System Sensor D4120W Watertight Duct Smoke Detector

The System Sensor D4120W is a watertight, 4-wire photoelectric duct smoke detector designed for use in challenging indoor and outdoor HVAC environments. Encased in a NEMA 4-rated housing, the D4120W provides reliable smoke detection while protecting against falling dirt, rain, windblown dust, splashing, and hose-directed water. This makes it especially suitable for rooftop units or installations where harsh conditions are present.

The D4120W features integrated low-flow technology for accurate detection even at low air velocities, and a pivoting housing that fits both square and rectangular footprints so it can be mounted to round or rectangular ductwork. The unit operates within a broad range of airflow (100–4,000 ft/min), temperatures (–4°F to 158°F), and humidity (0–95% non-condensing). A plug-in photoelectric sensor head offers excellent false alarm immunity, while a patented sampling tube design allows for tool-free installation from the front or back of the detector.

Features

• One easy-access Test/Reset button and improved LED status indicators
• UV-resistant, UL-listed enclosure and cover materials
• Two DPDT relay contacts and built-in short circuit protection
• Increased wiring space with a 3/4-inch conduit knockout for easier installation
• Supports code compliance and enhanced building safetySmoke Detector D4120

As the only truly watertight duct smoke detector on the market, the D4120W provides exceptional protection, simplified installation, and reliable smoke detection for commercial and industrial HVAC applications.