Having seen this webpage https://www.draytoncontrols.co.uk/news/opentherm-explained , which kind of modulation do you have? Long boiler runs are not always bad.
Also, are you able to use the living room TRVs to restrict the livingroom radiators heat output while keeping what you have set as the main setpoint, in the use case you detailed. That would avoid having the main thermostat triggered off too soon.
I’m really confused by your post. The questions don’t seem to match eachother’s. I feel you have not made clear the specific use case you’re troubleshooting.
I am an inexperienced knob on Homeassistant and home automation, that lurks here out of curiosity and to catch some easy crumbs left around.
But, I feel that I know enough about central heating, radiators and thermostats to justify commenting.
The central heating boilers, pretty much always, just work as on-off. With some internal (boiler) logic on safety limits, like the working temp of the radiator fluid.
Thus your obvious question has an obvious answer. The way to have the main thermostat sending a heating request is to lower it’s setpoint temp.
At the same time, the TRVs are supposed to limit/moderate the lowness of the main thermostat setpoint, i.e., to moderate the way in which the main thermostat activates the boiler ‘too soon’. And TRVs allow you to adjust the comfort of each room (as long as the main thermostat is already requiring the boiler to be on).
As for the presence sensors. Radiators take a long time to heat a room. Like dozens of minutes. If the presence sensors work as their name suggests, I feel they are not a good match with radiators. Plz teach me!! How do these work? What happens when you are sleeping, or when siting, reading, or watching TV, or in the computer.
“I’ve heard about central heating systems not enjoying a fully thermostatic valved circuit.”
‘Enjoy’? Ehh, the pump (usually a part of the boiler) and the tubing that make the radiator’s fluid circulate, from the boiler around the house and around the radiators, they are not contructed/designed to have the circuit closed. 100% closed. Thus the recomendation not to put TRVs in all radiators - which could potentially all close off at the same time and damage the circuit (with overpressure). The recommendation is to have at least one radiator with it’s manual valve always open. The recommendation is also improved to have this radiator in the bottom of the house or the closest to the boiler, instead of a radiator in the top floor bathroom where you’ve left open the window to let out the moisture or something.
Again, what is it really what you want to solve?
“Who would have known that the mighty people of Yemen would challenge the empires of the world,” he added, referring to the Houthi attacks on international shipping in the Red Sea that have led to two nights of retaliatory strikes by the US and UK.
This does not sound like somebody interested in promoting peace.
From the site: with opentherm modulation “the boiler will run for longer periods but it will be producing water at lower temperatures, resulting in less energy being used and maximising the time spent in the higher efficiency condensing mode.” So, longer running times should not be a problem in your setup.