Shop lighting
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Best bulbs for brightness and efficiency. February 12, 2003
Question
I'm in the process of putting a 24' x 40' shop in one end of my barn. What would you suggest I install for lighting? I will have 12' ceilings; I have installed radiant heating in the concrete floor but only think I will heat the shop area to low to mid 50's. I'm new to wood and cabinet working and would appreciate any help as to size, type, spacing, etc. of lighting.
Forum Responses
From contributor T:
Look into T-8 florescent lighting. It is brighter and consumes less electricity per lumen. These tubes have three different types of phosphorous and create a wider band of light. They also burn full bright from day one until the end. Regular florescent starts bright initially and gradually fades over time.
Location of fixture is significant. You are better off with one tube every four feet than two tubes every eight feet. This is because the dispersal of light will minimize shadow.
If you use larger wattage and dim it down, your bulbs will last longer than if you undersize the wattage and max out the bulb.
Paint everything that doesn't move bright white.
From contributor B:
The above is right about the T8 lamps. They have the highest light output per watt that you can get. They also produce less heat, resulting in longer life. I would recommend lamps with a color temperature of 5000K or higher. These are closer to natural sunlight.
I was a project manager for several years for an electrical construction company that did a lot of lighting retrofits. We would replace a building's existing fluorescent lighting with T8 lamps and electronic ballasts. They would end up with more light and lower electric bills. The energy savings would generally pay for the cost of the job in less than 2 years. (One hospital we did was able to sell power back to the power company when they ran their generator to keep it certified!)
To get back to the point, by my calculations you will need 24 4' 2-lamp fixtures to adequately light your shop. This will provide an average of about 100 footcandles at 3' above the floor, assuming you take the advice to paint everything white.
I had always thought metal halide was the cheapest way to go (witness Costco and Sam's Club). Any thoughts?
From contributor B:
Metal halide fixtures work well in large buildings with high ceilings, and are available in very large wattages specifically designed for these locations. The downside is that the initial fixture cost is very high, replacement lamps are very expensive, lamp life is only half that of fluorescent (10,000 hours vs. 20,000 hours for T8 fluorescent), and quality of light is much lower. Metal halides typically have an average output of 45-55 lumens per watt; fluorescents have 85-90 lumens per watt.
Light quality is a measure of the ability of a lamp to render an object in a natural way, and is called the "color rendering index" or CRI. This is a scale from 0-100, with 100 being natural sunlight. Most metal halide lamps have a CRI of 65-70, while most T8 fluorescents are around 86. Light quality is *very* important in a shop!
In addition to these considerations, if his shop is only heated to the low to mid 50's, he would have to wait 15-20 minutes after turning on the switch for the metal halide fixtures to warm up to produce enough light to work!
From contributor R:
Are you sure of those numbers? I was under the impression metal halide is more efficient and the light is closer to real sunlight.
From contributor B:
Yes, I am sure of those numbers. I have spent the last eight years working with lighting design on a daily basis, but just to be sure, I consulted the GE catalog. Metal halide is generally more cost effective where very large wattages are required.
From contributor R:
The reason I mentioned that is because locally, MH seems to be the lighting of choice in retro or new construction. There's a lot less wiring involved because there are a lot less fixtures, and the bulb life is measured in tens of thousands of hours and I've never seen a ballast changed! Besides, MH is a lot more efficient - rule of thumb is past 14' you go with MH if you can afford it. Look around - you don't see fluorescents on commercial jobs anymore. The one advantage of fluorescents is the warm up time - to get around that you have one small bank of fluorescents for instant light until MH warms up. Do you really want to wire in 20 fluorescent fixtures when 4 MH will give you more light?
From contributor B:
4 MH can put out more light that 20 fluorescent, but they will also consume more wattage. Also, the light will be very bright directly under the fixture, but there will be dark areas between the fixtures. For efficiency, even light distribution, and light quality, T8 fluorescents are the way to go.
As for bulb life, as I mentioned earlier, the most common MH lamps are rated at 10,000 hours. T8 fluorescent lamps are rated at 20,000 hours.
