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Radiators Cold at the Bottom!! (Plumber advice required)

Discussion in 'General Chat' started by Nilz, Nov 25, 2008.

  1. Nilz
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    Nilz Defo worth the wait :)

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    [Nov 25, 2008]
    OK guys, some help required please now that the cold is kicking in!!! :cold:

    I have a combi boiler in the house and a couple of the radiators in the house are warm at the bottom and roasting at the top.

    I have carried out the following steps to see if it makes any difference, but nope....

    Beled rads, so water is coming out of them, therefore no air, got temp setting on the highest one on the rad, pressure is ok on the boiler, the pipes going into the rad from the floor are hot, and the water released from the rads is clear, so no sludge im presuming, though i maybe wrong.

    Can anyone else advise on what needs to be done, or what I can do to heat my room up!! :uhm:

    Thanks in advance :anbet:
    Nilz
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  2. diesel-a4
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    diesel-a4 Stoned As Fuk

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    [Nov 25, 2008]
    if its bottom entry fed then i wud guess the rad is blocked.

    is it heat the whole way across the top and half of the bottom or is the whole bottom cold from one end to the other.
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  3. Nilz
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    Nilz Defo worth the wait :)

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    [Nov 25, 2008]
    It is bottom entry fed....

    The whole top of it is hot and it seems like parts of the bottom are cold, its not from end to end (if that makes sense).
    #3
  4. fingermouse
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    fingermouse thats me

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    [Nov 25, 2008]
    sounds like they are full of sludge, have you got adative in your radiator water ??? how old is the system ???? the only way the bottom can be cold is if you have a great deal of sludge in them. Nasty black stuff that will stain anything it touches.

    you could try isolating one radiator, drain it down, carefully remove it and take it outside then flush it out with a hosepipe. If this clears a load of black cr@p out of it then it might be worth draining the whole system and doing all the rads then refill the system with water and a addative like fernox
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  5. Nilz
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    Nilz Defo worth the wait :)

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    [Nov 25, 2008]
    I think the system is only about 5 years old, and dont know if it is sludge as when the water comes out of it when bleeding, its literally clear as tap water, so if it was sludge, wouldnt it be dirty???

    Also, its a combi boiler, so will that still have a tank, coz im pretty sure i dont have a tank in the loft...
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  6. fingermouse
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    fingermouse thats me

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    [Nov 25, 2008]
    no tank with a combi, the water can still run clear even if the there is sludge in the bottom. Its not on micro bore is it ??? Ive never had to deal with that stuff and it may act differently. But radiators normally suffer being cold at the top not the bottom
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  7. AndyMac
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    AndyMac Moderator Staff Member Moderator

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    [Nov 25, 2008]
    If it's not sludge then it could just be that the rads have not been balanced causing the water to circulate too quickly not giving it time to warm up the bottom. Check the lockshield valves with the appropriate tool to see if they have been adjusted. The lockshield valve is the return valve, the one with the tamperproof cap on it (not the adjustable inlet valve). If they are completely open then the rad has not been balanced and this is why you have the problem you describe. You need to wait for the heating system to be fully warmed up then with the inlet valve completely open, fully close the lockshield valve, then open it half a turn and wait 2-3 mins to see if the rad heats up, if not open it another half turn and so on until you have full heat top & bottom.
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  8. abdus
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    abdus Top Gear VCDS Map User

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    [Nov 25, 2008]
    as above: sludge or balancing needed
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  9. abdus
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    abdus Top Gear VCDS Map User

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  10. Caesium
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    Caesium My BM is fixed! VCDS Map User

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    [Nov 25, 2008]
    its balancing all right, this has to be done properly, and the TRV isn't always on the inlet, it depends on the TRV. but balancing is definitely done with the lockshielded valves, wind them all down to closed and then open them all up a bit, a bit at a time so that you slow down the flow and even it out through all the rads. Make sure the TRV's are fully open before you start.
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  11. fingermouse
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    fingermouse thats me

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    [Nov 25, 2008]
    I can see why that may have to be done , although I know all mine are wide open.
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  12. Nilz
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    Nilz Defo worth the wait :)

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    [Nov 25, 2008]
    How do i know what is open and what is closed??

    Im about to give it a go, but just want to make sure im doing it right....

    Just to confirm, I need to keep the temp knob on full on one side of the rad and then the other side, take the cap off and turn the little valve thing, on each rad at a time???
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  13. AndyMac
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    AndyMac Moderator Staff Member Moderator

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    [Nov 25, 2008]
    Fully clockwise is closed, fully anticlockwise is open.
    If you have a look at your bathroom taps, they use the same technology!!
    #13
  14. cornish_a3_turbo
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    cornish_a3_turbo Guest

    [Nov 25, 2008]
    the other way 4 australia tho eh???

    lol
    #14
  15. Nilz
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    Nilz Defo worth the wait :)

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    [Nov 25, 2008]
    Right guys thanks for all your help, I will give it a go and see what happens, I will let you know....
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  16. fingermouse
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    fingermouse thats me

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    [Nov 26, 2008]
    righty tighty, lefty loosy :)
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  17. Caesium
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    Caesium My BM is fixed! VCDS Map User

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    [Nov 26, 2008]
    lol
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  18. Nilz
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    Nilz Defo worth the wait :)

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    [Nov 26, 2008]
    LOL....thanks guys, i did give it a go and actually turned the temp up on the boiler considerably and it looks like we are 'cooking on gas'!!!
    #18
  19. Macduff
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    Macduff Member

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    [Dec 1, 2008]
    Yars ago when I had GCH installed in a flat I had, the installer told me to have the boiler thermostat at max all the time as the radiators are designed to have 80C water flowing through them.

    Just something to consider.
    #19

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