Expansion vessel OTTONE OT090105 – closed hydronic expansion tank for heating systems, model OT090105

OTTONE OT090105 expansion vessel is a closed membrane hydronic expansion tank engineered for sealed heating and hot-water systems. The vessel accommodates thermal volume changes and absorbs pressure fluctuations to help maintain stable system pressure and reduce stress on pipes, valves and other components. Designed for installation on central heating circuits, this model is suitable for residential and light commercial systems where a compact, membrane-type expansion solution is required.

Advantages

The membrane design separates the fluid from the pre-charged gas chamber, ensuring consistent pressure compensation and minimizing the risk of corrosion. Its closed construction reduces the need for maintenance and prevents direct contact between the heating medium and the gas cushion. The unit’s compact dimensions make it suitable for confined installation spaces while providing effective volume compensation for typical small to medium heating circuits.

Suitable for

• Sealed central heating systems in residential buildings
• Small commercial heating circuits with closed-loop water systems
• Hot-water systems requiring pressure stabilization and thermal expansion compensation
• Installations where a compact membrane expansion vessel is needed

When it may not be suitable

This expansion vessel is intended for closed hydronic circuits and may not be appropriate for open systems, potable water service without compliance checks, or applications requiring very large expansion volumes. For large-scale commercial or industrial systems with high thermal capacity, a vessel with greater volume or a different configuration could be required.

Key specifications

• Type: closed membrane (diaphragm) expansion vessel
• Function: compensates thermal expansion and stabilizes pressure
• Connection orientation: standard threaded inlet suitable for common heating fittings
• Typical application: sealed central heating and hot-water circuits
• Construction: steel shell with internal flexible membrane and pre-charged gas chamber
• Installation: wall- or pipe-mounted near boiler or circulation line (depending on system layout)

How to use

Install the expansion vessel on the return line or a suitable location near the boiler or primary circulation loop, following local regulations and the heating system design. Ensure the vessel’s pre-charge pressure is set to match the static system pressure before commissioning. After connecting, slowly fill the system and vent air from high points. Monitor system pressure during the first heating cycle and adjust the pre-charge or system fill pressure as necessary to achieve stable operation. Periodic visual checks and pressure verification are recommended to confirm proper function.

What to consider before purchase

• Required expansion volume based on system water content and maximum temperature
• System static pressure and matching the vessel pre-charge pressure
• Connection size and compatibility with existing fittings and piping
• Available installation space and mounting orientation
• Operating temperature range and compatibility with the heating medium

Usage recommendations

Verify pre-charge pressure with a pressure gauge before installation, follow manufacturer or local plumbing codes for mounting and connections, and perform an initial commissioning check to ensure air is fully vented from the system. For systems with frequent pressure loss or repeated cycling, inspect the membrane periodically and consider professional service if irregularities occur.