Expansionsapparater

Expansionsapparater, often referred to as expansion vessels or expansion tanks, are essential components in closed-loop hydronic systems, such as heating and cooling systems. Their primary function is to absorb the expansion and contraction of the water within the system as its temperature changes. Water, like most substances, expands when heated and contracts when cooled. In a sealed system, this change in volume can lead to dangerous pressure fluctuations.

An expansionsapparat typically consists of a sealed container, often made of steel, divided into two chambers by a flexible diaphragm or bladder. One chamber is filled with water from the hydronic system, while the other is pre-charged with a gas, usually air or nitrogen, at a specific pressure. When the system's water heats up and expands, it exerts pressure on the diaphragm, pushing it into the gas-filled chamber. This compression of the gas absorbs the excess water volume, preventing an excessive rise in system pressure. Conversely, when the water cools and contracts, the gas pressure pushes the diaphragm back, releasing stored water and maintaining adequate pressure within the system.

The correct sizing and pre-charge pressure of an expansionsapparat are critical for the efficient and safe operation of the hydronic system. An undersized or improperly charged vessel will not adequately accommodate the volume changes, potentially leading to pressure spikes, safety valve activation, or even system damage. Conversely, an oversized vessel may not provide sufficient pressure support. Regular inspection and maintenance, including checking the pre-charge pressure, are recommended to ensure continued optimal performance.