Good point so the temperature is point when boiler switches off, does not mean that is at that temperature all the time, so in real terms the point when boiler switches back on is more important, but is that not the same control?
It is of course clear that the hotter the radiator the more heat it can put into the room, but what I was wondering is how the boiler, pipe work, and radiator temperatures effects the air thermals and so heating of the room?
We have all seen the diagram
but in real terms in my main room I have two radiators at 90º to each other so that simply diagram does not work, and I know placing a thermometer around the room you can get 5ºC difference even at same height from floor, this is not all bad, as it means the air around windows can be colder than air around the chairs, and I am not that worried about air I walk through, more interested in air temperature when seated.
Under the window seems a daft place for a radiator, cooling the air before it does anything, but it is easy to work out how water goes from boiler (although at home they don't boil the water, only do that at work) and around the radiators, but how it goes from radiator into the room is harder for me to under stand.
So at the side of the radiator I have a TRV at the moment it shows 18ºC, and three meters away on a chest of draws I have a thermometer which shows 18.2º so clearly the TRV is doing it's job in this room. Some of my TRV transmit both current and target, but in this room a cheap one (£15) and it only shows the target.
At the moment all the expensive TRV heads are showing the current and target within 1ºC of each other, however as the schedule sets a temperature change then clearly the two part and it takes time for the new temperature to be achieved, either cooling or heating, not really interested in cooling, just the slower the better, but heating is what I am interested in.
So boiler set to minimum temperature house still stays warm, and even at maximum the anti hysteresis software in the TRV heads limits how fast any room can heat up, so in real terms no point setting to maximum, so I as I have just done I press the eco/comfort button on the TRV head then the now cold radiator will heat up next time boiler turns on or pump circulates already hot water, and the room will heat up, speed has a number of limiting factors, starting with temperature of water, then how much water in the radiator, I noted Myson fan assisted radiators heated up very fast, colour of the radiator again inside the Myson the matrix is black, and how fast thermals distribute the heat, and at what point the TRV starts to close again to reduce the hysteresis.
I am told the Drayton Wiser TRV head actually learns the time taken and adjusts to suit, but my heads are not that cleaver, at least I don't think so, the computer linked Energenie heads have got twin sensors so compensate for radiator direct heat, the eqiva eQ-3 can have an off-set set, but are much cheaper, but do have open window detection and a built in display, can set with phone, but once set use the buttons on the top.
My hall is the big problem, tends to over shoot, and the wall thermostat is in the hall, at about centre of house, and between four doors and a stair case, so most likely place to record average house temperature if doors open, but the radiator is two doors away from it, and tends to always show cooler than the wall thermostat.
So at moment wall thermostat shows target 20ºC current 20.5ºC so boiler is off, TRV shows target 20ºC and current 19ºC and using a thermometer both devices seem reasonably accurate there is a temperature gradient in the hall. OK if cold I can easy turn up wall thermostat, or move setting of hall TRV down a degree, but clearly the reason why no heating on at the moment is down to air movement which is likely affected by radiator temperature when it is allowing some flow.
So I have a number of controls, the TRV, the lock shield valve, the boiler temperature and the setting of the Nest thermostat. I am trying to get it into my head what does what, I tried linking the wall thermostat and TRV head, theory the TRV head should follow Nest, practice if I use the phone app to alter nest the TRV head does follow, but if a schedule or turning dial alters the Nest temperature the TRV head does not follow, so removed the link and set schedule to match each other, well not quite, morning TRV head goes to 20ºC but Nest goes to 18.5ºC then 0.5ºC per hour until at 20ºC as it tends to over shoot then turn off, and while hall is cooling other rooms are cooling faster so get cold.
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Just to add there are some modulating oil burners out there, not just 2 or 3 stage. Elco burners have one and other technology is moving things forward with other burners. Yours however i suspect is a fixed rate burner.
Reasonably sure fixed rate burner, mothers house had modulating gas, but our old house the boiler was also fixed rate gas, and likely this house main problem is over shooting or hysteresis. First fitted the programmable TRV heads in my mothers old house with a modulating boiler, and they took a little setting up to start with, adjusting the lock shield valves, in the main problem was TRV was on return, but once set it worked really well, I was very impressed, only had 4 programmable heads in that house, so when I came here I put old wax heads back on in her house and brought the electronic heads here. Then added a further 5 cheap eqiva eQ-3 bluetooth heads as well, if anything the eQ-3 work better.
But think circulation of air is the main problem, and to cure, first stage is to understand what is happening, hence the question on how water temperature affects things. Not simple if not hot enough house will not heat up enough that's easy, but if you turn it up higher how will that affect the heating of the home, clearly if when you turn it up the TRV auto compensates and turns down the flow, then no point turning it up.
But I am an electrical engineer not a heating engineer so asking those who know.
