DIYbanter - View Single Post - CFLs vs incandescent "max wattage" cautions in overhead fixtures....

Don Klipstein

In article ,
wrote:

On Mon, 19 Jan 2009 14:25:15 -0500, 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 ?)

You can install UP TO the wattage stated on the fixture. If the
fixture is rated at 60W (incandescent), you can use up to 60W (actual
wattage used - CFL).

Make that mid or upper 30's or so. I did once measure temperatures on a
fixture (with a non-contact thermometer) and got the fixture slightly
hotter with a 42 watt (150 watt incandescent equivalent) CFL than with a
60 watt incandescent.
Incandescents produce a lot of infrared - much to most of which escapes
the fixture and becomes heat where it is absorbed - usually mostly all
over the room it is in. CFLs produce conducted/convected heat more than
anything else, and after that visible light.

Any CFL which actually uses 60W, will actually be rated at several
hundred watts of light output.

If rated honestly, about 200-250.

If you put in a 150W equivalant CFL, it would only use about 30 watts,

Make that 42 watts. A 42 watt CFL typically produces 2600 lumens. A
150 watt 120V 750-hour incandescent of "Big 3" brand and with CC-8 style
filament (axial coiled-coil) typically produces 2980 lumens, maybe more
like 2900 even for "soft white".

which is only half what the fixture can handle. Of course the high
wattage CFLs get large and may not fit in the fixture dome.

As I said above, when I compared fixture heating by a 42 watt CFL and by
a 60 watt incandescent, the fixture got slightly hotter with the 42 watt
CFL.

Next lower common wattage I have seen is 30 watts, and I see those at
Lowes. Home Depot may have 30 waters also. My experience is that those
outshine 100 watt incandescents rated 1750 lumens by a small amount when
young and at favorable temperature. I suspect they fade to close to
1670-1750 lumens after 2 or 3 thousand operating hours. I suspect they
easily overheat in downlights and small enclosed fixtures.

Next lower common wattage of CFLs after that is 26 watts - usually rated
to produce 1750 lumens - when in a favorable range of temperature and
young. They typically produce something like 10% less after aging 2 or 3
thousand hours. 100 watt 120V incandescents of "Big 3" brand and CC-8
style filament are typically rated to produce 1670-1750 lumens.

Next lower common wattage of CFLs is 23 watts - usually rated to produce
1600 lumens. That is when in a favorable temperature range and in first
few hundred hours of operation. I would say more like mid-1400's after
aging 2-3 thousand hours and in a favorable temperature range - I would
call that "roughly halfway from 75 watt equivalent to 100 watt equivalent".
23 watts is the highest wattage of CFLs that appears to me to have
"fairly good" survival in downlights and enclosed fixtures. Philips
"triple arch" "Marathon"/"SLS" 23 watt non-dimmable is the highest wattage
and brightest CFL that I am aware of that is actually rated to take the
heat of recessed ceiling fixtures. The dimmable 23 watt and the 25 watt
versions of this one are not rated for this as of last time I checked.

- Don Klipstein )