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Just changed 3 port valve. Boiler wont fire up.

Discussion in 'Plumbing and Central Heating' started by Alex evans, 4 Sep 2021.

  1. Alex evans

    Alex evans

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    Ok so i changed a faulty 3 port valve.

    After turning the water back on.. the heating nor hot water works.

    The boiler may fire up for a minute or so then turn off... Im assuming its a saftey cut off, as maybe a blockage... No water going i to the boiler.

    Hotwater taps run... But run cold of course.


    After doing research it seems its likely crud/sludge... BUT..

    HOW am i ment to find out where the blockage is? Or... How can i "flush" it out? (I imagine that will just delay the problem?)

    Research suggests a typical place the blockage congregates is at a tee, from cold water feed from the tank... Where the hell would that be?

    How can i deduce where a blockage is... IF ITS EVEN THAT?

    When bleeding the rads... I just get.. nothing.. no water.. no rush of air.
     
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  3. flameport

    flameport

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    What exactly did you turn off before draining the water out of the system?
     
  4. fixitflav

    fixitflav

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    If you drained the system to fit the new 3-port, that could be the problem. Mine is the same, you would expect from the laws of physics that the pressure in the cold fill pipe from the header tank would force air out of the bleed points, but it doesn't. First time I did it I was getting worried, but after about 20 mins heard air coming from the vent, and it then filled. I found a way to speed things up - my cold fill pipe comes into the side of the header tank, and if I let the water in slowly, so about 1/2 way up the pipe diameter, I could fill it that way.
     
  5. terryplumb

    terryplumb

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    Do you have a small tank in the loft that feeds the boiler / central heating circuit and is it full of water ?
     
  6. Alex evans

    Alex evans

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    The cold water comming into the house.
    Then ran the taps and drained the CH from a rad with a hose pipe.
     
  7. Alex evans

    Alex evans

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    Yes, and yes it is full.
     
  8. HERTS P&D

    HERTS P&D

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    Air lock.

    Turn the heating on and adjust the pump speed up and down from 1-2-3 then back down again. You can normally here the air moving around.

    Andy
     
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  9. terryplumb

    terryplumb

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    Did you check the condition of the contents of the tank before draining down ? They can become full of crud ,which ( if not removed) will go into the pipework / system and block up .
    Or it may already have had a blocked cold fill. I doubt it's an airlock if no radiators have any water at all in them.
     
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  11. CBW

    CBW

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    Did you vent the radiators, any air vents and pump?
     
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  12. Alex evans

    Alex evans

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    Im worried that running the heating - or boiler- with this problem persisting may damage it? If the boiler isnt getting water.

    Maybe the boiler IS getting water? I dno.

    Like i say, the boiler will turn on.. for like 3 mins and then off. Im presuming... Because it doesn't have any water? Would i be wrong?
     
  13. Alex evans

    Alex evans

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    How do you mean? Sorry.

    Edit: i bled the rads.. but have since closed them up there are 2 fitttings of sometype either side of the pump.. are theese vents? Should i try to open theese?

    Theres also what looks like a "cap" with a spindle ending some upwards pipe, comming off of the 3 port valve side "A"
     
  14. Alex evans

    Alex evans

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    I didnt go into the loft before any problems.. no.
    Regarding the water in the rads.. i admit i didnt make this clear in my original post.

    Ok so.. the one downstairs that i drained from.. that does nothing when i "bleeed"

    The others downstairs have a tiny ... TINY dribble.. not a shoot as youd expect.

    The others upstairs are a bit of both.. if i remember.
     
  15. CBW

    CBW

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    When refilling the system, any air vents, the pump and radiators need bleeding of air - but having just re-read your post, you’ve tried the radiators.
     
  16. HERTS P&D

    HERTS P&D

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    How can you change a 3 port valve but not know how to bleed a radiator?

    Andy
     
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  17. Alex evans

    Alex evans

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    Im not sure where you got the "cant bleed a radiator" bit?
     
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