Which component prevents oil accumulation in the combustion chamber of an oil furnace?

The primary controller is the correct choice because it plays a critical role in managing the operational cycle of the oil burner in an oil furnace. It regulates the fuel flow to the burner and ensures that the combustion process is efficient and safe. One of its functions is to monitor the burner operation and shut it off if a malfunction is detected. This is particularly important in preventing oil from accumulating in the combustion chamber, as continued operation without proper combustion can lead to excessive oil buildup, which can create safety hazards and operational issues.

The other components listed, while important in their own right, do not specifically address the prevention of oil accumulation in the combustion chamber. The blower is responsible for circulating air and is not directly involved in fuel management. The oil tank stores the fuel but does not control its delivery to the burner. The flame sensor detects the presence of a flame, ensuring that the burner is operating correctly, but it does not manage oil flow or prevent accumulation. Thus, the primary controller is essential for maintaining safe and efficient operation of the oil furnace, effectively preventing oil accumulation.