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Thread: Boiler question

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    Team Starburst Ian@1904's Avatar
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    Boiler question

    One for the gas boiler engineers....
    We have a Worcester Bosch Greenstar CDi classic boiler. It is about seven years old. Until recently it has been very good. We had to have a gas engineer come out as the pressure was dropping rather a lot and it turns out that the condenser was full of water. Given that the boiler has a drain I am struggling to understand what would have caused this problem. Is this caused by chalk buid up in the boiler so that valves become gummed up or something similar?
    My Beloved did not think to ask the engineer about the most likely cause

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    The condensate is slightly acidic and will eventually wear away the material of the heat exchanger.

    The Worcester has an aluminium HEX so this will/could be accelerated due to the softer metal in comparison with stainless steel or copper.

    We only fit steel/copper HEX boilers for these reasons, aluminium is a good heat conductor but not great on the wet side of a heating system, or exposed to acidic condensate.
    Being aluminium it is dissimilar to the steel and copper in the system, and with copper being at the top of the tree, gradual breakdown if the aluminium occurs, so it is affected internally and externally.

    Internally the ph has to be tightly controlled, within 0.2 integers on the scale to avoid internal breakdown, typically this should checked at least annually and the ph balance adjusted.

    If the HEX pinholes you lose system pressure but the leak is hard to detect as it flows out with the condensate.

    The best way to spot this is to have the boiler off for 24 hours with a bag under the condensate, if it fills up you have a leak.
    Last edited by JonG; 13-12-2019 at 05:29 PM.

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    The Condense trap should drain out freely. I wonder why it is not. In really cold weather, just when you need the boiler the most if the condense drain is routed outside they can freeze which turns off the boiler. However for your boiler the claim for a correctly sized and installed drain is something like proof to -15C for 48 hrs.

    Is it a sealed loop and pressurised system?

    If the water pressure in the closed loop is dropping then the heat exchanger may be cracked and leaking water into the condense trap, but again that should drain away, however you can find out if you turn off the electric supply, disconnect the condense drain to the trap, pressurise the sealed system loop and put a plastic bag over the condense drain (hold it on with an elastic band if you can) from the heat exchanger for a few hours, as the bags fills from any leakage within the heat exchanger you will see the pressure drop. This has worked for me on other makes.
    Rgds

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    The aluminium oxide residue blocks the trap if not cleared st service or more regularly if required

  5. #5
    Team Starburst Ian@1904's Avatar
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    Thank you
    I will investigate further


 

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