Last Update: November 7, 2010
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Electric Lighting Controls

The terms daylighting and daylight harvesting refer to using electric lighting controls that automatically adjust electric lighting output through switching and/or dimming based on available daylight, determined through time of day or photosensor measurements and aimed at minimizing electric lighting without dropping below design light levels.

Electric lighting controls based on available daylight are implemented by controlling individual or grouped lamps or luminaires. Grouping of luminaires for switching or dimming follows the daylight distribution patterns, i.e., grouping luminaires over areas of equal daylight levels.

Switching & Dimming
Switching refers to adjusting electric lighting levels in discrete steps, while dimming refers to continuous adjustment of electric lighting intensity. Dimming can be continuous or through ten or more incremental steps.
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Determining Available Daylight
The key to successful control of electric lighting for daylight harvesting is determining how much daylight is available in the space, which is usually based on time of day or use of photosensors.
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Control Algorithm
Implemented by the Logic Controller, control algorithms are most important for the success of photosensor-based electric lighting controls. Control algorithms are functions that take as input the signal of the control photosensor and use it to compute the signal to the electric lighting power controllers, such as ballasts, which in turn adjust the electric lighting output based on their specific operation.
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Photosensor Controls Commissioning
The performance of photosensor-based controls depends on the context of their application, especially the geometry and reflectance properties of interior surfaces, i.e., walls, floor, ceiling, and furniture.
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