Honeywell UV detector U2-1018S

The Honeywell U2-1018S is an industrial flame sensor used for flame proving in burner control systems. It combines UV and IR detection principles with a detector type of UV + IR flame monitor, supporting all fuel types. The sensor provides analog output of 0-20 mA and 4-20 mA, with a maximum input current of 120 mA and power consumption of 3.5 W. It has a flame relay contact rating of 1 A at 30 VDC, and communicates via 2-wire RS485 with Modbus RTU protocol. The device features a capacitive TouchWheel with LED display, is IP66 rated, and weighs 2800 g, with dimensions of 11.7 cm diameter and 15.5 cm length.

Replacement sensors of this type are selected by detection principle (UV, IR, or combined), spectral range, response time, cable length and connector type, and mounting sleeve design. Ensure the sensor is positioned with a direct line of sight to the flame zone and that the electrical connection matches the burner control. Models in this series are available with quick connectors and pipe fit connections of 3/4" NPT, while the standard process connection is 1" NPT female. Verify the mounting thread and connection before ordering.

Typical failure modes for this type of sensor include a contaminated quartz window that blocks UV/IR radiation, an aged sensor cell with weakened output, or a broken sheath exposing internal wiring. When the sensor fails to detect flame, the burner control will not receive a flame signal and will enter lockout, preventing burner operation. Check the quartz window for cleanliness and inspect the cable and connector for damage.