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Combi-boiler no hot water/good CH/no flow in filling loop

Discussion in 'Plumbing and Central Heating' started by jk1_1, 10 Feb 2021.

  1. jk1_1

    jk1_1

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    I have a Heatrae Sadia Electromax Combi-boiler.

    CH works, but no hot water. This coincided with 2 events: a full bath of hot water the night before (may have emptied the tank), plus sub-zero temperatures overnight (our mains supply has frozen in the past - don't ask!).

    Pressure is between .6 and .8 bars, but can't no water in filling loop.

    *I have disconnected the filling loop and opened both valves, plus removed the plastic handle and manually rotated the copper valve on the mains water - still no water*

    I can hear water flow in the expansion vessel when I reduce flow via the stopcock.

    Mains cold water to the house is also fine.

    How do I know whether this is:

    - cold water to boiler is frozen (still sub-zero at the moment, but daytime reached 1C)
    - problem with the expansion vessel
    - dodgy cold water valve to the filling loop?
     
    Last edited: 10 Feb 2021
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  3. terryplumb

    terryplumb

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    Show us some pics of filling loop set up ,and expansion tank / connections to it.
    Is the boiler in an outhouse / garage or inside the property ?
     
  4. jk1_1

    jk1_1

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    Image here: https://www.diynot.com/diy/media/20210210_191008.106039/full

    Pretty sure mains enters far right, travels via expansion vessel, to boiler far left.

    Don't think freezing is the issue, as we have running cold water, and I'm pretty confident that that is the only mains entry point.

    This is all inside the property.
     
  5. terryplumb

    terryplumb

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    If you undo and take off the hose on the right hand side only ,direct it into a bucket , then open the valve on the left side , water should flow out at mains pressure . Does it ?
    If it does ,the non return valve is stuck closed on the right hand valve.
     
  6. jk1_1

    jk1_1

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    Yes, that's exactly what happened, thank you.

    Is it possible to fix/tweak the non-return valve?

    And the right hand valve is where the mains enters the boiler (am I right?) - so is the water coming out of the left valve coming from the boiler itself?

    Finally, would this explain the lack of hot water? Literally nothing coming out of pipes.
     
  7. jk1_1

    jk1_1

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    When I ask fix/tweak, I mean as a temp. solution!

    And is replacing it as simple as closing stopcock, replace valve, turn stopcock back on?
     
  8. terryplumb

    terryplumb

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    The left side of the filling loop is connected to the cold mains water supply. The right side with the non return valve is connected to the pressurised central heating system .As the central heating water is not pure / has chemicals etc in it ,the non return valve only allows water to flow into the system ,so cold mains flows in to top up pressure ,but the central heating water can not flow outward and contaminate the cold mains ( drinking water ). I know you said you have removed the black handle ,to turn the shaft below with a spanner , to ensure it is opening ,you do realise that both black handled valves have to be open at the same time don't you ?
    If you try again ,and tap the silver body of the non return valve with a spanner ,you may get lucky and free it if it is stuck.
    None of the above has anything to do with no water whatsoever coming out of hot taps . Or do you mean water flows from hot taps but it just isn't hot ??
     
  9. jk1_1

    jk1_1

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    Ok, so the initial problem is no hot water. I've been through this forum, and a lot points to the low pressure on the system (.6-.8bar) so I was trying to re-pressurise it. But then found no flow through the loop (and yes, both valves were open at the same time).

    I have tried *gently* tapping the non-return valve with the handle of a screwdriver. Maybe I should be a little firmer?

    If the low pressure isn't to blame, where should I look for the cause of no hot water?
     
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  11. jk1_1

    jk1_1

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    Sorry, to be clear, no water from the hot taps - neither hot nor cold!!
     
  12. terryplumb

    terryplumb

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    Hopefully someone who is more familiar with your boiler may join in ,as unfortunately I am not familiar with it. But the basic check would be to ensure the mains cold water supply to the boiler has not been isolated / turned off .follow the pipe that the left Flexi is connected to ,to see where it enters the boiler.
     
  13. jk1_1

    jk1_1

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    I thought that the mains entered from the right side? The pipe on the right is labeled DHW Mains Cold Inlet. And definitely haven't turned off any pipes/flow.
     
  14. terryplumb

    terryplumb

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    Apologies ,I have misled you . The non return valve is of course the right hand side and the left is the primary ( central heating side ).
    So when the filling loop hose is removed , mains water should flow out from right hand valve when opened. If it doesn't ,and coupled with the fact that no water flows from taps ,it would appear that there is no mains water getting there.
     
  15. ianmcd

    ianmcd

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    yes you are correct the pipe on the right is the cold water inlet
     
  16. ianmcd

    ianmcd

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    You are correct the pipe on the right is the cold water inlet, do the test again with the hose , but disconnect the left hand connection of the hose and open the right hand valve , you should get mains pressure out of the hose but I doubt that you will
     
  17. ianmcd

    ianmcd

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    Follow that pipe , there is either a valve closed on it, or it is frozen

    Inkedsadia_LI.jpg
     
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