Warming up Source Fours and Fresnels
- Thread starterJLNorthGA
- Start date
It's mostly a waste of time and electricity. There's some marginal value in preheating long filament lamps in order to achieve consistent fades at low levels, but it's not strictly necessary. There could also be some value for roasting any critters that have taken up residence, depending on what is meant by "a while".
farmerjo1111
Member
Personally I feel like it is a waist of time and electricity, if anything it will shorten lamp life.
JLNorthGA
Active Member
Given the lack of heat in our building (and the fact that it is a concrete box) - I think I will go for preheating.
Dionysus
Well-Known Member
Personally, if you look at heat transfer rates and other such things based on what I've heard "some" people call pre-heating (that is running all fixtures at some level before the preshow) is essentially no gain at all, just burning lamps and energy.... However Putting a fixture at an extremely low level right before use will give an improvement in low end response. Also it is good for a long filament if you are about to snap it on to full aggressively (often when I see older lamps blow most easily).
Other than that you are just paying to heat your building inefficiently.
Other than that you are just paying to heat your building inefficiently.
And cools down to almost stone cold within a few minutes. We know this because of lamp temp measurements and inrush current evaluations done as part of product development.
David
BillConnerFASTC
Well-Known Member
Many pre-S4 units made a lot of noise in expanding and contracting as they change temperature. A lot of noise. Pre-heating seemed to lessen the noise.
techieman33
Well-Known Member
If you really want better lamp life setting the max at 95% would ~ double the lamp life, and that is actually scientifically proven.
BillConnerFASTC
Well-Known Member
That would be 95% of the rated lamp voltage compared to actual voltage at the socket. Many things affect the actual voltage at the socket. Also 95% voltage is 86% intensity and the color temperature drops about 1500 degrees. To calculate try http://www.ushio.com/support/LampLifecalculator.php
RickR
Well-Known Member
Yup, so if it's off for a scene or a couple songs preheating is pretty pointless.
JLNorthGA
Active Member
Some background - our building is a concrete box. In the winter the heat is set to a toasty 60 degrees F in the auditorium - which typically means it is colder in the fly space above the stage as there are no registers for HVAC there. We used to have bats hibernate up in our fly space until we had the roof redone.
techieman33
Well-Known Member
I wish my fly space and catwalks were cool in the winter. In my building it's 85*+ up there all winter long.
Interestingly, I find that the Ushio lamps are noticeably bluer then the Osram HPLs. I'm not positive if one was the long life version or something like that, but a little dimming brings the temp back down, and tends to look fine to my eye.
BillConnerFASTC
Well-Known Member
You have to look at voltage at the socket under load to really know what's going on. 20 years ago, with 120 volt lamps standard, dimmers that dropped the voltage 3% or so, and long branch circuits with two 1k lamps, I always had the electrical engineer tap up the transformer so voltage into the rack was 125 to 128 volts and use #6 or #8 wire to get near 120 at the socket. I've measured other installs without such design in the 100 to 110 range and the #12 felt warm. Just saying there is a lot to this. I wonder how many installs with tapped up feeds have been replaced by an unknowing user with Sensors and 115 volt lamps and feel they are kind of short lived (but raves about how bright they are!)
I'm willing to bet...not that many, since every Sensor rack requires factory-authorized commissioning. And incoming line voltage is displayed right on the CEM, provided one knows where to look. @DavidNorth , @STEVETERRY , et al; Is measuring socket voltage part of the turn-on of a Sensor rack?
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Re-check your math. coltemp/COLTEMP = (volts/VOLTS)^0.42
BillConnerFASTC
Well-Known Member
Back to preheating.
Bill made a good point about the thermal expansion/contraction noise of some fixture housings - good reason for warming up a fixture before house opens: the fixture housing has enough thermal mass to stay pretty warm while off for a scene or two.
The theory is that warming the filament before use can improve response and may extend lamp life; however, keeping the filament warm over an extended period wastes energy and potentiallly shortens lamp life. I wonder if anyone has thought of putting control of preheating into the console insteand of the dimmers - it might be useful if the cue before an conventional is used could automatically preheat the instrument.
Bill made a good point about the thermal expansion/contraction noise of some fixture housings - good reason for warming up a fixture before house opens: the fixture housing has enough thermal mass to stay pretty warm while off for a scene or two.
The theory is that warming the filament before use can improve response and may extend lamp life; however, keeping the filament warm over an extended period wastes energy and potentiallly shortens lamp life. I wonder if anyone has thought of putting control of preheating into the console insteand of the dimmers - it might be useful if the cue before an conventional is used could automatically preheat the instrument.
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