New boiler - cold radiators

3 day old combi boiler nolonger heating radiators (they heat to a very tepid amount). Hot water is fine and the boiler turns on and off with our Nest Thermostat OK so it’s doing something but not heating the radiators!

have bled them all and they seem firne.

digital panel reading 1.4 bar, gauge on pipe to boiler is 1 bar. 

Any ideas? We’re freezing 😂
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  • daveyjp
    daveyjp Posts: 12,392
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    edited 16 January at 9:03PM
    A make of boiler would be useful.

    Is the heating circuit temperature set correctly?  Ideal is 50-60 degrees.

    If it is the diverter valve may be stuck or the pump isn't operating.
  • kittennose
    kittennose Posts: 142
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    daveyjp said:
    A make of boiler would be useful.

    Is the heating circuit temperature set correctly?  Ideal is 50-60 degrees.

    If it is the diverter valve may be stuck or the pump isn't operating.
    Sorry. It’s a Viessmann Vitodens 050-W.

    Flow temp is set to 60 which has been fine and too hot to touch. Tried increasing this to no avail.
  • ThisIsWeird
    ThisIsWeird Posts: 4,458
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    3 day old combi boiler nolonger heating radiators (they heat to a very tepid amount). Hot water is fine and the boiler turns on and off with our Nest Thermostat OK so it’s doing something but not heating the radiators!

    have bled them all and they seem firne.

    digital panel reading 1.4 bar, gauge on pipe to boiler is 1 bar. 

    Any ideas? We’re freezing 😂
    They would hopefully have carried out some form of system clean or 'power flush'? In which case, they will almost certainly have opened both valves on each rad in order to allow a good cleaning flow-through.
    So my suspicion is that they've re-shut the cool rads too far. 
    Q. are ALL rads cool? If some heat up, which ones?
    I presume that most of your rads have TRVs on them? What are they opened to? Are you familiar with 'lockshield' valves, the type on the other end? If you could show us a photo of them, we can guide you on opening them a little further.
    The room with the Nest - do these rads have TRVs?!


  • kittennose
    kittennose Posts: 142
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    3 day old combi boiler nolonger heating radiators (they heat to a very tepid amount). Hot water is fine and the boiler turns on and off with our Nest Thermostat OK so it’s doing something but not heating the radiators!

    have bled them all and they seem firne.

    digital panel reading 1.4 bar, gauge on pipe to boiler is 1 bar. 

    Any ideas? We’re freezing 😂
    They would hopefully have carried out some form of system clean or 'power flush'? In which case, they will almost certainly have opened both valves on each rad in order to allow a good cleaning flow-through.
    So my suspicion is that they've re-shut the cool rads too far. 
    Q. are ALL rads cool? If some heat up, which ones?
    I presume that most of your rads have TRVs on them? What are they opened to? Are you familiar with 'lockshield' valves, the type on the other end? If you could show us a photo of them, we can guide you on opening them a little further.
    The room with the Nest - do these rads have TRVs?!


    Yes we had a flush. I had to open some lockshield valves the day after as some rads were not getting very hot while others were too hot to touch, these ranged from 45 - 55 degrees.

    But now we have all 14 radiators very lukewarm, 25 degrees, not a single one is getting hot but clearly a tiny bit of warmth is getting into them but this isnt enough to even maintain temperature.

    only a few radiators have old school trvs on and they look like the attached. 


  • stuhse
    stuhse Posts: 250
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    edited 16 January at 10:02PM
    daveyjp said:
    A make of boiler would be useful.

    Is the heating circuit temperature set correctly?  Ideal is 50-60 degrees.

    If it is the diverter valve may be stuck or the pump isn't operating.
    Sorry. It’s a Viessmann Vitodens 050-W.

    Flow temp is set to 60 which has been fine and too hot to touch. Tried increasing this to no avail.
    There are usually 2 temperature settings, one for hot water tap temperature, one for radiator temperature....are they both set at high temp.  .?
  • ThisIsWeird
    ThisIsWeird Posts: 4,458
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    Kitten, which room has the Nest in it? Having a room stat like this is new to you? Silly Q - it's not that the room with the Nest is warm enough, and it turning off the Nest, and hence the rest of the house?
    Q's: which room has the Nest?
    What is the Nest set to?
    Does the nest show both 'actual' room temp and 'target' room temps? If so, is the target higher than the actual? Give us some figures.
  • ThisIsWeird
    ThisIsWeird Posts: 4,458
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    edited 17 January at 6:54AM
    3 day old combi boiler nolonger heating radiators (they heat to a very tepid amount). Hot water is fine and the boiler turns on and off with our Nest Thermostat OK so it’s doing something but not heating the radiators!

    have bled them all and they seem firne.

    digital panel reading 1.4 bar, gauge on pipe to boiler is 1 bar. 

