System Sensor D4240 Low-flow Duct Smoke Detector

Product Description

The SYSTEM SENSOR D4240 is a 4-wire photoelectric low-flow duct smoke detector designed for use in HVAC air-handling systems where early detection of smoke in moving airstreams is required. It operates on a photoelectric sensing principle, making it well suited to detect the slow-smoldering combustion events most common in mechanical and electrical equipment spaces. The D4240 is built for low-airflow duct applications, expanding installation flexibility beyond standard-velocity systems. Licensed fire alarm and HVAC technicians install this device as part of a supervised 4-wire initiating device circuit connected to a compatible fire alarm control panel.

The D4240 is used in commercial and light-industrial HVAC installations where duct smoke detection is required by local fire codes, NFPA 72, or NFPA 90A. It mounts directly to ductwork and samples air from the supply or return air stream. Its low-flow design makes it appropriate for variable-air-volume systems, fan coil units, and air handlers operating at reduced static pressure or low face velocity. This detector is categorized under aspiration smoke detection product lines and is sold as a single unit per package.

Key Features

• 4-wire configuration supports supervised initiating device circuits on conventional fire alarm control panels
• Photoelectric sensing principle provides reliable detection of slow-smoldering smoke in duct airstreams
• Low-flow design extends compatibility to low-velocity duct applications such as VAV systems and fan coil units
• Direct duct-mount installation samples supply or return air in-line with the HVAC system
• Sold as a single unit — no additional quantity multiplier required

Compatibility

Designed as an OEM-style replacement or new-installation duct smoke detector for 4-wire supervised fire alarm systems in commercial HVAC applications. Specific compatible fire alarm control panels or air handler model numbers were not provided in the available product data — consult the manufacturer datasheet for panel compatibility requirements.

Installation Notes

Installation of the D4240 must be performed by a licensed fire alarm technician in accordance with NFPA 72, NFPA 90A, and applicable local codes. De-energize the fire alarm control panel initiating device circuit before making wiring connections. Mount the detector housing to the duct according to the manufacturer dimensional requirements for the sampling tube length relative to duct width. Do not install in duct sections that are inaccessible for periodic functional testing, as duct smoke detectors require regular airflow and sensitivity verification per NFPA 72 inspection intervals.