Siemens Flame sensor QRB4A-B036B40B

The Siemens QRB4A-B036B40B is a photoresistive flame sensor designed for use with Siemens burner controls. It monitors the flame of oil-fired burners in the visible light spectrum, primarily for intermittent operation. This sensor detects the luminous flame and sends a signal to the burner control to confirm flame presence within the safety time. It is categorized as a flame sensor and is identified by SKU QRB4A-B036B40B.

When selecting a replacement flame sensor of this type, key parameters include the detection principle (UV or IR), spectral range, and response time required by the control. The cable length, connector type, and mounting sleeve dimensions must match the existing installation. Ensure the mounting orientation allows an unobstructed view of the flame and that the cable is routed away from hot surfaces. Always verify compatibility with the existing burner control before ordering.

Typical failure modes include a contaminated optical window that reduces sensitivity, an aged cell producing a weak signal, or a broken sheath around the cable. This can lead to nuisance lockouts or failure to detect the flame, causing the burner control to shut down the fuel supply. Regular inspection for dirt or soot on the sensing window can prevent such issues.