Durable Construction: Heavy-duty 2-tube stainless steel design resists oxidation and thermal fatigue in high-heat environments

consolidating truck stock for multiple D and E series units

the thermal limit has failed and the switch must be replaced

Universal Lennox Compatibility: Integrated into a wide range of Lennox Elite and Merit series furnaces and air handlers

System Sensor D4S Detector Sensor 30067439-890 Durable Construction: Heavy-duty 2-tube stainlessThe System Sensor D4S is a 4 wire photoelectric duct smoke detector sensor component designed specifically for integration with the D4120 duct smoke detector housing. Engineered for high performance HVAC smoke detection, this replacement sensor head utilizes an advanced optical sensing chamber to detect combustion particles across a wide range of airflow speeds. It is optimized for low flow duct smoke detection, maintaining reliable operation in