Say you've got an old circa 1954 ceiling light fixture. Spec'd for 2 max 40 watt incandescent bulbs.
My Sylvania 100w-output CFL's take 23w input.
100% safe to use 2 of these CFLs instead of 2 40w incandescents??Thx, Cathy
I would..........CFL's generate a lot less heat than incandescents.
Those original ratings were based on heat generation & dissipation.
I have several 1930's fixtures that we rated for 60 watt max, that I've been running 100 watt CFL's in for about a year....no problem.
As an examples a 60w incandescent is too hot to unscrew & handle when on.....a 100 watt CFL can easily be handle "hot".
cheers Bob
Yes. From a safety standpoint you go by input power i.e. the CFLs 23W, not the "equivalence" power i.e. 100W replacement. This still leaves a larger safety margin anyway since the rating are mostly based on heat output and with CFLs greater efficiency it's 23W produce more light and less heat than a 23W incandescent would. Something like the 42W or so CFLs, 150W equivalent would be fine as well and damned bright compared to two 40W incandescence. The "W" is capitalized BTW, Mr. Watt thanks you.
The CFL's will be fine so long as the fitting is adequately ventilated.
The electronics in the base of a CFL doesn't like heat and can cook up quite easily if the heat can't get away as in an unventilated fitting.
However, I have had no trouble in any of the light fittings I have put CFL's into. Most were quite adequately ventilated anyway.
Ross
On Thu 20 Nov 2008 09:30:24p, RMD told us...
I have installed CFL?s in enclosed ceiling fixtures where ventilation might be questionable. This was well over two years ago and have had no problems. The wattage, of course, was well under the total wattage rated for the fixtures.
As long as the INPUT wattage is within the fixture's rating you are fine. If the fixture is rated 40 W, then up to a 40 W INPUT lamp can be used. The output equivalence is irrelevant in this respect.
I wouldn't think any trouble. The old incandescents put out a lot more heat than the CF. Heat dissipation was the major concern, as I understand it. Use the 23 watters, and don't give it a second though. Well, if the 23 watters will fit. Many bulbs won't fit in the older incandescent devices.
Is that why our last president was known as "W"? His favorite conversational starter. "Watt, you say?"
"W" is our current president, you moron, and I bet you voted for him, didn't you. Birds of a feather. Dodo birds, in this case.
Hi Cathy,
There are two concerns with light bulb fixture ratings:
In the case of the CFL's, you would be drawing LESS current (23 watt vs 40 watt), and CFL's put out much less heat than incandescents. So you won't harm the fixture or wiring in any way by using the larger CFL bulbs.
However, if the fixture is enclosed, you "may" have problems with the CFL's themselves. Some CFL's aren't designed for even the minimal heat build up in an enclosed fixture and will burn out quickly. When you shop for the CFL, try to find ones that are specifically rated for enclosed fixtures (though many don't specify either way).
I have several 75 watt CFL's installed in enclosed ceiling fixtures around the house originally rated for 60 watt incandescents. They've been running for years now with no problems. A huge plus with our high ceilings that require ladders to reach the fixtures.
Anthony
I don't think you're going to find anything less than 18ga wire in a light fixture, and the allowed ampacity for 18ga in a fixture is 6A (NEC table 402.5) which equates to 720W at 120V.
Yes, due to the much lower percentage of input Wattage that is output as heat, you can use CFLs with input Wattages well about the incandescent Wattage rating on a fixture without issues.
Yes, some of the cheapest CFLs are pretty heat sensitive themselves and if they don't get good ventilation they have fairly short life spans.
75W equivalence rating I presume? That would be well under the max you could install, and if the area could use more light the 40+ input Watt CFLs would work well and be safe.
CFLs are more efficient at producing non-radiant heat than incandescents. I have found a 42 watt CFL to heat a fixture up very slightly more than a 60 watt incandescent did.
Incandescents produce a lot of IR, which becomes heat but the IR mostly escapes the fixture before becoming heat.
- Don Klipstein ( snipped-for-privacy@misty.com)
Actually, CFLs are more efficient at producing non-radiant heat than incandescents, despite being more efficient at producing visible light. What CFLs produce less iof is infrared.
I did actually heat a fixture very slightly more with a 42 watt CFL than with a 60 watt incandescent. I have a non-contact thermometer.
I would expect the maximum common CFL wattage to not produce more fixture heating than a 40 watt incandescent to be 26 watts.
- Don Klipstein ( snipped-for-privacy@misty.com)
Let's see... 40 + 40 =3D 80 and... 23 + 23 =3D 46
Okay... 46 < 80
No problem, and you'll have a lot more light in the area to boot.
I replace all my 100W incandescents with 40W CFLs, which are "150W equivalent" to incandescent. The rooms are way brighter, with a nice white light instead of a sickly yellow, and I'm still using less than half the energy that I was before.
Put three 23W CFLs in the overhead fixture in the kitchen. It's like full sunlight in there now.
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