Shop Lighting

[Chester]

I am installing new lighting in my expanded shop. The shop is 12 x 32 (384 sq. ft) but only has a 90" ceiling height. Almost all horizontal surfaces in the shop are at 36" in height.

We had a simple linear arrangement of four incandescent light fixtures down the middle. Of course, with the other improvements made in the shop, these fixtures were not enough. I have removed the old fixtures and installed metal junction boxes in their places. Out of these junction boxes, I am running steel 1/2" conduit to double T8 fluorescent fixtures. The T8's are 32-watts/bulb and with 2-bulbs/fixture I will end up with 10-12 bulbs in 5-6 fixtures (320-384 total watts).

Even after installing the first fixture over the table saw, I was shocked at how much light one of these 2-bulb units emitted. I have now installed two more and am working on the fourth. There seems to be a whole-lotta-light! When finished, I will be approaching 1-watt per square foot.

I recently read an article that said that a workshop should have 2-watts per square foot. Maybe there is something in this formula that considers ceiling height? I am not sure but my ceiling height is rather low. This brings the lights closer to the work surfaces. I think If I were to approach 2-watts/sq. ft. ... I would need to wear sunglasses.

What do you think?

[Sac]

Good light make all the difference. My shop is 24x30 and I have nine 4-bulb T8 units. It is very bright in here. I also spent the money on good bulbs too. I have the ones that the light is close to the same light that the sun produces.

[Chester]

Sac -

I also got the daylight t8's (6500K)and what a difference. I had replaced my incandescent bulbs with the screw-in fluorescents. They now look absolutely yellow next to my daylight T8's.

[Sac]

Sac -

I also got the daylight t8's (6500K)and what a difference. I had replaced my incandescent bulbs with the screw-in fluorescents. They now look absolutely yellow next to my daylight T8's.

Those are the same ones that I have. I was gonna spout some numbers but I didn't know them. Make sure you post a finished pic. I think that lights are a pretty cheap way to improve a workspace. I think that it is also overlooked quite a bit. I have tons, but I am still thinking of adding a few more. I still have a few dark spots in here..

[Chester]

Sac -

If my calculation is correct, you are currently at 1.6-watts/sqft. Keep your sunglasses handy.

I had trouble finding the 4-light fixtures. Maybe if I had looked at interior-type units?

[Sac]

Sac -

If my calculation is correct, you are currently at 1.6-watts/sqft. Keep your sunglasses handy.

I had trouble finding the 4-light fixtures. Maybe if I had looked at interior-type units?

Yes.. I got mine at HD. They were the best ones that they had. Weren't that expensive. And I don't have any problems with them in the cold either..

[Vic]

You should be more concerned with lumens/sq foot, not watts per square. As you have become aware, in lighting it is not apples to apples. You have both phototopic and scotopics involved. The reason why a lamp that is listed as a "daylight" lamp "seems" brighter is due to scotopics. It has to due with how your pupil reacts to "white" light. In my day job of energy efficiency consulting, I do a lot of lighting upgrade packages, that not only greatly reduces the wattage per square foot, but also increase the "perceived" lumens per square foot.

Most people will be very uncomfortable under a lamp rated at 6500K (Kelvin - the rating system for color temperature). I would suggest a younger set of eyes use 4100K lamps and an older set of eyes use 5000K lamps. Use 6500K in task lighting, where you are not immersed in that color but looking at it. Most households lighting schemes run about 2700K. This produces the warm red tones that you typically see in a home environment. As you move up in Kelvin, you will move from red to yellow to blue.

Another important factor to keep in mind - CRI Be sure any light you buy has at least an 80 CRI (Color Rendering Index) In a finish area get the highest possible CRI you can. CRI is how well a lamp actually renders color, a very important aspect in the finishing process.

In the next few years, be looking for induction lighting to slowly replace flourescents as the go to choice in "industrial lighting". 100,000 hour life and 5000 and up Kelvin. LEDs, while being a very low wattage option, still are very low in CRI, extremely high in price and have yet to be able to prove consistency. Maybe someday. I hope so, as I love the even distribution the fixtures can produce.

[Chester]

Sac -

Do you use all of the lights all the time? Or do you have the ability to switch on and off as needed?

[Chester]

Vic -

Do you think that 6500K is too much? So far, I have them just over my work benches and the table saw.

I don't see any reason to totally flood the shop with light just to walk around. I do have good daylight windows at either end (we are on the second floor of a barn).

[Vic]

Vic -

Do you think that 6500K is too much? So far, I have them just over my work benches and the table saw.

I don't see any reason to totally flood the shop with light just to walk around. I do have good daylight windows at either end (we are on the second floor of a barn).

