Garage Shop Fluorescent Lighting

baumgrenzeNovember 25, 2011

I'm hoping to learn from someone who knows more about fluorescent lighting than I've managed to accumulate through web searching.

I have an unheated garage workshop on the San Francisco peninsula. In the winter it is often around 50F, in the summer, especially near the ceiling where my lighting is installed, it can get quite warm. I gather from information at the Lighting Research Center at Rensselaer Polytechnic Institute website, the smaller the diameter of a fluorescent tube, the narrower its performance profile as a function of temperature. See:

At 50F, a T8 bulb is down to 75% output and a T5 is down to 40%. The optimum temperature for a T8 is ~75F and for a T5 it is 95F. See the thumbnail below from ImageShack:


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I did not find a similar graph for T12 bulbs, but suspect that it is shifted slightly to lower temperatures and is even less steep in its falloff.

I am accustomed to the light output of two ancient 4 bulb 40W fixtures equipped with magnetic ballasts that require starters. I am ready to scrap these. One ballast overheated recently and I've not replaced it.

I understand that the government has mandated the elimination of magnetic ballasts. See:;hl=en&source=hp&biw=1024&bih=587&q=%22magnetic+ballast%22+phase+out&btnG=Google+Search&gbv=2

There seems to be a move to eliminate the T12 bulb in favor of the T8, but I doubt this will be important in my working lifetime (~10 years at best.) Much of the attention seems to be focused on lumens/watt efficiency and not total lumens per fixture, especially over a range of ambient temperatures.

I have several 40W T12 fixtures, two 2-bulb units with electronic ballasts and many single lamp strip lights with magnetic ballasts. I understand that with T8 electronic ballasts installed, these fixtures would allow the use of T8 bulbs.

Does it make sense to move from T12 to T8 by changing out all of my ballasts?

Does it make sense for me to replace the T12 magnetic ballasts in my strip lights, or should I leave well enough alone and just install them as needed? I do not want to go to unneeded expense only to find that I am getting less light for my aging eyes than I now have.




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I would just change them as needed. My assumption is that the garage is used for storage and hobbies in addition to auto parking and the number of hours of use per day is limited. In my experience, fluorescent tubes tend to heat themselves a bit after few minutes of operation. This is not say the the temperature rise is to ideal levels, but light output gradually improves. I have the usual T-12 in my shop which can get below 20 degs. They work, dimly at first. Cold breezes on fluorescent tubes are not good for proper operation.

    Bookmark   November 25, 2011 at 4:19PM
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Make sure you get ballasts rated for low temperature operation.

    Bookmark   November 25, 2011 at 5:55PM
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Fixtures with magnetic ballasts that take T12 bulbs aren't even legal in the US anymore (the phase-out got much less public attention and controversy than the current phase-out of incandescent 60/75/100w bulbs since consumers are more familiar and dependent on these). Replacement ballasts and bulbs for existing fixtures remain available. I'd change over to the T8s anyway because they're more efficient, and the electronic ballasts don't hum or flicker. Cold-weather-start ballasts are available, but I've found standard T8 ballasts often work fine in garages even on 20F winter days.

    Bookmark   December 6, 2011 at 5:04AM
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