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Author Topic: Do you leave the Fan running?
Tony Milman
Phenomenal Film Handler

Posts: 1326
From: United Kingdom
Registered: Jun 2003


 - posted August 05, 2003 04:55 PM      Profile for Tony Milman   Author's Homepage   Email Tony Milman   Send New Private Message       Edit/Delete Post 
I was wondering if it is good practice to leave the fan running on the projector for a while after switching off the bulb to help cool it? Maybe it is an obvious question but then I thought perhaps this is not a good idea on the basis it may wear out the motor more quickly (albeit it is not under load).

Then I thought given it is an ST 1200HD with the original rubber wheel intact, if I left the bulb unfanned i.e. to cool naturally will this cause the rubber wheel to soften and come off?

All these thoughts.......anyone have a view on best practice?

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Tony

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Steven Sigel
Jedi Master Film Handler

Posts: 701
From: Massachusetts
Registered: Jun 2003


 - posted August 05, 2003 05:28 PM      Profile for Steven Sigel   Email Steven Sigel   Send New Private Message       Edit/Delete Post 
I always leave the fan running until the bulb has cooled down -- this will extend your bulb life dramatically -- it's especially important for Xenons....

I wouldn't worry about the motor -- let's say you leave it running 5 minutes extra after running a two hour show -- big deal.....

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Kevin Faulkner
Film God

Posts: 4071
From: Essex UK
Registered: Jun 2003


 - posted August 05, 2003 05:39 PM      Profile for Kevin Faulkner         Edit/Delete Post 
I go along with Steve's comments especially as it's not a good idea to pack up and move the projector with a hot lamp inside it. The filament is far more tollerent of knocks when cold.

Kevin.

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GS1200 Xenon with Elmo 1.0...great combo along with a 16-CL Xenon for that super bright white light.

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Douglas Meltzer
Moderator

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From: New York, NY, USA
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 - posted August 05, 2003 07:25 PM      Profile for Douglas Meltzer   Email Douglas Meltzer   Send New Private Message       Edit/Delete Post 
Gentlemen,
While I'm a firm believer in not putting the projector away till it has totally cooled, I'm not sure leaving the fan on is best for the bulb. I recall reading about a test that was done to see how to extend bulb life. The results showed that bulbs that were allowed to cool naturally after use lasted longer. Forced cooling (fans, blowers) put more stress on the filament by lowering its temperature too quickly, thereby shortening the life of the bulb.
Doug

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I think there's room for just one more film.....

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Steven Sigel
Jedi Master Film Handler

Posts: 701
From: Massachusetts
Registered: Jun 2003


 - posted August 05, 2003 08:03 PM      Profile for Steven Sigel   Email Steven Sigel   Send New Private Message       Edit/Delete Post 
Doug --

Do you have a reference for that study? I've always heard the resverse -- that fan cooling allows the filament to cool evenly which is better for it. Uneven cooling can lead to filament warping or potentially glass deformation in the lamp (I've seen it happen with a 1200W Incandescent - the lamp developed a bubble in it and then shattered).

I know for a fact that my DLP video projector leaves the fan running all by itself for about 5 minutes after the projector is switched off - so they obviously agree with me. Also - most of the Xenon projectors have a separate switch that lets you leave the fan running after you've shut down the projector -- why would they bother if they didn't want you to cool the lamp down before shutting it down?

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Douglas Meltzer
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From: New York, NY, USA
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 - posted August 05, 2003 09:03 PM      Profile for Douglas Meltzer   Email Douglas Meltzer   Send New Private Message       Edit/Delete Post 
Steven,
If I only had 30 minutes before I had to pack the projector up and leave a location, I’d be using those fans. However, Any thermal shock to a lamp will shorten it's life. Eliminating the source of heat while keeping the cooling system on is a shock.
I honestly don't know much about DLP technology, but when I'm on a set filming with HMI (daylight color temp) lights whose bulbs seem to cost one dollar per watt, the accepted practice is to let them cool naturally. Actually, these bulbs are very similar to the Xenons. One should avoid striking and re-striking as much as possible. When I fire up my 1200 xenon, that lamp stays on till the show's over!
I'll have to check about that bulb test, but here's a similar one I found at http://www.capital.net/com/jaytp/EQUIP.HTM
“About 15 years ago or so some one at the State University of New York (SUNY) was looking for a way to save money. They looked at how many projection bulbs SUNY went through in a year. So the did a study on how to make these bulbs last longer.

What they discovered was that bulbs that were allowed to cool down slowly last longer. If the cooling fan is allowed to run to cool off the projector, the uneven cooling of the bulb stresses the filament. Of course if the projector has to be moved right after the show it should be cooled one way or another because any mechanical shock to a hot filament causes greater stress than any about of uneven cooling.”
Doug

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I think there's room for just one more film.....

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Steven Sigel
Jedi Master Film Handler

Posts: 701
From: Massachusetts
Registered: Jun 2003


 - posted August 05, 2003 10:38 PM      Profile for Steven Sigel   Email Steven Sigel   Send New Private Message       Edit/Delete Post 
It seems to me that there would be more of a shock to the lamp by not letting the fan run -- while the bulb is lit, the heat is carried away by the fan, which yeilds a fairly even temparature, but if you shut the fan off, the heat (for a time) is going to build up around the lamp. I would think that damage from excess heat would be greater than from cooling. Also the fan doesn't instantly cool the lamp - it still takes quite a bit of time to bring the temparature down -- all it's doing is carrying away the heat that is being generated.

