Article
Sensor-based lighting control is becoming a must in many commercial and institutional settings. The drivers for this trend include ever-tightening energy standards and increasing scrutiny of energy bills by building owners and managers. How successful those sensors are in actually cutting lighting costs, however, depends on lighting designers and electrical contractors who understand the basics of how sensors work, and which models are best for each application.

Shedding Some Daylight on Occupancy and Vacancy Sensors

Chuck Ross
Sensor-based lighting control is becoming a must in many commercial and institutional settings. The drivers for this trend include ever-tightening energy standards and increasing scrutiny of energy bills by building owners and managers. How successful those sensors are in actually cutting lighting costs, however, depends on lighting designers and electrical contractors who understand the basics of how sensors work, and which models are best for each application.

For example, the phrase “occupancy sensor” is used frequently to describe the kind of device that shuts lighting off when it’s not needed. However, in many applications a “vacancy” sensor might be a more appropriate choice. This isn’t just a question of semantics – these two sensor types actually perform different functions that could either help or hinder energy-savings goals depending on where they’re used.

  • Occupancy sensors (also called “automatic on”) turn lighting systems on as soon as a building occupant enters a room or other controlled space. This is very convenient in spaces like supply closets or interior restrooms, which are otherwise very dark. The automatic-on function saves us from having to fumble for a light switch, while still ensuring the lights turn back off once we leave that space.

  • Vacancy sensors (also called “automatic off”) are paired with manual light switches. They are a better choice for spaces with access to natural daylight. Because the lights need to be switched on, it’s assumed occupants will only turn the lights on when they’re needed. Similar to occupancy sensors, these devices will turn the lights back off once they sense the space is vacant again.
Hopefully, with these descriptions you can see why using an occupancy sensor in a space with adequate natural light could work against any energy-saving goals your client might have in mind. Many occupants would just leave the lights on, instead of walking across to the switch to turn them off. With a vacancy sensor, instead, the lights likely would stay off most of the time the space was occupied.
Photo courtesy of Hubbell Lighting
Calpipe Conduit Fittings
advertisement
Why Calbrite?
advertisement