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Thread: Lighting Load calculations for nondwelling building

  1. #1
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    Lighting Load calculations for nondwelling building

    I have a question regarding general lighting loads table 220.12. We are building a multipurpose building, will have gym in center and classrooms/offices/storage rooms all around sides. This building will be used by a church for events or etc.... I am currently looking into what size service will be needed and when doing the lighting load calculations it was much higher than I expected or that I see practically being used. Schools call for 3va per sq/ft assembly halls call for 1va per sq/ft when using the schools for the offices and classrooms (approx 1,166sq ft) and the assembly halls (approx 8,481sp ft) for the gym area I come up with approx 11,980va. Just wasn't expecting 100amps of lighting.

  2. #2
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    Quote Originally Posted by darren12 View Post
    I have a question regarding general lighting loads table 220.12. We are building a multipurpose building, will have gym in center and classrooms/offices/storage rooms all around sides. This building will be used by a church for events or etc.... I am currently looking into what size service will be needed and when doing the lighting load calculations it was much higher than I expected or that I see practically being used. Schools call for 3va per sq/ft assembly halls call for 1va per sq/ft when using the schools for the offices and classrooms (approx 1,166sq ft) and the assembly halls (approx 8,481sp ft) for the gym area I come up with approx 11,980va. Just wasn't expecting 100amps of lighting.
    That looks like 33 amps of lighting to me, assuming 208V, 3ph. Of course, that is the minimum lighting load for load calculation purposes, not the actual lighting load, which should be quite a bit lower.
    Last edited by david luchini; 08-20-18 at 04:10 PM.

  3. #3
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    11908 VA would be about 100 amps, if it were all on one 120 volt leg. If balanced across 208/120 three phase is only about 33 amps.

    Those values are probably high compared to actual load with new designs with LED light sources though.
    I live for today, I'm just a day behind.

  4. #4
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    Quote Originally Posted by kwired View Post
    11908 VA would be about 100 amps, if it were all on one 120 volt leg. If balanced across 208/120 three phase is only about 33 amps.

    Those values are probably high compared to actual load with new designs with LED light sources though.
    What's bothered me about the NEC requirements for lighting calculations is local Energy codes are more stringent by more than 3x the amount required; it seems the NEC is starting to take this into account but it's still high and excludes many types of spaces and functions that are defined by the Energy Codes. (NEC 2017 220.12 Exceptions 1 and 2)

  5. #5
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    Quote Originally Posted by tw1156 View Post
    What's bothered me about the NEC requirements for lighting calculations is local Energy codes are more stringent by more than 3x the amount required; it seems the NEC is starting to take this into account but it's still high and excludes many types of spaces and functions that are defined by the Energy Codes. (NEC 2017 220.12 Exceptions 1 and 2)
    Values in those tables is mostly if not entirely unchanged for many years and accounts for less efficient lighting than we typically see today.
    I live for today, I'm just a day behind.

  6. #6
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    Quote Originally Posted by kwired View Post
    Values in those tables is mostly if not entirely unchanged for many years and accounts for less efficient lighting than we typically see today.
    Exactly; it's apparent though as part of those exceptions made within the past 2 cycles of the NEC, that they are aware of energy codes dictating more stringent designs, but it still leaves a majority of room/space/occupancy types unaddressed requiring larger service sizes than needed.

  7. #7
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    Quote Originally Posted by kwired View Post
    11908 VA would be about 100 amps, if it were all on one 120 volt leg. If balanced across 208/120 three phase is only about 33 amps.

    Those values are probably high compared to actual load with new designs with LED light sources though.
    Sorry forgot to mention that the utility service in the area is 120/240 single phase, guess I should have used 240 instead of 120 because the lights will be split off the 2 phases.

  8. #8
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    I guess a lot of what I work on lighting isn't a major part of load all that often. Some of this farm stuff I do, is outdoors and that table doesn't even factor into things at all on those installs.

    Got a grain storage facility right now I am doing some work on new addition to it. About 300 hp of motors that may all run at one time. One 15 amp 277 volt circuit for lighting is all that is there. - some 400 watt HID's on existing, new additions will probably be LED's, might add enough we will need an additional 15 amp 277 volt circuit this time. On top of that these lights only get used maybe 10-15 nights a year during harvest time and that is it.
    I live for today, I'm just a day behind.

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