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When the total daylight area under skylights plus the total daylight area under rooftop monitors in an enclosed space exceeds 900 ft2, the lamps for general lighting in the daylight area shall be separately controlled by at least one multilevel photocontrol (including continuous dimming devices) having the following characteristics:
  1. the light sensor for the photocontrol shall be remote from where calibration adjustments are made,
  2. the calibration adjustments shall be readily accessible, and
  3. the multilevel photocontrol shall reduce electric lighting in response to available daylight with at least one control step that is between 50% and 70% of design lighting power and another control step that is no greater than 35% of design power.
  1. Daylighted areas under skylights where it is documented that existing adjacent structures or natural objects block direct beam sunlight for more than 1500 daytime hours per year between 8 a.m. and 4 p.m.
  2. Daylighted areas where the skylight effective aperture (EA) is less than 0.006 (0.6%).
  3. Buildings in climate zone 8 with daylight areas totaling less than 1,500 ft2 in an enclosed space.