choosing occupancy sensors

Occupancy sensors are a great first step in making a lighting system more energy efficient, and can be integrated with day-lighting, dimmers and other lighting controls for higher energy savings.

Obviously, savings depend not only on the sensors but also on the efficiency of the lighting fixtures and lamps. With LEDs and CFLs, savings will be much higher (if the lights are on for significant periods).

Reliability

Today’s sensors work more reliably than ever, and you can get effectiveness as long as you choose the right sensor and the right location. Also consider a good manufacturer (See: Occupancy Sensors Basics).

When choosing an occupancy sensor, more than its price, pay attention to their type – passive infrared, ultrasonic and dual technology- and where they are best suited.

Passive infrared (PIR) occupancy sensors

Passive Infrared Sensors work by detecting body temperatures, and have their best performance within no more than 15-foot field of view. They also require a clear line of sight to operate.

They are best suited and mostly used in small-enclosed spaces.

Ultrasonic sensors

Ultrasonic sensors use high-frequency sound to detect motion.

They can be a good solution in large spaces, even if they involve obstructions (walls and other objects). They aren’t such a good solution in spaces involving HVAC systems or other sources of vibration. In these cases, they are prone to false triggering.

Combined dual-technology

Dual technology sensors (Ultrasonic-Passive Infrared combined sensors) are pricier, but are the most reliable occupancy sensors in the market. Since they combine Passive Infrared and Ultrasonic technologies they are less prone to false triggering, and are excellent for larger rooms.

Location

Location is also crucial for a reliable performance. In smaller spaces, occupancy sensors are typically located in walls; in larger areas they are installed on ceilings.