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Thread: 277 volt flourescent lighting wiring

  1. #1
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    277 volt flourescent lighting wiring

    Hello all,

    I am an E.E. working on the lighting drawing for the conversion of a warehouse into an office building. Typically for an office building I would spec out 120 VAC lighting that would be fed from either a 208/120 incoming line from the power company or use a transformer to convert the 480 incoming line to 208/120 for the lighting.

    I have a client that has specified that the flourescent lighting is to be 277 VAC rather than 120 VAC. I don't necessarily feel that this is the best option for office space but that's what is specified.

    My question is that although I am familiar with lighting contactors to control the 277 volt lighting is it normal to power up the 277 lighting in the same manner as with 120 VAC other than making sure all switches are rated fo 277 rather than just 120V. I don't think I really need lighting contactors based on the number of luminaires and the respective load but I have never seen an actual design where 277 VAC is distributed through wall mounted light switches just like 120VAC would be. I am sure it can be done but is there anything in the code that I need to be aware of and is this considered a normal way to wire up 277 VAc luminaires. All the designs I have seen before used lighting contactors for 480 or 277 VAC power wiring to the lights Thanks

  2. #2
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    In my area any building that has a 480Y/277 service will use 277 for all the lighting they can.

    You can control it exactly like 120 volt lighting, the correct wall switches are readily available.

    One thing to consider is the code prohibits more then 300 volts between adjacent switches.

  3. #3
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    You will also get far more fixtures on a circuit at 277.Foolish to go 120 if 277 is available.Why spend money on a transformer that is not needed.Most of the fixtures are dual rated so no extra cost.

  4. #4
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    I agree with the others. Most of my projects use 277 volt lights. We generally reserve one 480/277 volt branch panel per floor for lights, depending on the square footage of the floors.

    Welcome to the forum.
    Charles E. Beck, P.E., Seattle
    Comments based on 2014 NEC unless otherwise noted.

  5. #5
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    Talking ce2two

    Most high rise office buildings use 277vac . for lighting , even costs less to operate 277 compared to 120vac. lighting , .3 amps per .277v ballast (pink) , i can see using 120 for a small strip mall .....for an E.E. you should know this big dog no dis-respect to you ,yet if you don't ask, you will never know ...welcome to the forum ....never use a contactor for office lights ,thats un-heard of.......may be yard lights, street lights etc........:

  6. #6
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    Thumbs up Welcome to the Forum

    I know, but James does not, that you really do not mean to put him down. Consider, the schools today do not teach power courses and the NEC in depth. The EE has to work for a firm where he can learn what he needs to know in order to do his designs properly. He has the theory but not the practical knowledge and is in need of experience. When coming across something different, he has to ask questions. I can't think of a better place to ask these kind of questions.

    By the way, James, welcome to the forum. :smile:
    Charlie Eldridge, Indianapolis, Utility Power Guy
    Responses based on the 2011 NEC, unless stated otherwise.

  7. #7
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    Quote Originally Posted by ce2two
    even costs less to operate 277 compared to 120vac. lighting , .3 amps per .277v ballast
    Whether the voltage is 277 or 120 you will still be paying approximately the same cost to operate fixtures with identical input power.
    Last edited by ike5547; 10-20-08 at 03:57 PM.

  8. #8
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    Quote Originally Posted by ce2two
    Most high rise office buildings use 277vac . for lighting , even costs less to operate 277 compared to 120vac. lighting , .3 amps per .277v ballast (pink) , i can see using 120 for a small strip mall .....for an E.E. you should know this big dog no dis-respect to you ,yet if you don't ask, you will never know ...welcome to the forum ....never use a contactor for office lights ,thats un-heard of.......may be yard lights, street lights etc........:
    Contactors are used for office lighting all the time. It depends on the ammopunt of lights under a single source of control. Microprocessor scheduled area lighting used this for a long time now.

    The segregation of 480/277V lighting from the 208/120V convenience outlets is an important problem to address.

    Depends on the distances the elimination of separate lighting transformers or the reduction in size offer energy savings, not necessarily justifying a retrofit installation but good foresight in initial installation.

  9. #9
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    Quote Originally Posted by ce2two
    Most high rise office buildings use 277vac . for lighting , even costs less to operate 277 compared to 120vac. lighting , .3 amps per .277v ballast (pink) , i can see using 120 for a small strip mall .....for an E.E. you should know this big dog no dis-respect to you ,yet if you don't ask, you will never know ...welcome to the forum ....never use a contactor for office lights ,thats un-heard of.......may be yard lights, street lights etc........:
    Say what ? why no contactor ? You must be doing small stuff.Customer often needs 4 ways to control far more than a 20 amp switch can.

  10. #10
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    One thing to consider is the code prohibits more then 300 volts between adjacent switches.
    Hey, thanks! ....I learnt somthin today.

    Not a bad idea BTW (the 300V thing)

    It reminded me of my first week in the trade being concerned that there was 240V in a switch box (MWBC). The journeyman assured me it was safe. 480 on the otherhand does seem a bit dicey.
    Disclaimer: The opinions expressed here are solely mine and do not necessarily reflect the views of other members of this community. Do not misunderstand them as an encouragement to violate the NEC. Also, don't forget that the NEC is not necessarily the AHJ.

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