WattStopper WT-1100 Ultrasonic Ceiling Occupancy Sensor, 24VDC, 1100 sq ft

The WT-1100 is rated at 1100 square feet of coverage. It's part of a WattStopper ultrasonic ceiling family whose coverage spans 600 to 2200 square feet, plus a 90 linear foot pattern for corridors. If you're covering an open office or classroom larger than 1100 square feet, step up within that range rather than trying to stretch one head; for a hallway run, the linear-pattern option is the right choice instead of an area sensor.

It's a 24VDC low voltage sensor, so it does not switch line voltage on its own. You'll need a compatible low voltage power pack or a 24VDC lighting control panel to supply the sensor and do the actual switching of the load. Budget for that in the takeoff; the sensor head alone will not turn on a 120V or 277V circuit.

Ultrasonic, which is what the WT-1100 uses, senses motion by reflected sound waves and doesn't need line of sight, so it picks up minor motion and works around partitions, stall dividers and furniture. That makes it the usual pick for restrooms, open offices with cubicles, and rooms with obstructions. Passive infrared needs to see the occupant and is better where air movement or vibration would cause nuisance activations, such as near a supply diffuser or a loading area. The WT-1100 uses omni-directional ultrasonic detection, so it covers in all directions from the ceiling mount point rather than a single throw pattern.

Yes. Time delay and sensitivity are both set with DIP switches on the sensor, so a facilities tech can retune it on site without swapping hardware. If occupants are getting dropped while seated at a desk, raise sensitivity or lengthen the delay; if lights are holding on too long after a restroom empties, shorten the delay.

The WT-1100 includes an isolated relay in addition to its lighting control output. That contact can be tied to HVAC, an energy management system, or a second lighting load, so one sensor can drop a room's setback and its lights off the same occupancy signal. Useful in classrooms and conference rooms where you're chasing both lighting and mechanical energy savings from a single device.

The WT-1100 carries WattStopper ASP circuitry, which is there specifically to eliminate false on events. That matters with ultrasonic technology, since it responds to air movement and to motion outside the room's doorway. Still mount it away from the direct throw of a supply diffuser and out of line with an open door where corridor traffic passes, and use the DIP switch sensitivity setting to trim it once the space is in use.

There's an LED on the sensor that indicates occupancy detection. Walk the room at the far edges of the intended coverage and watch the LED to confirm the pattern reaches the seats and workstations before you finalize the sensitivity DIP switch setting. It's the fastest way to prove coverage on a walk test without metering the load.

Order by the manufacturer part number WT-1100. That is the WattStopper ultrasonic ceiling head rated for 1100 square feet at 24VDC. If your other rooms use a different coverage size, the model number will differ even though the mounting and 24VDC wiring approach are the same across the ultrasonic ceiling line, which runs from 600 up to 2200 square feet.

Country of origin on the WT-1100 ultrasonic ceiling sensor is China. Worth noting if you're bidding a project with domestic sourcing requirements on the material submittal.