To douse or not to douse? That is the question.

[DMXMatt]

Hi there.

After years of religeously dousing my moving light fixtures after use ( usually for 10 mins before powering the fixtures off ), I have been advised by a reputable veteren in this industry that 1) It is not necessary, and 2) that cooling the lamps themselves quickly after use is not as kind as letting them cool down gradually.

His rationale is that once a lamp is powered off the fixture is not going to get any hotter and that any components should at least be able to deal with that much residual convective and conductive heat. Furthermore a slow cooldown will benefit not only the globe but most of the other electrical components within the fixture.

Although I'm sure that many would baulk at this advice ( or even be horrified ) I do believe that there could be some merit to his suggestion. Most moving light manufacturers seem to stress that cooling fixtures after use by dousing the lamp is important for the longevity of their fixtures, but is this really a tool that is used occasionally against some warranty claims. Or does it pehaps just stem from some subconcious fear that heat is the ultimate enemy with lights and that any opportunity to remove heat from the equasion = a good thing.

 

[SteveB]

I just yesterday figured out how to get my MAC700's to correctly lamp off. My Ion profile had them power off then re-strike after 6 seconds. Now it's 15 minutes.

I use the lamp off function. My reasoning is if you simply kill power, you lose the fans. The fixture is still hot inside and with no fans you are relying on convection cooling to get rid of the heat. Yes, the heat will dissipate, but in a fan cooled unit, it will take longer as it's not designed to cool naturally using convection, that's why they put fans in it. So with no fans running, all that residual lamp heat is cooking all the electronics, belts and motors inside (I'm not even sure a MAC700 has belts,, but you get the idea) and I can't think that's good for the fixture. There's a lamp off function for a reason, where as my on Studio Spots, which are convection cooled, I simply kill power.

 

[jxgriffi]

For one venue...I just pull the power. I don't worry about the cool down. *****see note below.
For the other venue, I definitely do the lamp off, wait 10 minutes (usually this is when I have people do a final backup of the day!) and then shut down power.

Been doing it for 20 years this way...


*****NOTE: The first venue is all VL1000's and Studio Spots and Colors. As these fixtures are all convection cooled anyway, leaving power on will do nothing as there are no fans to run.

 

[JD]

While it is true that the lamp win not get any hotter and a slow cool-down is better for the lamp, this is offset because the electronics areas will get quite a bit hotter as the heat moves through the fixture.

Most movers have the lion's share of their electronics in the base, and only the motors and a few sensors in the head. Problem is, it only takes a bad sensor or motor to stop the light.

Don't know if anybody really did a study on this. I simply drop power on the ones I have, but they are fairly low wattage units.

If you are doing a load-out that will cause the fixtures to be handled soon after shutdown and they are above 575 watts, a cool-down is probably better. (Some lamps don't like to be bounced around when they are very hot.)

 

[SteveB]

From the Martin website forum:

"For longer periods when fixtures will not be in use, it is both safe and normal to cut mains power to the
fixture in order to reduce power consumption. When you do this, first cut power to the lamp from your
control desk but leave power applied to the fixture so that the thermostatically regulated cooling systems
can continue to stabilize temperatures. After 5 minutes you can then cut power to the fixture completely. "

 

[derekleffew]

http://www.controlbooth.com/forums/lighting-electrics/10119-moving-light-lamp-cool-down.html
http://www.controlbooth.com/forums/lighting-electrics/22377-lycian-spotlight-cool-down-time.html
http://www.controlbooth.com/forums/lighting-electrics/7785-strong-super-trouper.html

One of the (valid, I feel) points made by a member in one of the threads above is that: if one simply cuts power to a lit, unbalanced fixture (e.g., MAC 2000 Wash) the unit will slam lens upward into a tilt stop, causing undesirable mechanical shock which may reduce lamp life. Slamming a cool lamp is not as bad. One could set tilt at 00 or FL before removing power, but who's going to remember to do that on which type of each fixture? In the olden days, some fixtures required that a "pack-up macro" be run which closed some things and opened others, retracted lenses, etc., before a fixture was put in its case. One rarely sees that these days.

