Open-vented or sealed-system?

Open-vented or sealed-system?

  • Is an "open" tank safer? Open or Close

    No, an open container isn’t safer. In addition, it can be dangerous in case it is not installed properly! Also, as explained below, the system of the open tank has a much shorter lifetime compared to the closed circuit.

    The open container is established at atmospheric pressure and is permanently exposed to the atmosphere. The free surface bounds microparticles continuously as well as air from the atmosphere, the air dissolved in the water continuously erodes the installation, and fresh incoming air gets dissolved again in the open tank. The microparticles are deposited on inside installation and on operating components such as solenoid valves, pumps, safety valves. Thus, an open container system has a much shorter lifetime. On the contrary, the closed circuit of the dissolved oxygen creates a slight deterioration in the beginning by turning the water black and that is where the cycle of deterioration stops.

    A few more notes:

    • The idea that we don’t need pressure safety valves because the water is free to boil is technically wrong and dangerous. If the water in the tank or the tube leading to the tank freezes, then the circuit becomes very dangerous.
    • In an open circuit the water boils at 100°C while in a closed circuit it boils at 130°C with a pressure of 3 bars. In this case the safety of the circuit is increased.
    • During days when the facility does not operate, e.g. during holidays or in a five-day program operation, the defrosting operation of the closed circuit is easier and achieved by just putting the circulator in operation. At an open circuit, the water in the tank does not move with the help of the circulator; hot water is transferred simply because of gravity.
  • Many manufacturers suggest an open tank. Which is the best? Open or Close

    The Regulation states that the boiler should be left for 24 hours into pressure twice the working pressure, or a minimum of 5 bars, and after this period of time it should not have any leakage or permanent deformation. The forces deployed by the pressure are large but manageable. If the boiler is of poor quality, it cannot withstand a normal pressure test. Fear or ignorance of some manufacturers lead to such an advice.

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