What is the difference between an expansion vessel and a buffer vessel?

What is the difference between an expansion vessel and a buffer vessel? A buffer vessel and an expansion vessel have entirely different functions. A buffer vessel increases system water volume and stores thermal energy. It is normally a rigid, insulated steel or stainless-steel tank.

Expansion vessel

An expansion vessel contains a flexible diaphragm or membrane. It absorbs the increase in water volume that occurs as the system heats up, which helps control system pressure.

The main purpose of an expansion vessel is to absorb the increase in water volume that occurs when water is heated in a sealed heating or hot-water system.

Water expands as its temperature rises. Because a sealed system has no open outlet for this extra volume, pressure would quickly increase without somewhere for the expanded water to go. An expansion vessel provides this space.

Inside the vessel is a flexible diaphragm or membrane. One side contains system water, while the other side contains compressed air or nitrogen. As the water heats and expands, it pushes against the diaphragm and compresses the gas cushion. When the system cools, the gas pressure helps push the water back into the system.

A heating system may require both a buffer vessel and an expansion vessel.

Buffer vessels

Our full range of buffer vessels for heating or chilled water systems are detailer here –  Buffer vessels for heating and chilled water systems