Specifier Reports: Photosensors (March 1998)

A photosensor is an electronic control device that adjusts the light output of a lighting system based on detected illuminance. While some photosensors simply switch lights on and off, Specifier Reports: Photosensors focuses on photosensors that are used with dimming electronic ballasts to adjust the light output of fluorescent lighting systems over a continuous range. These photosensors are most commonly used in daylight applications to dim electric lighting when total illuminance exceeds a preset level. Photosensors have seen limited application for three principal reasons. First, the actual energy savings that photosensors can achieve is difficult to predict, making it hard to justify the purchase of a photosensor control for a lighting system. Second, although properly located, installed, or positioned photosensors may reduce energy expenses, they may also be a source of occupant complaints. Third, anecdotal reports of difficulties in properly installing and adjusting photosensors may have limited many specifiers’ willingness to use them.