Why to use the proper projector cooldown process

[LavaASU]

So to give a little demonstration of what happens when the correct cooldown process is used versus when the projector is unplugged:

This is a normal cooldown (lamp is turned off, fans run)

This is when power is cut (no fans running)

Lamp is generally going to be the most affected (especially if the projector is moved right after being unplugged), followed by components near the lamp.

 

[MNicolai]

Looks about right. Same principal goes for arc-source moving lights and followspots.

 

[LavaASU]

Looks about right. Same principal goes for arc-source moving lights and followspots.

Yup. Might eventually get around to doing this with a moving light.

 

[Footer]

This is a physics experiment that is beyond my thermal dynamics knowledge.

Here has always been my questions with this... One would think that the second the power is cut/IE the fuel is removed the lamp is NEVER going to get any hotter then it is at that moment. Right? Lets say the fan is keeping the lamp at 215 degrees during operation. When you cut power, the fan is no longer cooling the lamp.... but... the power is no longer making the lamp hotter. Reason would say that the lamp will begin cooling the second the power is pulled. You should not see a ramp up in temperature when power is pulled. So, why do we let things cool? Why do we care? Does it matter if the unit is not going to be moved for hours after power is pulled?

Any armchair physics people want to bite? Lava, want to take your camera and let me know if you see a ramp UP in temperature after power is pulled?

 

[LavaASU]

This is a physics experiment that is beyond my thermal dynamics knowledge.

Here has always been my questions with this... One would think that the second the power is cut/IE the fuel is removed the lamp is NEVER going to get any hotter then it is at that moment. Right? Lets say the fan is keeping the lamp at 215 degrees during operation. When you cut power, the fan is no longer cooling the lamp.... but... the power is no longer making the lamp hotter. Reason would say that the lamp will begin cooling the second the power is pulled. You should not see a ramp up in temperature when power is pulled. So, why do we let things cool? Why do we care? Does it matter if the unit is not going to be moved for hours after power is pulled?

Any armchair physics people want to bite? Lava, want to take your camera and let me know if you see a ramp UP in temperature after power is pulled?

Will the absolute hottest part of the lamp get hotter once power is cut? No. Will areas that are near the hottest parts get hotter? Yes.

Reason being the forced air cooling is moving heat away in a certain direction. When power is cut the heat dissipates to the surrounding components. The hottest parts of the lamp are the electrodes, when power is cut, the seals may exceed their designed temperatures. Unfortunately, direct line of sight access to the lamp for thermal imaging is not really possible on these, and theres also issues there with emissivity (and I can't put black paint on the lamp to compensate). Air temperature readings in the lamp area support the temperature exceeding operating temperature when power is cut.

This is normal operating temperature of this projector.

 

[Mwchris]

Great answer Lava! And while I don't disagree, I think this becomes most important we we are talking about moving or packing equipment away immediately.

 

[MNicolai]

Great answer Lava! And while I don't disagree, I think this becomes most important we we are talking about moving or packing equipment away immediately.

Yup. On fast load-outs, kill the lamps as soon as is practical, and leave power connected long enough for fans to run. Usually at little as 10-15 minutes is sufficient.

 

[LavaASU]

Yup. On fast load-outs, kill the lamps as soon as is practical, and leave power connected long enough for fans to run. Usually at little as 10-15 minutes is sufficient.

Yes, it is most critical when moving the projector (or light). When the components are hot they're more likely to get damaged from handling. Also packing them up will trap the heat.