Lighting Advice

[Jerry Bruette]

I bought some 4' T8 light fixtures at the local BORG and the dude there said I should have about one watt of light per square foot of floor space. The area I'm lighting is 23' long and 13' wide. Now I'm unsure where to hang the lights. Should I hang the fixtures one wide across the width of the space and equally spaced to fill the length, or should I hang two rows equally spaced on the width and running the length of the space?

Wish I knew how to use sketchup so I wouldn't have to confuse anyone with the way I worded the question.

Thanks And Have a Safe Holiday Weekend
Jerry

[Mike Holmes83]

I just added (4) 4' and (5) 8' T8 lighting to my 18x24 garage shop but I did no calculations of wattage. I like a lot of light and I have a mixture of "length wise" and "width wise" T8 fixtures, to light specific tool locations, to avoid shadows and to avoid interfering with the rail on my garage door opener. You didn't say how many fixtures you have but based on your space being 13' wide, I'd consider hanging them one wide, spaced out to fill the space. Hope this helps.

[Cliff Holmes]

I bought some 4' T8 light fixtures at the local BORG and the dude there said I should have about one watt of light per square foot of floor space.

That's a really simplistic way to do it. Reality is much more complex, it depends on the fixture height, work height, ceiling position/reflectivity, output efficiency, and your age. I have T8s @ 1.7 watts/sf and I wish it were a little brighter.

To do this right, you need to target a lighting level using a luxmeter. There are some fairly inexpensive ones on Amazon. The recommendation I've seen is 750 lux (lumens/sm). I don't know what mine is, my own meter isn't going to be here until Wed.

A couple years ago I saw an excellent if overwhelming article on workshop lighting but I can't dig it up right now. Perhaps someone else here can help out.

[Gary Kvasnicka]

My shop is 12 x 24'.
I installed 6 4' T-8 fixtures, in two rows of three lengthwise about 3' from each long wall. If my math is right I have 1.66 watts per square foot plus I use task lighting were needed. You can always add more if you think you need it.

[Ed Bamba]

Not to purposely hijack this thread, but for the number of fixtures already mentioned above, are they all on one circuit? If so, what is the amperage rating for it? I currently have one 4-foot fluorescent fixture in the garage, installed by the builder, and would like to add more lighting to the circuit it is on. Although I am not sure what else is on the same circuit. Guess I'll have to make that determination.

Ed

[Jim O'Dell]

I currently have 1.56 watts/sq ft. When I get the remaining 3 fixtures purchased and up, I will have 1.98. I have these split on 2 circuits so if I'm just at the bench, I can turn on just that light. If I'm at the multipurpose center or TS, I'll turn on the west bank. If I'm also using the router, BS or DP, I have a second switch on the circuit with the bench light to turn on the rest of that bank(east bank). Shop is 20 X 24. I have a 10 X 14 room that will eventually be the finishing/assembly room that will be 1.83 watts/sq ft when I get those fixtures purchased. All future fixtures are wired. My wife says I have too much light. But my eyes need it. She reads in the dark!! Jim.

[Don Kondra]

Hi Jerry,

I would hang them the long way

For the length, the lights would be ~3' apart, for the width ~4' apart, that should give you lots of light.

FYI, as my fluorescent ballasts wear out, I am replacing the units with a normal light socket and 45w CF bulbs (5500k). I like the "light" much better.... and will not miss changing fluoro tubes on a ladder.

lighting diagram.jpg

My shop is 26' x 36' with three rows of four foot double bulbs with reflectors on a 10' ceiling.

Cheers, Don

[Jack Lindsey]

The short answer is, based on the assumption that you have an 8' to 10' finished ceiling that is painted white and you are using 2 lamp strip fixtures, you probably should install 10 fixtures. If the ceiling isn't finished you should use industrial type fixtures (they have reflectors) using the same layout. If you use industrials I recommend the slotted type. Put them in 2 continuous rows of 5 fixtures per row, running the length of the room. Rows should be located 3 feet from the side walls, with 7 feet between rows. If the listed conditions don't describe your shop this layout might not be acceptable.

The logic behind this recommendation is really pretty simple. The recommended lighting level for most woodworking shops is 100 footcandles, or 100 lumens of light per square foot. For a 299 square foot shop you should have 29900 lumens of light at the work surface. We mount fixtures on or near the ceiling, though, and for the fixture types and conditions stated, only about half the light actually gets to the work surface so we need to install twice as many lumens (29900 x 2) = 59800. A 4' T-8 lamp produces about 3000 lumens so you need about 10 lamps. This isn't precise but a more detailed calculation would yield a number close to 10, which fits the space.

