What is the purpose of a high-limit control on a hot water boiler?

The purpose of a high-limit control on a hot water boiler is to protect the boiler against excessive water temperatures. This safety device is essential for preventing overheating, which can lead to dangerous conditions, including equipment failure or even explosions. The high-limit control monitors the water temperature and will shut down the burner if the temperature exceeds a predetermined safe threshold. This function is crucial not just for the safety of the equipment but also for the safety of the facility and its occupants.

Maintaining consistent boiler pressure is managed by different controls, typically not related to high-limit functions. Automating water filling is a different aspect of boiler operation and doesn't directly pertain to the high-limit control. Enhancing energy efficiency is an important concern for boiler operation, but the high-limit control's primary function is focused on safety rather than efficiency improvements. Therefore, the correct answer reflects the fundamental function of the high-limit control in safeguarding the boiler from excessive temperatures.