Siemens Flame sensor QRB1A-A033B40B

The Siemens QRB1A-A033B40B is a flame sensor/photodetector used to monitor the combustion process in oil burners running on diesel or heavy oil. It operates on the photoelectric principle and is built into the burner. The device sends a signal to automatic combustion control systems to confirm that the flame is present. It has high sensitivity and responds rapidly to a loss of flame, triggering an emergency shutdown of the fuel supply. The housing is made of heat-resistant plastic, and it is designed for use with Siemens LOA and LMO burner controls.

When choosing a replacement flame sensor of this kind, confirm that the detection principle, spectral response, and response time match the burner control requirements. The physical mounting must be compatible in terms of the mounting sleeve dimensions, cable length, and connector layout. Before ordering, measure the existing sensor’s sleeve dimensions and compare the electrical output characteristics with the control board specification. During installation, check the viewing path for obstructions, align the sensor so it has a clear line of sight to the flame, and clean the quartz window if soiled.

Flame sensors of this kind usually fail because the quartz window becomes contaminated, reducing the radiation reaching the photocell, or because the sensing cell ages and gives a weak signal. Moisture can enter through a damaged sheath and cause corrosion or a short circuit. The equipment will typically lock out because the control does not receive a flame signal within the safety time after fuel admission. Check the sensor’s optical window for dirt or deposits, and inspect the cable and sheath for damage.