Siemens Flame sensor QRB1A-A148B70B

This Siemens QRB1A-A148B70B is a photoelectric flame sensor for oil-fired burners operating on diesel fuel or heavy oil. It monitors the flame in boilers, heat generators, and burner devices, sending a signal to the burner control. If the flame goes out, the sensor triggers an emergency fuel shut-off. The device responds quickly to flame loss and offers high sensitivity. Its heat-resistant plastic housing and compact design allow easy integration into existing burner equipment. It is compatible with Siemens LOA and LMO series burner controls.

When replacing a flame sensor of this type, the detection principle (UV, IR, or another method) and the spectral response must match the burner control, as must the response time. The cable length and connector type also have to be compatible with the control. The sensor is mounted with a direct line of sight to the flame, typically through a sight tube or mounting sleeve, so the dimensions of the sleeve must fit the installation.

Common failure modes for sensors of this kind are a contaminated optical window, an aged detection cell that gives a weak signal, or a broken sheath or cable. During replacement, check that the sensor window is clean and that the sensor is correctly aligned to the flame without obstructions.