Siemens Flame sensor RAR9

The Siemens RAR9 flame sensor is a device for oil and gas burners, compatible with Siemens burner controls. It detects the presence or absence of a flame and sends a corresponding signal to the control. The sensor provides fast response to flame loss and features high sensitivity, stable operation, and durability.

Flame sensors of this type are selected by the detection principle required by the burner control (ionisation, UV, or IR) and by spectral range to match the fuel—luminous oil or blue gas. The sensor must be positioned with a direct line of sight to the flame, typically using a sleeve or bracket. The cable length, connector type, and mounting arrangement must match the original part, and the original manufacturer code or catalogue number should be used to verify compatibility with the burner control.

Common failure modes include a contaminated window or lens that reduces sensitivity, an aged sensing cell that gives a weakened signal, or a damaged cable that causes intermittent or no signal. When the sensor fails, the burner control may lock out after ignition because it does not detect flame within the safety time, preventing unburned fuel accumulation. Regular cleaning of the viewing window and inspecting the cable for cuts or strain can help maintain proper operation.