Expansion vessel
An expansion vessel is an important safety device in a sealed hydronic (water-based) heating or cooling system. Its primary function is to accommodate the changes in the volume of water as it heats and cools.
- How it Works: As water is heated, it expands. In a closed system, this expansion can damage different units of the heating system. The expansion vessel contains a flexible diaphragm or bladder that separates a cushion of air (or inert gas) from the system's water. When the water heats up and expands, the excess water flows into the vessel, compressing the air on the other side of the diaphragm. This prevents the pressure in the system from rising to unsafe levels.
- Why It's Important: The expansion vessel protects the components of your HVAC system—such as the boiler, pump, and pipes—from damage due to excessive pressure. It helps maintain a stable, safe operating pressure, ensuring the longevity and efficient performance of your heating or cooling system.
- Where It's Found: You will typically find an expansion vessel installed near the boiler or heat source in a closed-loop system, such as a radiant floor heating system or a sealed radiator system.
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