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Comment by Animatronio | Hacker News Reader

Pretty nice for a DIY project, but it turns out that the first guy in the article uses an Alpha e-tec boiler, for which the manufacturer also sells a "weather compensation probe" to adjust the heat output according to outside temperature. It's just under £45.

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Why would you want a weather compensation probe? Surely it's indoor temperature that matters.

Is it for heat pumps that work slower? It still implies to me that insulation is lacking.

I'm still somewhat dubious of 'better' thermostats though. I just turn it on when I feel cold. I don't see how a thermostat could improve on: 'The heat only goes on when it's cold enough for me to turn it on'.

I'm guessing it adjusts the boiler quicker (up/down/off) than simply by measuring indoor temperature, which is a lagging indicator. I can also bet that insulation is very much deficient, this being the UK.

Wouldn't insulation be the first thing to fix though?

I've got cavity wall insulation, 30cm of insulation in the loft and recentish double glazed windows and the bedrooms stay warm enough at night with just body heat and residual heat. The heating on goes on in the evenings (still hasn't gone on yet) unless it's really cold. I don't think any of those are particularly onorous jobs to undertake.

Yes, I'd say you are absolutely right in that insulation is the most important thing to improve. I'm not familiar with cavity insulation, but I suspect that it's not the best in terms of efficiency. On the other hand different kinds of wall insulation might ruin one's health or one's house, so I'm not really sure what can be done (if anything).

My house has something called ETICS* (basically a thick outer layer of polystyrene with a weather resistant paint. Ugly stuff, but it works wonders!), mineral wool insulation in the attic (which I'm supplementing just in case), underfloor insulation with extruded polystyrene and of course double glazed windows. We don't turn on the heat until it's 3 degrees or less outside. Thermostats and stuff like in the article bring too small benefits to really consider.

*) https://www.ea-etics.com/etics/about-etics/

I've half looked into external insulation. I don't think the roof overhang is enough though. So I'm not sure it's worth it as the roof would need sorting too.

Ultimately my direct debit for gas electricity is only £10pm at the mo after the govt bung so my house is about as good as I'm going to get it anyway.

For sure, but it doesn't cost £15 to fix your insulation.

For those of us with solid walls it's expensive and very disruptive to install internal/external wall cladding. I happen to live in an area where I'm not even allowed to install external cladding.

Insulation is great. But if you rent then you have limited control over what you can do. Insulation seems to be hard for Renters but maybe turning up and down a boiler is possible.

Well, outdoor temperature determines the heat load demanded of the radiators, and lower exhaust temperatures for a condensing boiler mean more condensing takes place. So unless/until the circulation pump starts to dominate, one wants to run the water in the heating loop towards the radiators as cold as will still suffice (though cold here is more important for heat pumps; the boiler cares more about how cold the water leaves the radiator), and often have a rather small temperature delta between the inlet/outlet ports of the radiator loop heat exchanger in the boiler.

Theoretically it could use feedback from all the thermostat valves (and adjust the burner to keep the most-open valve near (but not at) 100% flow), but that requires feedback from all valves rather than just an outdoor temperature probe and a parametric mapping curve that depends on radiator style, desired indoor temperature, and building insulation.

It's a modulating boiler, it's not on/off, rather it has levels.

The lower the level the more efficient it is. It's better to run the boiler on low for 3 hours, vs high for 1 hours.

How do you know if to run the boiler on low or high? You check the outdoor temperature. You also do a backup: If the boiler has been running for more than an hour, increase the temperature slightly every 15 minutes. Once it goes off, reset the temperature to the one determined by outdoor temperature.

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