Hey guys, for figurng out how much light you want/need and the number of fixtures, try out this link
http://www.metalux-lighting.com/common/CLDownloads.cfm?brand=Metalux
This is Cooper Lightings website, their Metalux brand of fluorescent strip lighting. Although there is probably slight differences between different brands of lighting, I imagine a fluorescent tube is a fluorescent tube and this should get you in the ballpark.
Once there, scroll down to "Strips" and you will see a bunch of fixtures listed. As you mouse over the names, the pic changes to show you a representative fixture. Click on the one you like (I clicked on Series SS, which looked like a twin tube fl. fixture). At the next page, click on IES files (Illuminating Engineering Society I think). That will bring up the files for all of the fixtures in that series. Click at the bottom (on the calculator) where it says "Calculate all Files". This will open a new window.
This is the useful window. You can input the length, width, and height of your garage (or any room), the workplane height (if you are at a bench, this would probably be around 3 feet), and the suspension height (if attached directly to the ceiling, I usually enter 0 for this. If you want to suspend the lights due to a high ceiling, you can enter that measurement). The isometric graphic to the right will chenge with your inputs.
The first tab is the fixture tab. By clicking on "Calculate all Files" previously, you can change the fixture you want on this tab. Most of the time it will give you a brief description (like 2 25 watt fluorescent tubes) and the model number.
After selecting a fixture and inputting the room size, th next tab is the Reflectance tab. I usually leave this alone since I don't know how to figure reflectance. Again, looking for a ballpark figure, so you can play around with those numbers if you like. A bright white painted garage will probably have more reflectance than a brick garage. If you really want to get into it, you can probably find different reflectance values by searching on the web.
The 4th tab is the specify tab. This is the good stuff. You can input the footcandles you want to acheive. An earlier poset mentioned 100 footcandle (I think a footcandle is lumens per foot, don't recall right now). Based on research on the web, I have seen some recommendations of 200 footcandles for detail work, 20-30 footcandles for general lighting. Depending on how you want to configure your garage and what you do in there will determine your needs. If you use it for woodworking or something and needed general lighting only (because you have a shop light at your bench), you can use less fixtures. If you want to daylight your garage because you detail cars in your garage, you will need more footcandles, therefore more fixtures. Only one input is require (footcandles, # of luminaires, or light density). I usually enter footcandles, but have fun and play around. If you already have fixtures, you can probably figure out how many footcandles you have existing and whether or not you want to add more.
After you enter your footcandle requirements, you can specify how the illuminance is calculated (by minimum, target, or maximum). You can play around with these as they are fairly self explanatory.
You will notice as you change the imputs, the picture to the right changes. It updates based on your room size and footcandles,etc. It shows a grid of the chosen fixtures needed to meet your inputs, with dimensions and everything.
For me, I chose fixture #9 (two 40 watt tubes), my garage is 18 feet long x 12 feet wide x 10 feet high, workplane at 2.5 feet, suspension at 0 feet (mounted directly to ceiling). No change to reflectance. Specified 50 footcandle (this is at your workplane specified above) and set it to Minimum Allowed. Based on these setting, I need 4 of these fixtures and I actually get 59 footcandles, with a watt density of 1.66 W/ft^2. Not too shabby. If I change it to Fixture #2 at the first tab, I now need 6 fixtures and only get 44 footcandles. Note how the fixtures change size. Since there is no description for Fixture #2, I imagine, based on the pic and footcandles, that they are probably 4 foot, single tube fixtures.
Once you find a layout that you like, you may need to do a little digging to match it to a model number and get the specifics (like Fixture #9). If you go back to the original window (where you clicked on the IES files), it looks like they have the files on order. So looking at the second one (I clicked on its calculator to verify the IES file number, which was ITL48326), I found out it is a SS-2BX40. Well, what the heck is that? Looking at the ordering info on the different spec sheets a couple of pages previous, it looks like the fixture is a 2 foot long, twin 40 watt tube fixture. Doing the same process for Fixture #9 (it was a little more difficult), I think it is a 4 foot, 40W single T12 tube fixture.
Anyway, sorry for the long post but I hope it helps some people out. I am by no means a lighting expert, but I have learned street lighting as a part of my job (Civil Engineer). I have just applied and passed on the knowledge I have gained to you guys. Do some research on suggested footcandle or watt density requirements for what you plan to use your garage for and use the above info to get you into the ballpark for what it will require to get you there. If anyone needs some additional help, feel free to give me a shout and I'll do what I can.
Thanks,
Neil
, If your going to be out there long enough for everything to warm up,it will go away eventually kerosene heater helps as well... 