Film-Tech Forum ARCHIVE: Removing heat.

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Posted by Alan Gouger (Member # 543) on 07-09-2017, 12:46 PM:

For those running 6k lamps what are you using to remove the heat.
Looking at the typical consumer in line Centrifugal duct fans its hard finding anything beyond 600 CFM which does not cut it especially if there is 10 feet of duct between the projector and fan.

Thank you!

Posted by Leo Enticknap (Member # 534) on 07-09-2017, 01:54 PM:

In the case of a screen I used to look after that ran a 7kW bulb in an NEC NC3240S for 3-D presentations, a Centri-Master PRN100 fan assembly with a Fasco UB91 motor (1/10 HP, 3.2 amps, 1550 RPM), mounted on the roof, with a 10" duct going straight up to it from the projector's lamphouse exhaust. This was a dedicated extract for that one projector (i.e. it didn't suck from multiple projectors through a manifold or plenum), and the other two in the booth had identical copies. I never had any overheating issues: every time I pulled the projector's log and looked at it, all the temperatures were comfortably within spec, even with the 7kW bulb running.

Posted by Chris Markiewicz (Member # 1415) on 07-09-2017, 02:32 PM:

In our drive-ins (West Wind) we use the 8" Fantech centrifugal duct fans (Grainger 4YM45) on our Barco 32Bs running 6500W lamps. 8" ducting to the roof. Fans are modified with a relay box to take commands from the Barco fan control socket. We have a spare fan ready in each booth in case of a failure. Maybe 6 failures in 5 years over 34 screens.

Posted by Richard Fowler (Member # 893) on 07-09-2017, 02:50 PM:

S&P - Powervent exhaust fan kit with reducer to 8 inch and rubber vibration collar can exhaust 654 CFM at 0 pressure. There are larger and smaller kits available.

Posted by Mark Gulbrandsen (Member # 72) on 07-09-2017, 06:01 PM:

I absolutely recommend the Fantech stuff. At least an FG12XL for more CFM. You want about 1000 CFM for a 6kw lamp.

Mark

Posted by Alan Gouger (Member # 543) on 07-09-2017, 10:56 PM:

Just what I was looking for, thank you!!!

Posted by Guy Burns (Member # 10062) on 07-11-2017, 02:57 AM:

I hope you don't mind a question from an outsider.

When I was shown around the projection room at the local cinema, in preparation for hiring it sometime, the operator said each of the four projectors used a 4KW bulb and the heat was exhausted to atmosphere.

A former electrical engineer, I immediately did some rough calculations: 16KW costs about $5 an hour. Say 10 hrs a day, seven days a week, that's about $20,000 of heat wasted every year. The theatres are heated most of the year, where I am. The response was: "Well, we don't worry about that."

Then you go the next step: multiplied by 10,000 theatres worldwide, that's $200 million, less some percentage for summer and hot climates.

Do any theatres use this heat to warm their cinemas?

Posted by Jack Ondracek (Member # 1466) on 07-11-2017, 06:51 AM:

You probably could, though I don't know anyone who does this. Using exhausted heat from radio broadcast transmitters was common and worked very well, back when everything had tubes in them.

At my drive-in, dust is our biggest problem. When we converted, we set things up so we dump all the heat into the booth and remove it with refrigeration. It may be a bit of overkill, but the room stays at about 74°, I've only had to clean my filters twice in 5 years and all the computers in there are happy.

Posted by Guy Burns (Member # 10062) on 07-11-2017, 07:34 AM:

Just don't let Al Gore get wind of your double whammy to the environment!

My rough calculations were based on resistive heating. The benefit when heating via reverse-cycle (more efficient) would be less than half the figures I gave.

Posted by Marcel Birgelen (Member # 6801) on 07-11-2017, 07:37 AM:

In many cases, the heat produced by those projectors isn't entirely lost as at least some of it finds its way into the building, where it can do its part in heating up the areas that need to be heated.

Recouping energy from hot air exhausts is a pretty expensive business. You could do it using heat exchangers and use this heat to pre-heat the water which would be fed into a more traditional heating system. I know just one cinema who did this and I'm not entirely sure what the benefits were.

It could be more efficient, if you could use the hot air coming out of those projectors directly and mix it into the air of the HVAC system.

The problem here is the ozone which might be present in the exhaust air. Although modern projectors with Xenon lamps produce far less ozone than older models, there will still be some ozone generated. You really want to have this vented instead of being mixed with the air you're pumping into your auditorium.

Posted by Carsten Kurz (Member # 5396) on 07-11-2017, 09:40 AM:

The larger, modern multiplexes in some (energy conscious) countries actually do use the hot air from projection (and other booth gear) to recoupe energy. But not in a dedicated way directly targeted at the projector hot air, but through heat exchangers that are part of the overall building ventilation and HVAC systems.

