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Electronic Ballast Shoplights: So Much For Efficiency

Just picked up a batch of electronic-ballast shoplights from Lowe’s, motivated by a 10% off card they sent a while ago. Not a killer deal, but it evidently got plenty of folks into the store on a Sunday morning.

The new lights don’t claim much about their abilities, other than “Electronic Cold Weather Start (0° F)” and that the reflector sizing requires T8 (1″ dia) fluorescent tubes. One would expect an electronic ballast to have a decent power factor and improved efficiency.

Because I’m that sort of bear, I opened one up to see what was inside. Here’s the ballast:

Electronic Ballast Dataplate

Electronic Ballast Dataplate

Although the fixture is sized for T8 tubes, the ballast would be perfectly happy with T12s. Similarly, the box insists on F32 tubes, but the ballast is OK with F40s.

I thought a comparison with one of my old magnetic-ballast fixtures would be of interest, so I hitched up the Kill-A-Watt meter and ran some comparisons.

The results…

Amp Watt VoltAmp PF
Old magnetic ballast
F40T12 0.64 60 76 0.79
F32T8 1.11 80 126 0.62
New electronic ballast
F40T12 0.75 47 89 0.53
F32T8 0.77 49 91 0.54

The electronic ballast has a much lower power factor and thus much higher current. The box & ballast don’t say anything about power factor correction and, wow, there sure isn’t any. The power company hates gadgets like this…

I cannot compare the brightness because the F40 tubes are several years old, but it’s interesting that the electronic ballast runs both tube sizes at essentially the same power (just as the dataplate indicates, sorta-kinda). The magnetic ballast really cooks the piss out of the smaller tubes, though… or it’s dumping a lot of energy into the ballast. Hard to say.

The T12 tubes are rated for 3000 lumens & 20 k hours. The new box of T8 tubes I got a while back are 2800 lumens and 24 k hours. Frankly, I don’t believe any of those numbers, particularly given the actual power consumption: it looks like either ballast runs them at just 75% of their rated power.

Anyhow, these were the cheapest shoplights in stock; I bought eight of ’em, because I’ve been replacing one dead fixture every month or two for the last year. I’d like to think I’d get a better ballast if I spent twice as much, but to a good first approximation the additional cost seems to have gone into black plastic trim and a burnished-chrome exterior finish; not what I need in the Basement Laboratory.

I wish the boxes were more forthcoming so you didn’t need to perform exploratory surgery.

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