CFL Wattage calculation

[Storm Blue]

I am hoping someone might be able to give me some desperately needed advice. I am remodeling a garage / gym / workshop area and have wired it with the intention of using CFLs (having seen Veno's post last year made that an easy decision for me.) The space is 22' x 30' with 9 foot ceilings. The space has 28 sockets made up of four rows off seven. The sockets are on two circuits that skip every other bulb so that if only one bank is lit the lights would sort of look like a chess board. The idea was that different wattages could be used in each circuit so that three different lighting levels could be achieved by using circuit A, B, or A+B.

Originally, I had intended to use 14 @ 105W and 14 @ 60W, but as I get closer to needing to order the bulbs I am getting nervous that this may not be as good as some alternative setup.

Can someone point me in the right direction or give me some advice? I really appreciate your help. Thanks.

 

[Charles (in GA)]

I think this is way TOO MUCH light. 105W CFL's are equal to about 400 watt bulbs. I think you don't need to vary the wattage between rows, well, thats just way too much light....... not sure of the bulb to use, but I think a bunch of 100 watt equivalents will be a plenty. I usually say you cannot have too much light, but in this instance, I think you can.

Charles

 

[Storm Blue]

Yikes! Thank you for the reply.

This is exactly the sort of thing I am looking to avoid. Is there a way for me to calculate the number of footcandles a particular setup will produce or to see what Wattage I'd need to reach a desired level of illumination? I have seen GE and A-Wall's calculators suggested in these forums, but neither seems to be designed for this specific task.

 

[Charles (in GA)]

You basically have a bulb covering every 5x4 ft square of floor space. I'm assuming you have flat painted (white) ceilings and walls. Even with workbenches and shelves and cars, thats pretty through coverage.

Not sure of the size of the CFL's in this pic (pic is from a post by Sharkin,) but using the smaller bulbs and the Y sockets is a good way to use the more in-expensive smaller bulbs, or get more light in certain areas.

If you already have the sockets and wiring installed, buy a few bulbs and try an area and see what you think. I just think that the 105w are too much.

Charles

 

[csp]

I have twelve light sockets in a 24x36 space with 13w CFLs installed and I'm very pleased with the light output. I doubted that the 13w bulbs (I already had the bulbs prior to chaning my lighting) would be enough and was pleasantly suprised how bright it is. Much brighter than the three 8' T12 flourescents they have replaced.

This change was made at the same time as drywalling was done, and it's been too cold to mud/tape/paint, so I expect it to be brighter once the ceiling is painted white.

The CRI rating is a very accurate 82 with these bulbs. I'm not sure what the color temperature is with them. My original plan was to use 28 watt (IIRC) CFLs.

 

[jvitez]

Without getting into minutiae, 75-100 lumens per sq ft is lots of light. Check the specs on the bulbs (properly called lamps) you're considering, multiply by the number of lamps, divide by size of garage, and there you have it.

23 watt CFL produce around 1600 lumens. 22x30=660 ft2. 28x1600=44,800 lumens, or 67.9 lumens/ft2.

26/27 watt CFL produce 1800 lumens each, or 76.4 lumens/watt.

Decide how bright you want it to be and go from there.