Light fixture ratings for CFL vs incandescent

[PandaBear]

I think the reason for 30W CFL rating is not due to heat but either resonance (noise on the line) or motion sensor interference. If you have a 60Hz flickers that's too strong on the light fixture, it may interfere with the motion sensor. Incandescent or Halogen do not flicker as much so it is not that big of a problem.

 

[Win]

I think, and it's just a guess, that heat dissipation in the fixture is the source of the limitation. As an aside, having used hundreds of CFL's in commercial and residential service, I can't predict any life difference between cfl bulbs that are switched on and off frequently, and those that run long periods, or even continuously. Some cfl's just last a long time, and some don't, and it doesn't seem predictable. As for the weak startup light, or weak light output in cold wx, I get around that by using dual bulb fixtures, and lamping with an incandescent and a cfl.

 

[HTSS_TR]

Originally Posted By: DBMaster

I agree. Market forces seemed to work very well in bringing down the price of CFL's without intervention. I got an "awesome" deal on a CFL replacement for 60W bulb in 1993 - $10. Now, you can buy a multi-pack of name brand CFL's for that price and there are a wide variety of shapes and color temps available. LED's are already coming down in price, too. There are still uses for incandescent bulbs as well. There are many lights in an average house that are only used intermittently, for seconds at a time. CFL's are not appropriate for those uses and LED's are still far too expensive to realize any efficiencies.

Local lumber store had CFL on sale once every 2-3 months for 10 cents each for 60W equivalent, 19 cents for 100W equivalent. The low price was subsidized by local power company SCE(Southern California Edition). But so far no LED bulbs are price subsidized by SCE, I think they will soon then the price may be as low as 25-30 cents per bulb.

 

[Kiwi_ME]

Originally Posted By: PandaBear

I think the reason for 30W CFL rating is not due to heat but either resonance (noise on the line) or motion sensor interference. If you have a 60Hz flickers that's too strong on the light fixture, it may interfere with the motion sensor. Incandescent or Halogen do not flicker as much so it is not that big of a problem.

I've found PIR motion sensors are quite sensitive to electrical noise and the CFL will generate high frequencies that may appear locally. However I don't see where a 60Hz flicker is going to come from seeing as the CFL rectifies the mains to DC and then generates a high frequency to run the florescent tube. Note also some CFLs stipulate that they are not to be used in a closed fixture (for heat dissipation) and some even require they not be pointed downwards.

 

[PandaBear]

Originally Posted By: Kiwi_ME

Originally Posted By: PandaBear

I think the reason for 30W CFL rating is not due to heat but either resonance (noise on the line) or motion sensor interference. If you have a 60Hz flickers that's too strong on the light fixture, it may interfere with the motion sensor. Incandescent or Halogen do not flicker as much so it is not that big of a problem.

I've found PIR motion sensors are quite sensitive to electrical noise and the CFL will generate high frequencies that may appear locally. However I don't see where a 60Hz flicker is going to come from seeing as the CFL rectifies the mains to DC and then generates a high frequency to run the florescent tube. Note also some CFLs stipulate that they are not to be used in a closed fixture (for heat dissipation) and some even require they not be pointed downwards.

Ah, you are assuming that they all use high frequency ballast, and the DC they rectify is "clean". In reality those cheap subsidized $1 bulb may use magnetic ballast (I have them, they produce a hum), and the DC that came out of it is not flat at all. Once upon a time I was trying to figure out why a machine wouldn't work when the hood light is on. I looked at the sensor's raw analog signal and discovered that the CFL light in the hood generates a 60Hz background noise that causes the signal to have funny reading. So for a cheap fixture with motion sensor, the 60Hz light or EMI from an unclean, cheap, magnetic ballast CFL could cause the sensor to detect something that isn't there or reduce its sensitivity. They may not be a problem at 30W but could be if it is much higher.

 

[JHZR2]

Originally Posted By: Win

Some cfl's just last a long time, and some don't, and it doesn't seem predictable. As for the weak startup light, or weak light output in cold wx, I get around that by using dual bulb fixtures, and lamping with an incandescent and a cfl.

That has been my experience wrt life, and the approach you mention is one that I feel works well.