The reason MH is used past 14' is that the fixtures are designed for high mounting heights, while most fluorescent fixtures are designed for heights of 16' or less. It is the fixture design, not the type of lamp, that determines how high they can be mounted.
GE's website has a lot of information about the different lighting options available and their appropriate uses.
I am just in the planning stages for my new shop and was wondering these same things. I did put one T8 in my existing shop and man, what a difference - about double the light output.
I have metal halide in half of my shop - 16' ceilings. I consider this the minimum height. I have HO fluorescent in the other half. The MH is closer to daylight. I have yet to replace a bulb in the 4-5 years they've been in. I've probably replaced 2/3 of the fluorescent.
From contributor B:
You are correct about 16' being the minimum mounting height. Do you know the color of the fluorescents you are using? If they are standard "cool white" then your metal halides may be closer to natural light. You have been really lucky on lamp replacement!
I have had metal halide lighting in my shop since 1992, and very few of the bulbs have been replaced (4 or 5 out of 10). All of my fluorescents have been replaced multiple times. We only have 12' sidewall height with approximately 13' peak height, and our fixtures are low bay, which is made for lower ceiling heights.
The light from the metal halide fixtures is good, but since there are fewer fixtures, there are lots of areas where shadows are a problem, which is where we use fluorescents. Basically, we consider the metal halide lights overall lighting, and use the fluorescents for task lighting over workbenches and at many of our machines.
I would like to change my 96T-12's and magnetic ballast to T8's and electronic ballast. I have not been able to find 96T8's. I hate to have to change all the fixtures as well. Also could not find T8's in daylight. Most of the ones locally are closer to cool white. Any suggestions?
From contributor B:
I know that GE and Sylvania both offer T8's in 8', but I am not sure about the other manufacturers. The 8' lamps are available in both standard and high output, but not in as many color options as the 4'. You may have to check with an electrical supplier, such as Graybar or W.W. Grainger.
If you can't find the 8' lamps in the color you want, retrofit kits are available to convert 8' fixtures to use 4' lamps. I have often converted fixtures with 2 8' lamps to use 4 4' lamps with 1 4-lamp ballast. This is much easier and cheaper than replacing the fixture.
I'm on the central coast of California. Temperatures in the shop are around 40 to 50 degrees when I come in, typically. What do I need in the way of ballasts and color of the lamps in an 8' T8? Part of what I do is finishing.
From contributor B:
Most electronic ballasts, which are normally used with T8's, are rated for 0 degree operation. They are far less sensitive to temperature than magnetic ballasts. You can ask your supplier about the rating of the ballast, or, if they do not know (which is very likely), open the fixture and look at the ballast. It will have the temperature rating on the label.
I recommend 5000K or higher lamps. More importantly, check the CRI (color rendering index). Higher numbers are better. In 8' lamps, you will not have as many choices as 4' lamps.
I have 2 bulb 8 foot fixtures with mechanical ballasts, T12 bulbs. Can I convert them to electronic ballasts without changing bulbs?
From contributor B:
Yes, electronic ballasts are available for 8' T12 lamps.
If I ever need a lighting problem solved, I'm going to remember you. And you work with wood too?
From contributor B:
I have about 20 years experience in electrical and mechanical (HVAC) construction, and have been building guitars, furniture, and cabinets on the side during that entire time. A few months ago, I decided to take my cabinet shop full-time, but I also still work part-time for an electrical contractor doing design and estimating.
If you think about it, ductwork fabrication isn't that different from cabinet building, but the end product doesn't look nearly as good!
From contributor T:
This is a purely anecdotal observation: I just installed two 4ft double T-8 fixtures in my office. They were so bright I had to aim them at the ceiling and bounce the light down. (I have 13 foot ceilings.)
The very first day I used them I went home and read the newspaper at the table like I usually do. The only difference was that I did not have to take my glasses off and get real close to the paper. I did not make any changes to the lighting at home. As near as I can figure, this must have to do with less fatigue on my eyes during the work day.
