessed that their reasoning in allowing us to have them run together is that the luminaire LV wiring (grey/violet) never physically leave the branch circuit they are running with, and the CAT5 connections seem to be isolated from the higher voltages by the solid state internals of the controllers etc.

    Where as typical LV circuit wires (ie data, sound, etc) (could otherwise contact higher voltages and then) run all over the place.

    (my reasoning is often done on a wobbly ladder while in a very hot ceiling, so my accuracy may reflect that)

  4. #4
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    Quote Originally Posted by Zelos Ravioli View Post
    I have wondered the same thing, I have guessed that their reasoning in allowing us to have them run together is that the luminaire LV wiring (grey/violet) never physically leave the branch circuit they are running with, and the CAT5 connections seem to be isolated from the higher voltages by the solid state internals of the controllers etc.

    Where as typical LV circuit wires (ie data, sound, etc) (could otherwise contact higher voltages and then) run all over the place.

    (my reasoning is often done on a wobbly ladder while in a very hot ceiling, so my accuracy may reflect that)
    You and the OP are talking about two different things. Don's reference answers the OP's question. Both class 2 and lighting wiring can terminate in the same enclosure. Class two wiring can't be run in the same raceway as power wiring though. Class 2 wiring is basically determined by looking at the power supply and it is clearly marked as class 2. 725.130 A exception 2 allows you to reclassify the power supply as class one. Be aware, though that this means to all wiring on the load side of the power supply must be run as class one. Here is a fairly good reference for 0-10v dimming a link because the file exceeds the limit. http://www.cooperindustries.com/cont...1_2_wiring.pdf


    I know what I don't know, and I know where to go to find it!

  5. #5
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    725.136 (D)(2)

    That works except that one little detail in subheading (2) that states "The circuit conductors operate at 150 volts to ground or less
    and also......."

  6. #6
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    They do now manufacture MC cable with the Class 2 cable included as a single cable.
    Since this is an existing system...you might be able to just install the Class 2 cable.

    Quote Originally Posted by Strathead View Post
    You and the OP are talking about two different things. Don's reference answers the OP's question. Both class 2 and lighting wiring can terminate in the same enclosure. Class two wiring can't be run in the same raceway as power wiring though. Class 2 wiring is basically determined by looking at the power supply and it is clearly marked as class 2. 725.130 A exception 2 allows you to reclassify the power supply as class one. Be aware, though that this means to all wiring on the load side of the power supply must be run as class one. Here is a fairly good reference for 0-10v dimming a link because the file exceeds the limit. http://www.cooperindustries.com/cont...1_2_wiring.pdf
    PJHolguin 8-)

  7. #7
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    This same question comes up about every month or so. Do a search for "0-10v dimming" so we don't have to rehash the same thing over and over again.

    -Hal

  8. #8
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    Quote Originally Posted by Patmandad View Post
    That works except that one little detail in subheading (2) that states "The circuit conductors operate at 150 volts to ground or less
    and also......."
    There is an "or" in the code text. You comply with (1) or (2).
    Don, Illinois
    Ego is the anesthesia that deadens the pain of stupidity. Dr. Rick Rigsby
    (All code citations are 2017 unless otherwise noted)

  9. #9
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    Pj, I wasn't giving Patmandad an answer, I was simply stating that I have 'wondered' 'why' it is allowed, not wondering 'if' it is allowed. I 'know' "Both class 2 and lighting wiring can terminate in the same enclosure..." obviously we terminate these them in the same enclosure all the time, as the MC luminaire 'comes with' the 16awg pair.

    Why would anyone naturally think this was a concern? Because one would think that if a low voltage circuit
    accidentally comes in contact with a higher voltage circuit (say 277), it may pose a dangerous or hazardous condition.

    My point was simply stating a 'reason' for maybe 'why' the NEC allows for it, where in most any other case class 2 circuits can't be run with higher voltages - 'because' of the obvious 'danger'.

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