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Linea 24 - DHW not getting warm enough (lukewarm)

Discussion in 'Plumbing and Central Heating' started by Firbel, 24 Dec 2013.

  1. Firbel

    Firbel

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    Having read through the forum on all the Linea 24 DHW issues I thought I had all the info I needed to repair mine. I replaced the Secondary Heat Exchanger, fitted an overhaul kit to the Diverter Valve along with a new DHW thermistor to find I still have the same problem :unsure:
    When the Hot Tap is turned on, the boiler fires up but doesn't get the water hot enough. if I restrict the water flow using the restrictor valve on the boiler, the temperature readout on the boiler will rise to 55 at which point the burner switches off until the water temp falls to 40/45 then it will fire up again in a repetitive cycle. I've checked the Diverter Valve Motor and that is functioning correctly. Anyone any ideas what I need to check next ???
     
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  3. ianmcd

    ianmcd

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    What is the DHW flow rate set at ?
     
  4. Firbel

    Firbel

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    At the moment its set as low as possible so that the flow switch can sense that hot water is required. I would expect the water to be scalding hot if the flowrate is set low but is only coming out lukewarm.
     
  5. ianmcd

    ianmcd

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    That doesnt mean anything, what is low to one person is not low to another, get a container that you know the volume of and time how long it takes to fill i.e. if it holds 10Litres and it takes 1 min to fill then the flow rate is 10L/min you get the idea
     
  6. Firbel

    Firbel

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    currently set at 3.5 Ltr/min to get warm water, any higher and the water gets progressively cooler.
     
  7. scatmanjohn

    scatmanjohn

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    Are you saying that the boiler is getting the water to 55 deg but at the tap the water is only luke warm?
     
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  9. ianmcd

    ianmcd

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    Thats far too low you should be able to achieve around 11L/min at this time of year, stand in front of the boiler with the hot tap running and when the boiler cuts out, turn the three way water valve below the boiler to the 9 ocklock position and see what number is displayed on the boiler when the water stops running
     
  10. Firbel

    Firbel

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    Hi Scatman, yes thats correct and thats only if I restrict the flow from the boiler. To recap, I've replaced the DHW Heat Exchanger, DHW Thermistor and fitted a Diverter Valve Overhaul Kit. I certainly can't get 11ltrs/min of hot water as Ian says I should be able to. At that rate it's just cold water.
    I wondered if it was pump related but the CH is fine, super hot rads all round.

    Ianmcd, I can't carry out your suggestion yet as I'm not at home for a few days.
     
  11. ianmcd

    ianmcd

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    that test will tell you if it is a restriction problem which you seem to have been chasing by changing the components that you have , if the figure on the display is in the 90s then it is indeed a primary flow problem if it is lower than that then we are looking at RGI stuff Im afraid
     
  12. Firbel

    Firbel

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    Hi Guys, here's what I found. I adjusted the DHW Flow Valve to achieve a flowrate of 10 Ltrs/min. Setting the Hot Tap running would give an indication of 45 on the boiler and 55 If I turned the Stop Tap to the 9'o'clock position.
    If I turn the room thermostat and boiler CH Temperature up to max for Central Heating, the boiler will happily run along at 85 giving hot rads throughout so the problem only seems related to the DHW.
    If the boiler was performing normally, what temperature could I expect the boiler to show for DHW at 10 Ltrs/min ?
     
  13. ianmcd

    ianmcd

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    your boiler will produce 11.3L/Min at 30 degrees C rise so lets say your incoming water is 9 deg C then at 11.3L/Min then your temp on the outlet of the boiler will be 39 derees C so by the sounds of things you are not far away but you will need to measure the incoming water temp, to be honest a 24KW boiler wont produce a great flow rate especially in winter
     
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  14. Firbel

    Firbel

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    Thanks Ian, I appreciate your help and comments.
     
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