Fluorescent lighting loads

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dinkelja

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How do you generally calculate fluorescent lighting loads. I have seen designers simply take the wattage of the lamps and multiply by the # of lamps. Might okay for a rough calculation, but not accurate when you get say 50 fixtures on a ckt. I use different lighting layout software programs, which supply me with fixture data, usually indicating that the fixture is listed at a lower power requirement than the lamps. i.e. Two-32W T-8 industrial strip with electronic ballast ? 58 W. How can I explain this better / understand it myself.
 
The lamps consume energy, but the ballast itself consumes energy also (they're not 100% efficient), which is where the disparity between the lamps wattage and the total fixture wattage comes from.
 
flo's

flo's

most ballasts have a maximum amperage rating listed that usually doesn't correspond to the wattage of the bulbs being used, maybe thats a better figure to use for load calculations..
 
I believe the assembled fixture is listed at 58W total with Two-32W lamps installed. I know, it sounds like you are getting something for nothing doesn't it. I guess I need to get to the bottom of the ballast rating here.
 
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Here's a link to Advance's page. Click on the second pdf from the top and it gives input information. They are all a little higher than the lamp wattage as you will see. I would verify with the ballast man. to make sure your lighting calc. program isn't incorrect. I bet the program has a disclaimer stating no liability for faulty load information. Good luck. Besides. They're not going to update the load information as diligently as the ballast manufacturer.

http://www.advancetransformer.com/resources/literature.jsp
 
spsnyder said:
Here's a link to Advance's page. Click on the second pdf from the top and it gives input information. They are all a little higher than the lamp wattage as you will see. I would verify with the ballast man. to make sure your lighting calc. program isn't incorrect. I bet the program has a disclaimer stating no liability for faulty load information. Good luck. Besides. They're not going to update the load information as diligently as the ballast manufacturer.

http://www.advancetransformer.com/resources/literature.jsp
Click to expand...

The way I read this document, the "Input Power in Watts" for some ballasts is higher than the total lamp wattage and some are lower. For example, for a fixture and ballast powering two 32 Watt lamps, the input power ranges from 48 Watts to 77 watts depending on the ballast used and nominal voltage, which does not make sense. Anyone know what's going on here?
 
To make a true apples to apples comparison you also have to take into account the ballast factor. Ballast factor is the percentage of light output compared to a reference ballast (lamp manufacturers specified setup). You could potentially have two 2X32 watt T8 ballasts one with a ballast factor of 1.0 (which means it is the exact same light output as the reference ballast) and another with a ballast factor of 0.9 which would mean they have different power consumption. But in the end nothing is free if it says it is way lower in power it is either a dim flourescent or there is another phenomena with flourescent lamps that I will not go into.
 
bccodes

bccodes

The way I see it ..If your doing load calcs you gotta use power consumed not power output in watts. Your load calcs are for sizing conducters and breakers and input amps are all that matters. All your other items (ranges and kitchen circuits and that stuff) are always in VA. I never understand why I get submittals that show light bulb watts and not the total amperage required to operate the fixture. I'm new at plan reveiw and this is my first post here, but it is a subject I've been puzzled with as well
 
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