Lights
9 400 watt lights on circuit
9 x 400 = 3600 watts
3600 x 125% (continuous duty) = 4500
4500 divided by 240 -= 18.75 amps
to close for 20 amp breaker?????
Could you jump wire up to #10 & put 25 amp breaker?
I'm getting this idea off 210.23 (c) 30 amp branch circuits (( 2014 NEC page 70-59.))
There are 9 plug connected 400 W fixtures on this circuit.
If can use the 30 amp rule =1 circuit two pole brk 25 amp
if not = 2 circuits two two pole brk 20 amp
Yoopersup
You have already taken into account the 80% factor. It should be fine on a 20 with #12. The only issue might be inrush if this is an inductive load.
Yoop:
You may want to check the spec on the fixture/ballast. You didn't say if MH, or HPS, or ??
MH 400 watt is 460 watts +/- operating current.
Good catch John. If that is true it does take you over the 16a max on a 20a circuit so you will be on a 25/30 or split it between 2 circuits for a little redundancy.
As the EC, I would do 2 circuits, 20 amp @ 240 volt. I did a lot of lighting as an EC back in the day, both interior and site lighting. A lot of design/ build, retrofit HPS to MH (no LED back then) . We even eliminated LPS site lighting.
Yoop has 9 fixtures, probably 3 rows of 3 ea., so a 5/4 split would not be bad, one row of 3 with the center of the next row, then the balance of 5.
I wonder IF he considered LED, or T-5 high bays??
There's a lot of LED retro going on here, and I'm amazed at the rapidly changing technology. I just started plan review today on some crazy 'arcade' in a mall, and it is 99% LED. A recent Apple retail store is 100% LED, with a gorgeous evenly lit ceiling in the whole retail area.
The total area is 6 rows of 9 Green house grow lights.
They want to be able to put each row on a time clock.
Led lights (which I brought up) four or more times the cost
Additional Info .
If John is right about the total load (ballast plus lights = 4600w) your original plan may be the way to go (25a/ 10ga wire). If you find out it is really only 400w per luminaire, you can do 20a / 12ga.
Greg:
As I do not have all the catalogs I used to have in my home office, and this is 'bugging' me, I found this limited info today.
https://unvlt.com/pdf/literature/navigator/pdfs/BNC_Sect_4_HID.pdfHopefully this paste job comes up as a link to ballast info.
The good info is on page 4-17, 'input watts'!
I see that. It appears that all of those lights carry an overhead beyond the nominal watt rating of the light. My only question is whether the "max amps" is the initial starting current or the continuous load once they start and settle down. That would make a difference when you were calculating the continuous load.
Greg:
From memory, HPS had a lower 'running' current after warm up; MH was the opposite.
There are 360 watt MH lamps, which were supposed to retro the 400 fixtures for 'energy saving'. I do not know what this did/does to the operating load. Comparative math (seat of the pants style) 10% reduction in lamp wattage should equate to 10% on line side of ballast; 460 -46 = 414.
Time to do the upsell to T5 fluorescents, or better yet LED with 100k hr life. ROI is quick too.
I don't know how well LED grow lights work. I suppose it depends on the wave lengths of the energy plants absorb in the various magical processes that take place. LEDs tend to be monochromatic.
A EC mentioned at a recent seminar that he completed a medical grow building with LED fixtures. The fixtures were supplied by the grower.
I think the fixtures were within the spec/plans that were submitted to the State for review and the jumping through hoops for the legal growers and dispensaries.
The discussion I had with him was these LEDs were within the spectrum for grow lights. That is a little beyond my scope.
Yoop:
Sorry if I’m getting off the path of your original question.