Safety valve 8115 3 bar 3/4 inch, solar 8115.20.151

Solar system over‑pressure protection

Membrane safety valve 8115.20.151 acts as an automatic pressure limit in closed circuits where there is a risk of exceeding the allowable value – especially in installations with solar collectors. It opens at 3 bar, which corresponds to the typical operating level of solar systems, and its design ensures repeatable and reliable operation even after many cycles.

For which media and conditions is it intended?

The valve is designed for use with neutral liquids and gases, including water‑glycol mixtures – up to 50 % glycol concentration. It is not suitable for aggressive media or high‑pressure steam, but works perfectly in heating circuits with antifreeze. Maximum operating temperature is 160 °C, meaning it can function even in collector overheating situations when the system is not cooled.

How to select the size for the installation?

The 3/4‑inch (DN20) valve is the standard choice for solar systems with collector area up to 100 m². In practice this corresponds to a thermal power of about 118 kW – illustrating the relationship between valve size and system performance. In smaller installations (up to 50 m²) a 1/2‑inch valve is sufficient; in larger ones using a smaller valve makes no sense because it may not withstand the flow when opened.

Construction and durability

The valve is made of brass, with a protective sleeve and seals resistant to ageing caused by temperature and chemicals. The spring, made of spring steel, has a galvanic coating – protecting it from corrosion while providing a stable force on the membrane. This is not a “one‑time” element, but a component designed for long‑term operation under cyclic opening and closing.

Where is it applied?

Primarily in solar installations – both residential and commercial. It protects buffer boilers, heat accumulators and pipelines between collectors and the circulation pump. It can also be installed in other closed liquid circuits where pressure rise is possible due to thermal expansion – e.g., low‑temperature heating systems.