Does the bypass flame on an FD thermostat go out if the flame is properly adjusted?

The bypass flame on an FD (Flame Detection) thermostat is designed to provide a small flame to ensure that the thermostat is functioning correctly while allowing for safe temperature control. When the equipment reaches its operating temperature, the primary burners take over, and the bypass flame will extinguish. This is indicative of the thermostat operating properly, as the bypass flame serves primarily to maintain the circuit when burner operation is not taking place.

Choosing the option that states the bypass flame goes out if the equipment has reached operating temperature accurately reflects the proper functioning of the FD thermostat system. Essentially, once the system achieves the desired heat level, the need for the bypass flame diminishes, thereby resulting in its extinction. This is crucial for maintaining efficiency within the system and ensuring that excess fuel is not unnecessarily burned, which could be the case if the bypass flame remained on continuously.

In contrast, flames that are stated to remain on continuously or only extinguish under specific conditions such as maintenance or set temperature limits do not represent the standard operational behavior of the bypass flame in a well-adjusted, functioning FD thermostat.