Cannot manually set radiator flow temperature

Discussion in 'Engineers' Talk' started by Baz zee, Mar 20, 2023.

  1. Baz zee

    Baz zee New Member

    Hi all I'm wondering if someone can help? We have recently had a valliant ecotec sustain combi boiler fitted with a valliant sensoroom pure thermostat and honeywell home 1 channel timer. Just to mention the sensoroom doesn't have a gateway fitted.

    The problem I am having is that I cannot manually adjust the radiator temperature, I know how to it just doesn't save the selected temperature.

    So when the boiler(radiator side) is off its @ 0°c and around 1.6 bar, when the boiler is on (radiator side) the flow temperature is 75°c and about 2.3 bar, then on top of that the return flow is about 70/71°c.
    We have young children in the house so the radiators are way too hot. I've also read that the boiler will not enter condensing mode if the return is too high.

    Does anyone have a solution to this? As mentioned everytime I manually set the temperature it get over ridden.

    Thanks
     
  2. Baz zee

    Baz zee New Member

    To add I have just read that if its connected with an eBUS which it is, you cannot change the flow temperature from the boiler, is there another way to lower it as 75/71 seems a bit high and in efficient. Thanks
     
  3. MGW

    MGW Screwfix Select

    I am an electrician so may be wrong, but mothers house setting the lock shield valves, the radiators ran a lot cooler.

    I am not sure what a wall modulating thermostat does? I had simple on/off, and as summer approached it turned boiler off, in winter it stayed on, and the TRV's controlled room temperature, as the TRV's close, the by-pass opens, sending hot water back to boiler which turns boiler down.

    So would guess lock shield valves not set correctly.
     
  4. quasar9

    quasar9 Screwfix Select

    Completely understand your concerns about safety , but, unless your system was designed to run a lower temperature of 60 which means bigger (or more) radiators, your rooms may not heat up. The rate at which heat is transferred from radiators to the air in the room is directly proportional to its temperature. The current govt advice of turning down everything is simply wrong for most people.

    flow temperatures are normally set on the boiler panel.

    a modulating thermostat simply tells the boiler to throttle down (or modulate) as the room temperature reaches the set temperature whereas a simple thermostat only stops calling for heat on reaching the set temperature. This can save some gas but only under certain conditions.

    The high return temperature suggests water taking a short circuit and returning to the boiler (rather than flowing through the system ) indicating an unbalanced system.

    As MGW says, you need to balance the system properly via the lock shield valves.
     
  5. Baz zee

    Baz zee New Member

    Thanks for the replies, I have gone round and bled the radiators and checked how long each take to warm up, there is very little difference in times on any of them, as they all reached warm then scalding hot around the same time, the one that took slightly longer is a large double one in the kitchen (also the one that's the farthest away, so I closed the other lock shields slightly and opened that one up a little more, which seems to of brought it upto speed.

    The issue I am still having is that the ebus controls are still telling the boiler to heat upto to 75°c. Which I have no control over as it locks me out of manually adjusting the flow temp from the boiler pannel, the option is still there but when I set it, it reverts back to 75°c. The only time this goes down is when it's around 0.5°c below the desired temprature.

    Also the return flow is still only a couple of degrees under the output, is it possible there is some incorrectly installed pipes somewhere along the system?

    We upgraded from an old water tank system but the radiator network/plumbing system was untouched (apart from the connection to the new boiler) would that make a difference?

    Is it possible to have the lock shilds too far open around even if the system is warming equally?

    I'm just not wanting them to heat up to ~75°c when it seems excessive and the boiler doesn't seem to enter condensing mode as the flows such a high temp.
     
  6. Mike83

    Mike83 Screwfix Select

    You can’t change it on the boilers front panel as you’ve used an Ebus control.
    Not sure if it can be altered through the parameters though.
    If you don’t have a programmer fitted then this could be an opportunity to upgrade the controls.
     
    quasar9 likes this.
  7. Baz zee

    Baz zee New Member

    We may have to get one, I will look into seeing if the parameters can be changed through the boiler settings first. Thanks
     
  8. MGW

    MGW Screwfix Select

    As said, my mothers house the radiators were either cold, or stinking hot, the cure was fitting a TRV in the hall, it went against all advice, which says the room with the wall thermostat should not have a TRV, however I think that advice was for old non modulating boilers.

    With no TRV in the hall, open the radiator valve in hall and all other rooms got cold, close it, and after front door opened, the hall too an age to recover.

    With TRV on hall radiator the opening of front door would cool hall, then the TRV would open to rapid reheat hall first few degrees, then it would throttle back before the wall thermostat reached cut off temperature, so in winter boiler did not turn off at wall thermostat, this only happened on warmer days.

    Because the boiler did not turn off, all rooms are controlled by the TRV heads, so radiators only just warm enough to maintain the room temperature.

    However unless the lock shield valves are set, you still get a hysteresis, the TRV's are slow to open and close, my electronic ones take 3.5 minutes to cycle open/closed/return to setting every Saturday at 12 noon, so the lock shield needs setting so it takes around 1/2 an hour for the radiator to warm up, this gives the TRV chance to adjust before the radiator becomes stinking hot.

    So try it, turn the wall thermostat to some really high figure so it does not turn off, then adjust the TRV's so no room is over temperature, let the TRV's control room temperature not the wall thermostat. Then set room thermostat just above room temperature set by TRV's so when we get a warm day the boiler will turn off rather than cycle on/off.

    And you will find the radiators only warm enough to maintain room temperature, rather than continually turning on/off and when on too hot.

    It worked well in mothers house, but this house boiler does not modulate (oil) so using programmable TRV heads is not quite as good as it was with mothers house.
     
  9. adgjl

    adgjl Screwfix Select

    Hi MGW, Please provide some verifiable figures to prove that your suggested method uses less gas than allowing the thermostat to turn the boiler off completely.

    I am assuming that you are still advocating the use of a time clock to turn the heating on / off during the night / day?
     

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