Film-Tech Forum ARCHIVE: HEAT & NOISE, Lanmps & Rectifiers

This is topic HEAT & NOISE, Lanmps & Rectifiers in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

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Posted by Bill Enos (Member # 440) on 08-06-2001, 01:15 AM:

The carbon arcs will be headed for the attic sometime this fall and while the exact deals haven't been done yet this is what is up. One possibility is a pair of 4000 Kneisley's with Irem rectifiers used but excellent this may not go thru but needs consideration, New would be two 3000 Strongs with rects. Question is----AC in the booth is marginal barely comfortable. What would be the heat trade-off between the Magnarcs with lots of hot surfaces and either of the above not as hot to the touch but much higher air flow to outside. Also arc rects are in the room below where temps hover around 95F, would Xenon rects. be happy in this temp range as I don't need their heat & hum/buzz in the booth unless necessary. Electricity is no problem in either place as there is 3 phase fused at 100 amps per leg at both. Any insight into these considerations? Many thanks, Bill

Posted by John Walsh (Member # 168) on 08-06-2001, 09:57 AM:

Well, xenon lamps will give off less heat. But you are right that xenon will require a much higher air flow (for lamp cooling) than carbon arc. The screen needs to be lit with the proper light

I would think that the amount of air flow required for 4000 watt lamps is not that much more than 3000 watts. Certainly, it requires more, but not that much. What size screen, throw? Do you really need 4000 watts, or is that over kill for your application? The screen needs to be lit with the proper light, but no more.

Check the manufacturers suggestions, and if you need to hire an HVAC company to redo the lamp exhaust system, make sure the required CFM air flow for every projector is specified in the contract.

Not having the rectifiers in the booth with the projectors can be annoying if you need to trouble-shoot problems, but I agree, it's nice not to have humming heat generators. 95F is a little warm; the 4000 IREM rectifers do not have a cooling fan in them; they rely on air convection only (don't know about the Strongs.) If you get the IREMs, can you rig up a fan to help circulate the air? How the fan would be rigged will take some thought, because the convection action must be created/maintained. You might want to wire up a remote switch (in the rectifer room) to turn them on for servicing/testing. For safety, I'd suggest indicator lamps both at the projector and in the rectifer room to alert personnel that power is applied. As for hum, we mounted large rollers under the rectifer. This reduces hum, and allows the back side to be serviced.

Be sure to install the rectifiers such that the diode-servicing side is accessable. On the IREMs, that's the "flat" side, rather than the side that has a 45deg bevel.