New Tall Rad 10mm Pipe not working

Discussion in 'Plumbers' Talk' started by Drak1, Oct 8, 2018.

  1. Drak1

    Drak1 New Member

    I have just converted my garage and ran 10mm plastic pipes inside 22mm plastic pipe to a new rad. The run is 5m. The rad is a new tall grey designer one. Problem is only one side is heating up. I have bled it many times and confident there’s no air.

    I have tried turning off all rads and leaving this one open, but did not work.

    The rest of my house is in 15mm Pipe and system works well.

    Is my problem common, and any advice I can try??
     
  2. Heat

    Heat Screwfix Select

    10mm pipe is not good for supplying heat to a large designer radiator.
    And plastic 10mm is worse than 10mm copper because the plastic pipe is heavier walled and therefore the bore is much smaller.
    First I would confirm if you joined to the correct sides of the radiator with flow and return. Some designer radiators are only one direction.
    Also got to check both valves are allowing flow through them the DIRECTION it is supposed to go.
    Other thing is designer rads that have very thin waterways can have partial airlocks.
    I would have used 15mm copper and only from 22mm at a short distance
     
    retiredsparks and KIAB like this.
  3. terrymac

    terrymac Screwfix Select

    As well as what heat said above ,some need to be fitted the right way up. If fitted upside down they wont work either. Why put 10 mm ( far too small anyway ) inside 22 mm ,is that in an effort to protect it from impact ?
     
    Heat likes this.
  4. KIAB

    KIAB Super Member

    Usually there a mark on reverse of radiator showing it's orientation.
     
  5. Drak1

    Drak1 New Member

    Thanks everyone. The rad is getting hot down one side only.

    I used 10mm as the floor is screed and wanted no joins in the floor. The 22mm plastic was used to protect the 10mm in the floor.

    Is there a way to connect both valves to each other to test the flow and to ensure the pipework is not blocked?
     
  6. Heat

    Heat Screwfix Select

    Am sure you could have used 15mm plastic pipes in a duct to avoid joints below floors.
    The 15mm barrier pipe in pipe (ducted in a roll) pipes are an option.
    Joining the valves together might be just a piece of 15mm plastic pipe connected to the valves using 15mm nuts & olives if valves are 15mm tails.
    But that won’t prove good flow, as heating the pipe isn’t a big draw
     
  7. Heat

    Heat Screwfix Select

    Laughably few people read anything.
    Came across a nice designer rad pipes from floor fitted with new kitchen. Had a look with angled mirror and rear of top said pipe connections this end only. o_O
     
    KIAB likes this.
  8. The Teach

    The Teach Screwfix Select

    Thats very true,some decorative radiators dont come with any instructions at all. There are reasons for that.

    Drak1 Are the new 10mm :( flow & return pipes installed correctly ie 2 pipe system layout ?

    Check they are not blocked,were you able to blow air through the new pipe runs before connecting up !

    Have you got a link to your new tall radiator ?
     
  9. retiredsparks

    retiredsparks Super Member

    From memory 10mm copper is good for about 11,500 BthU...in good conditions....no kinks bends fittings etc.... and what its fed from.
    How big is this flipping rad ?
    Rs
     
  10. Heat

    Heat Screwfix Select

    Probably even if it is a very large radiator it will be less the 10,000 BTUs, but 10mm pipes have very poor flow for to do restrictive radiators.
    The OP said the run was 5m, which is fairly long if that is just for each pipe.
    Also, as you know, the length of pipe runs (flow & return combined) for 10mm has to be fairly short to give reasonable flow.
    I wouldn’t even consider using 10mm.
     
    retiredsparks and KIAB like this.
  11. heatyman

    heatyman Well-Known Member

    Bleed the rad through both runs, running 2-3 litres on each side. Open flow and close return. Then close flow and open return. This will prove whether you have any airlocks or obstructions.
     
    Heat likes this.
  12. retiredsparks

    retiredsparks Super Member

    Given the option I would also prefer to use 15mm.
    At a push I would not be too concerned with 10mm copper for just one rad off a good system.
    I am not sure if specs have changed, but "in theory" 11,500 has a max length of 35 feet with head loss of 2.7 ins.w.g./foot
    20deg C drop.
    RS
     
    Heat likes this.
  13. Heat

    Heat Screwfix Select

    That would mean if the OP has a run of 10m (2 x 5m pipes) then the 10mm is at limits of near 35ft.
    Don’t forget the OP has used 10mm plastic pipes which are probably similar in actual I.D. to 8mm copper I.D. so that will be a lower max length.

    If you ever try blowing through 10mm copper that is 10m long, you will know the resistance is noticeable. Plastic 10mm obviously must be worse.
     
  14. retiredsparks

    retiredsparks Super Member

    Agree totally H.
    It's just that not many people know and understand tech limits, as you do, and shy away fro using 10mm when needed for shortish runs off 15 and 22mm pipe.
    Don't forget you can only blow about 1.3 PSI and a CH pump will blow 8 PSI.
    :)
    RS
     
    Heat likes this.

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