Expansion vessel Comap Solarix 35/2.5 (10 bar) for solar and heating systems

The Comap Solarix 35/2.5 (10 bar) expansion vessel is a diaphragm-type pressure vessel designed for closed solar and heating systems. With a nominal volume of 35 liters and a factory pre-charge around 2.5 bar, it provides hydraulic compensation for thermal expansion, stabilises operating pressure and reduces the risk of water loss or frequent topping-up. Rated for system pressures up to 10 bar, this vessel is intended for domestic and small commercial solar thermal circuits and heating installations that require a medium-capacity accumulator to protect pumps, valves and heat exchangers.

Advantages

The diaphragm design separates the system fluid from the gas cushion, which preserves the vessel’s responsiveness over repeated expansion cycles and limits gas diffusion. A 10 bar maximum working pressure allows use in higher-pressure circuits while the 35 L nominal volume offers a balance between compact size and storage capacity. The pre-charge value near 2.5 bar is suitable for typical domestic solar and heating installations, helping maintain stable pressure and reducing stress on system components.

Suitable for

• Domestic solar thermal systems and hot-water circuits
• Small commercial heating installations and closed-loop hydronic systems
• Systems requiring a 35 L expansion capacity with a nominal 2.5 bar pre-charge
• Installations where a diaphragm vessel is preferred to separate fluid and gas

When it may not be suitable

This expansion vessel is not intended for open systems or applications requiring working pressures above 10 bar. It may be unsuitable for large commercial or industrial systems where a significantly greater expansion capacity or different pre-charge pressure is required. Always verify compatibility with system design parameters such as maximum allowable pressure and required expansion volume.

Key specifications

• Nominal volume: 35 L
• Pre-charge characteristic: approximately 2.5 bar
• Maximum allowable working pressure: 10 bar
• Diaphragm (membrane) type separating fluid and gas
• Intended for closed solar thermal and heating circuits

How to use

Install the expansion vessel in accordance with system layout and manufacturer guidance, typically on the return line near the boiler or solar circuit manifold where hydraulic compensation is needed. Verify and adjust the pre-charge pressure of the vessel when the system is depressurised and empty, using a suitable pressure gauge and pump to match the static fill pressure of the heating or solar circuit. Secure mounting and correct orientation ensure reliable performance; connect using appropriate fittings and include isolating valves or a shut-off arrangement to allow service and replacement without draining the entire system.

What to consider before purchase

• Confirm system maximum working pressure does not exceed 10 bar
• Check that a 35 L nominal expansion volume meets calculated thermal expansion requirements
• Ensure the 2.5 bar pre-charge is compatible with system static pressure or can be adjusted as needed
• Verify available space and mounting options for a 35 L vessel

Usage recommendations

Check the vessel pre-charge periodically (for example, at annual maintenance) and inspect for signs of diaphragm failure or corrosion. When replacing or servicing, isolate the vessel and relieve system pressure before disconnecting. For best long-term performance, match vessel pre-charge to the system’s cold fill pressure and consider professional commissioning to confirm correct sizing and installation.