Siemens Flame sensor QRB4B-B036B40B

This Siemens flame sensor is a photoelectric detector for flame monitoring in oil-fired burners. Designed for use in boilers, heat generators, and burner devices, it operates on diesel fuel or heavy oil. The sensor monitors flame presence and is built into the burner. Its housing is made of heat-resistant plastic. The device is compatible with Siemens LOA and LMO burner controls. The sensor originates from Germany.

Flame sensors of this type are selected by matching the detection principle (e.g., ionisation, UV, or IR) to the original, not by brand alone. Verify the spectral range, response time, cable length, connector type, and mounting sleeve size before ordering. The sensor is usually mounted through a sleeve in the burner blast tube or combustion chamber and wired directly to the burner control. A mismatch in any of these parameters may cause lockout or no flame signal.

Common failure modes for this kind of sensor are a contaminated optical window, a weakened signal from an aged photo-cell, or a broken sheath letting moisture or dirt reach the internal parts. When the sensor fails, the burner control receives no flame signal after ignition and locks out as a safety measure. A fitter should inspect the optical window for deposits, check the cable and connector for damage, and verify the sensor output with a suitable tester.