Film-Tech Forum ARCHIVE: rectifier power requirements

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Posted by Scott Norwood (Member # 30) on 05-04-2004, 08:19 PM:

I'm trying to figure out the power requirements for a possible apartment theatre. Motors, etc. are easy; rectifiers are not. I have a pair of IREM "P1-X30B" rectifiers and Cinemeccanica "CX-20H" lamphouses with 500w xenons (all originally purchased circa 1995). I'm trying to figure out how much current these rectifiers will draw (at 120vac). In their previous installation, each had its own 20amp circuit, however I've tried them (for short periods) on various 15amp circuits (with other stuff connected as well) and they didn't trip circuit breakers or cause outlets or wiring to heat up. Would it be safe to allow one 15amp circuit per rectifier, considering that they worked fine on circuits where my vacuum cleaner (1000w) would trip the breaker?

Unfortunately, the manual that I have isn't very useful (I have only the lamphouse manual, not the rectifier one) and the electrical plate on the bottom says only "Input: 115vac."

Is the current draw relatively constant? Should I just go and blow $50 on a clamp-type ammeter?

On the same topic, I'm assuming that I should have separate circuits for a) projector motors and framing lights, b) zippers, and c) sound equipment. Am I missing anything? Keep in mind that my apartment wiring is pretty crappy.

Posted by Richard Fowler (Member # 893) on 05-04-2004, 08:50 PM:

The draw on 120VAC should be 11 - 12 amperes. A vacuum motor is a poor comparison since they can momentarily draw 2 - 3 times their average rating at start up and blockages. The rectifier should draw less extreme to maintain steady light output.the CX-20H / 21 lamphouse is nice....hopefully you have the rail adapter for the box to allow it to be easily adapted to American machines

Posted by John Hawkinson (Member # 1135) on 05-04-2004, 10:13 PM:

Scott, you should go out and buy a clamp ammeter (or clamp attachment for an existing DMM), definitely. It's very useful tool. Consider springing for a Hall Effect version that does DC as well. [thumbsup]

You should also pay attention to the wire runs lenths and what guage the wire is before deciding.

If you're actually going to have an electrician add circuits, then you might as well just get enough for everything plus some extras. You can never have too many empty slots in a panelboard! Otherwise, well, you can kludge it all together and probably survive, but it may not be pretty. Remember that you'll want to up the draw on the rectifier as the lamps get older (maybe not such a real issue with 500W lamps in a situation that is probably overlit anyhow...).

In a perfect world, of course you want seperate circuits so that if your #1 projector/rectifier blows a breaker, the show can keep running uninterrupted on the #2 projector. I guess you're not proposing sharing a 20A circuit between them both, though, so I shouldn't worry about that...

--jhawk

Posted by John Walsh (Member # 168) on 05-04-2004, 10:16 PM:

I have rail adapters if you need them. We ordered them by accident 20 years ago. Hopefully they can be put to better use than the door stop they are now.

Depending on how much sound equipment (mono or 5.1?) I would put each projector motor and framing light on it's own (the zipper power would share with one of the projectors.) Then amps and processor on another. Try to put all sound equipment on the same phase. Usually, apartments are wired pretty cheaply and there are no extra breakers left in the box, so this might be tough.

Posted by Scott Norwood (Member # 30) on 05-05-2004, 07:10 AM:

Rail adapter? These lamphouses have weird little metal brackets that stick out the front and hold some sort of translucent piece (diffuser? heat shield?). Is this the "rail adapter" or something else completely? The manual is not helpful. Everything was set up and working before I dismantled it. Picture was fine, if a bit dim on a 15' screen.

Sound will be SR mono, running thorugh a CP65, as I don't want to blast the neighbors with anything more. The lamphouse fans are super-loud, so I may have to resort to well-sealed headphones. [Roll Eyes]

Someday, I will have a house with space for a proper screening room; this is just a semi-temporary thing for the next few years.

I am missing the little tool that is necessary to align these lamphouses, so if anyone has one of these for sale cheaply, I'd be intereted.

Posted by Dave Macaulay (Member # 813) on 05-05-2004, 10:13 AM:

The rail adapter lest you easily mount the lamphouse on American style pedestals, CM systems mount rather differently. If it was all working then you probably don't need them but if the lamphouse mounts via a bastardized mess consider getting the rail adapters. If you have a domplete Cinemeccanica projection system you certainly don't need them.