Where dimming luminaires are installed, a truly intelligent system becomes possible. Daylight harvesting programming will dim up / or dim down continuously over the dimmable ballast’s range, allowing whatever light output is necessary to augment the available daylight to keep the lux levels within a predetermined range. Light harvesting when programmed well with dimming luminaires, should pass almost unnoticed by those using the space.
Low Level Lighting or Switched Off?
Traditionally when daylight harvesting was programmed, fluorescent lights were not switched completely off, even when natural light available exceeded required parameters. This was due to difficulties in switching the lighting back on at low light levels. With the emergence of solid-state lighting (SSL) most such lighting challenges have been resolved and continuous dimming control has become the expectation for today’s workplaces.
Despite this, building occupants who have not been educated around daylight harvesting controls can get confused when electric lights turn off automatically. Either a malfunction is reported to the facility manager, or the system is overridden with the lights turned back on manually, eliminating the energy savings. In this situation is is sometimes best to program the system to dim-to-low rather than to switch-to-off, to avoid confusion and potential negation of lighting savings.
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