Will drilling holes at the top of an otherwise sealed sphere encourage
air circulation and make a light bulb run cooler?

I have a lot of light fixtures that use spherical glass globes to
cover the bulb. There is no air circulation from inside the sphere to
outside, and if I put in a high wattage bulb, it burns out quickly, I
think.

One is a "chandlier", at least it hangs from the ceiling with a chain,
with a glass globe 8 inches in diameter with a 4 inch opening at the
top. Because it is not closely attached to the ceiling, I could drill
holes in the metal part at the top, without weakening it. But if all
the holes are at the top, would that make it run any cooler?

This fixture has a dimmer, and I'd like to use a 150 or 200 watt bulb,
running it at 70 watt brightness most of the time.

(The other fixtures use a 6 inch glass sphere with a 3 inch opening,
and they say not to use more than 60 watts. I don't know what max was
recommended for the chandelier.)

Meirman
--
If emailing, please let me know whether
or not you are posting the same letter.
Change domain to erols.com, if necessary.

meirman wrote:
Will drilling holes at the top of an otherwise sealed sphere encourage
air circulation and make a light bulb run cooler?

I have a lot of light fixtures that use spherical glass globes to
cover the bulb. There is no air circulation from inside the sphere to
outside, and if I put in a high wattage bulb, it burns out quickly, I
think.

One is a "chandlier", at least it hangs from the ceiling with a chain,
with a glass globe 8 inches in diameter with a 4 inch opening at the
top. Because it is not closely attached to the ceiling, I could drill
holes in the metal part at the top, without weakening it. But if all
the holes are at the top, would that make it run any cooler?

This fixture has a dimmer, and I'd like to use a 150 or 200 watt bulb,
running it at 70 watt brightness most of the time.

(The other fixtures use a 6 inch glass sphere with a 3 inch opening,
and they say not to use more than 60 watts. I don't know what max was
recommended for the chandelier.)

Meirman

You can not user lamps of a higher wattage than recommended in any
fixture safely, even after drilling holes. Not may fixtures call for 150 -
200 W lamps. Find out what it called for (often printed somewhere on the
fixture) and stay within that limit. Change fixtures if needed. BTW if the
maximum wattage indication has been burned off the fixture, that should tell
you something.

--
Joseph Meehan

26 + 6 = 1 It's Irish Math

Joseph Meehan wrote:

You can not user lamps of a higher wattage than recommended in any
fixture safely, even after drilling holes...

Then again, warm air rises. You might measure the globe temp with no holes
and the max recommended wattage, then drill the holes and turn up the dimmer
until the globe temp rises to the original value.

Nick

"meirman" wrote in message
...
Will drilling holes at the top of an otherwise sealed sphere encourage
air circulation and make a light bulb run cooler?

I have a lot of light fixtures that use spherical glass globes to
cover the bulb. There is no air circulation from inside the sphere to
outside, and if I put in a high wattage bulb, it burns out quickly, I
think.

One is a "chandlier", at least it hangs from the ceiling with a chain,
with a glass globe 8 inches in diameter with a 4 inch opening at the
top. Because it is not closely attached to the ceiling, I could drill
holes in the metal part at the top, without weakening it. But if all
the holes are at the top, would that make it run any cooler?

This fixture has a dimmer, and I'd like to use a 150 or 200 watt bulb,
running it at 70 watt brightness most of the time.

(The other fixtures use a 6 inch glass sphere with a 3 inch opening,
and they say not to use more than 60 watts. I don't know what max was
recommended for the chandelier.)

Meirman
--
If emailing, please let me know whether
or not you are posting the same letter.
Change domain to erols.com, if necessary.

If you need more light, use florescent bulbs. They will give you about 3
times the light at the same wattage and won't exceed the rating of the
fixture......Ross

wrote:
Joseph Meehan wrote:

You can not user lamps of a higher wattage than recommended in any
fixture safely, even after drilling holes...

Then again, warm air rises. You might measure the globe temp with no
holes and the max recommended wattage, then drill the holes and turn
up the dimmer until the globe temp rises to the original value.

Nick

You also will need to measure the temperature at the socket, it does not
rely on air temperature as a major issue, and the wires under it and other
areas. If you want to find out if it is really safe, have the UL do the
test.

--
Joseph Meehan

26 + 6 = 1 It's Irish Math

Joseph Meehan wrote:

You can not user lamps of a higher wattage than recommended in any
fixture safely, even after drilling holes...

Then again, warm air rises. You might measure the globe temp with no
holes and the max recommended wattage, then drill the holes and turn
up the dimmer until the globe temp rises to the original value.

You also will need to measure the temperature at the socket...

I don't think so. Just aim an IR thermometer at the globe. Basic heatflow.
If it's the same before and after, the socket will be close to the same...

If you want to find out if it is really safe, have the UL do the test.

