Film-Tech Forum ARCHIVE: Lamphouse exhaust booster recommendations

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Posted by Chris Hipp (Member # 1788) on 03-15-2004, 07:06 PM:

I am looking to install an inline booster for our lamphouses with 3k or higher bulbs(3k-6k).

They are currently pulling at about 400CFM according to one of our engineers. I do not have a meter so I cannot confirm that.

Question is how much is too much, is it possible to overcool a bulb? I am thinking around 700-750 cfm would more than enough for the 6k houses and around 550-600 for the smaller bulbs.

Thanks in advance.

Posted by Mark Gulbrandsen (Member # 72) on 03-15-2004, 08:09 PM:

WOW! only 400cfm on a 3kw lamp...thats insane [Roll Eyes]

at best. 900 cfm would be more like it and would give you good lamp life. 900 cfm is the smallest amount I reccomend for 2 to 3kw. Even more for larger lamps...thats a boatload of BTU's to get rid of!

I've never been able to overcool a lamp although with alot of cold air entering a booth it might cool down too fast after turning it off. As for sucking the air out of a booth, it certainly is possible to do that. Ask your HVAC dude to see how much air is entering the booth before upping the CFM on alot of exhaust blowers.

Mark

Mark @ CLACO

Posted by Gordon McLeod (Member # 33) on 03-16-2004, 06:12 PM:

It may not be possible to draw more than 500cfm if the lamphouse vent is 6" due to the static pressure on your fan
Also the air intake to the lamphouse needs to pressurize it to the level of the exhaust.
Also the booth will need sufficient fresh air introduced so the exhaust can suck out that volume of air of the booth will end up with a negative air pressure

Posted by Chris Hipp (Member # 1788) on 03-16-2004, 06:35 PM:

I think you guys might be onto something with the low pressure in the booth. Any time we open a door it is like you are standing in front of huge fan. I will look into that first.

Posted by Daryl C. W. O'Shea (Member # 1303) on 03-16-2004, 06:38 PM:

Which way? You should have positive air pressure... air blowing out of the booth.

Posted by Chris Hipp (Member # 1788) on 03-16-2004, 07:04 PM:

The air comes into the booth.

Posted by Daryl C. W. O'Shea (Member # 1303) on 03-16-2004, 07:06 PM:

That sucks. [Wink]

Posted by Mark Gulbrandsen (Member # 72) on 03-16-2004, 08:08 PM:

Never had a problem in a modern multiplex situation where you didn't have enough air entering the booth,nor in creating a negative air pressure. In a small booth that is very tiny this could be a problem, although for me it has not. We recently added a two screen addition to a theatre we built a number of years back and the local inspector was concerned about creating a negative air pressure in the smallish individual booths but he checked with the architect and all was ok for 900 cfm. Also you are definately NOT limited by the size of the exhaust hose or by the intake size on the lamphouse as what happens with a high draft blower in that the air velocity increases drastically. And that is the desired effect you want anyway. It will actually spin the seal cooling fans at a high rate without them being powered on!

Lamphouses and consoles we have cooled this way typically yield 10,000 hours(not my choice to run em that long though!) from a 2kw lamp. 3 and 4kw last as long as 4000 hours.

Mark @ CLACO

Posted by Gordon McLeod (Member # 33) on 03-16-2004, 08:53 PM:

If you take the exhaust requirments of a larger booth makeup air is a big cost
very few theatres provide a proper positive air pressure

Posted by Mark Gulbrandsen (Member # 72) on 03-16-2004, 08:59 PM:

I absolutely agree with you on the positive air pressure thing. I can't think of a booth with positive air pressure. Almost all theates I've been involved with have simple airflow HVAC systems that use either outsode air or recirculate it depending on outside conditions. But most booths are supplied with way more than sufficient air flow to accomodate a number of large exhaust systems.

Mark

Posted by Jack Ondracek (Member # 1466) on 03-16-2004, 09:07 PM:

quote:
Also the air intake to the lamphouse needs to pressurize it to the level of the exhaust.

Not sure how you'd go about this, Gordon. It may be possible with lamphouses like the Ultra-80, but there was no such attempt with older models like the X-60 series. The Xenex Pup didn't have a blower in it at all, if I recall right... so anything provided up the stack would create a vacuum in the lamphouse, wouldn't it? I'm also pretty sure you aren't getting 600cfm out of that little blower on the side of a Super Lume-X.

About the only way I could think of would be to have enough make-up air being forced into the booth to create a positive pressure in the whole room, with all exhaust blowers on. Assuming the intake vents on the lamphouse could handle the cfm's that you're looking for, that would be about as close as you'd get to equalling what the stacks would be pulling.

[Confused]

?????????? [Confused]

Posted by Paul Konen (Member # 41) on 03-16-2004, 09:08 PM:

Chris, I could show you what I did in my booth. I found a device (inline duct fan) in the Grainger catalog that would help. When a DLP was joined or tapped onto the existing exhaust stack, it wasn't pulling enough air out. Also, when it was windy, the backflow would throw down the exhaust failsafe and kill the bulb. Anyway, added this exhaust and it helped quite a bit.

