What must be provided when flame sensing detectors can fail in the flame proven mode?

What must be provided when flame sensing detectors can fail in the flame proven mode?

• A. Self checking feature
• B. Redundant flame sensor
• C. Manual reset
• D. Alarm relay

Answer: (A)

In flame proven mode, the safety logic relies on the flame sensing detector to confirm that flame is actually present before allowing fuel to continue flow. If the detector itself can fail, you need a self-checking feature that constantly verifies the detector’s operation and its wiring. This self-check actively tests the sensor and electronics, so any fault is detected and treated as unsafe, typically causing a shutdown rather than risking a false indication of flame. The goal is to ensure the system never assumes flame existence when the sensor is faulty, preserving safe operation even as components age or drift. Redundant sensors can improve reliability, but they’re not the requirement described here. Manual reset and an alarm relay may be part of the overall system, but they don’t fulfill the need for automatic verification of the detector’s health in flame proven mode.

In flame proven mode, the safety logic relies on the flame sensing detector to confirm that flame is actually present before allowing fuel to continue flow. If the detector itself can fail, you need a self-checking feature that constantly verifies the detector’s operation and its wiring. This self-check actively tests the sensor and electronics, so any fault is detected and treated as unsafe, typically causing a shutdown rather than risking a false indication of flame. The goal is to ensure the system never assumes flame existence when the sensor is faulty, preserving safe operation even as components age or drift.

Redundant sensors can improve reliability, but they’re not the requirement described here. Manual reset and an alarm relay may be part of the overall system, but they don’t fulfill the need for automatic verification of the detector’s health in flame proven mode.