Riiiight :-)

Nick

It's not practical to drill holes in glass, but I'm sure it will burn
cooler. Vibrations will make a bulb burn out faster than heat. You
need to find out the max wattage recommended for the fixture.

On Sun, 20 Feb 2005 23:48:32 -0500, meirman
wrote:

Will drilling holes at the top of an otherwise sealed sphere encourage
air circulation and make a light bulb run cooler?

I have a lot of light fixtures that use spherical glass globes to
cover the bulb. There is no air circulation from inside the sphere to
outside, and if I put in a high wattage bulb, it burns out quickly, I
think.

One is a "chandlier", at least it hangs from the ceiling with a chain,
with a glass globe 8 inches in diameter with a 4 inch opening at the
top. Because it is not closely attached to the ceiling, I could drill
holes in the metal part at the top, without weakening it. But if all
the holes are at the top, would that make it run any cooler?

This fixture has a dimmer, and I'd like to use a 150 or 200 watt bulb,
running it at 70 watt brightness most of the time.

(The other fixtures use a 6 inch glass sphere with a 3 inch opening,
and they say not to use more than 60 watts. I don't know what max was
recommended for the chandelier.)

Meirman

Phisherman wrote:

It's not practical to drill holes in glass...

meirman wrote:

...I could drill holes in the metal part at the top.

...Vibrations will make a bulb burn out faster than heat.

In a chandelier? :-)

Nick

wrote:
Joseph Meehan wrote:

You can not user lamps of a higher wattage than recommended in
any fixture safely, even after drilling holes...

Then again, warm air rises. You might measure the globe temp with no
holes and the max recommended wattage, then drill the holes and turn
up the dimmer until the globe temp rises to the original value.

You also will need to measure the temperature at the socket...

I don't think so. Just aim an IR thermometer at the globe. Basic
heatflow. If it's the same before and after, the socket will be close
to the same...

Personally I doubt it. The metal of the socket is physically connected
with metal (usually a good conductor of heat) directly to the heat source,
(the filament). I doubt if measuring the glass envelope is going to
properly measure the problem.

I might suggest that since it appears the OP would like to be able to
have both bright lights and be able to dim them, that maybe what he should
do is that his opportunity to add additional light creatively rather than
just over power the existing fixture.


If you want to find out if it is really safe, have the UL do the
test.

Riiiight :-)

Nick

--
Joseph Meehan

26 + 6 = 1 It's Irish Math

wrote:
Phisherman wrote:

It's not practical to drill holes in glass...

meirman wrote:

...I could drill holes in the metal part at the top.

...Vibrations will make a bulb burn out faster than heat.

In a chandelier? :-)

Yes, especially if it happens to be located under a washing machine or
some such thing.


Nick

--
Joseph Meehan

26 + 6 = 1 It's Irish Math

wrote:
Joseph Meehan wrote:

You can not user lamps of a higher wattage than recommended in
any fixture safely, even after drilling holes...

Then again, warm air rises. You might measure the globe temp with no
holes and the max recommended wattage, then drill the holes and turn
up the dimmer until the globe temp rises to the original value.

You also will need to measure the temperature at the socket...

I don't think so. Just aim an IR thermometer at the globe. Basic
heatflow. If it's the same before and after, the socket will be close
to the same...

I suggest you ask your local fire department what they think of that
idea.

Remember that the filament (the source of all the heat) is directly
connected to the socket with metal (great heat transfer). The socket is
going to get a lot of that heat. Cooling around the glass envelope is not
going to do much for the socket. There is a good deal of poor conductor
(air) between the filament and the glass. Your additional cooling air is
going to only come into play removing the heat that has made it post the
poor conducting air in the lamp and through the glass.


If you want to find out if it is really safe, have the UL do the
test.

Riiiight :-)

Nick

--
Joseph Meehan

26 + 6 = 1 It's Irish Math

This is the reason that I put all of my bulbs in the freezer while they
are lit. Safety first - that's my motto.

In article ,
wrote:
Joseph Meehan wrote:

You can not user lamps of a higher wattage than recommended in any
fixture safely, even after drilling holes...

Then again, warm air rises. You might measure the globe temp with no
holes and the max recommended wattage, then drill the holes and turn
up the dimmer until the globe temp rises to the original value.

You also will need to measure the temperature at the socket...

I don't think so. Just aim an IR thermometer at the globe. Basic heatflow.
If it's the same before and after, the socket will be close to the same...

If convection within the globe is greater (airspeed is higher), the
socket will be hotter - maybe not by much. You need to verify
temperatures of everything not being any hotter than when "used as
directed".

Now for another bad case: Suppose the chance of a fire starting is not
completely perfectly zero in the worst case of "using as dirceted". So
you do some usage other than "as directed" and verify no parts get any
hotter but a fire starts anyway. Now you have what I fear is the
liability problem of a fire starting from electrical equipment being used
"other than as directed".

- Don Klipstein )