# Xenon Lamp On/Off Cycle



## Repeater (Nov 4, 2010)

We have a Christie 18K HD projector. The questions often is asked-- is it worth turning it off for 30 minutes, 60 minutes, *enter favorite time period here*? 

I'm primarily interested in the effect on xenon lamp life, not necessarily the cost of electricity, although it is on the radar. So, knowing that each turn-on cycle removes a certain unknown amount of lamp life, where is the "break-even" point?

Thanks!


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## SteveB (Nov 4, 2010)

Good question

The cool down period as recommended by Lycian for their xenon follow spots is 15 minutes lamp off, with fan running, then cut power. 

Thus if i'm not using the machine for 30 minutes and 15 is cool down, I won't shut off. In practice, if it's less then an hr. I leave running. The typical useful life is around 750 hrs. or so, so what's another hour and at least I known the machine is working (since it's usually dinner then a show), so less then 60 minutes I leave on, more then an hr. and I shut off. 

Totally non-scientific.....


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## ruinexplorer (Nov 5, 2010)

Generally speaking, if I am going to be using my projector again the same day, I do not de-arc the lamp. So what is the magic number? No way to say for sure, but even if I have 2-3 hours without use, I will probably still have my projector on. If I know that I won't be using them for four hours, yeah, I'll probably de-arc them. One of the reasons that I keep my projectors arced is to keep the focus/alignment dead on. Every time you shut down your projector and let it cool, the internal mechanical components will also cool which could allow for a slight lens shift. If you are blending or stacking your image, that could be critical. 

So, if you are looking at a hard and fast number, maybe your lamp manufacturer could give you some better data. Otherwise, I think that it comes down to how you use your projector.


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## derekleffew (Nov 5, 2010)

Repeater said:


> We have a Christie 18K HD projector. The questions often is asked-- is it worth turning it off for 30 minutes, 60 minutes, *enter favorite time period here*? ...


A manufacturer of moving lights that use Xenon lamps once told me that a lamp strike takes one hour off the lamp life. Other people have said that with other discharge lamps it could be up to three hours off the lamp life. Thus I will not destrike if not gone for less than one hour (and SteveB has a very good point re: once it's working, keep it working--most problems are at lamp strike). Note with Xenon lamps there's also a minimum burn time of I believe fifteen minutes.

The Christie 18K HD uses a 3kW Xenon lamp, [750 hours (typical) lifetime], and [Power consumption: 3900W at 264 @ 14.8A]. At a national average of 12¢/kWh, that's 47¢ per hour, probably not something to fret over. Lamp costs ~$800, so add another $1 or so per hour. Also add the "relamping charge" as I believe the lamp module must be sent back to Christie to be replaced. Confirm or dispute, ruinexplorer?


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## ruinexplorer (Nov 5, 2010)

Derek, that sounds about right, although I believe the cost of the bare lamp for that unit is closer to $2700. Relamp cost is around $4000, unless you have been trained and have purchased a relamp kit (around $4000) from Christie. Of course your vendor could probably cut you slightly better deals.


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