Florescent lights for shop use...

[75Crew]

Shop Lighting Application Guide

A quick guide for shop lighting (I'll be submitting a more detailed article for future publication in the Power Wagon Advertiser magazine soon.)

Lighting choices have changed a lot in the last 5 years. The basics you need to consider are:

A) the color temperature of the light source (measured in degrees Kelvin - 2700 to 6000 is normal - with incandescant and halogen on the low end, metal halide and some fluorescents in the middle and other fluorescents on the high end of the spectrum. Most people prefer a light that is in the 4000-5000K range for industrial work.

B) the color rendering index (CRI) of the light source (measured 0-100% with the sun being 100%) In simple terms, this number approximates the % of actual colors you will see from objects illuminated by the light source. The sun allows you to see all of the colors. Most artificial light sources allow you to see between 20-95% of the colors illuminated by the light source.

C) Lumens per watt - The light output of a light source is measured in lumens. The power required to produce the light is measured in watts. Therefore, the lumens per watt rating is the measure of efficiency of the light source. Incandescants are in the 10-15 lumens per watt range. Standard fluorescents and CFL's are usually in the 50-60 lumens per watt range. Standard metal halide lamps fall into the 75 lumens per watt category while high efficiency fluorescents are in the 90 lumens per watt range. LED light sources are gaining popularity now with prices coming down each month, but these are still pretty expensive. They compare favorably to the high efficiency fluorescents in most cases from an efficiency basis but not always in the CRI and color temperature categories.

D) Fixture efficiency - most people fail to look at this number. You can have the best light source in the world but if it is placed in a poor fixture, it will not perform well. The fixture efficiency number is determined by a testing laboratory and published in data provided by the fixture manufacturer normally referred to as the IES (Illuminating Engineering Society) files. 80-95% is a good number here. That means that 80-95% of the light produced by the light source in a fixture leaves the fixture as useable light for the task illuminated by the fixture. Cheaper fixtures have lower efficiencies as you might expect.

(more info in the next post)

[75Crew]

Shop Lighting Application Guide (continued)

There are several other factors to consider also, including the environment that the fixture will be operating in, the voltage and stability of the power source feeding the fixture, the average number of hours per month the fixture will be operating, the availability of capital $ to purchase the fixture and the amount of heat you are willing to live with while working under the fixture.

In general fixtures have the following attributes:

Incandescants and halogens - low initial cost - relatively short life (800-2000 hrs) low on the color temperature Kelvin scale (produce a warmer - more yellow light), produce a lot of heat (more energy goes into producing heat than light) and fixture effiency is fairly low. Energy costs over the long run will likely be the highest of any light source but if you operate them less than 10 hours per week, it might be a good choice for you. Work well in cold temperatures.

CFL's (compact fluorescents) - primarily for use in replacing incandescants with a more efficient light source while using the same fixture. Advertised life is not usually accurate. Need to be left on for long periods to get close to advertised life. If frequently switched, life is not much longer than incancescants but energy use is quite a bit less.

Standard fluorescents - relatively low initial cost - decent life (12,000 to 24,000 hours depending on the lamp type), available in several color temperatures, acceptable CRI, produce some heat but not as much as incandescants/halogens. Energy costs over the long run will be acceptable unless you have shop with several hundred fixtures and you operate it more than 20 hours per week in which case you will likely want to look at high efficiency fluorescents or metal halides. Also, the T12 fluorescent lamps will not be allowed to be manufactured for sale in this country after July, 2012. If you are looking to purchase new fixtures, please take this fact into consideration. For the moderate cost option that is best in the long run, you may want to look at T8 fluorescent fixtures. Most of these fixtures don't work well in cold temperatures (less than 45 deg F) unless they are equipped with cold start ballasts which do cost more up-front.

