I am mounting my Mits HD1000u via a ceiling mount. The manual says to provide an a/c power switch and to shut down the main power when not in use.

one concern/question I have is if this "switch" was used constantly by the family wouldn't this possibly reduce the lamp life due to the fan shutting off while the bulb is still hot??
Lamps are not cheap, need to get the most life I can(wife doesnt knowour tv will need a 300 dollar maintenace fee)

Thanks
Chris

Always let the PJ cool down and shut off on it's own before you unplug it.
It will definitely shorten your bulb life to unplug it hot.
I don't know why the manual says to unplug after use, maybe to prevent damage from power surges and the like?
I leave mine plugged in all the time.

Thanks for the reply.
Your answer was excatly what I thought.
I will not wire an a/c switch on my setup.
Have a great day!!!!

Turn the auto on feature off, otherwise, when the power goes out and later comes back on, you'll eventually discover your projector has been running for days and days and days.....

I disagree about it being bad to turn off the fan (unplug) while the bulb is hot. I think its harder on the bulb materials to force the bulb to cool quickly than let it cool down naturally. The after run fan is to ensure the bulb is cool(ish) before moving the projector or powering on again. If your unit is ceiling mounted and you are not planning on watching it again soon, I see no problem. THAT SAID - I still let my fan work as designed and dont pull the power. I have mine on a ups so its not convenient to do anything else.

I disagree about it being bad to turn off the fan (unplug) while the bulb is hot. I think its harder on the bulb materials to force the bulb to cool quickly than let it cool down naturally. The after run fan is to ensure the bulb is cool(ish) before moving the projector or powering on again. If your unit is ceiling mounted and you are not planning on watching it again soon, I see no problem. THAT SAID - I still let my fan work as designed and dont pull the power. I have mine on a ups so its not convenient to do anything else.

The idea behind the fan running while the bulb cools down is to let it cool slower. It’s different scenario than what you are thinking that takes place. During use the bulb is generating a great deal of heat and the fans are designed to remove the heat at about the rate its being produced thus a stable operating temp. Once the bulb is shut off the heat does not instantly leave the bulb chamber the glass and surrounding chamber are very hot and if the fan were to stop instantly the temp in the area would increase rather than decrease for a short period of time as the residual heat was let out of whatever thermal mass there is in and around the bulb. The idea of the fan running and the sensors measuring the temp or calculated timers keeping the fan running is to ramp the bulb temp down at a constant rate.

IMO pulling the plug or flipping a switch is a very bad idea. I don’t have mine on a switched circuit but that’s not a bad idea if you feel the need to isolate the power when not in use. (power surges, lightning etc) but I would be reluctant to put the switch in any location where it could be mistaken for a light switch and accidentally shut down.

BUD, I like your aux fan idea in your signature. That seems like something I should invest in. Unfortunately, I dont agree with you summation of the projectors fans let it cool slower or to prevent an increase in temp. Thats just not my understanding of thermodynamics (all be it a very limited one).

After the projector bulb is turned off no more energy (heat) is being added to the system. The bulb is the only significant source of heat and the hottest part of the projector. If there was no fan, the components around the bulb may increase in temp as the bulb decreases to come to an equilibrium. The though conduction and convection, the projector as a whole will dissipate heat until it matches the room temp. There is nothing to add more energy or heat to the bulb and it can only decrease in temp.

The fan in most projectors usually amps up for a cool down cycle to cool the bulb as quickly as the engineers have deemed safe. Even a constant rate fan will accelerate temperature reduction and add some stress to the materials because. I still think letting it cool slowly and naturally would work best (if the projector was not going to be moved or used again soon). But again, not enough so to make me rewire.

BUD, I like your aux fan idea in your signature. That seems like something I should invest in. Unfortunately, I dont agree with you summation of the projectors fans let it cool slower or to prevent an increase in temp. Thats just not my understanding of thermodynamics (all be it a very limited one).

After the projector bulb is turned off no more energy (heat) is being added to the system. The bulb is the only significant source of heat and the hottest part of the projector. If there was no fan, the components around the bulb may increase in temp as the bulb decreases to come to an equilibrium. The though conduction and convection, the projector as a whole will dissipate heat until it matches the room temp. There is nothing to add more energy or heat to the bulb and it can only decrease in temp.

The fan in most projectors usually amps up for a cool down cycle to cool the bulb as quickly as the engineers have deemed safe. Even a constant rate fan will accelerate temperature reduction and add some stress to the materials because. I still think letting it cool slowly and naturally would work best (if the projector was not going to be moved or used again soon). But again, not enough so to make me rewire.


