System Sensor D4240

4-Wire Photoelectric Low-Flow Smoke Detector

Condition: New
Brand: System Sensor
Status: Active
SKU: 31624
Manufacturer Part #: D4240


D4240 photoelectric duct smoke detectors are 4-wire detectors that feature pivoting housings that fit both square and rectangular footprints and mount to round or rectangular ductwork. They operate in airflow speeds of 100 to 4,000 fpm, in temperatures of –4 to 158 °F, and a humidity range of 0 to 95% (non-condensing). Their plug-in sensor heads offer improved false-alarm immunity and simple installation, testing, and maintenance.

An improved cover design isolates the sensor head from the low-flow feature for simple maintenance. The InnovairFlex® housings provide ample wiring space, 3/4-inch conduit knockouts, and built-in short-circuit protection to prevent damage to sensitive components during installation.

High-contrast terminal designations make wiring easy. With its 2:1 sensor-to-power capability, the power board of the D4240 may be used to monitor a second sensor, D4S, simultaneously (i.e., supply and return side). As many as 50 InnovairFlex detectors can be interconnected. When one unit senses smoke, all interconnected detectors will switch their relays; only the detector sensing smoke will go into alarm, enabling the fire location to be pinpointed.

Additional information

Weight 1.2 lbs



Production Status



  • Photoelectric, integrated low-flow technology
  • Air velocity rating from 100 ft/min to 4,000 ft/min (0.5 m/s to 20.32 m/sec)
  • Versatile mounting options: square or rectangular configuration


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4-Wire Photoelectric Duct Smoke Detector-D4240


System Sensor - Data Sheet