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2 Radiators not getting hot

Discussion in 'Plumbing and Central Heating' started by WLF85, 17 Oct 2016.

  1. WLF85

    WLF85

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    I had a new central heating and hot water system installed a couple of years ago, and 2 radiators in my extension have stopped working this winter.

    Radiators.jpg

    • The radiators are on the downstairs zone, but are on their own section (see picture)
    • The rest of the radiators on the downstairs zone work fine
    • As pictured, the flow to the broken radiators feels hot until just above the isolation valve. The pipes to the radiator are therefore completely cold.
    • Boiler is Vaillant Eco Tec Plus 637
    • Cold system pressure is 1 bar
    I have tried:
    • Making sure the lockshield valves are open
    • Bleeding the air out
    • Draining and refilling
    • Removing the TRV heads to check for sticking pin
    • Balancing the system
    There just seems to be no flow to these 2 radiators at all.

    Any ideas?

    Thanks a lot for your help.

    (Note that I added the Magnaclean at a later date, and I know that it's missing the return flow from this section, I just had no room to put it anywhere else)
     
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  3. gigz

    gigz

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    If you turn the other rads off on that circuit what happens ?
    Edit just re-read post.
    Where you've written "return from broken rads" looks like a gas pipe ?
    Also don't understand the bit where you say it has no return flow section ??? It needs a return or it won't work.
     
  4. WLF85

    WLF85

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    The pipe to the right of the text is the return, for some reason my arrows didn't save.

    Not sure what you mean in your last question, I never said it doesn't have a return. I did say the magnaclean is missing the return (I.e it's not cleaning the return) but that's not relevant.

    Thanks!
     
  5. Steelmasons

    Steelmasons

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    Eh???
     
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  6. WLF85

    WLF85

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    Nevermind :)
     
  7. gigz

    gigz

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    You mean the magnacleans on the flow ?
    Have you tried turning the rest of the rads off on that circuit ?
     
  8. WLF85

    WLF85

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    I'm totally baffled.

    I turned off all radiators except for the 2 problematic ones, and they still didn't get hot.

    I stuck a bucket under the bleed valve of the 2nd radiator and let a load of water out, and the radiators started to fill with warm water. I let the system cool down fully and refilled it, turned it back on and the radiators STILL aren't warming up by themselves.

    Is it fair to assume at this point that there is some kind of blockage on the return from the second radiator?

    Is it worth me taking the radiators off and flushing them out with a hose? Shall I then reinstate them with new valves?
     
  9. oldbuffer

    oldbuffer

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    I'd try:

    1. Turn both isolation valves in your picture off.
    2. Turn both radiators off at lock shield and TRV
    3. Disconnect the return pipe into the top of its isolation valve (prepare for a little water)
    4. Hosepipe connected to disconnected pipe to run water somewhere safe
    5. Re-open radiator valves
    6. Open flow pipe isolation valve.

    If no water comes out of the disconnected return pipe you have a blockage somewhere in the circuit.

    If water does come out, then you have a blockage elsewhere. My money would be on the isolation valve(s). Many of these
    are not designed to work continuously at central heating water temperatures.
     
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  11. gigz

    gigz

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    Take a rad off then open both valves into a dish, then do the other. This will prove that you have no blockages. Do this first.
     
  12. gigz

    gigz

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    When you bleed loads of water out they will get hot, your just pulling the hot water through manually, if it doesn't have a flow/return it won't work. As oldbuffer says, take those bollofix valves out and either replace with full bore valves or straight couplings as the bore is only about 5mm ish (blockage waiting to happen)
     
  13. phod

    phod

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    Before anything else you could try flipping the pump from setting 1 to 3 and back again repeatedly, might give enough oomph to budge the airlock.
    As said those ballofixs will likely start weeping at some point. If you must isolate central heating use the lever ones with gland nuts that can at least be repacked.
     
  14. WLF85

    WLF85

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    Thanks everyone.

    I don't seem to have a regular CH pump (the one in the pic is just for the solar panels).

    I'm assuming the pump is on the boiler itself (Vaillant Ecotec Plus 637)? If so I'll get the instruction manual out to see how to adjust the pump setting.
     
  15. gigz

    gigz

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    It'll have a 2 speed pump and it comes factory set at the high speed, unless someones touched it.
     
  16. WLF85

    WLF85

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    Yep you're right. I think I'll leave it as it is and work through the other suggestions.

    Thanks again everyone.
     
  17. WLF85

    WLF85

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    Out of interest how do you know that my installer didn't use full bore isolating valves?

    I can't tell the difference between the ones he installed and these ones:

    http://www.screwfix.com/p/full-bore-isolating-valve-15mm/46860?kpid=46860
     
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