We have recently experienced some problems with daylight photosensors inside buildings not properly controlling the electric lights within their zones.  Most often, the sensors fail to detect daylight accurately and they therefore leave lights on or fail to dim them adequately.  This is a significant problem because electric lights account for a large share of energy use in a school building.  When we have both daylight and electric light, we are wasting resources.

As we began investigating the issue, we heard a variety of explanations.  Some made sense, others less so.  One very common excuse was that “the sensors are only rated for a certain distance above the floor.  Higher than that, they don’t work.”

This response drives me nuts!!!  I can just imagine the picture inside the mind of the sales rep, electrician, or even electrical engineer.  Itty bitty photons leave the surface of a desk, heading upward.  They valiantly attempt to reach the photosensor 16 feet above the floor, like Thomas the Tank Engine climbing the hill on the island of Sodor.  But the higher they get, the more they fight gravity, saying to themselves “I think I can, I think I can.”  Somehow knowing the photosensor is only rated for 12 feet, they fall back just short of the sensor.  And the lights stay on.

If you want to know what’s wrong with this scenario, look for Part Two early next week.