Expansion Vessel Reflex S 25 L for Solar Systems, Reflex 9704200

The Reflex Expansion Vessel S 25 L for Solar Systems is a diaphragm-type expansion vessel designed to accommodate volume changes and pressure fluctuations in closed solar thermal and hot-water circuits. With a nominal capacity of 25 litres, it provides hydraulic compensation to protect pumps, heat exchangers and piping from excessive pressure and to reduce water loss due to frequent venting or leakage. The compact design and solar-specific compatibility make it suitable for domestic and small commercial solar heating installations where a moderate expansion volume is required.

Advantages

This expansion vessel uses a pre-charged elastomer diaphragm to separate the system fluid from the gas cushion, ensuring reliable pressure buffering and minimizing air ingress into the system. Its 25 L volume offers a balance between compact installation footprint and sufficient buffer capacity for many residential solar loops. The vessel's construction reduces maintenance frequency by lowering the risk of overpressure events and stabilizing system operation under temperature-driven volume changes.

Suitable for

• Domestic solar thermal systems (solar collectors and storage tanks)
• Small commercial or light industrial solar heating circuits
• Closed-loop hot-water systems with moderate expansion requirements
• Installations where a compact expansion vessel is needed due to space constraints

When it may not be suitable

This 25 L vessel may not be adequate for large-scale solar arrays, district heating connections, or systems with very high fluid volumes and wide temperature ranges where a larger expansion capacity is required. It is not intended for open systems or applications requiring special materials compatibility beyond standard solar heat-transfer fluids.

Key specifications

• Nominal volume: 25 litres
• Diaphragm (membrane) type, pre-charged gas cushion
• Application: closed solar thermal and hot-water circuits
• Typical mounting: wall or bracket-mounted compact vessel
• Function: hydraulic pressure compensation and overpressure protection

How to use

Install the expansion vessel in the return line or a recommended location within the solar circuit where it can effectively absorb volume changes. Pre-charge the gas side to the system’s static fill pressure according to the installer or manufacturer instructions, and verify the system charge after filling and commissioning. Regularly check the vessel pressure and visual condition as part of routine system maintenance and before winter operation to ensure the diaphragm remains intact and the pre-charge is within specification.

What to consider before purchase

• Confirm required expansion volume based on the system’s fluid volume and maximum temperature range
• Check compatibility with the heat-transfer fluid used in the solar loop
• Ensure available installation space and mounting options match the vessel’s compact dimensions
• Verify recommended pre-charge pressure and any local regulations or installer requirements

Usage recommendations

For reliable performance, have a qualified installer size and set the pre-charge correctly during commissioning. Periodic monitoring of vessel pressure and occasional inspection of connections will help maintain system efficiency and protect components from pressure-related damage.