Heat Question

[blackhorse]

I made this paperweight nightlight with the bottom hollowed out to receive a 7 watt bulb. The little holes make it look "lighthouse-ish" and dissipate heat. Think this will be safe if left on all night?

http://www.woodturner.org/vbforum/attachment.php?attachmentid=&stc=1

 

[Larry Marley]

Try sticking a thermometer in there and see how hot we are getting.

I am thinking about a segmented lamp and I am wondering the same thing.

 

[Ken Grunke]

A 7 watt bulb probably won't cause any problem but the only way to tell for sure is to just leave it on for an hour or two and see how hot it gets. A little metallic heat shield might be in order on the inside around the bulb or you could replace the bulb with LEDs which run cooler.
I also have a project on the drawing boards using a low-wattage light, and my plan was to use a replacement LED flashlite bulb unit with a low-voltage adapter. Good luck!

 

[Ken Grunke]

I just had a cool idea.
Mount a miniature cooling fan from a computer processor in the base, with a little filter behind the holes. The downdraft will keep the bulb cool, and you have a mini-air freshener

 

[hockenbery]

WOOD burns!

I don't know of any experiment you can devise that will ensure that the lamp won't catch fire the next time it is left on.

In a wooden lamp you need to insulate or separate the wood from both the heat and the electricity.



be safe

Al

 

[Bob Chapman]

There isn't going to be a lot of heat from a 7w bulb, but a lot depends on the proximity of bulb to wood, and ease of combustion of the wood.

Why not try a controlled experiment? Leave it on all night in a metal bin/bucket outside or somewhere it won't matter if your lamp does catch fire.

One way or the other you'll have your answer next morning. Mind, you might not still have the lamp

Bob

 

[Charlie Harley]

Small holes may or may not allow for enough air circulation. You can plug it in for a few hours and look for problems. Then try it a little longer and a little longer 'till you're comfortable that you're safe.

I suggest you look at using LED's as light sources. They have extremely low consumption of energy with correspondingly low temperatures.

 

[MichaelMouse]

Safest way is the LEDs people keep mentioning. Second would be those neon lights they put in back of rocker switches. Not much heat there. Real bear is going to be the drying you'll do with the lower RH caused by higher temps.

http://www.fpl.fs.fed.us/documnts/fplmisc/rpt1464.pdf might be some help. Seems the volatiles in the wood or the finish are the most likely.

 

[David Somers]

I know this is getting pretty technical, but you might want to check UL Laboratories. They should have standards written up and available regarding the safe use of materials around lamps. I am guessing that a single overnight test with the lamp is not adequate to see if it will catch fire. Again, this is a guess, but I suspect the repeated use of the lamp over time will dry the wood and make it more flammable up to a point. And I suspect the real danger after that is arcing from a bad connection. That is where the real danger of fire would come from. Not from the heat of a 7 watt bulb.

LEDs would resolve the heat issue. An insulator shielding the wood in the cavity housing the lamp itself might protect against arcing if it occurred, as well as protect against heat. In any case....I would be cautious and see what info you can find on this before you sell it.

Good luck! Its a fun idea!!

Dave

 

[blackhorse]

The idea of "sticking a thermometer in there" conjures up images I'd just as soon forget . I like the LED idea.

I ordered some LED bulbs that should fit in the current sockets that I have (E12 base). I'll let you know how it goes.

 

[Al Neighbors]

It depends on the distance the bulb is from the wood. I'm a Texas Certified fireman. An incandescent light bulb emits heat, even the small ones. A normal 60 watt lightbulb, in a ceramic socket, located on a wooden wall, left burning, will ignite that wooden wall. It may take time, but it eventually will ignite. That is from the results of a fire investigation into a Church fire that I helped fight.
Now, having said that, I'll say this. The low heat from a 7w bulb is still enough to eventually dry the wood to the point that it will combust easier... (it might take a while for the wood to release the gasses that burn)... than it normally would. That's why I said above, that it depends on the distance between the bulb and the wood.
Do you have air holes in the bottom, to allow cooler air in, so the heated air will escape through the holes in the top? If not, I would design some into the piece. It needs air flow in order for the heat to move out.
Do you have a shroud of aluminum around the inside of the wood, which allows air to pass between the aluminum and the wood? If not, that would be another necessary feature. The airflow between the aluminum and the wood will dissipate the heat.
Sorry, this is so long... it's the only way I knew to get the point across. A house fire is an awful thing to experience.
I like the little night light, but it looks too small to have enough space between the bulb and the wood. JMHO Guess I've been a fireman too long.
BTW, it is a nice looking piece.

 

[blackhorse]

Just a follow up to let you know that I got a few LED bulbs to replace the 7 watt bulb and they work great. Bright, virtually no heat.


Thanks for all the advice!

BH