Cylindrical solar expansion vessel
The EPDM membrane is replaceable, so a qualified installer can renew a worn membrane without replacing the whole vessel. The vessel is supplied pre-charged with nitrogen. Before the solar circuit is filled, the installer checks the pre-charge and sets it to suit the circuit's cold fill pressure.
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Description and application
The THERMALINO cylindrical solar expansion vessel is a wall-mounted membrane vessel that takes up the expansion of the heat transfer fluid in the closed primary circuit of a solar thermal system, keeping the circuit pressure stable. It is built to EN 13831 with an EPDM membrane, is rated for a maximum operating pressure of 10 bar and comes in 12, 18, 24 and 35 L sizes.
The cylindrical solar expansion vessel from the THERMALINO Eternal line is a wall-mounted membrane vessel for the closed primary circuit of solar thermal systems. As the heat transfer fluid heats up in the collectors, the vessel takes in the extra volume. As the circuit cools, the gas cushion pushes the fluid back. This keeps the circuit pressure within its limits and stops the safety valve from opening unnecessarily. The vessel is designed for solar heating duty and built to EN 13831 for a maximum operating pressure of 10 bar. Inside, a high-quality EPDM membrane of Italian origin separates the fluid from the gas side. The membrane is made for the demanding conditions of solar circuits and can be replaced. It is supplied pre-charged with nitrogen and finished in ivory. Four sizes are available: 12, 18, 24 and 35 L. The vessel is mounted on the wall and connected to the solar circuit, usually on the return side near the solar pump station. It is placed so that steam from the collectors cannot reach the membrane directly. Choose the size to take up both the thermal expansion of the fluid and the collector content that steam pushes out during stagnation. Before filling, the installer checks the pre-charge and sets it to suit the circuit's cold fill pressure. Besides the standard connection size, the vessel can be supplied with other connection sizes on request. Dimensions and connection details are given in the technical data sheet.
- Solar thermal primary circuits for domestic hot water in houses
- Solar combi systems that also support space heating
- Apartment buildings, hotels, hospitals and sports facilities with central solar water heating
- Solar circuits with water-glycol heat transfer fluid, subject to the fluid and temperature limits in the technical data sheet
- Solar pool heating circuits with a heat exchanger
- Solar process heat in commercial and industrial plant, subject to the pressure and temperature limits in the technical data sheet
Technical summary
- SKU
- THL-E-EXV-0005
- Origin
- Made in Türkiye
- Size range
- 12 L – 35 L
- Application
- Solar
- Membrane
- EPDM
- Membrane type
- Replaceable
- Max. operating pressure
- 10 bar
- Mounting
- Wall
- Standard
- EN 13831
Questions
- What does a solar expansion vessel do in the closed circuit of a rooftop solar water heater, and what happens without one?
- A solar expansion vessel absorbs the volume increase of the heat transfer fluid as the solar circuit heats up, then returns the fluid to the circuit as it cools, keeping the pressure stable. Without a working vessel, the pressure rises with every heating cycle until the safety valve opens and fluid is lost. In the THERMALINO cylindrical solar expansion vessel, an EPDM membrane separates the fluid from the nitrogen gas cushion.
- How do I choose the right solar expansion vessel size, 12, 18, 24 or 35 L, for a solar thermal system with flat-plate collectors?
- The solar expansion vessel must take up the thermal expansion of the whole fluid content plus the collector content that steam pushes out during stagnation, so it is chosen larger than a heating vessel for a similar volume. The cylindrical vessel is available in 12, 18, 24 and 35 L. The size follows from the system volume, the collector content, the static height, the fill pressure and the safety valve setting, within a maximum operating pressure of 10 bar. If the vessel is undersized, fluid is discharged through the safety valve during stagnation.
- What happens in a solar heating circuit when the expansion vessel pre-charge is wrong or the system pressure rises too high?
- When a solar expansion vessel is undersized, wrongly pre-charged, has lost its gas charge or has a failed membrane, the circuit pressure climbs as the fluid heats up until the safety valve opens and heat transfer fluid is lost. Typical signs are pressure that rises sharply when the collectors are hot, discharge from the safety valve, and pressure that falls when the circuit cools. A qualified installer checks the pre-charge, the vessel size and the membrane, and refills the circuit with the correct fluid.
- Can a homeowner replace a solar expansion vessel on a domestic solar water heating system, or should a qualified installer do it?
- A solar expansion vessel should be replaced or serviced only by a qualified installer, because the circuit is under pressure and may contain hot heat transfer fluid. The installer isolates and depressurises the circuit, sets the pre-charge to suit the system, and refills and vents the circuit. In the THERMALINO cylindrical solar expansion vessel, the EPDM membrane is replaceable, so a worn membrane can often be renewed instead of fitting a new vessel.
Range
| Size | Ivory | Variant codes |
|---|---|---|
| 12 L✓ Ivory | ✓ | |
| 18 L✓ Ivory | ✓ | |
| 24 L✓ Ivory | ✓ | |
| 35 L✓ Ivory | ✓ |
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