One must say, though, that many of those modern cinema buildings have so much gear operating, so many people coming in, so many shows per day (think of a large 10+ multiplex with 5 shows per screen/day), that even in winter time, heating is not their dominant energy use, but HVAC/cooling during summer or even modest temperature days.

For smaller operations, direct use of the air exhaust heat is probably forbidden most of the time because of ozon, and fire precautions (strictly limiting direct air flow from parts of the building into the auditoriums). You could overcome the latter point with heat exchangers again, but using them only for this purpose is probably not worth the money. These would be built-to-order systems and to cover all design/engineering/security/fire precaution aspects would be very expensive.

We thought about that idea years ago when we were operating our 35mm equipment with a 2kW Xenon arc lamp. The heat it produced was impressing. However, we then looked at the specs of our gas operated auditorium air heating system, and it said '100kW'. So, how much would the heat of a xenon lamp running at 2kW max for 3hrs a day help, if we are not even allowed to feed it directly into the auditorium, but would need expensive and lossy heat exchangers?

Since we are digital, we run the same screen size from two 450W UHP lamps. The whole booth now runs probably from around 1.5-1.8kW average. We installed LED lighting everywhere in the building, and programmed our heating to the most economical scheme. That's all we can do for our 400 seat building. We did see quite an improvement in energy consumption over the last years.

- Carsten

Posted by Frank Cox (Member # 6258) on 07-11-2017, 01:20 PM:

I actually tried this a few months ago.

A problem that I've always had here is that my projector exhaust goes up into the attic and from there out a vent in the roof. This caused an issue in the winter since blowing warm air from the projection room into the freezing cold attic caused condensation and every spring I had a bit of water dripping back down from the projection room ceiling near the projector. (I actually built a little "roof" over the projection equipment for that reason. I think an ice block forms in the attic over the winter.)

This year I decided that enough is enough and I'm going to fix that.

My initial idea was to leave the existing exhaust in place and set something up re-direct the projector exhaust into the auditorium during the winter, thinking that I could save a few dollars on the heat bill that way.

The issue is noise. After getting this re-director installed I could hear air blowing into in the auditorium when it was quiet, so it wasn't acceptable. I never actually tried it when playing a movie; I just decided that this isn't something that I wanted to do since I've gone to great lengths to make my auditorium as quiet as possible (Soundfold on the walls, hot water heat and insulated ductwork from the air conditioner.)

I considered getting an duct muffler and adding that to the setup but then thought, what if this doesn't work either and how much money am I going to spend on this just to conserve a little bit of heat.

So after giving up on that idea I had it ripped back out again and just had a new exhaust pipe run from the projector across the projection room ceiling and out one of the exterior walls of the building.

This might work for someone who's less picky or who has a larger auditorium than I do. But I'm not prepared to do anything that will degrade my customer's experience (whether they would actually notice it or not) so it's just not something that I'll do here.

On the other hand, now that I'm not blowing hot air into the attic any more I hope not to see any more "rain" in my projection room next spring.

Posted by Mark Gulbrandsen (Member # 72) on 07-11-2017, 03:44 PM:

Fire codes usually don't allow an exhaust fan blowing into an attic. That can really cause a fire to spread quickly.

Mark

Posted by Frank Cox (Member # 6258) on 07-11-2017, 03:51 PM:

It didn't blow into the attic. It blew into an exhause pipe that travelled through the attic to the roof. Otherwise, there was no way for the pipe to get to the roof since the attic space was between the ceiling and the roof. However, I guess the fact that the warm air in the pipe would heat the pipe a bit on the way through the attic space was enough to cause condensation to form around it. Or so my theory goes -- there was condensation coming from somewhere and since it was right there I don't see what else it could be.

Now a similar exhaust pipe just runs across the ceiling in my projection room to the outside wall. Good thing I'm a short guy -- the projection room ceiling is very low to begin with and now that pipe brings it down even more. The service techs always hate me. [Smile]

I'm about the only guy who can walk around up there without combing my hair with the stucco on the ceiling.

Posted by Marcel Birgelen (Member # 6801) on 07-11-2017, 04:24 PM:

quote: Carsten Kurz
One must say, though, that many of those modern cinema buildings have so much gear operating, so many people coming in, so many shows per day (think of a large 10+ multiplex with 5 shows per screen/day), that even in winter time, heating is not their dominant energy use, but HVAC/cooling during summer or even modest temperature days.

You should indeed also not forget the "human factor". A human produces about 100 W of heat, so a room of about 200 people will produce about 20 kW of heat.

