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Solar Expansion Vessels


A complete range of solar expansion vessels to meet the requirements of most solar system designs.

SKU: 12 Category:


We are able to offer a complete range of solar expansion vessels to meet the requirements of most solar system designs.

The vessels are fabricated by welding the various sections together which results in a very reliable structure suitable for internal pressures up to 10 bar. They are Epoxy coated and available in white. The diaphragm has been specially developed for solar applications. Suitable for temperatures up to 130°C, resistant to ethylene or propylene glycol mixtures and has low gas permeability.

An expansion vessel must ensure the solar system can work safely, particularly during periods when hot water is not being drawn off. During this period modern solar collectors may reach temperatures up to 200°C and consequently the fluid within the system can either evaporate or reach levels that can damage all the components within the solar energy system over time.

In order to resist the highest possible stagnation temperatures, a special heat-resistant diaphragm has been developed that can withstand up to 130°C.

How it works

All our solar expansion vessels are suitable for installation in solar systems complying with DIN 4757 and EN 12977 and are suitable for use with a mixture of water and propylene or ethylene glycol. The expansion vessels are tested according to the Pressure Systems Directive.

The diaphragm within the expansion vessel ensures that the system pressure does not exceed or go below the limits specified.

The diaphragm separates the space inside the vessel occupied by the gas and by the solar liquid. The initial pressure of the gas side must be regulated before turning on the system.

The diaphragm allows the liquid to expand into the gas chamber when the volume of the solar liquid expands due to the raise in temperature, maintaining the pressure inside the solar system at the approved maximum value.

When the temperature of the solar liquid cools, the volume decreases, the diaphragm returns to its initial position and the pressure remains constant at the approved minimum value.

Additional information

Size (Ltrs)

12, 18, 24, 35, 50


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