It seems like you’re asking about expansion tank overpressure in a system. An expansion tank is typically used in heating systems to accommodate the expansion and contraction of water as it heats and cools. If there’s overpressure in the expansion tank, it could lead to issues in the system.

Here are a few potential reasons for overpressure in an expansion tank:

Faulty Pressure Reducing Valve: If the pressure reducing valve is not functioning correctly, it can lead to excessive pressure in the system. Wilo pump

Waterlogged Tank: Over time, expansion tanks can become waterlogged, meaning they lose their ability to accommodate the expansion of water. This can result in increased pressure.

High System Pressure: If the overall pressure in the heating system is too high, it can cause overpressure in the expansion tank.

Thermal Expansion: Rapid heating of water can cause thermal expansion, leading to increased pressure. This is one of the main reasons expansion tanks are used in the first place.

To address the issue, you may need to check and potentially replace the pressure reducing valve, ensure the expansion tank is functioning correctly, and verify that the system pressure is within the recommended range. Regular maintenance is essential to prevent and address these issues. If you’re not comfortable doing this yourself, it’s advisable to consult with a professional HVAC technician.