cold radiators downstairs and hot upstairs

Discussion in 'Plumbers' Talk' started by Aga, Jan 9, 2012.

  1. Captain Leaky

    Captain Leaky New Member

    If the pump is noisy it may be on its last legs and not working properly.....
  2. william7900

    william7900 New Member


    I am new to this forum and experienced in central heating trouble-shooting. A Properly designed system would be based on 2 pipes fed from the boiler - flow and return - to the upstairs radiators first then the downstairs radiators.

    The connections of the vent cylinder and  radiators is dependant on the type of boiler fitted eg low resistance or high resistance. The high resistance boiler is a low water content boiler.

    The normal configuration starting from the boiler flow connection is T1= vent, T2=cylinder and T3=radiators.
    From the return of the boiler T1=cold feed, T2=cylinder and T3=radiators. the pump is usually fitted between T1 and T2

    Prior to filling the radiators make sure that both valves either side of all the radiators are open. Usually the left valve varies the temp of the radiator and the right valve balances the radiator.
    When the system is filled this occurs via the return pipe so that as the system is filled air is pushed up the vent.
    Bleeding is now started form the lower radiators then the upper radiators.

    The boiler is now fired up and the pump circulates the water. The water gradually heats up and oxygen in the water usually gets trapped in the upper radiators and not the lower ones, as hot air rises. The upper radiators should now be bled to remove the trapped air. what normally happens with a new system is the upper radiators get hot first due to this being the path of least resistance. To allow the bottom radiators to heat up the system requires balancing. This is carried out by closing the lockshield valve on the return side of the radiator bit by bit of the hottest upper radiator, observe changes for about 20mins, then proceed to next hotest upper radiator then wait again. Do not completely close the lockshield valves as this turns off the radiator. Repeat this on all upper radiators until the lower radiators start to heat up. what you have done is slightly increased the resistance of the upper radiators and caused the water to seek a path of lower resistance which is the downstairs radiators.

    Following this sequence will solve your problem, on condition that your heating system follows the design principle that I have previously described. Normally when you have a system problem it is best to follow the commissioning process to locate the problem.


    Heating Engineer
  3. Or the noise is simply air being drawn in to a poorly designed system when the pump is set at 3. What kind of noise is it, Aga - a shrrrrrrrrruuurrrppsshhhhrrrrrppppggguuurrgllleeee? Or a 'tricklingish'? Or perhaps a ggrrrrrrrrrrrrrrrrrruuuunnnnngggppphhhhh?

    Aga, have you been up in t'loft to have a look at the small 'header' tank? Where is it located - on a framework a bit highish up, or just on the floor of the loft? It might be that the design of your system is causing an unusual amount of friction to the water flow which is forcing pumped water out the expansion pipe when the pump fires up, and then draws in air the same way every time it stops - especially when the pump is at 3. If the amount of  'head' of this tank is not great (ie - it ain't much higher than the top of the highest pipe runs) coupled with a maze of restrictive pipework, then this is - I think - a possibility.

    By the way - the amount you pay these plumbers should reflect the actual 'repair', not the full number of hours worked - 'cos they haven't earned it.
  4. Following Bill's post above^^, if it turns out that it's a simple matter of balancing the system, then - Aga - you owe the plumbers, I'd guess, around 2-3 hour's labour charge. In total.
  5. Aga

    Aga Guest

    The plumber was in my house again 3 days ago, with his boss - as we had said we do not trust the guy. And.... the good thing is that they changed something (water level?) in the tank on the loft and I think it stopped water dripping from the pipe outside of the house, straight on my window...or I just don't see it anymore as they put a curved pipe thing on it, to stop the water dripping straight onto my window.
    They kind of stopped the water dripping from the new radiator - kind of as it's still drips but very slowly....
    They managed to get all the radiators hot (by shutting off all of them and then  one by one they were turning them on) but ....again some of the radiators are already cold and the one in dining room is getting colder and colder....They checked the pump, the boss said the pump is fine (now is on2), they even tried to bleed the pump to check if there is any air but was all fine. So at the end the boss said the radiator in bathroom is causing all the problem as it catches air somehow - which kind of make sense - I'm not a plumber but we can here bubbling in the radiator, it sounds like someone is blowing an air into it using a big straw - sorry, not sure how to explain it. As far as I know it's the main radiator in the house....grrr
    as for the pump, noise it's not that bad now as it's on 2 now, it's quite loud (scary noises for me) when starts but after I don't know, few minutes is getting more quiet. I'm not sure but the boss of the company checked the pump few times as we were keep asking about it and said that the pump is fine and for sure that's not the reason for all our radiator problem....
    I'm not 100% sure but I think the tank on the loft is on the floor....
    As for the design, the boss said that some things are not quite where they normally are, i.e. pump so maybe there is a problem with the design, but people who used to live in the house survived all the winters somehow and lived there for quite a long time (I mean they didn't run away after the first winter) so not really sure if the problem didn't exist at that time or we just want too much from the system we've got....
  6. 1st get someone with a brain, it's basic circulation fault finding, do you have separate htg zone,s (2 room stats)?, do you have radiator cabinets? Have you added more rads to system? Is it balanced? May need AAV's, is pump purged & fitted correctly, don't put new rads on dirty sludged up system,
    SWodehouse likes this.
  7. The guy should be ashamed of himself, feel sorry for people like yourself, only work with highly recommended trades
  8. SWodehouse

    SWodehouse New Member

    Hi Aga, did you ever get this resolved? I have been reading this and it is almost EXACTLY the same problem that I have.
  9. neetie

    neetie New Member

    I had the exact same problem...upstairs rads hot downstairs cold. I called the people who do my annual inspection/ service and the first question was when did you last change the batteries in your thermostat? The thermostat has been in for 40 + years and I had no idea that it ran on batteries.2 new batteries were put in and it was fixed...I was £70 .00 poorer but wiser.....probably won't live long enough to profit from this knowledge but perhaps this can help someone else..It may be that it is only old thermostats that have batteries.
  10. sam spade

    sam spade Active Member

    That's correct for a boiler with a low resistance heat exchanger, but not for a modern boiler with a high resistance hex, where the cold feed is on the flow, ie T1= vent, T2 = cold feed, (pump), T3= cylinder and T4 = radiators. T1 and T2 must be within 150mm of each other.


    I have a Vaillon ECo combi boiler 3 years old just this week had it tested and serviced working perfectly, newradiators just fitted throughout house. My problem is radiators get hot, after 1 or 2 hours the downstairs radiators go cold. Have balanced radiators, bled them prior to fitting new radiators flushed lines drained off etc. Still radiators downstairs go cold??

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