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I think I have a CH airlock!!

Discussion in 'Plumbing and Central Heating' started by RichD1, 8 Oct 2020.

  1. RichD1

    RichD1

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    I recently drained down our CH system to carry out some repairs on the ground floor. Once done I filled the system back up and bleed all the rads. The system fired up and I got heat to all rads apart from the ones on the 2nd (loft) floor.

    The 2nd floor has three rads and a towel rad. After some time with the boiler on the three rads do get warm. The towel rad remains stone cold.

    All the rads bleed water even the towel rad. They have their trv and lock shield fully open.

    I’ve tried turning off all the other rads in the house but when I turn the boiler on it turns on and off as the temp in the boiler reaches the trip level which suggests the water is not circulating to the upper rads. I then opened a small rad on the ground floor which allowed the boiler to heat the circuit but still no change with the rads on the 2nd floor.

    When we had the loft converted to a master/en-suite bedroom I can remember that the pipe work did take quite a difficult route with at least two up and downs! However the system has worked like that for all most twenty years.

    So I’m suspecting there is an air lock somewhere near the towel rad.

    What is the best method of clearing this lock?

    Richard
     
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  3. JohnD

    JohnD

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    Go into the loft and look at the small water tank.

    How deep is the water in it?

    How deep is the mud?
     
  4. RichD1

    RichD1

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    Sorry, should have said it was a combi system.
     
  5. What repairs did you carry out?
     
  6. RichD1

    RichD1

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    I changed a downstairs rad which works fine. Going to try taking out the bleed valve on the towel rail and putting a hose on it and then letting a good flow of water through whilst keeping the pressure up on the boiler.
     
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  7. Any valves not open? Eg are you on zone valves? Have you tried to balance the system? Did you upset the balance of the system from the downstairs rad?
     
  8. RichD1

    RichD1

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    All valves have been opened. Have balanced the system by fully opening all trv and then just opening the lock shield by a 1/4 of a turn. All the rads came on on the first two floors with just a couple needing a little more lockshield open. The top floor rads were all fully open with the larger one in the master bedroom just getting warm after some time.

    I’m convinced that there is an air lock on the top floor near the towel rad. I even closed all the downstairs rads and they still did not get hot.
     
  9. Have you tried bleeding the pump?
     
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  11. RichD1

    RichD1

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    Why would I need to do this as the lower two floors are circulating fine.

    Richard
     
  12. To release any trapped air, but as you say the lower two are circulating so should be fine.
     
  13. alan999

    alan999

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    When you took the bleed valve out and attached the hose did you then close each valve in turn?
    Was there always a good flow?
     
  14. RichD1

    RichD1

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    Hi Guys,

    Belatedly I've only just got round to trying to clear what could be an air lock on our 2nd floor causing three out of the four rads not to work. Connected up as we discussed and got running water out of all of the three rads which weren't getting hot. One had significant amounts of black oxide but ran clear after a few minutes. The large rad which was only getting hot at the top did initially come out with a spurt and some lumps of black but ran clear fairly quickly. I did give the rad a good banging with a rubber mallet but that didn't produce further black.

    I then turned the heating back on and no change!!! All rads were exactly the same as before.

    Interestingly on the rad which was only getting hot at the top I thought the flow was on the TRV pipe so put my hose connection at the other end. When I turned on the TRV no water came out of the hose. When I turned on the lock shield side water then water came out. So I changed the hose over to the other side of the rad and then proceed to run water through. When I turned the heat back on the flow was on the TRV side as I originally assumed. Any thoughts to why this should happen?

    Could there be an air lock in the return side of the pipework on the 2nd floor?

    Richard
     
  15. alan999

    alan999

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    Did you understand the significance of my earlier post Richard
     
  16. RichD1

    RichD1

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    Hi Alan, no I only opened the flow side on each rad. That might be my error!! Going to start over again tomorrow and open one side first and let it run. Close it off and then open the other side and let it run. Then go onto the next rad until all the non-working rads have been bled. Hopefully that should clear both flow and returns of air locks.

    Richard
     
  17. alan999

    alan999

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    Good luck. Remember to keep the pressure topped up.
     
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