Posted by David Sherman on Thursday, September 28, 2006 at 1:10PM :
In Reply to: Re: OT: Fluorescent Lighting - HO vs Electronic Balast posted by MoparNorm on Thursday, September 28, 2006 at 11:21AM :
I've scrapped out a lot of old electrical equipment, and have yet to find a fluorescent lamp ballast with any kind of oil in it, much less PCB. They're all wound with plenty of copper wire on an ample iron core (so they don't get as hot as modern ballasts) and then the whole thing is potted in tar. I keep hearing about the "hazards" of PCB in old ballasts (usually when the school district is trying to pass a levy to demolish the "toxic" old school and build a new one), and I'm sure they exist, but all the PCBs I've found are in larger transformers, including big industrial ballasts, and of course in capacitors.
PCB was developed as a safe alternative to mineral oil for insulating and cooling electrical equipment. They used to have serious fires due to transformer oil. Now that they're back to using oil, there's once again the risk of fires. PCB is a non-flammable oil with good insulating properties. It also really is carcinogenic, but so are lots of things, and I don't know how much you have to be exposed to to have any real risk. The trade name of PCB was "Pyranol", and GE used lots of it. If you see any old GE transformer, ballast, or capacitor, look and see if it says "Pyranol" on it. I have quite a lot of pyranol capacitors, but if they leak, I'm careful to throw them out, clean up the leakage, and wash my hands thoroughly. Long ago I called several government "environmental" offices, thinking there would be some place where I could take them to be safely disposed of, but all they told me was to either throw them in the regular garbage or pay hundreds of dollars to some haz-mat place to get rid of them. PCBs are basically destroyed by burning, so for a while after PCBs were banned, the power companies drained their transformers and capacitors into the fuel tanks of oil-fired boilers and got rid of it that way.
Anyway, I think the main thing that makes old ballasts (and old motors) last longer than new ones is that the insulation wasn't considered to be as heat resistant (tarred cotton vs PVC, etc) as it is nowadays, which meant they designed with more iron and more copper for the same power rating, so as to keep them cooler. Of course they were also hand-wound in American factories by American workers and probably cost a heck of a lot more in real terms than modern replacements cost. Now they design them with just barely enough copper and iron to keep them from getting quite hot enough to melt the insulation. But what happens inevitably, is the warm insulation (it's just enamel over the wire) creeps slowly due to heat and tension, and pretty soon you have a shorted turn somewhere. The motor or transformer keeps working, but maybe it buzzes a little more and the shorted turn makes it get hotter. Then another turn shorts out. Pretty soon the whole thing overheats and fails. The general rule of thumb with electronics is that the lifetime of a component is cut in half for every 10 degree increase in operating temperature. Modern insulation will last longer than old insulation when run at the same temperature, but when they design it to run hotter, it can more than cancel out the improvement due to the material.
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