What is the purpose of an expansion tank in a heating system?

The purpose of an expansion tank in a heating system is primarily to accommodate the pressure fluctuations that occur due to the expansion and contraction of water as it heats and cools. When water is heated, it expands, increasing the pressure within the system. An expansion tank provides a designated space for this expanded water to flow into, thereby maintaining system pressure within safe and operational limits. This helps prevent excessive pressure that could lead to potential damage or failure of system components such as pipes, valves, and boilers.

The expansion tank also allows the system to maintain a consistent operating pressure, ensuring efficient transfer of heat throughout the system. By mitigating pressure spikes, the expansion tank contributes to the overall safety and longevity of the heating system.

In contrast to other options, the role of an expansion tank is not primarily about cooling water before it returns to the system, forcing hot water or steam through the system, or acting as a collection point specifically for condensate and steam. Option C accurately captures the key function of the expansion tank in managing pressure fluctuations within the heating system.