mrklawuk

Hi, I’m about to replace my combi boiler and the likely candidate is a vitodens 050-w 25kw. I have a question related to getting the most out of lower flow temperatures. I’ve done some calculations and had an initial visit for potential heat pump and the radiators and pipework seem ok except the spare room. The reason I’m going combi is mainly lack of space for a HW tank (its now our ensuite). In the next ‘some’ years I’ll look at getting a porch extension and carve out some space as a mini plant room. But not today. I have a tado wireless thermostat and receiver, and smart TRVs on all radiators. Being a UK model it is only on/off, but Tado have just released the EU version in the UK which I could buy which would give me opentherm controls and should be ok on the vitodens. So I think I have two options and I’d appreciate your input. 1) keep the on/off tado, buy the external temperature sensor for the vitodens and ask the installer to connect to the boiler. This would enable weather compensation where the vitodens has a single fixed curve and would lower the flow temperature based on the outside temperature. 2) replace the tado wireless receiver with the opentherm one and use that to enable load compensation driven by the tado. This will vary flow temp based on the delta between room temp and called for temp. I can’t tell if one is noticably better than the other. I can see ups and downs for both. - with load compensation if the called for temperature gap is wide, it’ll use a high flow temperature even if outside isn’t cold which would be inefficient. However if it isn’t cold outside the gap shoudln’t be wide, right? so maybe a false use case? - with weather compensation if its cold outside the flow temperature will be high even if the call for heat is only small? could this lead to cycling? Although again if its cold outside the heat loss would be greater Maybe they’re both as good/bad as each other. I checked the viessman manual and they are one or the other - they can’t both be active at the same time.