Also, it has helped when on Friday night, the roof motor goes out and it can be temporarily installed to exhaust the air out into the booth space.

Posted by John Pytlak (Member # 331) on 03-16-2004, 11:08 PM:

For those who don't know, "positive air pressure" is recommended for film handling areas, so airborne dirt from outside is not "sucked" into the projection room. In other words, the system should be balanced so that when you open the door, the air flows outward.

Incoming air from the HVAC should be well-filtered. High Efficiency Particulate Air filters (HEPA) are available at moderate cost, capable of efficiently filtering airborne dirt particles as small as a micrometer in size. (e.g., 3M Filtrete, Purolator, etc.)

It's already been suggested that having a dedicated air source for lamp cooling would be a good lamphouse design feature, and make it easier to maintain the proper projection room environment.

Posted by Jason Burroughs (Member # 68) on 03-17-2004, 10:16 AM:

I'm not sure about Chris's location, but this is certainly true at the AMC Grand, which is the prototype for their currently gigaplexes. The booth is part of the return system.

Air is drawn from the auditoriums and into the booth, from there the HV/AC system draws the air and redistributes though a high velocity vectored duct system by use of various controlled dampers etc.

The booth as no HV/AC system of its own, and relies on the air, complete with particulate matter, from the auditoriums for cooling and heating.

This creates a negative air pressure in the booth to start with, add to that 10 exhaust fans running in the same room, and you end up with a pretty healthy inflow of air from open doors etc. [Eek!]

AMC MAY have changed this method since construction of the Grand, but I doubt it. [Roll Eyes]

Posted by John Walsh (Member # 168) on 03-17-2004, 01:11 PM:

This has become a big issue with our circuit...

Almost always during construction, the HVAC people are not told what is required by the projection people, so the booth is not properly set up to provide the correct amount of air. We have booths with 13 projectors in one room. Times 900 cfm each, that is an incredible amount of air that we pay to cool or heat, then immediately throw it away. Note that in some states, making the booth part of the return system is not allowed; the air must be dumped outside. This is because mixing all the air confuses the fire alarm if there is smoke. Some lamphouses seem to be more 'cooling' efficent than others: I'd be interested in knowing what make lamphouses Chris uses.

Totally agree with Mark and Gordon about making sure enough air is coming into the booth. Other suggestions:

We have consoles where the manufacturer put an exhaust fan on the top of the console, presumably to help. However, this fan had less cfm flow than the roof-top fan, so it actually reduced the airflow. You might want to check yours, and/or be sure the booster fan is greater than the roof fan.

Change the ducting from the roof to the projector (or even just a section) to the largest size you can. Just like resistance in a wire is less with a larger gauge, a larger duct will allow the air to flow easier. This photo looks dumb, but it sucked like crazy.

Consider getting a cfm meter; it should specifically state it can measure in cfm's. I have an Extech 407114. Although a good idea, none of our booths have positive air... we'd go broke... [Smile]

Posted by Scott Norwood (Member # 30) on 03-17-2004, 01:56 PM:

I'm still trying to figure out how one would create a positive airflow in the booth with lamp exhaust that pulls the air out. Does it require an HVAC system with HEPA filter to blow air into the booth (at a greater rate than it is being exhausted by the lamp blowers)? Sounds expensive; presumably this would be more easily achievable in smaller booths than larger ones.

[Confused]

I gather that this is mostly a design/architectural issue and not one which can be easily addressed in existing buildings.

Posted by Daryl C. W. O'Shea (Member # 1303) on 03-17-2004, 02:30 PM:

That's pretty much it Scott. Although it is possible to do with existing buildings it can be difficult since some older buildings leak pretty badly.

As for the cost of heating or cooling all that air, we've got some plastic factory clean rooms with high volume heat exchangers that handle upwards of 15,000 cfm while maintaining positive air pressure. So it is possible, but it isn't cheap.

I've found most booths in a typical multiplex can keep at least neutral air pressure if they use about the same size HVAC system for the booth as one of their large auditoriums.

Posted by John Hawkinson (Member # 1135) on 03-17-2004, 03:24 PM:

In a proper HVAC system, every room should have a return fan and a supply fan. Negative or positive pressure is just a matter of balancing them.

--jhawk

Posted by William Hooper (Member # 71) on 03-18-2004, 01:46 AM:

quote:
I'm still trying to figure out how one would create a positive airflow in the booth with lamp exhaust that pulls the air out.

Is there any sort of construction code which prevents the cooling air for the lamphouses to be ducted from the outside? Lamphouse design probably precludes most cases, & it's probably a legacy from the carbon arc days of huge theatres with hot booths & little financial reason for divorcing the lamphouse cooling air from the huge auditorium. It seems like it would be no big deal to pull it all into a distribution manifold at multiplexes.

quote:
Change the ducting from the roof to the projector (or even just a section) to the largest size you can.

