Bitter experience they in real terms don't work. I spent ages working it all out, planned down stairs at 70°C and upstairs at 60°C but ended up having to fit TRV to upstairs to reduce temperature and extra two radiators downstairs.
The problem is heat raises so upstairs heated by the downstairs, and air movement is so important when working out how much heat is lost. So a tiny black radiator mounted in a box with circulating fan can put out far more heat than a huge white radiator.
So you can look up a Myson radiator and yes the output it says it has is actually what it gives out, so 3.4kW to 4.9kW depending on fan speed at 50°C and also there is a set of figures for 30°C temperature difference. Because the air flow is controlled by fan speed there are very precise figures.
But place a normal radiator where there is little air movement and it can have such a low output compared to if placed in a draft. So my house after all the careful work simply did not work. Until two extra radiators added and TRV's fitted upstairs.
Mothers house is completely different to mine, To start with she has doors to each room, so doors closed each room is independent or it should be, however the idea of fitting TRV's to each room so you can select different temperatures may work in theory but not in practice.
I have spent 2 years trying to get my mothers house so the rooms stay at a reasonable temperature without needing to keep tweaking the thermostats. The aim was simple, bedroom needed to cool down at night, but needed to be warm in the morning and evening, and the living room wanted to remain at a constant temperature all day, the hall, kitchen and wet room did not really matter, the latter has under floor heating which is put one before going for a shower.
Why I don't know, but the main thermostat is in the hall, I really don't care what temperature the hall is, so why put the thermostat there? But in general the problem is lack of information.
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