054 MUSEUM LIGHTING / NATIONAL GALLERY & NATIONAL PORTRAIT GALLERY, LONDON, UK
is less heat. I’ve actually downsized our chillers because the electric load has gone down so much. SV: LEDs are also great for our budget be- cause we don’t have to lamp change. AT: Oh yes, if we had LED fittings over two floors, which is my aim, I could reduce our maintenance levels enormously because we’re not employing the maintenance con- tractor to do so much. SS: Don’t you currently change all your tungsten lamps every time you have a new exhibition? DC: In a special exhibition you don’t want any lamps blowing so you just change them all every time. SS: That’s a massive wastage! SV: You’re talking 2-3,000 hours for tung- sten to 50,000 hours for LED so it makes a massive difference to our exhibitions. NS: And the 50,000 hours represents the time when it gets down to 70% of output and as the degradation is slow you won’t even notice. AT: Won’t the problem be that within that, say, twelve-year period, ERCO will be developing new, brighter versions and we’re going to be buying them to supplement the
Mark 1 versions we already have? SS: Even if LEDs do become even more powerful, the development and design of the luminaires will still be geared towards the user requirements. Future luminaires will probably have the same lumen output but from less power, so it could advance from 12W to 10W, say. So it shouldn’t affect you too much. SV: One other thing is the lack of UV in LED, so there is no need for filters. We worked out we got a 50% reduction in light output through the UV filters and lenses of the tungsten lamp. SS: The thermal tests that the NPG has done are staggering... AT: Yes, we used a thermal camera and found that the heat output from the halogen fittings was between 300 – 350°C, whereas it was 30°C from the LED ones. In other words, ten times less heat. SV: That’s when I can factor in the reduc- tion of our air-conditioning load. PJ: So you are confident that LED lighting is here to stay for museums? DC: I ask our scientists all the time if there is any possibility that we are going to rue the day that we used LEDs in twenty years from now. They think that, looking at the data overall, we’re not dealing with some- thing we’re going to regret in the future. The spike in the blue has the conservation- ist scientists concerned about what it’s going to do to fugitive blues over a long period of time. But we assume you’re going to even that out eventually. NS: The LED starts in the blue spectrum and you put phosphor coatings over it. So
the LEDs with the better colour rendering will have a lot more coatings on it, thus kill- ing the light levels. SS: This also means you can’t direct the beam so well. ERCO, of course, specialises in different types of light distribution, but if you add too many coatings you’re just going to get a splodge of light. You can’t do anything clever with it like pick out detail in sculpture. When we’ve slightly reduced the blue to the red side and the colour render- ing will be slightly higher, we think that’s going to end the argument. DC: Another advantage is the size of the fitting and the reduction of visual clutter in the ceiling, especially in the small gallery rooms. SS: The new Logotec LED range has an even slimmer profile because we design our own electronic circuit boards and control gear that don’t require a separate housing. NS: The Logotec LED is the first product developed by ERCO purely around the LED, whereas the Optec, prior to its LED adop- tion, was based on conventional technology. So where you’ve got trailing edge dimming on track you can set the Logotec LED spot- lights to 60% for instance. In the past you could not dim it externally, but now, with the new electronics, you can set an upper limit to each individual spotlight and then dim the whole system. DC: I like the sound of these! I think we should look at those next...
www.erco.com This article was first published in ERCO’s in-house magazine Lichtbericht issue 92 in April 2011 with the help of the editor.
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