When can you expect an FD thermostat's bypass flame to extinguish?

The bypass flame of a float discharge (FD) thermostat is designed to maintain a certain level of operation and safety within the equipment. It typically remains lit to indicate that the thermodynamic process is ongoing. However, the bypass flame will extinguish when the equipment cools down. This cooling occurs because the thermostat is no longer engaged in its heating cycle, resulting in the cessation of necessary heat generation.

In practical terms, once the temperature drops to a point where the thermostat determines that it is no longer needed to keep the burner operational—in other words, when the thermal demand is satisfied—the bypass flame will safely extinguish. This mechanism helps in conserving energy and ensuring that the equipment does not run unnecessarily when the demand for heat has been met.