EricMark
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- Reaction score
- 96
To start with it all seems to make sense, the TRV measures the room temperature and controls the radiator temperature to suit, as the water flow is restricted the by-pass valve lifts, and hotter water is returned to boiler, so the boiler is throttled back (modulated) so the heat exchanger is cool enough to keep the flue gases below the critical temperature where moisture will condense out of it. Until the point where the boiler can’t be modulated any more, at which point the boiler will start to cycle, there may be anti-cycle software which if on switch on the water returns hot will extend the off time, and if not reduce off time, however it can’t ever switch completely off, as there is nothing then to kick start it into running again. That is OK can understand it so far.
But then we get into the muddy area, it would seem what we need is for the wall thermostat to simply kick-start the boiler, so when wall thermostat is satisfied the boiler will remain stopped, and when wall thermostat shows a demand it will run again until it reaches minimum output again. If while boiler is running and the thermostat is satisfied, it will continue to run, as the wall thermostat is only in one location, and other locations must require the boiler to run or the return water would be hot and it would auto turn off.
However this is not the case, when the wall thermostat is satisfied, the boiler turns off, even if still at maximum output.
To my simple mind there should be two inputs to the boiler, time clock and wall thermostat, the time clock will switch the boiler both on and off, the wall thermostat will only turn it on.
Since this does not happen, I have clearly got it wrong, so can some kind sole take the time to explain how a wall thermostat is installed to stop boiler cycling without it switching off boiler prematurely? Especially with programmable TRV heads.
On another thread it was suggested a number of ways to sense when boiler is fully modulated, however I would not have expected to need to add gas flow switches or other sensors, I would have expected this to be already built into the boiler.
But then we get into the muddy area, it would seem what we need is for the wall thermostat to simply kick-start the boiler, so when wall thermostat is satisfied the boiler will remain stopped, and when wall thermostat shows a demand it will run again until it reaches minimum output again. If while boiler is running and the thermostat is satisfied, it will continue to run, as the wall thermostat is only in one location, and other locations must require the boiler to run or the return water would be hot and it would auto turn off.
However this is not the case, when the wall thermostat is satisfied, the boiler turns off, even if still at maximum output.
To my simple mind there should be two inputs to the boiler, time clock and wall thermostat, the time clock will switch the boiler both on and off, the wall thermostat will only turn it on.
Since this does not happen, I have clearly got it wrong, so can some kind sole take the time to explain how a wall thermostat is installed to stop boiler cycling without it switching off boiler prematurely? Especially with programmable TRV heads.
On another thread it was suggested a number of ways to sense when boiler is fully modulated, however I would not have expected to need to add gas flow switches or other sensors, I would have expected this to be already built into the boiler.