jona1984 Posted March 17, 2012 Share Posted March 17, 2012 I'm not strictly a lampie so forgive me if this is like 'Lighting 101' stuff but - I'm wondering if we should be manually 'lamping off' our moving head fixtures before cutting the power to allow them time to cool down under their internal fans (like you might do with a projector etc...) or whether just turning the rig off at the mains breakers is perfectly acceptable? Will I be killing the lamp life significantly by not doing this? Link to comment Share on other sites More sharing options...
Young Johnstone Posted March 17, 2012 Share Posted March 17, 2012 Realistically, try to lamp off and let them cool before you cut the power! it's not always possible though! It may cause some damage to the inside of your fixtures if you just kill them!! Link to comment Share on other sites More sharing options...
JDLX Posted March 17, 2012 Share Posted March 17, 2012 Yes ideally try to lamp off first. Although I don't tend to bother if its 250W fixtures that have been on for an hour. I guess it depends on what units you are using and how long they have been lamped on. Link to comment Share on other sites More sharing options...
Ynot Posted March 17, 2012 Share Posted March 17, 2012 In simple terms, follow the manugfactirers' guidelines - if they say lamp off, then lamp off. As with projector lamps, yes it IS to allow cooling before cutting the power and failure to do this on a regular basis WILL reduce the eventual life of the lamps. Even on MSD 250 etc. SOME fixtures are OK for powering down without lamp-off, and are also good for restriking whilst hot, but I'd check the manual before you assume anything. Link to comment Share on other sites More sharing options...
greenalien Posted March 18, 2012 Share Posted March 18, 2012 Lamping-off isn't just good for the lamps - the fans will stay on for a few minutes and help to dispel residual heat from the fixture - this is particularly important with more modern plastic-based enclosures, that will eventually become brittle from heat damage - the longer you can postpone this, the better. Link to comment Share on other sites More sharing options...
gyro_gearloose Posted March 18, 2012 Share Posted March 18, 2012 I'm not certain whether running the fans after lamping off is done to preserve the lamp or to save the rest of the fixture from heat damage. If you simply switch a fixture off without lamping off and using the fans to cool everything down, then the heat thats still being given off by the lamp won't be pushed out by the fans and may eventually damage other parts of the fixture. I don't see how switching off a lamp will damage the lamp itself, after all once you stop putting energy into it it cannot get any hotter than its operating temperature. Link to comment Share on other sites More sharing options...
Ashley R Posted March 18, 2012 Share Posted March 18, 2012 Cant it get hotter than its operating temperature? As the fans would be keeping that operation temperature down, would they not? And in those few seconds after you have switched off the fixture, and the fans are no longer going, wouldn't the lamp temperature then increase? Link to comment Share on other sites More sharing options...
ramdram Posted March 18, 2012 Share Posted March 18, 2012 But where would the energy come from? The lamps run at a hotter temperature anyway...the fans reduce the internal heat build up around the rest of the fitting, more to stop the components cooking off or perhaps preventing any lube becoming liquid and draining away, or, as mentioned above prevent premature ageing and incipient brittleness if a plastic housing. The lamps themselves are still at whatever the burning temperature is anyway for them to function properly. The wire elements are designed to burn white hot and the glass used has to have become hotter when being blown into shape, shirley? We have read of some lamps becoming deformed in use but that is rather the exception and might be down to a poorly designed lamphouse, orientation of the lamp itself and ventilation thereof. Link to comment Share on other sites More sharing options...
greenalien Posted March 18, 2012 Share Posted March 18, 2012 At its running temperature, the lamp glass is almost hot enough to melt, or certainly to be close to softening. The fan stops this temperature from rising excessively, but if the power is cut suddenly, there is still a lot of heat to disperse but the fan isn't removing that heat - it takes time, a second or two, for the heat to travel from the arc or filament to the outside of the lamp, so the capsule could potentially get briefly hotter as the power is cut. Clearly this will vary from fixture to fixture as some are much more reliant on effective fan cooling than others. Link to comment Share on other sites More sharing options...
Jivemaster Posted March 18, 2012 Share Posted March 18, 2012 The lamp capsule runs at 250+C the fans and cooling guides remove a lot of that heat before it damages the plastics and semicoductors. On power off the heat from the lamp (and holder and reflector) has to go somewhere and inside is the major place so things can cook (Chips cables and sensors and plastic pieces) On Lamp off the fan keeps blowing the heat out of the unit til it's a safer place for the components to have a more normal life. Link to comment Share on other sites More sharing options...
jona1984 Posted March 18, 2012 Author Share Posted March 18, 2012 That's great folks - many thanks - seems like a unanimous "ya doin it wrong!" :) I will definitely start to allow the fixtures time to cool down from now on. Link to comment Share on other sites More sharing options...
Jivemaster Posted March 18, 2012 Share Posted March 18, 2012 In a typical (UK) temperature range lamps will go off to save power costs, a lamp strike usually needs a cool lamp so a break of say twenty minutes would be left lamp on but a longer break (say between mattinee and evening show) may be lamped off. There is also an estimate of the lamp life used for each strike as a guess a lamp strike uses some life so short breaks would be lamp on but again long breaks would be lamped off. There was a post here long ago about a gig in Arctic Scandinavia where things were done differently to avoid condensation settling on cold luminaiers causing then to fail to come on later - but that's an oddity for well sub zero jobs. Link to comment Share on other sites More sharing options...
Recommended Posts
Archived
This topic is now archived and is closed to further replies.