In article , ropeyarn wrote:

The ceiling fixtures in our house all have labels indicating the maximum
wattage (incandescent) bulb to place in the fixture.

I assume this is a heat-based limit...

If I'm replacing the incandescents in one of these fixutures with
CFL's...which stay cool to the touch....are there any issues with going
to a higher light output in (say a CFL packaged with "75 watt"
incandescent output indicated on the package ?)

I have one data point of experimentation indicating that a 42 watt CFL
produces slightly more non-radiant heat than a 60 watt incandescent.
Therefore, it appears to me that CFLs of wattage much lower than 42 watts
will not overheat fixtures rated for 60 watt incandescents. This means
that CFLs of wattage up to low 30's should be OK, and those tend to
outshine 100 watt incandescents.

Meanwhile, CFLs can overheat in some fixtures. My experience is that
ones over 23 watts have a significant rate of overheating in downlights.
23 watt CFLs tend to be "lowish 100 watt" incandescent equivalence,
usually outshining 75 watt incandescents.

You may ask - how could a CFL be more efficient than an incandescent at
producing both light and non-radiant heat? The answer is that the CFL
produces much less infrared than an incandescent does, especially much
less in the 700-2500 nm range.

- Don Klipstein )