# Light bulb heat question

#### ItzRav

##### Newly Enlightened
We have a bed with a light bridge mounted on the wall at the head of the bed. There are six light bulbs that hang downward from it from six "can" fixtures. Originally each fixture contained a small 40W incandescent bulb, which produced WAY too much heat. Years ago I replaced the bulbs with 9W CFL bulbs, and that definitely reduced the heat, but not as much as we would have liked. Each CFL is still quite warm when on, and since our heads are just inches away, we feel the heat (especially in the summer). Now I'm considering replacing the CFLs with some 4.8W LED bulbs that I've found (same base, about the same shape, and around the same number of lumens). The question is, does essentially halving the wattage mean that will reduce the heat by about half? You can see the LED bulb I'm considering at:

http://www.lowes.com/pd_424737-75774-LG1612DMIF300LED_

Thanks.

#### electronupdate

##### Newly Enlightened
When you say "heat" I presume you are really talking about "temperature".

There are a few relations between temperature, heat, and wattage....

1. A watt is a measure of power per unit time. In this case a watt is a joule per second (J/s).
2. A joule is a measure of energy
3. The energy ("joules") will heat up the surrounding air which will be perceived as a temperature rise.
4. The conversion between joules and temperature depends on a property called "specific heat capacity"... google that for more info
5. The relation for many materials (including air) is not quite linear. i.e. a doubling of the energy may not double the temperature.

You would probably notice and appreciate a lower wattage bulb.

You did not include a picture, but a typical can fixture tends to trap all of it's heat.... if openings are made convection flow could be achieved which would allow the heat to rise which also would be less bothersome...

#### CoveAxe

##### Enlightened
It will indeed be about half as hot, but it's only running at about half the number of lumens (ie. it's going to be only about half as bright). It's dimmable though, so that's a plus.

Unfortunately, globe lamps are currently an afterthought and no decent bulb maker has tried to move into that area yet. The ones that are there either have a lower brightness, or are just as hot as the CFLs.

If you don't care about the form factor, you could get the Cree 40W equivalent bulbs which run at about 5 Watts and have the appropriate brightness, and can be dimmed.

#### ItzRav

##### Newly Enlightened
<First part snipped>

You did not include a picture, but a typical can fixture tends to trap all of it's heat.... if openings are made convection flow could be achieved which would allow the heat to rise which also would be less bothersome...

I have a picture of the fixture, but this forum won't let me post it ("You may not post attachments"). However, I've now posted it at ImageShack:

https://imageshack.com/i/eyhwTsUoj

There are two slots on either side of the reflector that I assume allow some heat to rise. Note the cracking at the top of the reflector: I assume this is from excessive heat, which I assume was from the early days when I had the 40W incandescent bulbs in there.

#### ItzRav

##### Newly Enlightened
It will indeed be about half as hot, but it's only running at about half the number of lumens (ie. it's going to be only about half as bright). It's dimmable though, so that's a plus.

Unfortunately, globe lamps are currently an afterthought and no decent bulb maker has tried to move into that area yet. The ones that are there either have a lower brightness, or are just as hot as the CFLs.

If you don't care about the form factor, you could get the Cree 40W equivalent bulbs which run at about 5 Watts and have the appropriate brightness, and can be dimmed.

Thanks. Indeed, the CFLs are 450 lumen, and these are 300 lumen. So you're right, less heat but less light. But I think the 450 lumen is a little bright anyway (in this application), so I was willing to give this LED lamp a chance assuming it did produce less heat.

As far as form factor, a regular A19 bulb would be too large. The other issue is that the fixture contains an intermediate socket. (I do realize that the LED bulb I'm considering has a candelabra base, but I was going to use intermediate to candelabra reducer sockets to deal with that.)

#### LEDninja

##### Flashlight Enthusiast
What exactly is the socket size for your bulbs?
E12 candlelabra?
E17 intermediate?
E26/27 medium? (normal household bulb)

Search A15 LED light bulb. They are available from 4 to 8 watt, candelabra and medium bases.

To post pictures add {img}link{/img} USE SQUARE BRACKETS LIKE [. you are missing the img part.

#### ItzRav

##### Newly Enlightened
What exactly is the socket size for your bulbs?
E12 candlelabra?
E17 intermediate?
E26/27 medium? (normal household bulb)

Search A15 LED light bulb. They are available from 4 to 8 watt, candelabra and medium bases.

To post pictures add {img}link{/img} USE SQUARE BRACKETS LIKE [. you are missing the img part.

The fixture socket is intermediate. The base of the LED globe bulb I am considering using is candelabra. That's why I was going to use a intermediate to candelabra socket reducer. I found nothing in an intermediate base; I'll try your suggestion and search for an A15 candelabra. Thanks.