Before draining a boiler, what should be allowed to cool?

The correct answer is that the setting should be allowed to cool before draining a boiler. The setting refers to the structure and components surrounding the boiler, such as the furnace and piping systems that can retain heat. Allowing the setting to cool helps prevent thermal shock; sudden changes in temperature can lead to cracking or increased wear on boiler components.

While the water inside the boiler is also an essential consideration, it is important to ensure that the structural elements of the boiler are stabilized before draining to minimize risks. Draining while the setting is still hot could also lead to potential safety hazards.

Understanding the importance of cooling the setting is crucial for preventing injuries and damage to the equipment, ensuring safe maintenance practices when draining a boiler.