Another huge detriment to airflow in a duct or windline is turbulence. Use smoothest interior duct (that's tin!), the fewest bends possible, & then the easiest. Curves work beter than elbows, 2 45 degree bends are better than a 90 or steeper, which contribute enormously to turbulence.

Posted by John Walsh (Member # 168) on 03-18-2004, 07:49 AM:

-Is there any sort of construction code which prevents the cooling air for the lamphouses to be ducted from the outside?-

Been thought of before... but if it's raining outside, a lot of moisture will be brought in, rusting the inside of the lamp... or if you live in a sunny area, the air coming in may be so hot the lamp is not kept cool. It's a good idea, but might not be workable everywhere.

Posted by Jack Ondracek (Member # 1466) on 03-18-2004, 09:32 AM:

So, William...
You're using recycled pipe-organ air to pressurize your booth?
[beer]

Posted by Brad Miller (Member # 2) on 03-18-2004, 02:28 PM:

What are the opinions here regarding bringing air from above the ceiling grid to the air intake of the lamphouse?

Posted by Daryl C. W. O'Shea (Member # 1303) on 03-18-2004, 02:42 PM:

I'm against it. It's a good way to suck dirt and humidity into your lamphouses.

Posted by Joshua Lott (Member # 240) on 03-18-2004, 03:00 PM:

A question that I have in regards to the lamphouse exhaust is for a portable set up.

It will have to be run directly into the room that the projector is in.

Strong Lamphouse Page

The lamphouse at the bottom of the page is what I am looking at. (ultra 80) If I was running a 2k or 3k bulb would adding a second unit like the one that is already there work?

Or do I need to consider something different?

How much air would I need to run out of the lamphouse for a 3k bulb?

Josh

Posted by Scott Norwood (Member # 30) on 03-18-2004, 03:14 PM:

Interesting question.

What's the maximum size lamphouse that can be vented into the booth? I suspect that this is a no-no with carbon, but I've run a couple of booths with two 16mm xenon machines with 1kw bulbs in each. The booth gets warm, but not excessively so. Otherwise, I don't think there's any issue with 1kw (at least not with modern "ozone-free" lamps).

Posted by Christopher Seo (Member # 7) on 03-18-2004, 05:32 PM:

I think it just depends on how warm you want the booth to get. [Smile]

When I visited Strong International a couple of years ago, I saw them testing repaired switching power supplies by hooking them up to a 7 kW lamp. The lamphouse was simply vented into the room. Although they switched power supplies often, I suspect the bulb was on a good part of the day. Of course, this was early January, and they said it gets pretty toasty in the summertime....

In the real world, I have seen 1600 W lamps (I think... they were in the range of 1000-2000 W anyway) vented into the booth.

Posted by John Pytlak (Member # 331) on 03-18-2004, 05:40 PM:

If you smell ANY ozone, the lamphouse should be vented to protect your health. [Eek!]

Posted by John Walsh (Member # 168) on 03-18-2004, 06:02 PM:

Regarding bringing air from above the ceiling grid... it depends on what's up there. If it's closed (required in Connecticut) then you can't, since the lamps would be sucking for air. If it's a part of a return air plenum (sometimes shared with other auditoriums, sometimes not) it would work, but might mess up the air balancing for the auditoriums if the additional load of many projectors was not calculated for.

The Strong lamphouse manual states the exhaust should be 700cfm. If the second fan unit matches that rate, it should work.

I guess venting the lamp exhaust into the booth is OK (disregarding local codes and using ozone-free bulbs) but if the temperture in the booth gets to 90'F or so, I might be concerned that the supply might be too warm to cool the bulb.

Posted by Mark Gulbrandsen (Member # 72) on 03-18-2004, 06:31 PM:

"The Strong lamphouse manual states the exhaust should be 700cfm."

Good Lord John, I hope you don't totally rely on all the manuals that everyone puts out. Thats a bare minimum spec for decent cooling of a 2kw lamp!

Mark @ CLACO

Posted by John Walsh (Member # 168) on 03-18-2004, 07:02 PM:

700cfm for a little 2K lamp? I would think that to be fairly excessive...

But this is an example of how different equipment can be... I'm at a theater right now (I don't rate a 'real' office, so I have a storage room [Smile]

) and have a 3K console doing 680cfm, and it's cool as a cucumber. Bulbs last 3-4k hours; I change them just because I get scared, not because they darken or flicker. I also just happen to have received my brandy-new Fluke 61 IR thermometer... The hottest place I can measure is 135'F at the snood, which seems reasonable.

Although, not trusting everything stated in a manual, is well taken!

Posted by Gordon McLeod (Member # 33) on 03-18-2004, 08:22 PM:

Some of the blue cinemecanica console installations were done up here with a hose supplying forced air into the console (this also ensured that as operators walked by they didn't accidently shut the console airflow switch down)
For a 2K lamp I usually go for 500cfm (measured in the stack) and get terrific lamp life