Minnesota Boiler License Practice Exam

What primary function does the expansion tank serve in a hot water heating system?

1. To increase pressure

2. To absorb water expansion

3. To provide additional heating

The correct answer is: To absorb water expansion

The primary function of the expansion tank in a hot water heating system is to absorb water expansion. When water is heated, it expands, and if there isn't a means to accommodate this expansion, increased pressure can build up within the system. This increased pressure can lead to potential damage or failure of components in the system. By incorporating an expansion tank, the excess water that results from thermal expansion is directed into this tank, where it can safely expand without causing undue pressure on pipes and other components. The tank is designed to handle fluctuations in volume due to temperature changes, thereby protecting the system from pressure spikes that could lead to leaks or even burst pipes. In contrast, while increasing pressure could be a result of expanded water when the system is functioning normally, it is not the primary role of the expansion tank. It is more of a safeguard against high pressure conditions, rather than a mechanism for pressurization. Providing additional heating does not describe the function of an expansion tank; instead, it refers to the function of the boiler itself, which is responsible for heating the water in the system.