What is the maximum distance for positioning an ultraviolet scanner from the flame?

The maximum distance for positioning an ultraviolet scanner from the flame is correctly identified as 18 inches. This distance is crucial for ensuring the effective detection of ultraviolet (UV) light emitted by the flame. UV scanners operate by detecting the specific wavelengths of UV light, which are a reliable indicator of combustion.

If the scanner is placed too far from the flame, it may not accurately sense the UV light intensity, leading to false readings or failure to detect the flame altogether. Therefore, maintaining a distance of 18 inches ensures that the scanner can effectively monitor the flame while avoiding potential interference or obstructions that might occur at greater distances.

This optimal positioning is also important for the safety and efficiency of the HVAC system, as proper flame detection is essential for preventing hazardous conditions, such as flame failure or excessive fuel consumption.