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

The main purpose of an expansion tank in a heating system is to absorb excess pressure and accommodate thermal expansion of the fluid. As a heating system operates, the water or other heating fluids inside it heat up and expand. If this expansion were not managed, it could lead to excessive pressure buildup, which can cause damage to pipes and other components of the system. The expansion tank provides a space for this heated, expanded fluid to go, thereby maintaining a safe pressure level within the system.

Additionally, when the heating fluid cools down and contracts, the expansion tank allows the system to draw in the fluid, thus keeping the system at an optimal pressure and ensuring efficient operation. This is crucial for the longevity and safety of the heating system as it prevents potential failures or leaks that can arise from uncontrolled pressure fluctuations.