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Old 06-18-2009, 11:20 PM   #1
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Multiple Fluorescent's


I thought of another question if you very knowledgeable folks could help me again.

I am also running 6 4ft 4 tube commercial type fluorescent light fixtures in my garage with the t 12 tubes, I believe they are with the magnetic style ballasts.
I already installed them and ran the wiring for them. I used 2 runs of 12/2 the whole way
My question is that I split each fixture so that I can switch either the inside and or the outside lamps independently,or have all 24 lights ( 12 ballasts) kickin at the same time. There will be 3 switches in total 2 for the celing fixtures and one for the two regular lights on the front of my garage. Can I run 6 fluorescent light fixtures and 2 decorative 60 watt hallogen style lights all from 1 20 amp breaker? or should I have a feeder for each circuit?
seems like a lot to have 3 pig tails to each of the #12 wires on the main feed from the panel to the switch box, not to mention the inital draw when I switch the lights on.

I am also thinking of stealing power from that circuit for a motion sensing dual light flood for the rear of my garage

Thanks
Mark


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Old 06-18-2009, 11:52 PM   #2
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Multiple Fluorescent's


Do a load calcuation. I found this article, which states that fluorescent fixture load is calculated using the rating of the ballasts, not the total wattage of the lamps:

http://www.ecmag.com/?fa=article&articleID=6907

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Old 06-19-2009, 12:17 AM   #3
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Thanks for the link KeithM62948 very helpful, I figured I would need to go by the ballasts but was not sure of the formula that I would use to figure the loads with. would just figure the load for all the fluorescents and the figure the other lighting add them and then I know how many total watts are being drawn.and for my case it would need to be below less than 2400 watts with a safe capacity of 1920 watts and16 amps for a 20 amp circuit. right?

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Old 06-19-2009, 12:39 AM   #4
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That sounds right. You've got me wanting to get inside one of the kitchen fixtures and see what their ballasts are rated.
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Old 06-19-2009, 12:59 AM   #5
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Quote:
Originally Posted by KeithM62948 View Post
That sounds right. You've got me wanting to get inside one of the kitchen fixtures and see what their ballasts are rated.
Might be easier to look it up online or go to the hardware store and check it out.

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...it would need to be below less than 2400 watts with a safe capacity of 1920 watts and16 amps for a 20 amp circuit. right?
Ah here we go again with the 80% rule.......

Unless you are running a business out of your garage and running the lights all day long this rule doesn't even come into play (but then again there would be other things to worry about with a business). If I remember correctly this rule deals with FIXED loads being operated continuously for more than I think 10 hours. Someone will correct me if I am wrong here, but honestly I don't see how this rule will apply in your situation. I also doubt that you will be close to maxing out your 20 amp circuit with a bunch of flourescent light fixtures.
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Old 06-19-2009, 02:02 AM   #6
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Ok so if I did the math right:
  • 1 dual ballast fluorescent fixture @.73 amps per ballast = 1.46 amps
  • 5 dual ballast fluorescent fixtures @.76 amps per ballast = 7.6 amps
  • 2 single bulb incandescent fixtures @ 60 watts/120v = 1 amp
  • 2 100 watt flood lights 200 watts/120v= 1.7 amps
thats 11.76 amps or 1,411.2 watts. if thats right then I can run all of that from the 20 amp circuit. guess I need to put up some more lights lol.
if I did it right?
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Old 06-19-2009, 02:05 AM   #7
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now I need to figure out what I am drawing from the 60 amp feeder circuit from my house to my sub panel
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Old 06-19-2009, 11:32 AM   #8
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Originally Posted by theatretch85 View Post
loads being operated continuously for more than I think 10 hours.
3 hours at peak current draw, methinks. And very applicable here -- there's a very good chance he'll have the lights on for >3hrs at a clip. Though ballasts don't pull their full rated load continuously, so I'm not sure what that means, if anything.

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thats 11.76 amps or 1,411.2 watts. if thats right then I can run all of that from the 20 amp circuit. guess I need to put up some more lights lol.
if I did it right?
...the math looks OK to me, and you're well under 16A anyway, so the 80% rule is irrelevant (unless you add more lights).
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Old 06-19-2009, 11:49 AM   #9
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Ha Ha scott I was kidding about putting up more lights,its a 20x16 garage so I think Im good with what I have, and yes I figured the highest amp ratings for all of the light fixtures, and I actually rounded the floods up by .1amp since they were actually 1.66666666 amps. but now Im just splitting hairs..lol
and the peak would only be reached with the fluorecents when I first turn them on correct then it would drop a bit, they are all rapid start ballasts which I think are the initial startup energy hogs out of the three typs right? and the floods would only be drawing power when motion is detected and the front lights are on a photo cell so they only come on at night. I think Im in good shape with the light. now I just need to get my sub panel sorted and right because I think I will have everything inspected by the city just to cover my rear, just need to get ahold of my city codes now...
Thanks for your help guys and or gals
Mark
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Old 06-19-2009, 11:51 AM   #10
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ScottR is hicksville 4 real?
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Old 06-19-2009, 12:28 PM   #11
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ScottR is hicksville 4 real?
Oh man, I really gotta change that to Long Island.. Yup, it's real..
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Old 06-19-2009, 12:30 PM   #12
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I had no idea there was a hicksville NY I thought you were just being a smart LOL
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Old 06-19-2009, 01:45 PM   #13
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[quote=ScottR;289867]3 hours at peak current draw, methinks. And very applicable here -- there's a very good chance he'll have the lights on for >3hrs at a clip. Though ballasts don't pull their full rated load continuously, so I'm not sure what that means, if anything. quote]

Ah, for some reason I had thought it was 10 hours; 3 hrs does seem to make more sense and yeah that could certaintly come into play with garage lighting for a workshop. With all that lighting in that space and still only at 11 amps thats pretty good.
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Old 06-23-2009, 04:19 PM   #14
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this was great sounds very similar to my setup thanks guys.

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