I also stuck some meat thermometers in the stack ductwork to monitor the air temperature. Without the blowers, the air temp was hovering around 130 degrees....Way too hot!

With the blowers installed, it brought it down to about 120 degrees....still too hot.

I throttled the xenon bulb current down from 95 amps to 85 amps, and the temperature dropped to about 100 degrees. Finally, I almost rest my arm on the front top of the lamphouse without saying, "Damn!"

I also sent one of the kids up in the attic to find out what in the devil is up there for stack blowers. They looked like toilet bowls to me.....He will provide me with the make and model of the blowers that are up there, and maybe I can finally find what the rating is. I'll bet they are about 200cfm's.....with an additional 10 feet of stack on the output end, which will derate them to about 175 or so.

Are the temperatures within parameters?

I hope so....I have nothing to compare it with....What do you think?

PS - I am running 2500-watt lamps. 85 amps at 26 volts = 2210 watts.

The installer of the equipment outfitted the lamps with Q-Arc 3000's, and set them up to 100 amps. All of the Q-Arc lamps failed.

I am now burning LTI's in No. 1 and 2, and a Christie in No. 3. The Christie just went out of warrenty, but it is about shot. It was running too hot, and that is what ruined it.

Couple of obvious questions again; is the incoming air system (the intake fan on the side of the lamphouse) operating properly? Is the ammeter lying to you?

I have a couple of situations with this lamp/bulb combination. I will take your ingenious idea of the meat thermometer along with a millivolt measurement across the lamphouse meter shunt and report them at my earliest opportunity.

Yes, the intake blower is running properly, and it is the right ones in these lamphouses. I have thought the ammeter might be lying to me for quite some time, but I never checked it that closely. I think it is within at least 10%, though. I'll "clamp" it next week to see how far it is off. Since I only run that booth once a week, my time is limited and have to do one thing at a time.

OK, here is the scoop. I have inspected the duct work we are using with our Strong Super Lumex Lamps, and here is what we have.

Sitting on top the lamp house, I have a Grainger EF-8 325 CFM Booster fan. The output end of the fan is reduced to 6 inches, and proceeds up to the ceiling (about a 4-foot run to the ceiling.)

There are two 6 inch 90-degree elbows, one below the ceiling, and one above. Continuing up from the attic-side of the ceiling is another booster fan manufactured by Fan Tech, which is a Model No. FR-200 rated at 360 CFM. The output side of that unit is stacked out an additional 12 feet through the roof, with a diffuser/blast defector to keep the rain out of the ductwork. To my knowledge, all ductwork in the attic is 8 inch in diameter, but I can’t be absolutely sure since it is insulation rapped.

With 2500 watt xenon lamps running at 80 to 85 amps, my exhaust temperatures are running around 115 degrees F.

A question for the ductwork engineers……does this make sense? I still think the temps are too high. Seems to me that if I increase the size of the booster blower on the lamp house to the next Grainger size of 475 CFM, it would be fighting the booster fan in the attic.

Any comments, caustic or otherwise, would be greatly appreciated.

Thanks, guys.

 

This problem was from day one of this new theater. I want to make it clear I had nothing to do with it's design.

Rick: Yes, you are right. The 90-degree elbows are partially the cause of the problem. Each 90 degree elbow is equivalent to what one would lose in a 10 foot straight duct. That comes close to 20 CFM for both joints.

Unfortunately, there is not much I can do about eliminating the 90 degree elbows because the way they were built into the building's ceiling. The way the ductwork is designed, I am certain I am losing at least 40 to 50 CFM including the loss across the elbows. It is a guess, because I don't know how to calculate the loss exactly.

What is up in the attic looks like public outhouse fans that you would expect to see in a two-hole low usage outhouse. That's the best description I can give right now.

It sure gives me the impression that if I want to get good milage from the xenon bulbs, I am going to have to re-do the whole kit and cabootle as money becomes available.

Furthermore, I might have to check with the city to see if we can do it right. Our building is a peaked roof, and that's what the city wanted so I have been told. Now it becomes an issue to how much more junk we can put up on the roof to without compromising the city's beautification rules.

Only problem I can think of that may happen is higher booth noise and possible vibration issues.
 

If I can obtain the plans for the building, I can draw a picture of it for posting. But for me to get up there and measure and see just exactly what it is really like, is physically impossible for me because age-related problems.

I had to send one of my kids up there just to find out what kind of blowers were up there. About as far as I could go safely because of my condition is to stick my head up through the ceiling hatch.

I am afraid my days of bouncing around in attics and climbing latters, snaking around things, and balancing on ceiling trusses are over.

Before you let it gall you, remember that many components have expected lifetimes based on cost analyses made prior to manufacture. I suspect it is possible to design 2500 watt lamps that are internally water cooled, but such a design was determined not to be cost competative.

I think I will take your suggestion about getting a mechanical contractor and measure the actual air flow at the stack and tell us what has to be done to get them within specifications.

Jerry, it was not really a cost vs design problem. It was designed by someone who was not familiar with the problems. Some of these guys thought a projection booth is nothing more than a small room with a 16mm projector using a 1,000 watt incandescent bulb. There are some contractors that still think all that is needed for a lamp vent is a bathroom fan!

It appears the contractor made some incorrect calculations. A 360 CFM unit was used. Apparently, they forgot to calculate how much airflow was lost in the duct work run, elbows, and reducers.

At an old theater we have, I wanted to significantly increase the air flow. (The booth used to run carbon, but now has two xenons.) I just replaced the smaller roof fan with a big honking fan, and all was well - got great bulb life.

Some years later, at a newer theater, I wanted to do the same thing. (This theater was designed only for xenon lamps.) After I did it, the air flow was still poor. It had the same size fan and ducts, with the same lamp as the previous theater. It took a while, but finally I figured out why it wasn't working.

Although I had a bigger exhaust fan, I still had the same supply fan. That is; I was trying to pull more air out, than was going in, to the booth. The old carbon booth had two external ducts at each end of the room that went directly to the outside, so air flow "in" was no problem. The new theater had never been designed that way - the only air into the booth was through an AC unit.

As a side note, in Connecticut, you are not allowed to mix "booth" air with anything else (like an auditourium); also, you can't return, mix and use it again. You pay to heat (or cool) it, then it goes into the booth, then right out the exhuast vents. Also, you can't vent the lamps into the booth; the exhaust air must be vented to the outside.