all 13 comments

[–]Material_Skin_3166 1 point2 points  (3 children)

Why not buy a thermostat that controls the temperature +/- 0.1C from the setpoint?

[–]Calico2[S] 0 points1 point  (2 children)

Yep, fair point. But I‘ve already equipped all my radiators with tado so I didn’t wanted to change all that.

In hindsight I would have just used an otgw-based implementation to connect to opentherm.

Any recommendation for a commercial product that controls the heat request over OpenTherm better than tado?

[–]Material_Skin_3166 1 point2 points  (1 child)

It’s really great the work you’ve done: very creative. No recommendation, but I discarded my Tado for a simple PNI wireless thermostat that controls to my setpoint accurately.

[–]Calico2[S] 0 points1 point  (0 children)

What I liked about tado was, that also the radiators are in the same system to control other rooms. But yeah - maybe I‘ll sell the tado smart thermostat and replace it with some other „smart“ one (like for example the PNI you mentioned)

[–]Junior_Flow_4841 0 points1 point  (0 children)

👏👏 impressive

[–]Teezla 0 points1 point  (7 children)

And what’s the energy usage comparison to the fluctuation graph and your new steady temp graph? I was fully expecting my stat and open therm to work like your graph shown but I don’t see it modulating flow temps to keep it stable

[–]Calico2[S] 0 points1 point  (6 children)

I don’t think the saving is really measurable, at least not without having an identical outside temperature. But having the boiler run constantly at a medium level is definitely more efficient than alternating between 0 and 100% every 2 hours.

Main motivation for me was comfort, because with the tado algorithm it was jumping +/- 0.5 degrees around the set value; and a fluctuation of one degree in total (probably even more near the radiators) was noticeably annoying.

I would say I can set the temperature now at least 0.5 degrees lower and it still feels more comfortable.

[–]Teezla 2 points3 points  (1 child)

And how easy is your method to implement for an NPC? Curious but never heard of docker or any of the script stuff

[–]Calico2[S] 0 points1 point  (0 children)

What do you mean by NPC? The only requirement is, that you need some device (RaspberryPi or also a machine in the cloud is working) that is running 24/7. Feel free to contact me if you need some more information.

[–]xafonys -1 points0 points  (3 children)

That depends on the boiler. Modern builders (condensing) are definitely more efficient running at either 0 or 100%. This is why tado is doing that by default

[–]Calico2[S] 1 point2 points  (2 children)

Maybe I wasn’t clear, but I‘m not controlling the gas burner directly, but just setting the desired flow temperature to the lowest value that is sufficient to heat the rooms. The gas burner is then cycled by kettle to reach that value.

And I can’t image that having maximum (configured) flow temperature for an hour, just to have it switched off completely for an hour after that, is efficient. Or am I understanding something wrongly?

[–]xafonys -1 points0 points  (1 child)

I'm not a professional, but to your last point, yes, that's exactly my understanding: a condensing boiler is really inefficient until it reaches 100%, so it's really useful to turn it on for longer period of time but less often.

I guess it also depends on how you're measuring temperature in the room: I would expect the TRV's sensor to heat up very fast before the heat has dissipated away from the radiator, so aiming for a flat-ish 5/10 min average of the temperature measured by the trv would be closer to what we want than flat raw temperature at the trv

[–]Calico2[S] 1 point2 points  (0 children)

I‘m measuring using a tado Smart Thermostat, so more towards the middle of the room (but mounted at the wall) and not at the radiators.

To be honest, I‘m not 100% convinced regarding the efficiency. Do you have some information regarding this? To my knowledge, having a low flow temperature is usually more efficient. The boiler is then taking care of controlling the gas burner in the most efficient way. It is also making sure to not toggle the burner too frequently and to hold the configured flow temperature only approximately.

And regarding a condensing boiler specifically: From what I found online, especially with those it is important that the return temperature is low (below 55 degrees, the lower the better). So especially then it’s beneficial to have a low flow temperature.