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[Appliance Module]

If I put two CFL in a enclosed light fixture that can accept two 60W incadescent, each rated at 15 watts and giving the equivalent light of 60 W, will the heat build up be more, less or same as if I had used two 60W bulbs.   

Reason I ask, is it seems like when I tried it the fixture got very hot.

[TakeTheActive]

If I put two CFL in a enclosed light fixture that can accept two 60W incadescent, each rated at 15 watts and giving the equivalent light of 60 W...

...Reason I ask, is it seems like when I tried it the fixture got very hot.

What does it say on the packaging that the bulbs came in?

For example:

CAUTION: Do not use in lighting fixtures controlled by a dimmer, electronic timers or photocells, totally enclosed recessed lighting fixtures, or where directly exposed to weather.  Do not use with emergency fixtures or emergency lights.

I put a 60 watt CFL [13] in a ~8" diameter enclosed glass bathroom ceiling fixture and it didn't last long. I replaced it with a 40 watt CFL [9] and it's doing much better.

[Brian H]

Mine also have the Enclosed Enclosure warning.
With no air flow they can overheat.

[Appliance Module]

Thanks,  that seems to imply that CFL give off more heat than regular bulbs.   Right    Wrong?

Assuming wattage equivalent

[Charles Sullivan]

Thanks,  that seems to imply that CFL give off more heat than regular bulbs.   Right    Wrong?

Assuming wattage equivalent

No, only that the electronic circuitry in a CFL requires a lower ambient temperature than an incandescent lamp.  CFLs are more efficient than incandescent and a greater proportion of the electrical energy consumed by a CFL is emitted as visible light and less as wasted heat.

[Appliance Module]

That makes sense.   Mine do not say to not enclose them.  In fact it says they must be enclosed if in an outdoor fixture.

My problem was that I replaced two regular bulbs of 60W each in a glass globe type enclosed light with two 23 W (100W equiv) and  the fixture and it got extremely hot (assuming like you said they were more efficient and should be ok).   Hotter than if it had two reg bulbs.  I don't know , but decided not to mess with Mother Nature and put two 40W reg in it.

So now I have got some 13W (60 equiv) that I would like to use in a fixture rated 2x60 and is enclosed.

So I guess I should be ok.

[Charles Sullivan]

That makes sense.   Mine do not say to not enclose them.  In fact it says they must be enclosed if in an outdoor fixture.

My problem was that I replaced two regular bulbs of 60W each in a glass globe type enclosed light with two 23 W (100W equiv) and  the fixture and it got extremely hot (assuming like you said they were more efficient and should be ok).   Hotter than if it had two reg bulbs.  I don't know , but decided not to mess with Mother Nature and put two 40W reg in it.

So now I have got some 13W (60 equiv) that I would like to use in a fixture rated 2x60 and is enclosed.

So I guess I should be ok.

Maybe, maybe not.  It probably depends on just how hot it gets within the enclosure and whether the CFLs will run at that temperature without going into the apparent thermal runaway you observed with the pair of 23W GFLs.

[ArtClark]

Just to throw in my 2 cents, I have been using the CFL's for a long time, and they always run MUCH cooler than normal light bulbs.  That being said, they are also VERY sensitive to heat as far as their circuits are concerned.  (as Charles already said.)  It seems, for what it's worth, that I have had good luck with using the CFL with the same Light equivilency as the bulb that is supposed to be there.  I have done with with at least 10 fixtures (Of course this is terrible for X-10, I can't use the dimmer on these circuits anymore.), but if I push a little, even though it's "SAFE" from the fixture heat point of view, the CFL's seem to die quickly.

LIttle note / Question:  I have a lot of trouble with these things when they are cold.  Any Ideas?  They are useless for unheated areas in winter for me.  (Unless I wanted to warm them, quick put in fixture and leave on 24/7. )

[Appliance Module]

That makes sense.   Mine do not say to not enclose them.  In fact it says they must be enclosed if in an outdoor fixture.

My problem was that I replaced two regular bulbs of 60W each in a glass globe type enclosed light with two 23 W (100W equiv) and  the fixture and it got extremely hot (assuming like you said they were more efficient and should be ok).   Hotter than if it had two reg bulbs.  I don't know , but decided not to mess with Mother Nature and put two 40W reg in it.

So now I have got some 13W (60 equiv) that I would like to use in a fixture rated 2x60 and is enclosed.

So I guess I should be ok.

