What is the purpose of a spoiler screw or adjustable shutters on a burner?

The purpose of a spoiler screw or adjustable shutters on a burner is to mix primary air with gas effectively. When burning gas, proper combustion requires the right ratio of air to gas. The adjustable shutters allow for tuning this mix, ensuring that there is sufficient primary air introduced into the burner for optimal combustion. This adjustment can improve efficiency and reduce the production of harmful emissions, contributing to safer and more effective furnace operation.

In contrast, regulating gas volume is typically managed by separate gas valves, while controls for ignition and burner height are distinct mechanical aspects unrelated to the air-gas mixture process. Therefore, the primary focus of spoiler screws and adjustable shutters is indeed about enhancing the mixing of primary air and gas.