[OpenTRV-interest] Programmable TRV performance

[Damon Hart-Davis]

Hi,

> On 19 Feb 2015, at 16:20, Geert Steyaert <EMAIL ADDRESS HIDDEN> wrote:
> 
> Sure, thanks for the answers, I have some more questions though :) As expected ...
> 
> ...for the plastics, will there be a downloadble version we can print/have printed ourself in a fablab or at friends place, for the less 'visually' interested people?

Yes.

We’re still debating the fine details, and 3D printing and 3D-printable plastics are usually not going to be ideal mechanically (ie the design is for different plastics and construction techniques), but the sample that I have on my desk is indeed 3D printed.

> 
> ... When reading boiler manuals and seeing manufacturer (Junkers in my case) boiler options, there is always a 'special' thermostat for modulating boilers, 'different' from the ones for older standard pump/boiler on/off switch. How does that work then? More on this, I have read this on a Nest forum: "All a thermostat like the Nest can do is send an on/off signal, or if you're lucky, a stage 1 or stage 2 signal. Modulating furnaces vary in how they respond to this signal, and I forget what Goodman does. Some will not modulate at all without the matching thermostat, becoming a single or multistage furnace. Others will modulate, but based on an internal algorithm that guesses how the modulation should go based on the length of heat calls. In other words, it doesn't actually know the room temperature like the thermostat would. The latter is better than the former, but using the [boiler matching] matching thermostat beats both.”

Unfortunately AFAIK ‘standards’ like OpenTherm aren’t that open nor standard, and I still think that the boiler is often going to be in the best place to decide how to modulate heat input based on flow and return temperatures.  Weather compensation is probably a good idea but can be done independently of the call for heat.

I think trying to control modulation could be a massive distraction for little improvement in result at the moment, but I’m happy to be corrected.

> Another comment (on the Junkers boiler, the one I intend to use) and the modulating process I found here: http://forum.loxone.com/enen/software/5664-question-intelligent-room-controller-2.html
> So I'm not sure how much actual use of the modulation there will be in this only on/off situation.
> Something interesting I also found, on the same link as the 1st quote: "Most of the new "modulating" variable-speed systems are using a ClimateTalkcompatible protocol.". https://community.nest.com/message/42434
> 
> So is there any plan to support that in the future, in that case then I need to figure out if my new boiler also supports that 'standardized' protocol.?

Maybe, but only if it looks like it’s actually going to offer sigificant improvement for the complexity involved!

Rgds

Damon