That web page you quoted seems to be arguing that the fan would cause uneven cooling -- I think the oposite is true -- if you pass air over the lamp and draw away the heat, you will help it cool more evenly -- if there's no fan, then the parts of the lamp closer to the vent will cool faster than the other parts of the lamp.

The other thing to think about is what you are protecting -- even if you are correct about filaments, the glass still might be affected by the heat. And of course Xenon lamps don't have filaments, so any argument about filaments is irrelevant when talking about xenons (or any other ARC lamp)... I've got an Elmo 16-CL Xenon that I've been cooling with the fan since I got it (2 years ago), and I've easily run it for well over the lamps rated life with no problems, so I think I'll just keep on doing it that way until I see some scientific evidence that natural cooling is really better.

I absolutely agree with you that you should not strike a Xenon any more times than you have to -- I too always leave my GS fired up until I'm done with the show.

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Barry Johnson
Master Film Handler

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From: United Kingdom
Registered: Jul 2003


 - posted August 07, 2003 04:57 AM      Profile for Barry Johnson   Author's Homepage   Email Barry Johnson   Send New Private Message       Edit/Delete Post 
Regarding this heat dissipation:Obviously getting rid of excess heat from your machines is very desirable but I would ask you to bear this in mind:
Xenon lamps are designed to run at fierce internal temperatures and if they are overcooled,the glass envelope will blacken.This is not good for light output.Rarely though does this affect lamp life.So let it run hot,leave it on during your shows and leave the fan running after you have finished.Five minutes will be ample for xenons of the size used in 8mm or 16mm projectors.

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Standard8 rules!!

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Kevin Faulkner
Film God

Posts: 4071
From: Essex UK
Registered: Jun 2003


 - posted August 07, 2003 03:31 PM      Profile for Kevin Faulkner         Edit/Delete Post 
Just one point to remember guys and that is that with the std non xenon version of the GS you can't let the fan cool the lamp down because the lamp is allways on in pre-heat mode when the fan on its own is running.
I turn off my GS and then leave it to cool down before moving it arround and normally use that cooling period to clean the film path etc. [Smile]

Kevin.

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GS1200 Xenon with Elmo 1.0...great combo along with a 16-CL Xenon for that super bright white light.

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Steven Sigel
Jedi Master Film Handler

Posts: 701
From: Massachusetts
Registered: Jun 2003


 - posted August 07, 2003 04:10 PM      Profile for Steven Sigel   Email Steven Sigel   Send New Private Message       Edit/Delete Post 
O.k. -- so here is an authoritative answer I got from Dennis Losco who runs Superior Quartz products (a manufacturer of Xenon lamps).

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Steve,
We suggest to keep the air on for about 15 minutes.
The anode is very hot on shut down and the quartz will cool much faster causing thermal stress. Not good for the quartz
Denny
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So at least in terms of Xenon, the fan should be left on for 15 minutes....

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Tony Milman
Phenomenal Film Handler

Posts: 1326
From: United Kingdom
Registered: Jun 2003


 - posted August 11, 2003 12:30 AM      Profile for Tony Milman   Author's Homepage   Email Tony Milman   Send New Private Message       Edit/Delete Post 
Guys, fascinating stuff. For those of us without a Xenon to worry about is there a view on best practice for halogen bulbs?

Tony

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Tony

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Douglas Meltzer
Moderator

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From: New York, NY, USA
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 - posted August 11, 2003 08:19 PM      Profile for Douglas Meltzer   Email Douglas Meltzer   Send New Private Message       Edit/Delete Post 
Tony,
On 8/5 I sent e-mails to the tech support departments at a number of different bulb manufacturers. This is from Peter Heintz of Eiko:
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Subject: Cooling and Lamp Life

Dear Mr. Meltzer,
I recommend always following the projector manufacturer's instructions. In most projectors the cooling is not to protect the lamp from high temperatures but to protect components inside the projector from high temperatures.
The average life of any lamp is established by burning a minimum of 500 lamps base down in open racks on regulated voltage. There is no forced cooling. The elapsed time at which half the lamps have failed becomes the average rated life of that lamp. The same procedure is uses for arc lamps such as xenon lamps.
It is unlikely that uneven cooling places any stress on the filament. More stress to the filament results from shock and vibration while the lamp is under normal operating conditions.
Please let me know if I can be of further assistance.
Peter Heintz
Quality Assurance Manager, Chicago
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I think there's room for just one more film.....

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Tony Milman
Phenomenal Film Handler

Posts: 1326
From: United Kingdom
Registered: Jun 2003


 - posted August 12, 2003 01:42 AM      Profile for Tony Milman   Author's Homepage   Email Tony Milman   Send New Private Message       Edit/Delete Post 
Thanks Doug, right just about to link in the last bulb ......
.....will report back on how long it takes to burn through 250.....phew it is hot in here.......can't get to sleep either since it is so bright............but hey the wife says the tan is real good............ [Big Grin] [Razz] [Cool]

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Tony

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Joe Taffis
Phenomenal Film Handler

Posts: 1538
From: United States
Registered: Jun 2003


 - posted August 12, 2003 06:41 PM      Profile for Joe Taffis   Email Joe Taffis   Send New Private Message       Edit/Delete Post 
if I were refereeing this "fight"...i'd call it a draw! Great info guys....

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Joe Taffis

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