Thanks for the complement on my aux fan setup.

I do understand your logic surrounding what’s going on or could be going on inside the lamp chamber in the projector. If we assume no more energy is going into the bulb when the projector goes off normally and that the bulb itself is what the fans are intending to cool and not the thermal mass around the bulb and or electronics inside the projector no fan would let the bulb cool at its slowest rate and all the mass would sink down in temp together. The bulb itself has very little thermal mass thin glass etc. the area around the bulb if assumed to have some mass could be storing more heat and would try and cool both inward and outward maintaining the temp of the bulb for a longer period thus a gentle cool down.

Then why are we warned repeatedly not to hard stop the projector and then also against re-firing the bulb within less than an hour.

I notice my projector doesn’t shut the bulb off at once it projects the test screen image and then the screen goes blank. If I look into the lens at this point the light isn’t out but is diminishing in brightness slowly. I always assumed that was the light cooling off but now that I’m thinking about it could the projector be sending a lower power to the bulb to temper the cooling cycle. (slow stop)

I know cars with electric cooling fans after shutting down the fans will run for a short time and will sometimes restart even though the engine is off but without the coolant flowing the engine will gain temp at least in the area of the thermal switch and restart the fan.

Lets assume the air around the bulb needs to be 200F based around the measurements I have been taking of the exit air. And with air in the 200F range the bulb itself is in its good working temp mode that air is kept at that temp by the fans bringing cool air in and by convection heat is removed. In the case of a DLP all the light off time on the screen the micro mirrors are diverting light into a area they call the light dump. This is a black body that converts this light into heat by absorbing it by radiation. Could this light dump and surrounding parts perhaps be 500F and the way heat is removed from them is once again convection of the moving air stream. When that flow stops the heat needs to be transferred and it will combine with the 200F air and heat it past the good 200F point. Much the same as the heat moving thru the engine block could heat the coolent to the point the fans would restart.

Just some more thoughts and to be honest I don’t know the truth behind all the inner workings of the cool down. I can see both scenarios. Maybe someone with some actual projector design background will come and straighten us out. :confused:

From the HD1000u manual.
Page 5:
Do not unplug the power cord during operation.
It can lead to lamp breakage, fire, electric shock or
other trouble. It is best to wait for the fan to turn off
before turning the main power off.
Page 18:
After powering down. During this period of one minute in the standby mode, the intake fan and exhaust fan rotate to cool the lamp.
• The lamp can’t be lit again for one minute after turning off the projector for safety purpose. It will take another
one minute for the STATUS indicator to go out. If you want to turn on the projector again, wait until the indicator
goes out, and then press the POWER button.
• The air outlet fans rotate faster as the temperature around the projector rises.
• Do not unplug the power cord while the STATUS indicator is blinking. Unplugging the power cord immediately after use may cause a lamp breakdown.
• Though the fan makes loud sound during cooling, such symptom is not a malfunction.

Also from page 18:
Unplug the power cord from the outlet.
• The POWER indicator will go out.
• If the power cord should be unplugged accidentally while either the air inlet fan or the air outlet fans are
operating or the lamp is on, allow the projector to cool down for 10 minutes with the power off. To light the
lamp again, press the POWER button. If the lamp doesn’t light up immediately, repeat pressing the POWER
button two or three times. If it should still fail to light up, replace the lamp.

So it seems that if your power goes out accidentally your bulb may never fire again.

The Hound

Thanks for the info from the HD1000u manual. That is pretty common in most projector manuals and what I remember reading in my Sharp manual as well. I have also seen some of the long-term members post similar warnings a few times. I know Claus has posted on fan issues quite a few times.

So I’m 99.9% sure there is residual heat transfer someplace in the projector and areas that store greater heat than what the bulb would want to see even in a off state. But not really sure what all takes place inside the unit.

In the case of what I did I first used a non contact temp measuring gun and looked at several temps of the case top bottom and the air outlets when running in different modes with and without the aux fan running. Others have mounted fans that actually ram the air into the air inlet to help with the cooling. I didn’t want to do that as much as moving all the air near the ceiling past the projector cooling it’s outside and allowing it cool air at the intake at least as cool of air as can be found in the room. Just running that little fan did a great deal to break up that bubble of hot air around the projector and in the winter months was a nice little heating unit for the room.

Quieter fans could be found than the one I had on hand but mostly when I have it on the sound system is rocking pretty good as well and I never hear the fan. Most times it’s the first thing I turn on and the last thing I turn off.