Siemens Flame sensor QRB4B-B036A25

The Siemens QRB4B-B036A25 is a flame sensor, specifically a photodetector, designed for flame monitoring in oil-fired burners. It operates on the principle of photoelectric flame detection and is intended for use with diesel fuel and heavy oil. The sensor is built with a compact design and heat-resistant plastic housing, making it suitable for automatic combustion control systems. Its primary purpose is to detect flame presence and provide a fast response to flame loss, ensuring safe operation of the burner.

When selecting a flame sensor of this type, ensure the detection principle matches the burner design—photoelectric sensors are used for luminous flames in oil burners. The physical mounting arrangement, cable length, and electrical interface must be compatible with the existing burner control. Installation typically involves mounting the sensor into the burner, and it is designed for easy installation due to its compact form.

Common failure modes for flame sensors include a contaminated or fogged detection window, an aged sensing cell with weakened signal output, or a broken sheath. When a sensor fails, the burner control may not detect a flame within the safety time, leading to a lockout and closure of fuel valves. To diagnose, check the sensor's window for dirt or damage and verify its signal output.