[OpenTRV-interest] Question from Steve R

Simon Hobson simon at thehobsons.co.uk
Sun Nov 22 10:55:43 GMT 2015

Mark Wigmore <mawigmore at gmail.com> wrote:

> If you've got the cash to splash then Evohome works well, but for a fraction of the cost you can get a similar effect using programmable motorised TRVs. 

Yes, similar if you're happy going to each rad to change it's program any time you want to change it, and not be able to see what any room is set to without visiting it's TRV. And that's assuming the TRV is actually accessible !

My goal would be (eventually) to have feedback from each TRV as to it's valve position, and regulate the flow temp accordingly. That way, under light heating load, the flow can stay up a bit but at low temperature - avoiding the "rad cold but for a small (very) hot spot at one end" effect. Or depending on the setup, avoiding the noisy system pumping water round through the bypass because the stupid boiler design* can't cope with normal heating loads.

Next stage is to feed that back to a motorised TMV to control the flow temperature, and to an intelligent stat that will only maintain the lower section of the thermal store to a little above that.

A thermal store, modulating pump, and all TRVs makes for a wonderfully quiet system :-) An "intelligent" TMV on the flow and "intelligent" store thermostat would make it even nicer.

* Which is universally the case unless someone can tell me otherwise. I've never found a boiler designed for other than a  flow rate that gives around 20˚C delta-T.

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