Hi all,

I'm planning on building an incandescent-ballasted F14T12 fixture. According to the Advance fluorescent lamp troubleshooting guide, the F14T12 is rated for 0.38A of current. I've gone through all my incandescent light bulbs, and I've narrowed it down to two bulbs; a 40 watt unit which feeds the lamp with 0.27A, and a 60 watt unit which feeds the bulb with 0.39A.

My question is, which do you guys think would be better for the bulb, a 25% underdrive or a 3% overdrive? Normally I would accept a slight underdrive over a slight overdrive, but given how little the overdrive is, I'm willing to consider both. I'm also considering the 60 watt bulb because the higher current lets the bulb start easier, which is a challenge on an incandescent ballast. However, a vintage lamp which I just acquired will be used for this fixture, so preserving lamp life is my top priority in choosing which incandescent bulb to use.

Thanks for any imput.

The 3% overdrive won't be of any problem at all.
I assume the currents are the measured ones, which type of meter have you used for that?

Thanks for the input. I'll probably use the 60 watt then since it will make starting a lot more reliable. Current was measured using my Kill-A-Watt meter.

But there will be quite severe losses, the whole assembly will emit less light than a 50W incandescent...
I would rather use two lamps in series, the ballast would be most likely a 100W or 75W incandescent (you will have to try, which gives the closest current value)

As always with my experiments, efficiency is the least of my concerns.