What action can be taken to stop oil flow in the event of excessive vacuum readings?

To stop oil flow in the event of excessive vacuum readings, closing the shut-off valve is the appropriate action. In oil burner systems, excessive vacuum readings can indicate that the oil supply is being impeded, which could lead to operational issues or even damage to the system. By closing the shut-off valve, you effectively cut off the supply of oil to the burner, which mitigates the risk of further complications that may arise from continued oil flow under these conditions.

This is a critical safety measure; addressing excessive vacuum readings promptly is essential to prevent potential issues that could cause system failures or accidents. In contrast, opening the vent would not stop the oil flow and might exacerbate the situation. Increasing pressure could worsen the problem by adding strain to an already compromised system. Adjusting the pump speed may alter the flow dynamics, but it does not directly stop the oil flow, which is necessary in this scenario. Therefore, closing the shut-off valve is the most effective and immediate action to take in response to excessive vacuum readings.