If you're older like me, I'd go with 5000K, 85CRI or better lamps. If you're buying new fixtures, specific HO, which will come with a high output ballast. Ballast for T8s come in low- .77 Ballast Factor, Normal - .87, and high 1.15 or a little higher. So, if you have a lamp that is rated to deliver 3100 lumens in a 4 Lamps fixture. The fixture, with a HO ballast will produce (3100x4)x 1.15 = 14260 lumens. If you really want me to geek out on ya, PM me with the specifics of your shop. Mind you, since I don't do design, I don't have lumen spread software. You should be able to take your shop design to a lighting store and have them do a foot candle layout for you.

Personally, I have a 30x40 shop and my 4lamp, 4 foot fixtures are every 10 feets. It works quite well. I also am still running 4100K lamps. As I age and my eyes worsen, I will move to the 5000K.

[Chester]

Vic -

Thanks for all the info. I don't understand it all but I do like to get into the specifics and I can do some more research.

Before about 2-weeks ago, I didn't even know about Kelvin numbers. When I bought a number of fixtures, I also bought a box of 10-bulbs. Like most uninformed people, I figured that a bigger number (6500K) was better. When I lit-up the first fixture, I was kind of blown-away with the light output. Unlike most shops, my shop is entirely wood (mainly plywood) ... floors, walls and ceiling. This all wood shop really sucks-up the light. I had previously thought that I would need 4-bulb fixtures but when I had trouble finding them in T8, I brought home a couple of 2-bulbers. And then I put up the first one with two 6500K's and was amazed.

Will the 6500K be bad for my eyes? I have a box to use-up.

[Lawrence Brown]

And just to throw everyone into information overload, for anyone producing works that will go in other people's homes, their workspace lighting should try to match as close as possible to that of the client. for example, if you use 6500K daylight balanced lights, you will be seeing your colors through bluish light, but if the client is using incandescent in the room the piece is going in, the light will be a lot warmer, resulting in a color change.

Having said that, it's not usually so critical with woodworking because the finishes are normally pretty warm anyway and they're not usually compared to anything else, but if you are doing some kind of colored art pieces, you may want to look into it more. I used to have to deal with this all the time when I was doing photo prints and had to balance what I saw "in nature", with what was on the screen, with what was on the paper, with what was in the client space, and it got to be a real headache. (Oh, and lighting in nature doesn't stay the same either: time of day, time of year, etc, etc.) People don't normally notice these things because your brain compensates for the color shift. That's why pictures take in older flourescent light seem green or yellow: the light actually is that color, but your brain compensates. Your camera doesn't unless you set the "white balance" properly. It's even worse under mixed lighting because the camera can only be balanced for one color. (For the ultimate in nightmare lighting, try photographing something in mercury vapor lamps like big factories use!)

Don't worry too much about anything I just said. I just thought some would find it interesting. Ultimately you should just do what works best for you. The two main facts that I would add would be: 1> the brighter the light, the more constricted the pupil, the sharper the eyesight. (it's an optics thing) 2> I personally prefer the bluer (as in closer to 6500K) light just because the brain responds to the blue by waking you up, which is something I can always use. I've also got one of those blue LED "alarm clocks" that gets brighter and brighter when it's time to get up, and that makes a world of difference to me. Ever notice how vibrant and inviting a plant store is? That's the blue in their grow lights.

Dang, how come my replies are never as short as I intend them to be?

[gmcevoy]

There is a fairly good article in Fine Woodworking about shop lighting, issue 154. The article can be found on their website if you are a subscriber.

[Lawrence Brown]

Oh, and then there's also the inverse-square law which states when you double the distance to the light, the intensity is 1/4th of what it was. For instance: You have your lights mounted 6 feet above the bench and that gives you 1000 lumens per square inch on the bench. If you raised those lights to 12 feet, you would then only be getting 250 lumens per square inch, or 1/4th the amount of light, so the height of your ceilings definitely can make a difference.

That's all the facts from me today, I promise

[Sac]

Sac -

Do you use all of the lights all the time? Or do you have the ability to switch on and off as needed?

I have a lot of natural light in my shop. Sometimes I use them during the day and sometimes I dont. It just depends on what I am doing. I have the light set up in banks of three from left to right. Each bank is on its own switch. So I do have some choice of which lights I want on..

[wilburpan]

You should be more concerned with lumens/sq foot, not watts per square.

True.

If you want to figure out your lighting requirements, here's what I did for my shop.

1. My goal was 75-100 foot-candles of light at my workspace. My shop is 10'x20', or 200 square feet.

2. Multiply 75-100 foot-candles by 200 square feet gives me 15000-20000 lumens of light total in my shop.

3. Throw in some fudge factors to account for the distance from the fixture to the work surface and loss of efficiency over time due to dust and aging bulbs, and that essentially doubles to 30000-40000 lumens.

4. I wanted to use 4' "Natural Daylight" T-8 tubes which put out about 2200 lumens apiece, this means I'll need 13-19 fluorescent tubes in my shop, which works out to about 6-10 2 bulb fixtures.

So ideally, my plan was to put in a total of 8 4' 2-bulb fluorescent fixtures in my 10' x 20' shop.

