GE-Made F25WT12 F40T12 Lamp

Special thanks to fellow member Icefoglights for a pair of these. Had been wanting a set ever since I really got into fluorescent lights, well, now I finally have a set!

These are oddball in a few ways. They were intended for the cheap, low-power-factor, low-output magnetic rapid start ballasts found in inexpensive shoplight or wraparound or striplight fixtures sold at box stores in the '90s and '00s. (In this photo, it's even running on a cheap Metalux striplight from the early 2000's

These ballasts power a 40 watt lamp at about 25 watts (i.e ridiculously underpowered, dim!) After the EPACT rulemaking of the early 1990's, the decades-old standard workhorse of the linear fluorescent light, the F40CW lamp, was banned. The rule was either high CRI or reduced wattage at the time. The bizarre loopholes allowed lamps like this, with wimpy cathodes intended for their wimpy residential-grade ballast counterparts, hence the NOT FOR COMMERCIAL USE. By comparison, buried somewhere back home I also have some GE Watt-Miser 34-watt energy saver lamps that are stamped with FOR COMMERCIAL USE ONLY, as those krypton-filled 34-watt tubes had a tendency to cook many residential-grade, low-power factor ballasts of their time in very short order.

The funny thing about these oddball 25-watt tubes is that they will operate as an F40CW both electrically and physically/optically if used on a proper high power factor, full output ballast. However, with their wimpy cathodes, they only last a rated life of 6,000 hours, versus 12,000 on their proper ballasts (They were cheap lamps anyway, the "real" 40-watt lamps were rated 20,000 hours on rapid start, 15,000 on preheat, so I assume on low-output preheat these would do about 9000 hours, and on high-output, high-power factor preheat, probably something like 4500. Not long. Cheap, low-quality, economy-grade lamps.

Yet the 40-watt lamps still last a normal lifetime on these cheap ballasts. So really the 25 watt lamp was a gimmick.