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An expansion vessel absorbs pressure differences in heating systems, heat pump installations, boiler setups and other hydronic heating circuits. When water heats up, it expands and the system pressure rises. The expansion vessel absorbs this volume change and helps keep the installation stable.
At Hewa, you will find expansion vessels for installation, service work, renovation and technical replacement. When selecting the correct vessel, always check volume, pre-charge pressure, maximum operating pressure, temperature suitability, application and installation position.
Brands
Zilmet Zilflex H UR0181809CS0000 - Expansion Vessel (18L)
Item no. 320918EAN 8721082877725
Price excl. VAT€ 53,70Price incl. VAT€ 64,98
Op nalevering
Added
Zilmet Zilflex H UR0252509CS0000 - Expansion Vessel (25L)
Item no. 320925EAN 1302002500
Price excl. VAT€ 62,30Price incl. VAT€ 75,38
Low stock
Added
Zilmet Zilflex H UR0353509CS0000 - Expansion Vessel (35L)
Item no. 320935EAN 8721082877732
Price excl. VAT€ 78,40Price incl. VAT€ 94,86
Low stock
Added
Varem UR19231CS000000 - Expansion Vessel (18L)
Item no. 463118EAN 512239405
Price excl. VAT€ 50,70Price incl. VAT€ 61,35
Op nalevering
Added
Varem UR25231CS000000 - Expansion Vessel (25L)
Item no. 463125EAN 512239410
Price excl. VAT€ 67,60Price incl. VAT€ 81,80
Low stock
Added
Varem UR035231CS000000 - Expansion Vessel (35L)
Item no. 463135EAN 512239420
Price excl. VAT€ 84,50Price incl. VAT€ 102,25
Low stock
Added
Varem UR050271CS000000 - Expansion Vessel (50L)
Item no. 467150EAN 512239425
Price excl. VAT€ 112,70Price incl. VAT€ 136,37
Low stock
Added
Varem UR100371CS000000 - Expansion vessel (100L)
Item no. 461003EAN 8034108707273
Price excl. VAT€ 273,00Price incl. VAT€ 330,33
Low stock
Added
Varem R8018241S4000000 - Solar expansion vessel (18L)
Item no. 468018EAN 8721225900723
Price excl. VAT€ 49,55Price incl. VAT€ 59,95
In stock
Added
Universal Wall Bracket for Varem Expansion Vessels (up to 25L)
Item no. 461010EAN 1013948572813
Price excl. VAT€ 16,90Price incl. VAT€ 20,45
In stock
Added
Selecting an expansion vessel
An expansion vessel is designed to absorb the volume change of water in a closed heating system. When water heats up, its volume increases and the pressure in the installation rises. The expansion vessel absorbs this pressure increase, reducing stress on pipework, heat exchangers, fittings and other system components.
When selecting an expansion vessel, volume in litres, pre-charge pressure, maximum operating pressure, temperature class, application and installation position are important. An expansion vessel for a standard heating system is not automatically suitable for every boiler, heat pump or solar setup. Always check the technical data of the system and the specifications of the vessel.
Important when choosing expansion vessels
- Select the correct volume based on system volume and temperature range
- Check the pre-charge pressure and match it to the installation height
- Check the maximum operating pressure of the expansion vessel
- Check whether the vessel is suitable for heating, heat pump, boiler or solar applications
- Consider temperature class and fluid type
- Install the expansion vessel in a technically correct and accessible position
- Have installation, inspection and replacement carried out by a qualified installer
Pressure absorption in the installation layout
An expansion vessel works together with other safety and connection components in a hydronic heating system. For reliable pressure control, expansion, protection and filling must be properly coordinated. Also review related components such as pressure relief valves for pressure protection, boiler safety groups for heating systems and filling hoses for controlled system filling.
An incorrectly selected expansion vessel can cause pressure fluctuations, water loss through the pressure relief valve, faults or unnecessary stress on system components. During service, renovation or replacement, always check the system volume, static height, required pre-charge pressure and technical application of the vessel.
Frequently asked questions about expansion vessels
What is an expansion vessel used for?
An expansion vessel is used to absorb pressure differences in a closed heating system. It takes up the volume change of water when the temperature rises.
What size expansion vessel do I need?
The correct size depends on the system volume, temperature range, static height and required pressure control. Always check the technical calculation or the data of the existing installation.
What does pre-charge pressure mean?
Pre-charge pressure is the gas pressure on the membrane side of the expansion vessel. This pressure must match the installation height and required system pressure so that the vessel can function correctly.
Can an expansion vessel be used with a heat pump?
Yes, expansion vessels are also used in heat pump systems. The vessel must be suitable for the system volume, temperature, operating pressure and hydraulic layout of the heat pump installation.
When should an expansion vessel be replaced?
Replacement is recommended if the vessel is defective, the pre-charge pressure no longer remains stable, the membrane is damaged or the installation continues to show pressure problems. Inspection during maintenance is therefore important.