Maybe, maybe not.  It probably depends on just how hot it gets within the enclosure and whether the CFLs will run at that temperature without going into the apparent thermal runaway you observed with the pair of 23W GFLs.

How do I know when I get thermal runaway?   Will they catch fire?  Explode?

I do not think I got thermal runaway, I just discontinued their use after a few days, as I thought the globe was warmer than it needed to be.  So I plan on using the smaller CFL and expect the results of the above posters.

BTW  neg 20 F that they need to be above when used, per the package on the 13 W ones.   I know out in my garage where I have the 23 W units, they are quite dim and slow to brighten during the cold weather.

[Charles Sullivan]

That makes sense.   Mine do not say to not enclose them.  In fact it says they must be enclosed if in an outdoor fixture.

My problem was that I replaced two regular bulbs of 60W each in a glass globe type enclosed light with two 23 W (100W equiv) and  the fixture and it got extremely hot (assuming like you said they were more efficient and should be ok).   Hotter than if it had two reg bulbs.  I don't know , but decided not to mess with Mother Nature and put two 40W reg in it.

So now I have got some 13W (60 equiv) that I would like to use in a fixture rated 2x60 and is enclosed.

So I guess I should be ok.

Maybe, maybe not.  It probably depends on just how hot it gets within the enclosure and whether the CFLs will run at that temperature without going into the apparent thermal runaway you observed with the pair of 23W GFLs.

How do I know when I get thermal runaway?   Will they catch fire?  Explode?

They'll probably just smoke something in the circuitry and quit working.

I do not think I got thermal runaway, I just discontinued their use after a few days, as I thought the globe was warmer than it needed to be.  So I plan on using the smaller CFL and expect the results of the above posters.

How warm was the globe compared to when you had the incandescent bulbs in it?

BTW  neg 20 F that they need to be above when used, per the package on the 13 W ones.   I know out in my garage where I have the 23 W units, they are quite dim and slow to brighten during the cold weather.

Just put them in a globe and they'll keep themselves warm.   

[gil shultz]

Thermal Runaway is self destructive.  It is a condition where a semiconductor device starts heating and is generating more power then it can dissipate.  This causes it to get even hotter and generating more heat until it fails and quits producing heat usually ending in flames or molten metal.

Dr. Dold states in the “Analysis of thermal runaway in the ignition process:” “The evolution of a thermal runaway event is studied from the time a self-sustained temperature growth first sets in to the time deflagration flames begin to emerge.”

You can find it on line at http://eprints.ma.man.ac.uk/806/01/covered/MIMS_ep2007_86.pdf.

Therefore I believe that you did not experience Thermal Runaway but you did get a very hot device. 

CFLs (Compact Florescent Lamps) (coiled florescent lamp) take your pick.

Maybe the following will help explain why they get hot.  They have an electronic ballast (swotched mode power supply) which is designed for a sinusoidal power waveform (standard AC waveform in the US) input..



Although Compact florescent light bulbs may be more efficient than incandescent lighting, the  CFLs contain a very small amount of mercury sealed within the glass tubing - an average of 5 milligrams (roughly equivalent to the tip of a ball-point pen). Mercury is an essential, irreplaceable element in CFLs and is what allows the bulb to be an efficient light source.

Fluorescent light bulbs (including CDLs) are more energy-efficient than regular bulbs because of the different method they use to produce light. Regular bulbs (also known as incandescent bulbs) create light by heating a filament inside the bulb; the heat makes the filament white-hot, producing the light that you see. A lot of the energy used to create the heat that lights an incandescent bulb is wasted as heat. A fluorescent bulb, on the other hand, contains a gas that produces invisible ultraviolet light (UV) when the gas is excited by electricity. The UV light hits the white coating inside the fluorescent bulb and the coating changes it into light you can see. Because fluorescent bulbs don't use heat to create light, they are far more energy-efficient per lumen than regular incandescent bulbs.

The primary difference is in size; compact fluorescent bulbs are made in special shapes (which require special technologies) to fit in standard household light sockets, like table lamps and ceiling fixtures. In addition, most compact fluorescent lamps have”integral" ballast that is built into the light bulb, whereas most fluorescent tubes require a separate ballast independent of the bulb. Both types are basically the same and offer energy-efficient light.

To conclude they get hot because the electronics does not like a chopped sinusoidal wave form which causes the ballast to work harder creating more heat.

Hope this helps
Gil Shultz