Lighting Advice

[David Wong]

David - What LLF did you use? Did you input a CU or did the program calculate one?

The program used a Light Loss Factor (LLF) of 1.0 and a Coefficient of Utilization (CU) of .0.656.

The exact explanation and calculation of these numbers is beyond me. I only know enough to know that lighting design is a very complex subject.

[Cliff Holmes]

I think you meant *compact" fluorescent bulbs

As Ken already pointed out, equal distribution of the number of tubes vs CFLs give a much better light quality with tubes unless your putting up a LOT of CFLs.

And, as many other sources are pointing out, the lifespan of the newer inexpensive CFLs is vastly overstated, *especially* if mounted upside down.

[Ken Fitzgerald]

Cliff,

After thinking about it there is probably a valid second reason for using single point globe bulbs. Nathan and probably Don are using the shadows to "highlight" surface deficiencies on the wood. That would be handy when finishing.

As I age, I do need a lot more light to see as well as I used to... My wife on the other hand has the opposite problem. If I walked around in our home of 27 years with the lights out like she does, I'd be in an ambulance headed for the ER in 10 minutes. I think we might be living the Jack Spratt fable.

[John Schreiber]

What is the difference between continuous fluorescent bulbs and compact fluorescent bulbs?

When I Google continuous fluorescent, all the references are to photography equipment.

[Don Kondra]

What is the difference between continuous fluorescent bulbs and compact fluorescent bulbs?

When I Google continuous fluorescent, all the references are to photography equipment.

Yikes, yes. Mea culpa

This is from the Alzo Digital site -

These special Photo CFL (Compact Fluorescent Light) bulbs have a natural "daylight" balanced color temperature of 5500K. These special energy saving bulbs are "flicker free" and specifically designed for digital photo imaging. They produce a soft diffuse light with CRI of 91 and bulb life is exceptional at about 10,000 hours.

When used for photography, the technique is called "continuous lighting" as opposed to flash or strobe.

Cheers, Don

[Steven DeMars]

My shop is 22' x 20' with a 10" ceiling.

I have 24 (2) bulb T-8 fixtures in mine.

That's a total of 48 bulbs, @ 32 watts each.

I have no shadows anywhere & it is a little on the bright side.

Steve

[Jack Lindsey]

[QUOTE=David Wong;1210709]The program used a Light Loss Factor (LLF) of 1.0 and a Coefficient of Utilization (CU) of .0.656.

Thanks, David, that's about what I expected. The light loss factor is the product of several factors that cause a lighting system to initially produce less than the rated light output of a lamp/ballast system, and to cause a decrease in lighting levels over time. The major factors applicable to lighting our shops are ballast factor, lamp lumen depreciation, and luminaire dirt depreciation. There are several other factors that are minor players or don't apply at all so I'll skip them but explain the main ones.

Ballast factor: when a lamp manufacturer tests a fluorescent or HID lamp they use a "reference ballast". This is a large transformer that is designed to maintain steady voltage and current waveform to the lamp. It's a lot better that the small transformer or electronic device we use in our fixtures, and generally causes the lamp to produce less light than it produces on the reference ballast. There is an exception in that some electronic ballasts overdrive the lamp to produce more light but that is a rare exception. CBM rated magnetic ballasts can be expected to drive full wattage lamps at about 95% rated light output. Electronic ballasts vary considerably from that number based on their design. Some intentionally drive lamps at lower output as an energy conservation measure. Since there is no standard it is necessary to consult the ballast manufacturer’s test data or obtain a test from an independent testing lab to obtain reliable information. Many electronic ballasts perform in the .90 - .95 range so we will use that number for this discussion.

Lamp lumen depreciation: as lamps operate they decline in light output. This is due to a deterioration of the phosphors that are the actual light producing element in a fluorescent lamp, and the evaporation of cathode material which deposits on the inner surface of the lamp envelope and absorbs light. These factors are well known and can accurately be predicted. A RE phosphored T-8 lamp can be expected to maintain about 89% of it’s initial light at 70% rated life, which is the point typically used in lighting calculations.

Luminaire dirt depreciation considers the loss of light due to dirt accumulation on lamp and fixture surfaces over time. Empirical data are published in the IES Lighting Handbook and are generally based on the dirt conditions in the space and frequency of fixture and lamp cleaning. Based on an annual cleaning and average dust conditions is a typical hobby type shop I’m going to estimate a factor of .90.

The product of these factors is: .93 x .88 x .90 = .74

Based on this information the illuminance of 107 fc in the Lightolier program could be expected to drop to about 79 fc over time. A better option would be 10 fixtures producing about 99fc over time.

[Leo Graywacz]

What is the difference between continuous fluorescent bulbs and compact fluorescent bulbs?

When I Google continuous fluorescent, all the references are to photography equipment.

Use linear fluorescent bulb

[Gary Radice]

My shop is 22' x 20' with a 10" ceiling.

I have 24 (2) bulb T-8 fixtures in mine.

That's a total of 48 bulbs, @ 32 watts each.

I have no shadows anywhere & it is a little on the bright side.

Steve

I bet that IS a little bright! I have just a slightly larger shop (24 x 20) with 12 foot ceilings and 32 T8 bulbs plus a couple of T12s in a reflector dropped over my workbench. With white ceilings and walls and 57 year old eyes I have plenty of light and wouldn't want any more.

[Ken Fitzgerald]

My shop is 32' x 24' with 10' ceilings. I have 11 T-8 fixtures and each fixture has 4 4' T-8 bulbs. It is well lighted and has no shadows. Everyone who comes in remarks about the great lighting I have.

I used Jack Lindsey's FWW article as the master reference and it resullt in a well lighted shop.