Metal halide (HID - high intensity discharge) fixtures - somewhat expensive initially but have a relatively long life (12,000-24,000 hours depending on the size). Very heavy. Produce a lot of heat (because they are a high wattage fixture) and need to be mounted at heights greater than 15' due to the intensity of the light emanating from a small area. Mounting at higher elevations also allows the light to spread out more eliminating "hot spots" under the fixture and providing more even illumination thoughout the facility. These fixtures work well in cold temps but usually take at least 5 minutes to warm up to full brilliance when first turned on and as much as 15 minutes to re-start after a power outage. One good thing about them is that there are a lot of them out there available for little or no money (used/salvage) due to the fact that many factories and large building owners are changing them out for high efficiency fluorescent fixtures because of the energy efficiency savings to be had.

High efficiency fluorescent fixtures (T8 and T5HO) - Comparable in cost to a new HID fixture but much lighter weight. On a lumen output basis, use about 1/2 the energy as HID fixtures to produce the same amount of light. Lamp life of up to 60,000 hours with new XL lamps. High CRI and many available color temperatures. Very good light source to use in body shops due to available color characteristics. Instant on - no wait for re-strike after power loss. Will start at temperatures as low as 0 degree F but may take a while to come to full brilliance in cold temps. May also have shorter life in extremely hot environments (> 125 degree F) unless equipped with high temperature ballasts. Extremely energy efficient - a good choice if you are installing many fixtures in a large shop. Don't generate a lot of heat. Can be installed at about any height from 6' to 50' (with the proper reflector design) and can be installed vertically on a side wall with very pleasing effects to eliminate shadows and to see under vehicles while working under a lift.

(more later about LED fixtures)

[75Crew]

Shop Lighting Application Guide (continued)

A bit more about CFL's - they work well when applied in the right conditions - but as noted earlier, they do not like to be switched off and on a lot. (i.e. - don't put them in a closet or bathroom if they will only be on a few minutes at a time - use an incandescant or halogen lamp for these applications.) Also, most CFL's have electronic ballasts located in the base of the lamp. These ballasts have many components, several of which are extremely heat sensitive. They will experience less than rated life if:
1) installed in a base-up configuration (heat rises so all the heat produced by the lamp is directed to ballast
2) installed in a recessed fixture (heat gets trapped in the fixture around the ballast
3) if installed in an enclosed fixture - either base up or base down - heat can't escape the fixture well and cooks the ballast.

LED lamps and fixtures - LED's (light emitting diodes) have been around for many years but recently manufacturers have tried to move them into the mainstream as general lighting sources. They do not contain mercury. HID and fluorescent lamps do contain mercury but many are now manufactured with much smaller amounts than in years past.) They also don't emit UV (ultraviolet) or IR (infra-red) light. This makes them a great light to use in an outdoor patio application as they don't attract insects. LED's typically have a rate life of from 10,000 hours to greater than 50,000 hours. LED's are not cold sensitive and, as such, are good in applications that may reach temperature levels below 0 degree F. However, they are heat sensitive and if a fixture is not designed to deal with the heat dissipation properly, the life of the LED light source will be much less than the published value. Also, many LED fixture manufacturers, in an effort to boost their claims of efficiency, will over-drive the LED light sources (boost the voltage in the electronic driver) in their fixtures to get more light with less capital expense. This has the resulting effect of a bright fixture that fails in a reduced number of hours, usually right after the warranty expires. Bottom line...LED's, in my opinion, haven't made it to the point of being good general lighting fixtures. They are still too expensive to be deployed on a large basis and it is hard to evaluate the many claims coming from the large number of manufacturers, most from China. They have their niches, as discussed, and some day, as the prices keep falling, they will be a good choice for general lighting, just not yet.

