Siemens Flame sensor QRB1B-A033B40B

This Siemens flame sensor (type QRB1B-A033B40B) is a burner component that confirms the presence of a flame during the starting sequence. It is listed under the manufacturer part number QRB1B-A033B40B and replaces former numbers 4012341, 04012341, and 537D8106. The sensor is used to verify that a flame is established before the burner continues to run; if no signal is received within the safety time, the control locks the burner out.

Sensors of this kind are selected by the detection principle: ionisation for gas burners, and UV or IR for oil or industrial burners where the flame is luminous and must be viewed directly. Verify the spectral range, response time, cable length and connector type, and the mounting sleeve diameter against the original installation. Wiring and mounting arrangement must match the existing burner before the replacement is fitted.

Typical failure modes for this kind of sensor include a contaminated optical window, an ageing detection cell that gives a weakened signal, or a damaged sheath. When the signal is missing or below threshold, the burner control waits for flame confirmation during the safety time and then locks out. A burner that refuses to start or goes to lockout shortly after ignition is a common indicator; check the sensor window for soiling and compare the signal output to the specification.