Also, a 2 kW lightbulb will not produce 2 kW of heat via the exhaust. Obviously, some of the energy pumped in gets "lost" as light and the lighthouse will get hot, so some heat also dissipates via radiation. If you have a full multiplex of those heat sources, you might collect them to some central point, but in order to preserve energy, your air ducts would need to be isolated. Once you've recouped the energy in a somewhat useful form, usually warm water, you still need to find a purpose for it.

Modern multiplexes in moderate and hot climates indeed don't have a heating issue very often, more likely a cooling challenge.

So, even if you extract the heat from the exhausts, the use of it is, unfortunately, pretty limited. Even if there is, for example, a municipal heating system present. The energy left after the heat exchanger usually isn't sufficient to dump into the system, because the water you've warmed with it, just isn't sufficiently warm.

In the end, all you usually can do with it, is use it for your HVAC heating, which isn't running most of the time or to pre-heat your warm water.

quote: Frank Cox
My initial idea was to leave the existing exhaust in place and set something up re-direct the projector exhaust into the auditorium during the winter, thinking that I could save a few dollars on the heat bill that way.

You might also violate local health and fire codes this way. The first one, because of the ozone which might be present in the exhaust. The second one, because a fire inside the projector could lead possible toxic smoke directly into your auditorium.

Posted by Monte L Fullmer (Member # 2797) on 07-11-2017, 06:42 PM:

Might be lot of heat coming out of the stack, but not enough of it to use it effectively. Need 100 units burning a 6k bulb to make it worth while, but the expense would be totally idiotic.

Now, when you got a 300 seat house full of people, and each person put off close to 4000 BTU, and you have no air circulation in that house, it doesn't take much to raise the temp of that house in one hour, plus the 100 percent humidity each person emits with each breath exhaust...you got a sticky mess.

Posted by Frank Cox (Member # 6258) on 07-11-2017, 06:58 PM:

quote: Marcel Birgelen
You might also violate local health and fire codes this way. The first one, because of the ozone which might be present in the exhaust.

I don't see this as a problem since my projector (Christie 2210) can be run with or without external venting. The vent kit is actually a separate optional accessory for that projector. Without it, the exhaust just vents into the projection room directly. Unless it's a conspiracy to kill the projectionist? [Smile]

quote: Marcel Birgelen
The second one, because a fire inside the projector could lead possible toxic smoke directly into your auditorium.

I suppose that's a possibility, but there's really no particular fire separation between the projection room and the auditorium now and there never has been. I've got a big port window that's made of glass, for one thing, plus the air conditioner ducting comes down into the projection room and then goes out through the wall into the auditorium. Not to mention the wires for the sound system and so forth and so on.

It's all academic now anyway; I've routed the exhaust out through the wall and hopefully that will solve the condensation problem.

Posted by Marcel Birgelen (Member # 6801) on 07-12-2017, 07:01 AM:

quote: Frank Cox
I don't see this as a problem since my projector (Christie 2210) can be run with or without external venting. The vent kit is actually a separate optional accessory for that projector. Without it, the exhaust just vents into the projection room directly. Unless it's a conspiracy to kill the projectionist?

You know DCI is just a heinous plot to kill all projectionists? Those who survived the initial killings now will face extinction via slow ozone poisoning. [Wink]

It probably depends on your local regulation. For example, around here the maximum concentration permissible in public spaces is 0.1 ppm, which is pretty low, still, it seems to be too high for some very sensitive people. A modern digital projector usually doesn't produce much ozone, if everything is in perfect working order.

But, since you're working with high voltages and high amperages, if there's some arcing which is exposed to the outside airflow, you might see ozone production sky-rocket.

Nowadays, projection booths are usually far less occupied than they used to be, so better lamphouse and lamp designs combined with shorter periods of possible exposure reduce possible health dangers. I would still try to vent the hot air exhaust of any DCI projector with light sources considerable into the air, just to avoid prolonged exposure to ozone.

I know a few locations were they have their projectors vent into the booth and in turn vent this air directly into the lobby. I personally do think, those kind of constructions are pretty bad and you're potentially exposing the people working inside the lobby to ozone in the long term.

quote: Frank Cox
I suppose that's a possibility, but there's really no particular fire separation between the projection room and the auditorium now and there never has been. I've got a big port window that's made of glass, for one thing, plus the air conditioner ducting comes down into the projection room and then goes out through the wall into the auditorium. Not to mention the wires for the sound system and so forth and so on.

Even if there's no real fire separation, most people don't die from fire, but from smoke inhalation. Before there is fire, there is almost always a lot of smoke. The most likely place for a fire to start, in a cinema, is the booth. The projector is by far the hottest thing in the room and most heat is concentrated in and around the lamphouse.