I too am in the process of creating a new workshop and the lighting is most important. I also have to have a 12' ceiling and in-floor heat. The above info on lighting will be most helpful. A new shop is the place to apply everything you learn. Every woodworker and other shop rat I've talked to has said "windows and lights, as many as possible." I'll heed this advice. I'm building my shop from the ground up. 30x50 with a basement. Poured walls and floors. I will probably install the lighting myself after a pro wiring job. This thread has firmed up my desire to go with fluorescent lights.
From the original questioner:
I am in the process of completing the walls to the shop area and will soon have most of the wiring completed. At my current pace, I expect to have the lighting installed within the next month. I appreciate all the encouragement I've received and am really looking forward to spending time in the shop working with wood.
Call AM Electric Co Lighting in Lou., Kentucky for wholesale bulbs. The manager knows his stuff and you all are in need of a real pro. I love my lights. He helped me for my new shop.
The comments below were added after this Forum discussion was archived as a Knowledge Base article (add your comment).
Comment from contributor A:
(February 28, 2003) Here in San Diego, the utility company (Sempra Energy) offers rebates for replacing "old" t12 fixtures with magnetic ballasts and putting in new t80 fixtures with electronic ballasts. It doesn't make the lighting *free* (darn!) but it softens the blow a bit. According to the SDGE web site, they'll cough up $9.75 per fixture to replace an old fixture with a new one.
Comment from contributor S:
As a lighting engineer for the past 15 years, I agree with contributor B. Fluorescent lamps now have a higher CRI than that of the metal halides. However, anything below 16' must be fluorescent, from a uniformity and comfort factor, regardless of how much brighter it looks.
Is it evenly spread? Am I burning my head as I pass underneath? Am I getting headaches or feeling tired because it's too bright or too dark? Do people want to come in?
We can put 4 MH fittings in a room as opposed to 20 T8 and may receive higher lighting levels, although we will pick up a lot more shadowing between those lights than the T8. You will also find a lot more heat directly under those fittings. At the end of the day, there are many factors to consider when lighting the shop.
1. Appearance to customers. Will it invite them in like a moth to the flame? Nice bright and fresh, or dark and gloomy?
2. Uniformity. Does it adequately light the area without creating dark spots and a 'cave' effect?
3. Comfort. Is there enough light for customers and employees to adequately go about their tasks? Or is there too much? Looks sterile?
4. CRI. Are we reproducing the colors the way they appear in daylight? Are we going to create more problems later? Customer complaints and returns for not matching their requirements?
If in doubt, consult a lighting designer. We in sunny Australia offer this to clients as a free service.
Comment from contributor M:
I have worked under a very knowledgeable lighting consultant for a little more than two years. Those recommending electronic ballasts and T-8 lamps must enjoy changing out failed ballasts, because most do not operate much past the five-year warranty period. Also, the lamps don't hold their lumen levels much better than a standard T-12 lamp, and oftentimes lumen maintenance is actually worse with electronic than with magnetic. True, there is an energy savings, but you'll be spending it on increased maintenance costs. If you don't believe it, just ask the man who owns one. You'll rarely find an electronic system 7 or more years old that hasn't gone through a lot of reballasting. As proof, at one time there were 18 ballast manufacturers in the U.S., while today it's down to a handful. The ones who failed went broke trying to honor their warranties. (There must be a disadvantage to having more than 120 components in a ballast.)
Concerning metal halide lighting, it should be unlawful to install it anywhere where humans and other living things must be under it for any extended period of time. Next time you're under one, look up at it for 10 seconds, then look away and try to see something. If it can affect your vision that much in 10 seconds, think of what it's doing to the poor souls that have to work under it 8 hours per day. Just remember, the cheapest light or brightest light isn't necessarily the best light for the job, especially where employee performance, customer comfort, and eye health are concerned.
The comments below were added after this Forum discussion was archived as a Knowledge Base article (add your comment).
Comment from contributor L:
One overlooked option is t-5. You still have the benefit of instant on, although the price is a little steep. You can get bulbs in the 5000k range. I use these everywhere we grade lumber. We actually switch from 4 400w MH to 4 6 bulb t-5 with 52w 5000k bulbs and every grader told me it really helped them. Just remember that every scenario is different due to ceiling height and etc. Do remember that more fixtures will create less shadowing. You want the fixture above or in front of you as you work not behind.
