Understanding lamp size codes

Lamp sizes are confusing, but it helps to be a little bit familiar with the terminology used on lamps. You often see sizes expressed as "F32T8" or "F71T12", and those numbers do means something. First, the T number. Think of T as standing for "thickness" or diameter. This is the measured diameter of the lamp in 1/8" increments. Thus, a T8 lamp = 1 inch in diameter. A T12 lamp = 12/8ths of an inch (1 and a half inches) in diameter. A T5 would be 5/8ths of an inch in diameter, and so on. So the T number is pretty easy to understand.

The F number is more confusing since it doesn't always correspond to a length or wattage, just a series. The F itself stands for "fluorescent". An F32, F34 or F40 lamp will always be about 48" long, similar to an office light. For smaller lamps (less than 5 foot) the F number often indicates the recommended wattage. The old office lights were F40T12 lamps, and used 40 watts each. The new F32T8 lamps use 32 watts each. There are a few F34T12s out there, but they are more rare, and yes, they use 34 watts each.

You would think that a 40 watt T12 would produce more light than a 32 watt T8, since it has 24% more power and 50% larger diameter, but you would be wrong. In office lights, the F40s are typically around 2700 lumens, while the F32 produce about 1000 more. When you are talking about ultraviolet, it gets even more complicated.

With longer lamps, the F number often corresponds to the approximate length. Sort of. The F71 lamps used in many tanning beds is around 69" long (almost 71 inches....) and an F59 is about 58" long. The F73 is around 71 inches, and to make matters more complicated, an F72 is shorter than a F71 by about 1/8th of an inch. F96 lights (the 8 footers you see in warehouses) are around 96 inches long. But the numbers are fairly close the F number, so if you are looking at a F71T12 lamp, you know it is around 6 foot long and 1.5" in diameter. This is why when you are building your first rig using lamps longer than 48 inches, you need to have all the parts in hand, and size the rig according to the lamps you have.

Fortunately, we currently only offer the T12 and T8 lamps, and as you can tell from the photo, they use the same spacing bi pin configuration, so the same lamp end will work with either size lamp.

You should take the time to read about powering fluorescent lamps as well, since you can power a 32 watt uv curing lamp with a variety of power ranges. I told you this can get confusing at times....

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