My understanding is that use of compact fluorescent bulbs in enclosed and recessed fixtures is discouraged because the bulbs can overheat. I'm not entirely clear on whether the problem is primarily reduced bulb life, or if there is also a safety issue due to overheating the fixtures. I've heard the claim that CF bulbs heat up a fixture more than an incandescent bulb of higher wattage. How that is possible is a little mysterious to me since it seems to me that the CF bulb is producing a much smaller percentage of a much smaller wattage as waste heat. But maybe the CF heat is somehow better captured.
So... throwing caution to the wind, I accidentally left a CFL bulb (Feit 23w spiral, 100w equivalent, available all over in California for $0.25 due to PG&E credits) on overnight in an enclosed, recessed ceiling fixture. This morning I tentatively touched the glass cover plate... a little warm, not hot. I opened it up, felt around inside, the reflector and casing are only warm. I grab the bulb itself by the ballast and by the spiral itself... warmer, but not too hot to hold.
I know from experience that these fixtures (unvented metal boxes) get VERY hot with a standard 75w incandescent bulb. Can I conclude from these observations that the CF bulbs are fine? What sort of reduction in life should I expect from what seems like a very modest increase in operating temperature?
-- Dave