What is an occupancy sensor with dimmer?
An occupancy sensor detects whether a space is occupied and sends a control signal to lighting or HVAC systems. A dimmer adjusts light level rather than switching lights fully on or off. Combined units both sense presence and change light output, enabling vacancy/occupancy modes, daylight harvesting, and smooth ramping.
- Occupancy sensor: detection methods include passive infrared (PIR), ultrasonic, microwave, thermal, and dual-technology blends.
- Dimmer: types include leading-edge (triac), trailing-edge (ELV), 0–10 V, and digital protocols like DALI.
- Combined unit: built-in dimmer and sensor enable integrated control strategies and simpler installations.
Why choose an integrated sensor-dimmer?
Integrated sensor-dimmer units combine presence detection and light-level control in a single device to deliver energy savings and a better occupant experience.
- Energy savings: dimming during partial occupancy or when daylight is present reduces consumption and peak demand.
- Simpler wiring and installation: fewer devices and reduced wiring complexity.
- Improved user experience: seamless dimming avoids abrupt on/off cycles and preserves preferred light levels.
- Privacy-friendly sensing: thermal, camera-free sensors provide anonymous occupancy detection for sensitive spaces.
Key selection criteria
1. Detection technology and reliability
Different technologies suit different spaces; choose one that balances detection accuracy and false-trigger resistance.
- PIR (Passive Infrared): Good for open areas with direct line-of-sight; reacts to heat movement and has low false-positives from ventilation.
- Ultrasonic: Detects motion via sound reflections; effective around obstacles but can be over-sensitive.
- Microwave: High sensitivity and range; can penetrate thin partitions and may false-trigger through walls.
- Dual-technology: Combines PIR plus ultrasonic or other pairs to reduce false positives and negatives.
- Thermal / camera-free: Uses heat signatures to detect occupancy while preserving anonymity; ideal for privacy-sensitive environments.
2. Dimming compatibility with lighting loads
Not all dimmers work with every light type; verify compatibility and dimming quality.
- LED and CFL require dimmers designed for electronic loads; look for LED-compatible listings and supported lamp models.
- Dimming method matters: 0–10 V and DALI provide reliable control for LED drivers; triac/ELV can work for retrofits but risk flicker if mismatched.
- Check minimum and maximum load ratings to ensure proper operation.
- Assess quality of dimming: smooth graded dimming without flicker, color shift, or strobing.
3. Control protocol and integration
Decide between standalone and networked operation and confirm protocol support.
- Standalone vs networked: networked sensors enable centralized control, analytics, and BMS integration.
- Common protocols: BACnet, Modbus, LonWorks, 0–10 V, DALI, Zigbee, Bluetooth Mesh, BLE.
- If analytics or real-time occupancy metrics are desired, select devices that export anonymous occupancy data and integrate with analytics tools.
4. Daylight harvesting and light sensors
Daylight harvesting reduces electric lighting when ambient light is sufficient.
- Look for integrated ambient light sensors (ALS) or compatibility with external ALS.
- Choose devices that support calibrated lux thresholds and adaptive algorithms to avoid oscillation.
- Ensure ALS coverage aligns with areas affected by daylight (perimeter zones, atria).
5. Installation considerations
Physical and electrical installation affects performance and cost.
- Mounting height and field of view: ceiling-mounted sensors offer wide coverage; wall-mounted sensors may suit irregular rooms.
- Wiring and power: determine if devices are line-voltage, low-voltage, or battery-backed; verify neutral wiring for line-voltage dimmers.
- Retrofit vs new construction: retrofits need compact devices and fixture compatibility; new construction allows more wiring and network options.
6. Configuration, commissioning, and user controls
Ease of setup and commissioning tools matter for long-term performance.
- Commissioning tools: smartphone apps, web interfaces, or push-button programming for timeout, sensitivity, and dim levels.
- Occupancy vs vacancy mode: vacancy mode requires manual on with auto-off for greater savings; occupancy mode turns lights on automatically.
- Override and manual controls: local switches or presets let occupants adjust light levels without disabling energy-saving features.
7. Privacy and security
Protect occupant privacy and system integrity when collecting occupancy data.
- Camera-free thermal or anonymous presence sensors avoid image capture and are preferred in privacy-sensitive areas.
- Networked devices should support secure communication, encryption, authentication, and firmware updates.
- Confirm vendor policies on data storage, retention, and anonymization for analytics use.
8. Codes, standards, and certifications
Ensure devices meet relevant codes and have appropriate certifications.
- Energy codes: support strategies required by ASHRAE 90.1, IECC, and local codes (vacancy controls, daylighting).
- Certifications: UL, ETL, CE, RoHS, and local safety listings; verify interoperability certifications for networked devices.
- Warranty and support: look for multi-year warranties and accessible technical support for troubleshooting and firmware updates.
