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Author Topic: Protecting xenon bulbs in power failure Frank Angel Film God Posts: 5305 From: Brooklyn NY USA Registered: Dec 1999 posted 02-28-2005 07:59 AM                        Maybe I am a worrywart, but I sit and look at the 4500w lamphouses and picture a power failure in the middle of a show where we loose AC. The fans stop. The bulbs explode. Do you guys have any kind of failsafe for such an eventuality? I am thinking some kind of UPS for an auxiliary fan in the lamphouse. I know this probably doesn't come up much, but power failures do occur -- it's not like New York hasn't had a few. I mean, what happened in all the theatres during our last black out? Power failed in the afternoon when every booth in the city was running. Did bulbs explode from overheating when the fans stopped? Or am I being paranoid? Thing is, in our park venue, it's a portable system. That's a more risky setup than permanent installations. I've taken to tapeing over the booth breakers so stagehands who need to switch circuits on and off pretty routinely in that same panel don't accidently throw the rectifier circuits.  |  IP: Logged John Walsh Film God Posts: 2490 From: Connecticut, USA, Earth, Milky Way Registered: Oct 1999 posted 02-28-2005 09:12 AM                     I don't think there's a problem. I've worked many places where the power to the lamps were just cut at the end of the night; that is, the lamp and fan were wired this way. No one should wire a place like that, but since I've seen it done routinely for years I don't think the rare power failure will effect the bulbs.  |  IP: Logged Darryl Spicer Film God Posts: 3250 From: Lexington, KY, USA Registered: Dec 2000 posted 02-28-2005 09:25 AM                    I don't worry about the bulb more so than the possibility that the power does not return in full phase. I have seen this happen and I have to start running turning things off before 3 phase equipment starts burning up.  |  IP: Logged John Pytlak Film God Posts: 9987 From: Rochester, NY 14650-1922 Registered: Jan 2000 posted 02-28-2005 09:58 AM                        I'll let the lamp manufacturers answer definitively, but a few hot shutdowns due to power failure are unlikely to significantly increase the risk of lamp explosion. However, a regular practice of not letting the lamphouse cool properly should be avoided. I agree that you want to be sure the power supply is correct and unlikely to fail again before you restart. I would hope that after any line work, the power company would endeavor to energize all three phases at the same time.  |  IP: Logged Robert E. Allen Phenomenal Film Handler Posts: 1078 From: Checotah, Oklahoma Registered: Jul 2002 posted 02-28-2005 12:11 PM                     We've had two or three power failures in the seven months I've been at our ten-plex and all 10 machines shut down including the 4500w lamps and fans. It has had no visible adverse affect on the lamps.  |  IP: Logged Frank Angel Film God Posts: 5305 From: Brooklyn NY USA Registered: Dec 1999 posted 02-28-2005 12:34 PM                        Cool.....I mean HOT.  |  IP: Logged Jarryd Beard Expert Film Handler Posts: 229 From: Hellertown, PA Registered: Jul 2004 posted 02-28-2005 12:55 PM                     Why would there be any adverse effects? (From a pure temperature/fan related standpoint.) I mean, if the power to the bulb and fan are cut at the same time, it's not getting any hotter in the lamphouse. In fact, it seems the more gradual cooldown with no fan might even be better for the bulb. That's why I never understood things such as overheads or slide projectors that keep a fan running after the bulb's been shut down. Why is it necessary to cool the bulb if it no longer generates heat? Perhaps, in the case of slide projectors, it would be useful for faster storage of the machine. Also, my theatre is on the worst possible power connection for a theatre. High winds, a distant t-storm, or even heavy rains can cause brownouts or blackouts as often as once a week during the summer months. It just takes a lot of monitoring the booth, especially the takeup platters. However, as ofter as we have electrical problems, I've never heard of a bulb exploding around here.  |  IP: Logged Dominic Espinosa Phenomenal Film Handler Posts: 1172 From: Boulder Creek, CA. Registered: Jan 2004 posted 02-28-2005 01:11 PM                     I'd imagine the continuous cooling is better than air just standing in the lamp house since the lamps are so hot. In power failures my biggest worry is getting everything back online fast for the next set if we're out that long.  |  IP: Logged Monte L Fullmer Film God Posts: 8367 From: Nampa, Idaho, USA Registered: Nov 2004 posted 02-28-2005 01:36 PM                     True, bulbs DO need the fan to help cool down, since bulbs cannot dissapate the heat like a vacuum bulb can. One of the only fears would be if a sudden rush of cold air hits those hot bulbs, then a good explosion could exist. I've seen theatres immediately turn the console power off when closing after the show is over with. I jumped on these personnel hard and tell them that the bulb needs to be cooled down before turing off the console power. I've had power drop off when running 6k bulbs with no effect when the power came back on. -Monte  |  IP: Logged Mike Spaeth Phenomenal Film Handler Posts: 1129 From: Marietta, GA Registered: Jul 2000 posted 02-28-2005 04:50 PM                        Most theatres I've worked at have a relay installed in the console that keeps the exhaust fans running for approx. 10-15 minutes after the power to the console is cut.  |  IP: Logged Robert John Jeromson Master Film Handler Posts: 264 From: Auckland, New Zealand Registered: Jul 2004 posted 02-28-2005 04:56 PM                     Our exhaust fans are all BMS controlled, they start automatically when the power to a machine is switched on in the morning and run for 30 minutes after power shut down, it is company policy to let the lamp houses cool for at least 15 minutes before tuning the power off.  |  IP: Logged Darryl Spicer Film God Posts: 3250 From: Lexington, KY, USA Registered: Dec 2000 posted 02-28-2005 05:43 PM                    quote: John Pytlak I would hope that after any line work, the power company would endeavor to energize all three phases at the same time. I have had the power lose a phase on a cople occasions while working at different theatres. I think both were caused by accidents involving telephone poles. Half the lights would be on in the building we would have to run and shut down anything 3phase and shut down air conditioners before things burnt out on them.  |  IP: Logged Randy Stankey Film God Posts: 6539 From: Erie, Pennsylvania Registered: Jun 99 posted 02-28-2005 09:15 PM                     quote: Jarryd Beard In fact, it seems the more gradual cooldown with no fan might even be better for the bulb. I have to agree with Jarryd on this one. I think a gradual cool down is better for a lamp in the long run. When the lamp is LIT... Yes! Keep the fan(s) ON! I have seen, first hand, what lack off air flow can do to a xenon lamp! There is no doubt in my mind. On the other hand, cool down after the lamp is out should be gradual as possible. In fact, I read a research report from a guy who ran an AV department at a college that said just that. Leave the fan OFF when you shut off the lamp. Basically, thermal expansion and contraction takes its toll faster if the lamp is force cooled. Letting it cool naturally lets the lamps last longer. Caveats: 1) These results were for halogen lamps with filiaments. Allowing lamps to cool slowly allows tungsten to redeposit on the filiament instead of coating the surface of the glass. Xenon lamps, having no filiament, are not subject to this problem. 2) The projectors could NOT be moved during the cooling period. Moving a projector with a hot lamp markedly increases the chance of lamp failure because the hot filiament is being jostled around. In my booth, I split the difference. I shut off the forced cooling fan inside the lamphouse but I leave the roof exhaust turned on. Thus, my theory is that the lamp cools slower than it would under forced air but there is some air to cool the lamp.  |  IP: Logged Mike Babb Master Film Handler Posts: 250 From: Norwich UK Registered: Jul 2002 posted 03-01-2005 05:28 PM                        Randy's post made me think of this (possibly stupid) question. If the lamp power is cut and the fans are cut, does the bulb actually get hotter or does it just cool more gradually from the temp it was at when the power was cut?  |  IP: Logged Jarryd Beard Expert Film Handler Posts: 229 From: Hellertown, PA Registered: Jul 2004 posted 03-01-2005 07:26 PM                     It seems to me, the bulb couldn't get any hotter. I mean, there's no more electricity. Our fans run as soon as power is supplied to the rectifier. We use the actual breakers to power up/shutdown. As soon as the rectifier breakers are hit, the fans are on. The roof exhausts are controlled by separate circuits, of course. I don't see the necessity for the lamphouse fans to be on constantly. It just seems to ensure a constantly noisy booth, even before projectors are running.  |  IP: Logged

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