As it turned out, I could only install 5 fixtures, due to low ceilings, and the way that ducts and plumbing ran across the ceiling of my basement workshop. I wish I had room for three more, so this method seems like a really good predictor of your lighting requirements.

[Vic]

Vic -

Thanks for all the info. I don't understand it all but I do like to get into the specifics and I can do some more research.

Before about 2-weeks ago, I didn't even know about Kelvin numbers. When I bought a number of fixtures, I also bought a box of 10-bulbs. Like most uninformed people, I figured that a bigger number (6500K) was better. When I lit-up the first fixture, I was kind of blown-away with the light output. Unlike most shops, my shop is entirely wood (mainly plywood) ... floors, walls and ceiling. This all wood shop really sucks-up the light. I had previously thought that I would need 4-bulb fixtures but when I had trouble finding them in T8, I brought home a couple of 2-bulbers. And then I put up the first one with two 6500K's and was amazed.

Will the 6500K be bad for my eyes? I have a box to use-up.

Chester, you brought up a very important aspect I ommitted, reflectance. Because my walls are painted white, I don't need the same amount of lumens close to the wall, as you will.

[Chester]

Oh, and then there's also the inverse-square law which states when you double the distance to the light, the intensity is 1/4th of what it was. For instance: You have your lights mounted 6 feet above the bench and that gives you 1000 lumens per square inch on the bench. If you raised those lights to 12 feet, you would then only be getting 250 lumens per square inch, or 1/4th the amount of light, so the height of your ceilings definitely can make a difference.

That's all the facts from me today, I promise

Thanks for all the good info.

So, my low ceilings (90") do make a big difference in lumens on my work surfaces. That explains a lot. When I mounted my first 2-bulber, it was right over a small (18" wide) white melamine table that is between my 2-tablesaws. This first view of the light potential of two 32-watt, 6500K, T8's, mounted at about 85" over a 36" melamine and polished cast-iron surface ... was incredibly bright. But, especially over my double table-saws, I really like it.

[Bobby Slack]

You guys are so technical about this, amazing. I just add lights when I notice that is too dark. As a matter of fact I have to add a couple more sets of double fluorescent lights.

[Chester]

You guys are so technical about this, amazing. I just add lights when I notice that is too dark. As a matter of fact I have to add a couple more sets of double fluorescent lights.

Bobby -

For me, this is all new. But it is amazing to learn about all of the choices there are. I just thought that a 4-foot fluorescent bulb was a ... 4-foot fluorescent bulb. I didn't know a T12 from a T8 ... or even that some work in the cold and some don't. Then you add the greatly different affects of the various Kelvin ratings and it gets very interesting. If you don't have any high Kelvin bulbs in your shop (5000K and above), you should take a look at some display samples if they are available to you.

I hear some guys talk about painting everything in their shop(s) white ... or some bright color for better light reflection. That is never going to happen in my all-wood shop. But, I think that if I did have all of this whiteness in my shop, 6500K might be too much.

[Aggie83]

You just can't get enough light. In addition to adding fixtures, painting the walls and ceiling with a nice, reflective paint can help.

[Vic]

You just can't get enough light. In addition to adding fixtures, painting the walls and ceiling with a nice, reflective paint can help.

Actually, you can have too much. Just sayin'.<<<Sorry Marc.

[BenBreeg]

My first post but also the only thing I'm qualified to comment on so far I do human factors work and the recommended amount of light used to be 100 foot candles for an office environment. They've actually dropped that dramatically to 30-50 fc now. I would just make sure you have even lighting from multiple sources as opposed to the same amount of light from fewer fixtures. Too much or too little will cause eye strain. The task being performed, the age of the worker, and the reflectivity of the background will all factor in.

At the end of the day you will be able to tell if you have enough. If your eyes ache or you get headaches lighting may be an issue.

[JohnnyNoName]

Wow there are a lot of numbers and symbols flying around in this discussion. It's making my head spin.

My shop is 20' x 30' and I have 12 double-bulb fluorescent lights. Half are on one switch and half on another so I can only use what I need. I also have four windows on my North wall, so most of the time, I only use the natural light. I find that the quantity of light isn't as important as the placement. I want it where it isn't casting a shadow onto my work.

You can see some pics of the shop here:

http://www.theworkshopproject.com/photos.php

Jonathan

=========================================

[Vic]

Wow there are a lot of numbers and symbols flying around in this discussion. It's making my head spin.

My shop is 20' x 30' and I have 12 double-bulb fluorescent lights. Half are on one switch and half on another so I can only use what I need. I also have four windows on my North wall, so most of the time, I only use the natural light. I find that the quantity of light isn't as important as the placement. I want it where it isn't casting a shadow onto my work.

You can see some pics of the shop here:

http://www.theworkshopproject.com/photos.php

Jonathan

=========================================

Nice shop, Jonathan. I didn't take quite as many pics of my build. One of these days, I'll post those.