Central heating

[Oldgreybeard]

So far I think this experiment has been a qualified success. Ran the heating for about four hours, when there was enough PV generation to cover it. Warmest it got outside today was about 10°C and the heating has pushed the indoor temperature up from about 21.5° first thing this morning to 22.1°C right now. The floor surface is sitting at around 22.3°C, so is only delivering about 150W to the house at the moment. The heat pump chucked about 7.7kWh into the slab, so that's enough heat to keep the house at this temperature for a couple of days or so (assuming it doesn't get colder outside, which I think it will).

So, not a bad result. Four hours heating from PV for free that will keep the house comfortable for at least the next 24 hours or so (assuming it does get colder as forecast). Been around measuring surface temperatures, when I was checking the floor surface temperature, and the inside surfaces of the external walls are sitting at between 21.8°C and 21.9°C, so very slightly cooler than the room temperature. Coldest surfaces are the door and window frames, they are around 21°C, as they have a poorer U value than the glazing, and massively poorer U value than the walls. The absolute coldest points are the locks in the outside doors, they are nasty thermal bridges so are only slightly warmer than the outdoor temperature. Unfortunately no one seems to make thermally broken locks, probably because of the security risks they might present.