    Any ideas? We’re freezing 😂
    They would hopefully have carried out some form of system clean or 'power flush'? In which case, they will almost certainly have opened both valves on each rad in order to allow a good cleaning flow-through.
    So my suspicion is that they've re-shut the cool rads too far. 
    Q. are ALL rads cool? If some heat up, which ones?
    I presume that most of your rads have TRVs on them? What are they opened to? Are you familiar with 'lockshield' valves, the type on the other end? If you could show us a photo of them, we can guide you on opening them a little further.
    The room with the Nest - do these rads have TRVs?!


    Yes we had a flush. I had to open some lockshield valves the day after as some rads were not getting very hot while others were too hot to touch, these ranged from 45 - 55 degrees.

    But now we have all 14 radiators very lukewarm, 25 degrees, not a single one is getting hot but clearly a tiny bit of warmth is getting into them but this isnt enough to even maintain temperature.

    only a few radiators have old school trvs on and they look like the attached. 


    That old school TRV is not a TRV but a 'manual' valve. It's like a tap - you open it a certain amount, and it stays at that setting. 
    These are the type you'll want in the room with the Nest.
    The rads in the other rooms should ideally be TRV type. 
    You've been adjusting the valves, so obviously have an understanding of what's required, but please answer all the Q's first.
    Of course, the real.answer is to get the installer back out :-) but I guess you want to make sure you ain't doing anything daft first.
  • FreeBear
    FreeBear Posts: 14,262
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    kittennose said: Yes we had a flush. I had to open some lockshield valves the day after as some rads were not getting very hot while others were too hot to touch, these ranged from 45 - 55 degrees.

    But now we have all 14 radiators very lukewarm, 25 degrees, not a single one is getting hot but clearly a tiny bit of warmth is getting into them but this isnt enough to even maintain temperature.

    only a few radiators have old school trvs on and they look like the attached.
    First pic is not a TRV, just a regular radiator valve that you can use to turn it off. The second pic is of a lockshield valve - This is the one you should be adjusting when balancing the radiators.
    Get yourself a pair of cheap thermometer modules plus a couple of pipe clips. Shut off all the lockshields and open up the valves fully on the other end of the radiators. Fire the boiler up and give it 20 minutes or so to heat the water in the pipes. Starting with the radiator closest to the boiler, pop a thermometer on the inlet & outlet pipes. With a flow temperature of 60°C, you want to adjust the lockshield so that you get a temperature difference of 10-12°C. Open the lockshield very, very slowly, giving it about 5 mins between each tweak. The radiator will be slow to react, so don't go winding the lockshield fully open to start with.
    Once you have done the first, move on the the next radiator and repeat, and so on for all the other radiators. After an hour or three, go back and check each one again.
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  • kittennose
    kittennose Posts: 142
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    stuhse said:
    daveyjp said:
    A make of boiler would be useful.

    Is the heating circuit temperature set correctly?  Ideal is 50-60 degrees.

    If it is the diverter valve may be stuck or the pump isn't operating.
    Sorry. It’s a Viessmann Vitodens 050-W.

    Flow temp is set to 60 which has been fine and too hot to touch. Tried increasing this to no avail.
    There are usually 2 temperature settings, one for hot water tap temperature, one for radiator temperature....are they both set at high temp.  .?
    Yes flow is 60/50 by default and we’ve tried increasing to no avail…
  • kittennose
    kittennose Posts: 142
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    Kitten, which room has the Nest in it? Having a room stat like this is new to you? Silly Q - it's not that the room with the Nest is warm enough, and it turning off the Nest, and hence the rest of the house?
    Q's: which room has the Nest?
    What is the Nest set to?
    Does the nest show both 'actual' room temp and 'target' room temps? If so, is the target higher than the actual? Give us some figures.
    Nest is new but I am well used to modern thermostats coming from a hive. The Nest thermostat is in the landing and the target temp is 19 and the current temp is 16°. 

    I have reset the nest and it still reads the same.

    Note  can turn off the thermostat or reduce target temperature which will turn off the boiler so they are obviously communicating.

    if I leave it set on our schedule (19°) or turn to any temperature above the current temperature the boiler kicks in and is running and making the right noises etc just not doing anything for the rads. 
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