Hi all,

I'm a happy owner of a EvoHome that controls my heating system. I recently finished to fit my 12 radiators with HR92 heads, my condensing boiler is controlled by an R8810 OpenTherm bridge and everything seem to work ok (let alone minor issues that I'm stubbornly trying to fix when I have some time to spare).

Quick question: would it be possible to replace a traditional radiator with a fan coil (a hot water radiator with an electric fan) and still drive it by means of my EvoHome using HR92 heads? Does anyone know of fan coils that have some temperature sensing device to control the fan, so they would start when they heat up and stop when no heat is left to distribute?

Background: lately I found in an old backup drive my original heating system sizing chart (15 years old), and noticed the heating engineer had to size everything based on a temp differential of 50, since my house is an old countryside building, surrounded by ...nothing, insulated as the builders could do (that means they threw some glass wool under the roof and stuck some styrofoam into the thinner walls), yet dispersions are huge and this means big radiators (not to mention big gas bills) to keep the house warm.

Now I installed a condensing boiler, that works best when the return flow is lower than the dew point (normally 48), with an output flow of about 63. This would be 60 at the radiators inler (or even less), meaning a temperature differential of 40 to the conventional 20 room temperature. I took a look at my radiators specs and noticed that their power at a TD of 40 is some 30% less than at a TD of 50 that means either I have to use my boiler in non-condensing mode, or to replace my radiators with something more efficient. An obvious possibility would be to use 30% larger radiators, but such bigger radiators won't fit into the spaces they are in now (mostly under my windows), thus the idea of replacing some of them with fan coils...