One luke warm radiator - need help tried everything!

Discussion in 'Plumbers' Talk' started by marc1977, Dec 11, 2010.

  1. marc1977

    marc1977 Member

    Hi,

    Need some help with a radiator in a bedroom that does not get above luke warm. I have fiited a new 6 metre pump, the water pressure is good and flows well from both inlet and outlet valves. Today I fiited a new radiator as (following a plumber who came outs advise) the old one may have been corroded and therefore causing a blockage - but still no change! What can this be? the inlet valve is really hot but the water is clearly not flowing through the radiator well. I flushed the system and let both valves run for a long while to clear out any blockage and they run fine???

    Is a 5 bed house with standard open vented gravity fed central heating

    Thanks

    Marc
     
  2. tom.plum

    tom.plum Screwfix Select

    could be bad pipe work, somebody s piped both pipes off the flow/return, or maybe its pipes in series off another rad, or it could be a kinked pipe, only further investigations will tell.
     
  3. Crowsfoot

    Crowsfoot Screwfix Select

    Hi Marc,
    You mention fitting a 6m head pump, I'm curious to know was this because this lukewarm radiator is at an high level?
     
  4. marc1977

    marc1977 Member

    thanks,

    I fitted a  6 m pump as we have 14 rads in the house. also the cold radiator is the furthest away from the boiler in an extension. Im also beginning to think it must be bad pipework - however the extension was done 25 years ago so i cant believe it never worked! we have just moved in BTW.

    I suppose the only way to tell is too lift up the floor boards and view the pipework?! its really weird cause with the rad off both inlet and outlet pipes have a really good flow of very hot water.
     
  5. marc1977

    marc1977 Member

    sorry, yes it is at a higher level as it is upstairs and the boiler is downstairs
     
  6. howlsatthemoon

    howlsatthemoon New Member

    tom could be right about both pipes off the flow or return, so dont believe for one minute that it must have worked cos youd be suprised at what folks will put up with. if its 10mm then its probably been linked to another rad in which case it needs serious modification. try turning rads off nearest to it one by one to see if you can work out if it is linked to one in particular. does it work ok with other rads in the house turned off? if so then have a serious balanceing session.
     
  7. Crowsfoot

    Crowsfoot Screwfix Select

    Mmm, I was thinking more on the lines of it being located in an atic bedroom, hence a very little head of water.

    Your discription of it being at an "higher leve"l dosn't seem to tally with what I was thinking.

    If it was really high I was going to tell you to vent it with the pump (ch) off, It's probally still worth a shot if you've been trying to vent with the pump on though..
    Tappy,
     
  8. marc1977

    marc1977 Member

    its seems i have the unsolvable plumbing problem!
     
  9. Crowsfoot

    Crowsfoot Screwfix Select

    Nah, turn off all the other radiators in the house so that the pump can concentrates on just the one lukewarm radiator and it shouldl become hot.
    That should do it.
    Then if need be carry out a bit of balancing on the system.

    One more thing to check is if the lockshield valve has a screw to attach it to the valve it's not unheard of to actually turn the valve back off when you are turning the screw.
     
  10. marc1977

    marc1977 Member

    yeah tried that..the problem is the boiler temperature cut off kicks in. However I still left it as the only radiator for around 4 hours and it just stays luke warm...any other ideas?
     
  11. midnight cowboy

    midnight cowboy New Member

    NO! it's time to lift a few boards and check the supply pipework. 
     
  12. Crowsfoot

    Crowsfoot Screwfix Select

    Give this a go disconect the boiler thermstat (remove probe from boiler) so that it won't shut off - it's fairly commomn practice in the trade to do this.on your kind of system.
    After that, it's up with the boards!!
     
  13. marc1977

    marc1977 Member

    OK thanks guys. Crowsfoot, if I am feeling brave I may try the above! any ideas what it means though if the radiator does or does not get hot using this method?
     
  14. tom.plum

    tom.plum Screwfix Select

    no disrepect to tappy, but i think boiling the water up won't move it if 4 hours on a pump with all other rads shut did't, time for board liftin i'm afraid, cold weathers coming back soon so it'll have to be done,
     
  15. Crowsfoot

    Crowsfoot Screwfix Select

    Non taken tom, in-fact I just love these little bits of trade chat.
    I'm now thinking on the lines that the lukewarm radiator feeds may have been taken from the primaries and  the circuit simply has too much resistance.
    I can't think of anything else it maybe.
    It's a strange one this un
     
  16. Farmacist

    Farmacist Guest

    Mark says " its really weird cause with the rad off both inlet and outlet pipes have a really good flow of very hot water."  This must mean that both inlet and outlet pipes are connected to the flow (or possibly the return) especialy if they both heat up at the same rate when the boiler is turned on from cold. This is the only thing that explains the lack of circulation.
     
  17. marc1977

    marc1977 Member

    well after taking the radiator off yet again i have come to the conclusion it must be something to do with the pipework...im sure one is a flow and one is an return pipe as there is a clear temparature difference. The return pipe has signifant pressure in it -as much as the flow, im and thinking this is what is stopping the water circulating. I dont think it is a coincidence that this is the furthest away radiator in the house. Could the pressure in the return be too great???

    Thanks

    Marc
     
  18. Crowsfoot

    Crowsfoot Screwfix Select

    No it's nothing to do with too much pressure on the return.
    Because your rad is getting lukewarm there is some form of restricted circulation taking place.
    Maybe you have a one ppe system and the lukewarm radiator has been pipe up wrong from the start - all those years ago.
    That's yet another explanation were all the pieces do fit in with the problem.
    It's still all ifs and buts though.
     
  19. longscrew

    longscrew New Member

    I have come across this when a extra rad has been added to a one pipe system without diverting the main circuit near the new rad some times even piped up in 10mm .


    Usually in the new conservatory where the builder has done it himself.

    pete
     
  20. marc1977

    marc1977 Member

    Thanks all. Whats the easiest way to tell if I have a one pipe system?
     

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