No Flow to Radiator

Discussion in 'Plumbers' Talk' started by David492, Mar 29, 2019.

  1. David492

    David492 New Member

    I have a pressurised system and I removed a radiator which never seemed to get warm. I assumed that it was probably full of gunk. My wife wanted the radiator on a different wall so I removed the old pipes and moved them to the new position. I also bought a new radiator but cant get it to warm up. I flushed the pipes through before fitting new valves and then attaching to the radiator.

    All other radiators are fine.

    So far I have tried:-
    1. Turning all other radiator off to force the flow to the new radiator
    2. Draining new rad down and ensuring that there is sufficient flow through the pipes to the new rad.
    3. Removing TRV and replacing with a traditional value.
    4. Pressuring system to 2Bar

    When I open the valves (after refitting) water flows to the radiator and it warms up then slowly goes cold.

    Any other suggestions please.
     
  2. NoOhmToGoTo

    NoOhmToGoTo Screwfix Select

    You sound pretty clued up so I hesitate to suggest this but is the lockshield valve fully open?
     
  3. David492

    David492 New Member

    Hi NoOhmToGoTo, Thanks for the suggestion, it was brand new and I checked it before fitting
     
  4. sam spade

    sam spade Active Member

    Am I correct in thinking that you have moved one radiator and associated pipework, and added an extra rad? If so, how was the new rad piped in, i.e what was it connected to?
     
  5. David492

    David492 New Member

    Hi Sam,
    Basically I lifted floor and cut pipes to old rad at nearest point to where I wanted new rad and ran new pipes and valves. So flow pipe is now shorter and return about 3 ft longer to new rad. The old rad never really warmed up properly either but I assumed that there was a build up in the rad and as the new rad needed to be physically smaller I bought a new rad as well.
     
  6. David492

    David492 New Member

    Update, when recommissioning the system I set the pressure to 1 Bar, it has now gone up to 3 Bar. Also the boiler switched itself off and had to be reset and the pilot light lit.
     
  7. sam spade

    sam spade Active Member

    I understand.

    Have you tried the "bucket test"? It goes like this:

    1. Turn off both rad valves. (Be careful if one is a TRV as it may still pass water if the lowest setting is *. Use the decorators cap if you have one.)
    2. Remove radiator.
    3. Pressurise system to 1 bar
    4. Put a bucket under the flow pipe
    5. Open flow valve a and time how long to half fill bucket
    6. Turn off flow valve and reset system to 1 bar
    7. Do the same using the return valve.
    The flow rates should be approximately the same. If they are not there is blockage in the slower pipe.
     
  8. David492

    David492 New Member

    Hi Sam,
    Thanks for the suggestion.
    I did as you suggested and the flow rates were almost exactly the same, 4.5L in 33 seconds which seems about right for starting at 1Bar.
    They only other thing I noticed was that on the flow side the water was hotter than I expected given that the heating had been off for about 3 hrs.

    Any other thought?
     
  9. Peter208

    Peter208 Active Member

    What size are the pipes?
    Boiler flow and return?
    Tails too and from main flow and return?
     
  10. Peter208

    Peter208 Active Member

    Size of your boiler?
    How many rads and sizes?
    Is this the last rad before the boiler?
    How close is this rad piped in to the one before it?
     
  11. sam spade

    sam spade Active Member

    So we know the flow and return pipes are not blocked.

    Has the system been balanced? If you don't know, check how far open the lockshield valves are on all radiators; they should be no more than one turn open.
     
  12. David492

    David492 New Member

    Problem solved... I couldn't understand why I could not get the rad hot when I closed off all other rads and switched heating on. So I lifted the floor boards in the dining room where the rad was and in a bedroom and traced the pipes. And when the house was build 30 years ago the rascals piped in the rad to 2 returns. That's why it never got really hot. So all I have to do is run a new flow pipe to the new rad.

    What I don't understand is why the by the pressure is building up in my system to 3Bar when its set at 1Bar.

    Thanks to all who contributed.
     
    Pollowick likes this.
  13. sam spade

    sam spade Active Member

    The filling loop valves may be passing water, even though they are closed. Disconnect the filling loop at the supply end and check what happens. If it stops rising you will know that the supply valve if leaking.

    If you have a combi boiler, water may be leaking from the HW side of the heat exchanger to the CH side.
     
  14. Peter208

    Peter208 Active Member

    Two returns and no flow! That's a new one, some people!!
     

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