If the flame is lifting a burner port, what should be done?

When the flame is lifting from a burner port, it typically indicates that there is an imbalance in the air-to-fuel mixture, often due to excessive draft or insufficient primary air. Adjusting the primary air by closing off the air shutter helps restore this balance by reducing the amount of air that is mixing with the gas. This action allows the flame to stabilize and ensures that it remains properly seated in the burner ports.

The other choices do not address the fundamental issue of flame stability caused by excess air. Increasing gas pressure might lead to a stronger flame but does not solve the problem with the air-fuel mixture. Relocating the burner could inadvertently introduce new issues rather than resolving the immediate concern. Increasing draft in the system would likely exacerbate the lifting flame situation by further increasing the amount of air entering the burner. Therefore, the most appropriate action is to adjust the primary air to achieve optimal combustion conditions.