Siemens Flame sensor QRB1B-A042B20B

The Siemens QRB1B-A042B20B is a flame sensor based on a photosensor, designed for monitoring the flame in liquid fuel burners. It operates on the photoelectric principle, sensing the light emission of the flame and sending a signal to the burner control. The device is intended for use with diesel fuel and fuel oil, and is installed inside the burner equipment of boilers, heat generators, and burner devices. It is compatible with Siemens burner controls, has a compact design for straightforward installation, and its housing is made of heat-resistant plastic. Its response to flame loss is fast, and its sensitivity is high.

When selecting a replacement flame sensor for this class of equipment, confirm that the detection principle (ultraviolet or infrared) and the response time are compatible with the burner control system. The sensor's cable length and connector type must match the existing wiring, and the physical mounting sleeve or bracket must fit the burner. The sensor must have a direct line of sight to the flame, and the spectral range should be compared with the original part before ordering.

Typical failure modes for this type of sensor are a contaminated window that reduces light transmission, an aged photocell that produces a weak signal, or a cracked sheath that allows moisture ingress. When the sensor fails, the burner control may lockout during startup because it does not detect the flame within the safety time, or it may interrupt operation after a sudden flame loss. Inspect the sensor window for dirt and the cable for damage, and verify that the sensor is aligned with the flame.