When must a post purge control be used in a burner?

A post purge control is necessary in a burner particularly for direct venting applications to ensure safety and efficiency. This control functions to clear unburned fuel from the combustion chamber after the burner has been turned off, preventing potential hazards such as explosions or the accumulation of harmful gases.

In a direct venting system, where outside air is used for combustion and exhaust gases are expelled directly outside, this mechanism becomes even more critical. If unburned fuel remains in the combustion area without proper purging, it poses a higher risk due to the pressure differential and flow patterns specific to direct venting setups, which may not sufficiently vent the combustion chamber otherwise.

While maintaining safety protocols can involve purging at various times, the primary focus of post purge control is its role in the immediate aftermath of burner operation, particularly under the unique conditions of direct venting systems.