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CH System faulty after drain down (Open Vent)

Discussion in 'Plumbing and Central Heating' started by Karl50uk10, 23 Jan 2021.

  1. Karl50uk10

    Karl50uk10

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    Hi

    Due to noisy radiators and some noisy pipework. I decided to drain down my CH sytem today and refill with inhibtor.

    Drained using a drain valve from downstairs rad. due to stopcock not being the best. All seemed to go well and filled the system back up.

    Downstairs rads all drained of air but not enough pressure to force the air out on the upstairs rads?

    Problems encountered when putting CH back on: -
    No water in the pump. Pump seems to be pumping.
    Therefore no water being circulated and no rads coming back on.
    The boiler is making a hissing noise (a bit like a kettle being boiled) when the heating is swtiched on.

    Any ideas?
     
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  3. terryplumb

    terryplumb

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    Fed from a small tank in loft ?
    Y plan or s plan system?
     
    Last edited: 23 Jan 2021
  4. Karl50uk10

    Karl50uk10

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    Hi Terry yes small tank in loft. Not sure if You plan or S plan.
     
  5. terryplumb

    terryplumb

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    Is the tank full ?
    Did you clean it before draining ?
    Can you post pics of pipework around cylinder ?
     
  6. Karl50uk10

    Karl50uk10

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    I would say an S plan based on quick research. I have 2 off 2 port valves in the airing cupboard.
     
  7. terryplumb

    terryplumb

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    Possible gunk got into system ?
     
  8. Karl50uk10

    Karl50uk10

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    The feed tank was full of gunk which I tried removing as best I could before draining.

    Pics attached.
     

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  9. Karl50uk10

    Karl50uk10

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    Tank full up again no problem. Although didn't seem much went in if I am honest when refilling.
     
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  11. terryplumb

    terryplumb

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    System is full of air ,and short of water. Blocked feed from the F&E tank probably. Do you have a strong magnet ? If so follow the pipe from F&E down ,running the magnet around pipe . Any magnetite in pipework will attract the magnet .
     
  12. Karl50uk10

    Karl50uk10

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    OK will try that thanks
     
  13. oldbuffer

    oldbuffer

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    1. Switch off boiler.
    2. Manually set both motorised valves open. Push lever across and latch. They will automatically reset when system is next used.
    3. Bleed all radiators. Start with ground floor and work your way up.
    4. If upstairs won't bleed, you have a pipework blockage somewhere. If so, you will need to find it and clear it.
    5. Bleed the hot water cylinder primary coil. The automatic air valve (top of picture 2 between tun dish and silver coloured valve) should have its cap loosened (assuming its for the water cylinder). When all air gone re-tighten cap if it otherwise leaks.
    6. Bleed pump (slacken central chrome screw).
    7. Make sure there is about 100 mm of water in the F&E tank in the loft, and that if you depress the ball, more water comes in. Shouldn't be too full.
    8. Turn system back on and hope for the best.
    9. You may have to repeat once or twice to get all air out.
     
  14. Karl50uk10

    Karl50uk10

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    Thanks Oldbuffer.

    I get all that excpet the hot water cylinder coil. What does that look like?
     
  15. terryplumb

    terryplumb

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    It's inside the cylinder !!
    See the label on cylinder marked COIL ,that's where one end of it connects to ,there is another pipe on the cylinder that connects to its other end.
     
  16. Karl50uk10

    Karl50uk10

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    so just disconnect them both?
     
  17. terryplumb

    terryplumb

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    No you don't. Follow both pipes ,there should be an air release valve on one , possibly the automatic one in your pic ,brass body and little black cap on top.
    You would be wasting your time until you prove the feed isn't blocked as I advised already.
     
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