I believe it was ship who has mentioned that the fixture manufacturer and lamp manufacturer might have conflicting interests. The lamp may prefer to cool slowly and naturally, whereas the fixture wants to exhaust heat as soon as possible; or the other way around. It's an on-going discussion, and a conundrum that may never be solved, much like the controversial "pre-heating conventionals" issue.

Another conundrum: if you (as the programmer) are leaving for an hour say during lunch, should you a)de-strike lamps, b)leave them lit at 50/50 in OW, c)leave them lit @ wherever, d)lit with douser closed ?

All good fodder for discussion.

 

[mstaylor]

If I am packing them then they certainly need to fan cool. If they are staying then maybe, maybe not, depends on how close to last call we are.

 

[SteveB]

http://www.controlbooth.com/forums/lighting-electrics/10119-moving-light-lamp-cool-down.html
http://www.controlbooth.com/forums/lighting-electrics/22377-lycian-spotlight-cool-down-time.html
http://www.controlbooth.com/forums/lighting-electrics/7785-strong-super-trouper.html


I believe it was ship who has mentioned that the fixture manufacturer and lamp manufacturer might have conflicting interests. The lamp may prefer to cool slowly and naturally, whereas the fixture wants to exhaust heat as soon as possible; or the other way around. It's an on-going discussion, and a conundrum that may never be solved, much like the controversial "pre-heating conventionals" issue.

All good fodder for discussion.

On that note, a 700 watt lamp for a MAC700 is around $130. How much to fix overheated components or replace a motor ?. Seems the lamp is the cheaper item to replace as well as being user replaceable. I'll power off the lamps and save the fixture.

 

[Beans45601]

http://www.controlbooth.com/forums/lighting-electrics/10119-moving-light-lamp-cool-down.htmlAnother conundrum: if you (as the programmer) are leaving for an hour say during lunch, should you a)de-strike lamps, b)leave them lit at 50/50 in OW, c)leave them lit @ wherever, d)lit with douser closed ?
All good fodder for discussion.

Isn't this already an issue with a pretty known answer? If we assume that you are taking 3 hours off the life of a lamp during every strike, then the answer is yes, leave the lamp struck for that hour. In what position and pointed at what, is still to be said. If I had movers (which I don't), I would leave them open pointed in whatever orientation the instrument wanted to go naturally, generally straight down I would imagine (this putting the least strain on the motors). If the unit was shining on my grandmothers 200+ year old oriental rug, then I would certainly point it somewhere else.

After a hour, I would say the conversation gets a little more complicated. Towards 2 hours, it might start to make sense to turn the fixture off. Someone should make a graph charting cost of lamps vs. cost of power to run that lamp vs. mercury (and other awful stuff) put off by your local power plant to power the lamp vs. amount of mercury and other nasty stuff in your lamp. Oh and don't forget to factor in the season. Leaving the lamp struck in the winter means free heat! In the summer, more heat to cool.

Now that would be interesting.

 

[tdrga]

Another conundrum: if you (as the programmer) are leaving for an hour say during lunch, should you a)de-strike lamps, b)leave them lit at 50/50 in OW, c)leave them lit @ wherever, d)lit with douser closed ?

Another factor to take into consideration is that some fixtures will automatically "throttle-down" the power to the lamp if the shutter/dim flags are closed. So if you leave them lamped on with intensity at full during a break, you are defeating this power saving feature.

In general, the shows that come through will leave lamps on at 50/50 in OW for meal breaks and between shows on a two-show day. This seems to be almost 100% the case with rigs of VL's- sometimes shows with other brands of fixtures will leave lamps struck but shutter closed.

Personally, I will leave lamps struck and shutter closed (my fixtures do "throttle-down" the lamp power) for meals but if nothing is happening for more than 2 hours, I'll lamp off.

-Todd

 

[Grog12]

Another factor to take into consideration is that some fixtures will automatically "throttle-down" the power to the lamp if the shutter/dim flags are closed. So if you leave them lamped on with intensity at full during a break, you are defeating this power saving feature.

