Film-Tech Forum ARCHIVE: Horrible exhuast on my SLC's

This is topic Horrible exhuast on my SLC's in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

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Posted by Michael Rourke (Member # 1142) on 06-11-2004, 04:32 AM:

One of the biggest problems I've had since I started at my 7 screen has been my bulb life and it is due to the poor exhaust system in place.

The exhaust fan is a dual squirrel cage motor that is more than adequate to cool the lamphouse but it is in a box about 2 feet above the lamphouse and the duct goes into the bottom of the box, so the squirrel cages are pulling hot air from below rather than straight across. Also all the exhaust fans empty into one long horizontal duct run to the outside with only gravity to help it out and because our set up is like a big T the two exhausts at the end of the line are battling all that hot air from the other 5 projectors.

I have cut into the sides of the box and run two ducts to a Y on the output of the lamphouse on two units but the CFM did not increase much. My next thought is to add boosters to each duct, but I would like to overspec the exhaust and get more life out of my bulbs for a change and booster just aren't powerful enough.

I think the best thing to do would be to get some nice squirrel cage motors and mount them directly to the top of the lamphouse and leave the existing exhaust simply to empty to the outside.

Can anyone recommend a good motor/squirrel cage to use and the best way to mount it so as to not add vibration or lose CFM?

Posted by Paul G. Thompson (Member # 655) on 06-11-2004, 11:31 PM:

I suggest having it done right. The SLC Console At one theater I was associated for a short period of time (With Christie Bulbs) easily rang up 4,000 to 6,000 hours before the bulbs needed changing.

Each console was "stacked out" separately. Also, as I understand, the mechanical contractor who installed the ductwork and blowers knew what he was doing. The stack runs, static pressure losses, and ductwork size blower size, etc. was very carefully calculated.

It may cost you a few bucks to do it, but by the way you are talking, it'll pay for itself by less premature bulb failures.

Posted by Michael Rourke (Member # 1142) on 06-12-2004, 11:23 PM:

Sadly Paul, that is not an option. I was quoted over 3,000 dollars just to redo the duct work from the lamphouse to the box for all 7, as I have already done in 2 units for much much less. I'm not too worried about the exhaust once it gets to the main gangway to the outside, I just want more suction out of the lamphouse.

Posted by Matt Hefright (Member # 2470) on 06-20-2004, 08:53 PM:

what is your actual ductwork size and current fan configuration?
we have an inline centrifugual fan mounted directly on the lamphouse, it goes into a 6" duct and is enhanced via two squirrel box fans.
these units don't cost much {around $250}.

Posted by Paul G. Thompson (Member # 655) on 06-20-2004, 09:02 PM:

I agree. The cost should not be to big of an issue. As an example, a 350CFM blower placed in line costs about 70 bucks each. In my situation, they already paid for themselves by adding hours to the bulb life.

A word of caution...if you only have a 200CFM (as an example) blower in line with the 350 CFM unit, they will buck each other.

A blower cannot pull 10 pounds of crap through a 5 pound bag. It is impossible to do as I understand the configuration. The algebraic difference (or sum, depending how you look at it) is what you can expect to see if you try that. I see it as the "difference."

Posted by Samuel Hynds (Member # 2610) on 08-09-2004, 11:27 AM:

There may be an easier fix. Put in a 7" box fan just about the mirror, then use reducers to go down to the 4" output stack. You also may want to put heat filters in. I did this to four 3KW SLC's and to two 4KW SLC's. With the 4KW, I put in a 10" box fan - for more air movement. Christie does sell a Aux. blower kit for the SLC.