System Sensor D4120 Photoelectric Smoke Detector

The System Sensor D4120 photoelectric smoke detector is a four-wire, duct-mounted device in the InnovairFlex line, designed for HVAC smoke detection and fire protection in air handling units, ventilation ducts, commercial buildings, and industrial facilities. Using photoelectric sensing, it initiates a DPDT alarm relay and a SPST trouble relay to support signaling and control functions, and its pivoting enclosure accommodates both round and rectangular duct configurations. It operates effectively across an air velocity range of 100 to 4,000 ft/min (0.5 to 20.32 m/s) and withstands temperatures from -4°F to 158°F (-20°C to 70°C) with 0% to 95% non-condensing humidity, making it suitable for varied HVAC environments. Common replacements include System Sensor D4120W, DNR, and DH100ACDC for retrofit or expansion within fire protection networks.