Hot radiators upstairs but cold downstairs

Discussion in 'Plumbers' Talk' started by Froja, Feb 13, 2013.

  1. Froja

    Froja New Member

    We have moved in to our new house only 3 weeks ago. When we turn the heating on the upstairs radiators were working fine but the downstairs radiators were ice cold. We have tried bleeding it and draning the system. If we turn the radiators off upstairs than we do have heating downstairs. But if we turn the radiators upstairs on again then after a few minutes the downstairs radiators are getting cold again.
    We had 2 servicemen here from 2 different companies. The only thing they have done was tearing up the floorboards and the second one have changed the flow switch .. but still no luck.
    The boiler was replaced 4 years ago, so it is relatively new. The plumber said that the pump is working. The property was empty for quite a while before we have moved in. But it is 3 weeks since we have moved in and still no heating and it is snowing again .. it is really cold in the house. Either we have hot radiators upstairs or downstairs. Many thanks!
  2. ramseyman

    ramseyman Member

    It sounds to me very much as if the pump, although running, is failing and not providing adequate flow.  Are there different pump speeds available if so set it to 2 if on 1 and 3 if on 2.  Otherwise your radiators may not be balanced,  Peter has put some excellent advice on here for doing that if you search - as you say turn upstairs/downstairs off - are you tweaking these down at the lockshield valve ends rather than the on/off and leaving fully on thus restricting flow to the horttest radiators and forcing flow to the cooler.
  3. petertheplumber

    petertheplumber New Member

    Balancing central heating radiators The radiator nearest the boilers pump will tend to get hot quickest and so the need to be adjusted to control the water flow through them. The radiator is fitted with a 'lockshield valve? which needs to be adjusted when the system is first installed. The 'lockshield valve' is normally covered by a push on cover to hide the adjustment.  It is the lockshield valve that needs to be adjusted, ideally using a small spanner across the flats on it when cover cap is removed. The intention is to even out the flow of water through each radiator so that with the system in its normal operating condition, the temperature drop across each radiator is about 20°F (12°C).  Problems with setting up the system may be experienced if the outside temperature is above the design operating temperature - if the outside temperature is above the system design value, the heat dissipated by each radiator will be less than intended by the design, and the temperature drop across each radiator will be less than 20°F. If balancing on a hot summers day, adjust to achieve a lower temperature difference.   Once the radiators in a system have been balanced, the valves should not need to be adjusted again unless the pipe work or radiators are changed.  The easiest way for a diy'er to measure the temperature drop across the radiators is to use a pair of radiator thermometers; they can be purchased or better still hired or borrowed. These thermometers just clip onto the pipe work and indicate the temperature of the pipe (which is, effectively, the temperature of the water flowing within it). Most professional plumbers do not use these thermometers; years of experience have enabled them to balance a system just using a hand to check the temperature differences. Hope this helps?
  4. petertheplumber

    petertheplumber New Member

    Balancing radiators.  (1) As a first step close any rads that are getting hot and see if that heats any of the other rads. You can quickly work out which rad heats first by letting them all get cold and when they start heating up find out which pipe gets hot first, use the pipe temp to test rad for heat it is quicker than waiting for the rad panel to heat up. (2) The radiators that are nearest the pump are usually getting hot first.  First make sure system is on heating only no hot water and any bypass if fitted is closed.  (3) If they have a lockshield valve one end and a hand control valve the other end, make sure hand control valve is fully open and then closed just a touch. Close the lockshield valve with a small spanner on the flats of brass shaft exposed when the plastic knob is pulled off, then open it 1/8-1/4 of a turn. (4) If there is a trv then make sure they are all open and the pins are up not stuck down. (5) Then move to rad that is next one from pump and repeat, and so on until you are downstairs then open lockshield valve ¼ -1/2 a turn. By the time a valve is open by 1 turn it may as well be fully open. (6)  That should work all rads. Then open bypass valve to same position it was in. If you manage to get all the rads working, once the hot water starts heating it will unbalance the rads so set the programmer to heat the hot water continuous or hot water 1.5 hrs before heating. Good luck This one may be easier to follow.
  5. Froja

    Froja New Member

    Thanks for the quick answers.
    We have balanced the radiators yesterday. have done all the turning off and back on thing with all the radiators .. but nothing happend. Radiators still cold downstairs. I was trying to find a switch on the pump to set it to a higher speed, but couldnt find any. Our boiler is a Combi Boiler.
  6. petertheplumber

    petertheplumber New Member

    If it is a combi then pump speed often fixed. I assume combi is downstairs or should I say ground floor? Are the flow and return pipes on the boiler that take the heating circuit, in 22mm copper pipe? do they then go down to the floor or up to the ceiling? Are all the rads downstairs fully open on both ends of the radiator, trv's fully open and valve on other end fully open. And are the rads upstairs only open a little bit on the adjustable lockshield end and on the other end trv's caps off altogether to make sure trv's are open and the pin isn't stuck down? Answer those first please.
  7. Froja

    Froja New Member

    The boiler is upstairs. The copper pipes are going down. the radiators are fullyo  open on both ends.
  8. Froja

    Froja New Member

    I was told by the previous owners that the radiators were working that they know of no problem with the central heating or boiler before we have moved in and that the heating was left low and on constant over the period in winter when the property stood empty.
  9. ramseyman

    ramseyman Member

    you say the valves are fully open both ends but do you have thermostatic valves (trv's) if so take the top off and check the pin is not stuck down by giving a little tug and twist with a pair of pliars.  Failing that if you have balanced as described by peter I think can only be the pump not providing output it should.  you say you have balanced but taking the scenario of all hot upstairs and cold downstairs what happens when you close down the lockshield valves upstairs, do both the up and down get warm, but not hot, if only warm again points to pump
  10. ramseyman

    ramseyman Member

    By closedown I meant turn down not completely close
  11. petertheplumber

    petertheplumber New Member

    Sorry Froja but you need to do exactly what we say, any explanations of what happened previously are irrelevant. All the upstairs rads need to have the valves NEARLY closed on 1 end only open 1/4 turn. Do that first with downstairs rad fully open and upstairs rads NEARLY closed. And have you checked trv's have not got pins stuck down.
  12. Froja

    Froja New Member

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    I am sorry, I`ll might sound a bit stupid but is the lock shield valve the one for the returning water? in this case the right side of this radiator? and the hand control valve is where the hot water meets the radiator? there are no plastic lid on the rest of the radiators so i cant really make any difference which one is which..
  13. petertheplumber

    petertheplumber New Member

    Ok fair enough, the lock shield is whichever one YOU choose to adjust and agree that once adjusted you will NEVER touch it. It doesn't matter which end of the rad it is. It makes no difference to any new valves which way the water flows. It helps you to know because whichever pipe gets hot first tells you the rad is going to start getting warm or hot.
  14. retiredsparks

    retiredsparks Member

    Hi Guys
    Just out of interest are you talking combi boiler here ?
    Initial suspicion would be impellor shaft sheared on pump.(rotor turning making noise..... not moving water)
    Just a thought.
  15. retiredsparks

    retiredsparks Member

    lol.........just re read the post and its a combi......
  16. petertheplumber

    petertheplumber New Member

    Yes sparki and half the rads work so any thoughts since can't seem to get him to balance it properly.

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