[Ken Fitzgerald]

Jerry,

Take Jack Lindsey's advice to heart. Jack is IIRC a retired lighting engineer and wrote an article that was published in the Feb. 2002 Fine WoodWorking....."Shop Lighting". When I built my new shop, I used Jack's article when buying and installing lighting. The lighting in my shop is fantastic and I've not had one problem with it. In the article Jack explains the differences in ballasts....balast quality.....the amount of light need based on age......positioning of the lighting depending on ceiling height and work bench height. It is a very well written and thorough article. It was well worth what I paid online for it!

[Jim O'Dell]

I also used Jack's article when I designed my lighting, and I agree with Ken's assessment of it. Great article, and the down load was something like $7.00 IIRC. In fact, I just found my printed copy of it last weekend when I took everything out of the guest bedroom where my computer and paper copy archives had been stored. It's now out in the shop waiting for a new filing system. Jim.

[Randy Bonella]

Jerry,
My shop is 14 x21 and I have 8 fixtures using T8's. If my pix won't post go to the link and you can get an idea. I haven't calculated my Watts/sqft and I do plan on putting in 2 more over some future bench space. Won't necessarily have them all on at one time.

I put switched outlets in the ceiling so that I can move lights around easily if needed. One other thing to look for is light color rendition. I spent a bit more on CR92 lamps vs the generic soft white which is usually somewhere between CR76 and CR84. Costs for lamps that are CR96 to CR98 get real expensive.



http://picasaweb.google.com/rmbonell...Pjg7dzB2LGRfw#

[Don Kondra]

With all due respect, I believe the new Continuous Fluorescent bulbs are a contemporary lighting option that should be considered.

Much easier to install a light socket, no ballast to wear out, changing bulbs is easier and initial cost is quite a bit lower.

A T8 double four foot unit with metal shade is running ~$45 without tubes from Home Depot or Canadian Tire. Tubes are available in 5000k @~$2.50 for a total cost of ~$50 plus tax. CRI is 75

A decent quality light socket is ~$5 and a 45w CF bulb is ~$10. 2400 Lumins @ 1m. Equivalent to 150 watts of Tungsten light. CRI is 91 and rated for 10,000 hours.

All other wiring costs are the same.

Just food for thought.... if you do decide to go with the standard double tube arrangement, consider the higher K rated tubes for a closer to natural sunlight quality.

Cheers, Don

[Randy Bonella]

Not to purposely hijack this thread, but for the number of fixtures already mentioned above, are they all on one circuit? If so, what is the amperage rating for it? I currently have one 4-foot fluorescent fixture in the garage, installed by the builder, and would like to add more lighting to the circuit it is on. Although I am not sure what else is on the same circuit. Guess I'll have to make that determination.

Ed

Hi Ed,
You can follow a pretty simple formula for current loading. If you have a 15 amp service this gives you about 1800 Watt load for a 120V line. If you do the simple math of 32 watt per bulb you can put in 56 bulbs or up to 28 double 4' bulb fixtures per circuit. Thats assuming you have no other loads. Each fixture is like a 60W incandescent light bulb.

Randy...

[Ken Fitzgerald]

With all due respect, I believe the new Continuous Fluorescent bulbs are a contemporary lighting option that should be considered.

Much easier to install a light socket, no ballast to wear out, changing bulbs is easier and initial cost is quite a bit lower.

A T8 double four foot unit with metal shade is running ~$45 without tubes from Home Depot or Canadian Tire. Tubes are available in 5000k @~$2.50 for a total cost of ~$50 plus tax. CRI is 75

A decent quality light socket is ~$5 and a 45w CF bulb is ~$10. 2400 Lumins @ 1m. Equivalent to 150 watts of Tungsten light. CRI is 91 and rated for 10,000 hours.

All other wiring costs are the same.

Just food for thought.... if you do decide to go with the standard double tube arrangement, consider the higher K rated tubes for a closer to natural sunlight quality.

Cheers, Don

With all due respect,

IMHO...a tube gives a better light distribution pattern than one eminating from a single globe.

10,000 hours....compact fluorescents? ...they have not gone that long in my home and they don't give the same color of light as other fluorescents or incadescents ....again.in my experience and humble opinion.

[Bill Arnold]

I can't speak to any particular recommendation, just from my experience with lighting my shop. My shop is 36' by 24' overall which is divided into two areas. The original shop is 16' by 24' and I built a 20' by 24' addition onto it. In the larger side, I installed 12 T8 2-bulb 4' units -- the smaller side has eight T8 2-bulb 4' units. All bulbs are cool white 32W. In each case, I wired them so I can switch on half at a time. The average Watts per square foot is about 1.3 with all lights turned on in either area. I can easily do general work with only one bank (half the fixtures) turned on. With all lights on in an area, I haven't had a need for individual task lighting.

I purchased basic 2-bulb fixtures and built my own light boxes using 3/8" plywood. The fixtures are sized to fit between the ceiling joists which are on 24" centers -- interior length is the length of the fixture. I painted the inside white before mounting the fixtures.