Specific use - most of the lighting that has been discussed in this succession of posts has been geared to general area lighting. However, many lighting tasks are not general in nature, but very specific. Take inspection lighting for instance. I have seen more than one automotive manufacturing plant add more and more light to their inspection areas (over 1000FC in some instances), trying to achieve lower reject values by identifying more and finer imperfections. They would keep adding more fluorescent lamps to the booth, but more light doesn't always mean improved defect detection. Many times, it is the direction and the size of the light source that determines whether one can see an imperfection. Defects are usually noted by changes in contrast from one area of the part under inspection to another. For instance, a run in the paint of a car finish is better detected by positioning a very tight point source light (halogen or single wafer LED for instance) to shine across the surface horizontally, rather than bombarding the surface with a flood of lumens from an overhead fluorescent light source. The same goes for trying to find waves in a recently filled and sanded quarter panel before painting. That is why vehicles always look best when photographed at sun-up or sun-down rather than when the sun is high in the sky. Contrasts are more visible and humans enjoy contrasts when viewing cars and other scenery. The same holds true for looking at the autumn leaves. They always look more vibrant in the morning or late in the afternoon. Contrast is the operative word here.

My recommendations - over the workbench stuff and ceiling areas of small to medium sized shops. As a recommendation, I'd say that the best overall fixture to put over your workbench would be a 4' or 8' T8 using 4' lamps. (4' lamps are much more available than 8' lamps and last much longer.) I would agree that in the ceiling, if your ceiling is lower than 15' above your floor, you should also go for 8' T8 fixtures (or T5HO fixtures) with white reflectors that have a reflectivity of at least 92%. You can spend the money for XL lamps if your fixtures will be on more than 40 hours per week, but at that rate, even a standard T8 lamp (24,000 hours life) should last you around 10 years. By that time, you may want to switch to the latest and greatest technology. As far as color goes, I like the 5000degK lamps. I have T5HO lamps of this type in my shop and am very pleased with the performance. Ballast type is also a consideration but for the general shop lighting application, it doesn't make sense to discuss it a lot here.

Hope this series of application notes has helped. Have a great New Year and go find you some good lights. Life is too short to be lived in the dark!

[Gordon Maney]

I must say I don't care for the CFL's. Slow to come on and don't seem to last very long, which fits with your comments.

Are T8's the thinner tubes?

[75Crew]

Fluorescent terminology

Sorry - forgot to explain fluorescent nomenclature. Fluorescent lamps are classified according to the diameter of the tube as measured in 1/8" increments. So...a T12 lamp (the lamp most people are familiar with) is 12/8" diameter (or 1.5") A T8 lamp is 8/8" diameter (or 1") and a T5 is 5/8" diameter. HO stands for "High Output"

[Gordon Maney]

Interesting. I was just wondering what, if anything, those numbers meant. Thank you.

[Gordon Maney]

It seems so many of the common, cheap fixtures have trouble getting the tubes fitted between the white plastic end pieces. I have purchased such fixtures that literally did not have enough space between the two ends to get the tube where it belongs. Do the T8 fixtures use the same type of connectors as the older, thicker tubes?

[75Crew]

Fitting the lamps in between the tombstones

Those white plastic pieces are referred to as "lampholders". Many people call them "tombstones" for obvious reasons. As in anything else, all lampholders are not created equal. A manufacturer can pay anywhere from a couple of cents for the cheap ones to several $ for the really nice ones. (more on this in the magazine article) The T8 lamps use the same lampholder as the T12 units but the T5 and T5HO use a different style. Also, the T8 lamps are 48" long like the T12 lamps, but the T5 and T5HO lamps are about 46.5 inches long (having originated in Europe, they were built to a metric standard). I have found, on some of the cheap fixtures, you can sometimes loosen the screws holding the lampholders in place and get a little more clearance for installing lamps (if they are installed with screws in the first place) but, as in most other applications, there is no substitute for quality. You get what you pay for and you pay for what you get.

[712edf]

This is an informative thread, on a subject that I have thought about, but didnt really know where to go for "enlightenment".

Being a housepainter, I always knew not all light is the same.

Now if I could just afford to build a shop to light up.

Bucky