In general, the shows that come through will leave lamps on at 50/50 in OW for meal breaks and between shows on a two-show day. This seems to be almost 100% the case with rigs of VL's- sometimes shows with other brands of fixtures will leave lamps struck but shutter closed.

Personally, I will leave lamps struck and shutter closed (my fixtures do "throttle-down" the lamp power) for meals but if nothing is happening for more than 2 hours, I'll lamp off.

-Todd

Throttleing down the lamp power is still a struck lamp and a struck lamp still generates heat. This practice comes from the thought that eventually enough heat will cause issues with dowsers/shutters/irises and other parts of the mover.

I don't know how far back the "throttle-down" is but IMHO I'd rather leave it open and white.

 

[porkchop]

First to the OP. One part of your original post was that manufactures might try to void your warranty if you don't follow proper lamp off instructions. I can assure you that most manufactures don't ask or care. I've sent hundreds of packages in for warranty. Pretty much everything in the light other than the covers and the lamp itself. I've never been asked about lamp off practices. Furthermore sometimes in testing it's beneficial to cut power to a stuck light, if you do it at the right time it makes the lamp least likely to restrike. I've been know to do this to lamps to test that the fixtures strike function is working very reliably and is worth sending up into the rig.

Now on to the hijacked topic of short breaks. If you're using Clay Paky 1200 Washes and you leave them struck you had better leave them in OW. The lights do cut power to about 600W, but it's still enough power to melt the dimmer blades in unfortunately short order. Also just cause you're leaving the space doesn't mean that it's empty. Our performers spend a lot of time rehearsing under the rig when it's in 50/50 OW. It's way easier than tracking down someone for houselight control, and the fixtures are struck anyway.

 

[soundman]

One of the (valid, I feel) points made by a member in one of the threads above is that: if one simply cuts power to a lit, unbalanced fixture (e.g., MAC 2000 Wash) the unit will slam lens upward into a tilt stop, causing undesirable mechanical shock which may reduce lamp life. Slamming a cool lamp is not as bad. One could set tilt at 00 or FL before removing power, but who's going to remember to do that on which type of each fixture? In the olden days, some fixtures required that a "pack-up macro" be run which closed some things and opened others, retracted lenses, etc., before a fixture was put in its case. One rarely sees that these days.

On my last tour we had a bunch of PRG's BAT truss out with us and we had the LD write a pack up macro. It put the lights in the best position to go into the carts and dowsed the lamps. The VLs would drift from the 'tucked in' position during load out but the Bad Boys were pretty rigid. In thanks I'm sure to their servo motors. Not a hard thing to write for a long tour and it saved us time on the out. I am pretty sure the dimmer techs killed power to the lights soon after they were dowsed. I know the floor lights were not given a chance to cool.

 

[rochem]

Another conundrum: if you (as the programmer) are leaving for an hour say during lunch, should you a)de-strike lamps, b)leave them lit at 50/50 in OW, c)leave them lit @ wherever, d)lit with douser closed ?

One of the first things I do when I sit down at the console for the first time is make a "ML Works" preset and exclusive sub. I start off with everything at 50/50 and open, focus the FOH units at the ceiling to bounce some light around, then move some lights around to highlight potentially dangerous spots. At one theatre I worked at, the creative team got sick of walking the "normal" route between the house and the stage, so they would just precariously walk the small strip of deck between the edge of the pit and the wall every time they wanted to give notes. Since the MLs had to be on anyway, it made sense to focus one or two on this area so we didn't have directors falling into the pit. Although I've also been known to make pretty color-changing slowly-rotating patterns on the ceiling to keep bored ALDs entertained.

 

[tdrga]

Throttleing down the lamp power is still a struck lamp and a struck lamp still generates heat. This practice comes from the thought that eventually enough heat will cause issues with dowsers/shutters/irises and other parts of the mover.

I don't know how far back the "throttle-down" is but IMHO I'd rather leave it open and white.

Well, now I'm interested to see what the actual head temperature difference is between a struck lamp that is throttled-down and one at full power in OW.

Maybe I'll have a chance to test soon and see what the real-world difference is.

-Todd