DIY

I have an underfloor heating system, a boiler and a nest thermostat and I don't understand how the three things interact with each other, and I have a feeling they're set up wrong. The underfloor heating has a manifold with a water temperature dial on. In the winter I have this value reading 35°C. The gauge on this manifold always shows a consistent reading of around 35°C throughout the day. The Nest thermostat is linked to the boiler and we tend to have the temperature on a schedule between 16 during the day, which is essentially 'off' as our house rarely drops below that temp and 20 in the eve. The floor definitely feels warmer in the evening so the thermostat is doing something. Where I am confused is if the manifold is always reading a consistent temperate then it must be asking the boiler for more hot water when it needs it, even if the nest isn't asking the boiler to turn the heating on. In fact, if I go and watch the boiler during the day when the Nest is 'off', it's constantly turning on and off, with the heating light going on and off – for a few seconds at a time. So how is the nest controlling the underfloor heating system? Does the nest actually need to speak directly to the manifold and not the boiler? Our bills are always really high and I think thats because the boiler is always heating the underfloor heating system, even if the nest doesn't think it is.

Hope i've explained this well enough, I find it quite confusing but really hope someone can help as I need to get this system figured out before this very expensive winter.