Although the separation between your booth and auditorium might not be entirely airtight, it might be sufficient to stop most smoke from entering into that room. What's important in the situation of an uncontrolled fire is that people have sufficient amount of time to escape. So, most efforts in modern fire proofing are put in 1. not allowing a fire to happen and 2. make sure people are alerted in time and 3. make sure the smoke is contained sufficient to allow people to escape.

quote: Frank Cox
It's all academic now anyway; I've routed the exhaust out through the wall and hopefully that will solve the condensation problem.

You might still see some condensation inside the airduct, so it's best to have some kind of bend in it, to avoid this condensate reaching the exhaust of your projector. Also, you should regularly inspect it, to avoid nasty mold build-ups.

If condensation is a real problem, there are also condensate collectors which you can put into your air ducting.

Posted by Frank Cox (Member # 6258) on 07-12-2017, 12:34 PM:

I actually have the pipe angled (very) slightly down toward the outside wall.

I don't think I'll see any condensation in or on it now since the pipe is now in a heated area right to the point that it gets to the wall so there's very little area exposed to a low temperature now.

Posted by Jim Cassedy (Member # 4115) on 07-12-2017, 05:20 PM:

quote: Guy Burns
Do any theatres use this heat to warm their cinemas?

I had someone ask me about this several winters ago, when the
heating system at a 70 seat screening room broke down and it
was going to take a couple of days to get the part.

What was suggested was to get some flexible ducting and
exhaust the heat from the Xenon lamphouse into the back
of the auditorium.

I said that the screening room xenon was only 2K, and that the
auditorium would probably be losing heat at a rate faster than
we could pump what little hot air we had, into it.

Also, I pointed out that the lamphouse blower was anything but
'silent' & that its' noise would be easily heard in the small auditorium.

The idea of using the 'wasted' heat is bascialy a good one. Perhaps
there are some limited applications where it could be used to heat a
stock room or manager's office located next to the projection room.

I've read about, and seen pictures of, old radio stations where in the
winter they would use the excess heat from the transmitter to heat
their studios or office space. This was back in the days when most
radio stations had their studios & transmitter space co-located.

But from what I've read, it wasn't all that uncommon to do back then.

Posted by Arnold Chase (Member # 7988) on 07-12-2017, 11:22 PM:

For a number of years I have successfully used a setup that utilized an extraction fan, two motorized dampers, and a little bit of ducting. Rather than just dumping the waste heat from my 6 KW lamp into an auditorium, I use the motorized dampers to alternately select either outside air dump (in the Summertime), or feeding the heated air into the return duct system of the HVAC unit that feeds the auditorium in the Wintertime. That way, the waste heat gets supplied and circulated properly. The small amount of Ozone created (relative to the volume of air the system supplies) isn't such a bad thing and serves to slightly deodorize the auditorium as well!

Posted by Tom Bert (Member # 5719) on 07-25-2017, 03:00 AM:

Don't know if it was already covered, but it is important to match the external exhaust (-CFM) to the projector CFM. We have seen cases where a tight connection was literally sucking -too much- air through the projector, making it de facto the booth vacuum cleaning system. Not good for dust management in the unit you can imagine.

Posted by Mattias Mattsson (Member # 4308) on 07-25-2017, 07:19 PM:

quote: Tom Bert
it is important to match the external exhaust (-CFM) to the projector CFM. We have seen cases where a tight connection was literally sucking -too much- air through the projector, making it de facto the booth vacuum cleaning system. Not good for dust management in the unit you can imagine.

Do you have a recommendation for an instrument (make/model) to measure that the airflow is up to spec?

Posted by Tom Bert (Member # 5719) on 07-26-2017, 01:27 AM:

Afraid not (at least not field-usable)

Posted by Steve Guttag (Member # 268) on 07-26-2017, 09:04 AM:

There are many air flow meters (Anemometer) out there and the prices on them range a bit. I use one that has a vane type sensor and it has been accurate enough.

Tom, you mention having too much air flow causing problems. To the best of my knowledge, Barco (like everyone else) only mentions minimum air flow requirements (by projector model). Does Barco have any maximum values? If this is as important as you say (and I agree with you, by the way), why not publish the range/preferred amount rather than just the minimum. I realize that the preferred amount would be lamp size dependent but that could also be part of the spec.

Posted by Tom Bert (Member # 5719) on 07-26-2017, 12:05 PM:

The maximum only applies if there is an "airtight" fit between projector exhaust and HVAC. Otherwise, the extra air will just be sucked out of the booth. I'll inquire if we have an advise on max value.