CFL vs Incandescent fixture rating

[Gordon Shumway]

SWMBO just bought a new table lamp for the desk in our computer room. This lamp will be replacing one that uses two (2) 75 watt Incandescent bulbs. This new lamp uses only one (1) bulb. The label says "60 watt Incandescent or 15 watt CFL maximum." This will probably not be enough light for my old eyes.

I was under the impression that maximum wattage for a given fixture was because of the fixtures ability to withstand the heat produced by the bulb. If that's true wouldn't one be able to use a higher output CFL relative to the incandescent because of the lower heat the CFL bulbs produce?

I would like to use the equivalent to a 100 watt incandescent, a 23 watt CFL. Good or bad idea?

[David Nebenzahl]

On 11/14/2009 6:34 PM Gordon Shumway spake thus:

Bad idea. It's a myth that CFLs don't produce lots of heat. They do.

I now turn the discussion over to Don Klipstein ...

[LouB]

It would seem the worst you are going to have is a quicker failure of the CFL so I think it is a good idea. OTOH you should probably try the smaller CFL first to see if the light is actually OK

[Gordon Shumway]

The particular Philips, 23 watt CFL bulbs that we have definitely produce much less heat than an incandescent. I don't know what the normal operating temperature is but after they have been on for more than 10 minutes I can easily hold the bulb in my hand for a very long period of time without any problem. Yes, the bulb is very warm but definitely not hot. That's why I asked.

[David Nebenzahl]

On 11/14/2009 7:10 PM Gordon Shumway spake thus:

Yes, of course. The question is, does that 23-watt CFL produce more heat than what the fixture is rated for (75-watt incandescents)? (I don't know.)

[Tony Hwang]

Hi, What about the base of the bulb hich is in the socket? The specs. on the label is there for a reason. I use SAD LED panel which is pretty bright near the computer.

[Don Klipstein]

Non-enclosed table lamps with bulbs pointed upward (base-down) can take CFLs up to 42 watts OK if they fit.

As for heat - a 42 watt CFL makes slightly more non-radiant heat than a

60 watt incandescent does. Despite being more efficient than incandescents at producing light, CFLs are also more efficient than incandescents at producing non-radiant heat.

What CFLs are less efficient than incandescents at producing is infrared, which mostly escapes the fixture and heats the room but not the fixture.

If a CFL is enclosed or operated base-up, especially both or operated base-up in a downlight, it can easily cook itself. If the fixture is rated for 60 watt incandescents, then CFLs up to 23 watts and rated for use in recessed ceiling fixtures should be OK. One such CFL product line is Philips "triple arch style" Marathon, non-dimmable versions up to 23 watts (and not the 25 watt one and not the dimmable ones).

- Don Klipstein ( [e-mail])

[cjt]

My guess is the limit specified has more to do with a bright spot showing through the shade (i.e. an aesthetic consideration) than any concern about heat.

[cjt]

Incandescents turn most of their power consumption into heat, while CFLs are much more efficient. If the only consideration is the heat, I think it should be able to take a 75 watt CFL. However, such a big bulb might not physically fit, and also might look like heck.

[cjt]

make that 23 watt

[Gordon Shumway]

Actually I didn't give that much thought. I just checked and the base itself is barely above the ambient temperature. The glass portion is where all of the heat is. Good point though.

[Gordon Shumway]

Thank you for this information. You have been very helpful.

[ransley]

CFLs produce about 75% less heat than incandesant. Why do you think they are more efficent. Obviously the lamp was mislabeled.

[trader4]

Good grief. In an incandescent 75watt bulb, almost all that energy is heat. In a 23watt bulb, the most heat it could generate would be less than 1/3 that of the 75watt bulb.

In other words, I don't see why the fixture would restrict the bulb size so low for a CFL based on TOTAL heat. Now, I could see an issue with how the heat is distributed in one bulb versus another or that a CFL having electronics inside can't tolerate being raised to as high a temp as an incandescent

[George]

But "lots of heat" relative to what? I have honestly never heard this myth. CFLs produce heat buy way less than a comparable output incandescent lamp.

[ransley]

Sure they put out Lots of Heat, relative to his AA battery flashlights.

[RicodJour]

Since the OP said it was a table lamp, and we don't know the configuration, I would imagine that the seemingly low and arbitrary CFL rating has to do with bulb longevity, and not heat output being a problem with respect to fire. If the top of the shade is solid - more of a reflector - and not vented - the CFL will operate at a higher temperature and the bulb will die much sooner that it's rating (don't they all?). Many people would blame the lamp and manufacturer, so perhaps the lamp manufacturer is heading off complaints about their 'defective' lamp. Just a guess.

R

[Tony]

CFL's are inductive loads. Many things electrical are rated differently for resistive vs inductive loads. Return the lamp and find one with higher ratings.

[JRStern]

Should be fine, subject to Don's excellent posting about enclosure etc.

I've found some of the mid-sized CFLs put out more light than expected, a little 55 watt spot bulb equivalent, and a little candelbra-base 40 watt equivalent, seem much brighter than the incandescents they replaced.

Perhaps they're down-rated because they're brighter when new but tend to dim more than incandescents as they age?

I've been having excellent luck replacing all sorts of bulbs with CFLs from Home Depot.

Tried a cheapo from the 99c store, went dead in three days.

I also have a collection of CFLs from the last ten years, I've been a fan since before they became fashionable, and the new ones seem much, much better overall.

However, when the room needs heat, I do miss the several hundred watts that I used to get from the lighting! I suppose it's cheaper to run the gas heat for an extra minute or three, but I do see the difference!

J.

[Don Klipstein]

Modern spiral CFLs draw less current than equivalent-light-output incandescents do, despite these CFLs having low power factor.

One more thing - the usual spiral CFLs are not inductive. Their low power factor is almost entirely from harmonic content in the current waveform, not much from lead or lag. However, the non-dimmable ones are largely incompatible with most electronic switching devices not rated for fluorescents or motors.

For those who are concerned anyway - dimmable versions have high power factor and have recently started to become almost reasonably available, though they are more expensive than non-dimmable ones. I have seen dimmable CFLs at Target for most of this year already.

- Don Klipstein ( [e-mail])