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Solar System Pressure?

  • 11-05-2011 04:35PM
    #1
    Garfin
    Registered Users, Registered Users 2 Posts: 158 ✭✭


    Hi all, we have a 50 tube collector with a 300l store, from <SNIP> the plumber who installed it doesnt inspire confidence so I am trying to educate myself on maintaining the system for best performance.
    What should the system pressure be and how will it vary with temperature?, what should the pressure vessel be set to and what should the flow rate be?
    Thanks in advance


    Mod edit: No need to name the supplier. Please read the forum charter.


Comments

  • #2
    quentingargan
    Registered Users, Registered Users 2 Posts: 1,627 ✭✭✭quentingargan


    The pressure shouldn't move very much, unless something is wrong with the system.

    What is critical, and often forgotten, is the maximum panel temperature. This must be below the boiling point of fluid in the system. The default setting for this on most controllers (EMAX) is 140C. If the system is pressurised to 2 bar or less, the fluid can boil at this temperature, so the pressure should be about 3 bar.

    If your pressure is set to 1 bar, the maximum panel temperature needs to be well below 120. That may be problematic on some systems, especially if you are bringing the cylinder to 85. Some 300L cylinders have been coming into Ireland with low surface area coils and poor heat transfer, so they may allow the heat differential to rise during hot weather.

    You shouldn't just increase the system pressure without first pre-charging the expansion vessel with a bicycle pump at the other end.

    The flow rate should be at least 2.5 to 3L per minute for 5 sq m. There is some discussion about the benefits or otherwise of reducing that if the flow rate is higher while the pump is on the slowest setting. I see no benefit whatsoever, unless you can reduce it with a variable speed pump to save electricity. My own belief is that the flow control valves are there as part of the flow meter because they are mass manufactured for other purposes.


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