DamonHD

As the inventor of one of those smart TRVs there is indeed typically only a very limited range over which most valve bases show an analogue response (and sometimes being in it causes undesirable noise), but yes that particular TRV does try to make use of the bit in between on and off where it can.

I use my Eddi with remotely driven boosts from my RPi: the heat pump doesn't get a look in. (I also limit the grid demand while boosting to 2kW.) I appreciate that this may not be at all what you are after of course!) All this to do smarter and less frequent pasteurisation, basically only when the grid is relatively green.

Taking the emergency out of water heater replacement — and slashing emissions: MCE, an electricity provider for three-dozen communities in Contra Costa, Marin, Napa, and Solano counties [San Francisco Bay Area, CA, US], launched a [Emergency Water Heater Loaner] program in September that offers contractors a $1,500 per-unit cash incentive for the installation of an electric heat pump water heater after the installation of an emergency loaner. The big points here are that (1) a temporary heater is only used if the main job cannot be completed in a couple of days and (2) that the loaner is subsidised. So the expectation is for a fast replacement, but with a good cheap plan B.

I am brewing up to writing an open letter to Ed Miliband and Greg Jackson saying how and why most UK domestic heat pump installs should be doable in a couple of days, such as to catch the distress purchases, and how other countries help make this kind of thing work. Some of it is not even Adia's claimed cleverness, but such dull stuff as pre-fabricating pipework etc off site to connect in seconds to the existing boiler pipework (they know the boiler brand, and where it is on the wall, so what all the pipes do) and getting pre-auth from the DNO to install one of several ASHP models depending on what the concurrent survey indicates is needed. Will not make me popular in some quarters, and obvs it's easy for me to claim not doing the work!

I'm likely missing this above but I'm too tired! Is there some sort of mixer for the UFH that's reducing the UFH flow temperature compared to the rads? If so, without damaging the floors, can you just not mix it down (so much)?

For us the Thermino was able to fit under the then extant combi, but hold ~2 days' heat. https://www.earth.org.uk/note-on-solar-DHW-for-16WW-UniQ-and-PV-diversion.html#2022-03-09

I'd quite like a small lump to sit on top of my Thermino, maybe to instill a sense of mortality in it! B^>

No and no.

Avoiding getting the batteries out of balance is important, and what @ProDave suggests seems like a decent temporary workaround.

I do not think that 'everything open' is always right (formal paper https://www.mdpi.com/2071-1050/16/11/4710 - TL;DR https://www.earth.org.uk/To-Zone-Or-Not-To-Zone-with-TRVs-for-Retrofit-Heat-Pumps.html - discussion on the Heat Geek thread here), but definitely go for weather compensation: you do not need to run at anything near the maximum temperature most of the time and so WC will improve CoP and reduce cycling.

There are standard calcs I suspect, likely in part dependent on 99% percentile windspeeds in your area.

To add: being the H&S governor too, I did ask for additional steel fixings / ropes to the edge of roof surfaces to further reduce the risk of takeoff or at least stuff sliding on to kids below, but I don't think there was any evidence of anything shifting in even quite high winds. The panels were initially on frames with ballast weights. I think that on the new roof trays may have been used in part, but it is the ballast that is doing most of the ... uh ... heavy work... as suggested above, AFAIK.

16kWp on a school roof many years ago - all fine. Largely survived building works and some being shuffled to an entirely new roof also. https://www.earth.org.uk/solar-powered-schools.html

See live-ish charts of TRV open %-age further up the thread. To avoid various problems they open fairly fast but close as slowly as they can without temperature overshooting too far. They do not close fully if temperature does not significantly overshoot.

I have been out all day so I may not get to respond to everything... OpenTRV / Radbot are intended to just this where possible by bringing rooms up to temperature when occupancy is predicted. And indeed my bedroom Radbot did so this morning. Some of the other things that you mention are things that I have considered since handing over the Radbot IPR and there is space in my research plan to think about and maybe model or prototype some of them.

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But plain WC does not increase flow temperature in response to anything other than falling outside temperatures. If you are saying that someone might shift the whole WC curve up then that is a different matter which I address as "fiddling with the settings". Notionally that WC curve is *computed* from the heat loss calcs at installation time and left alone. 😀

@JamesPa I hear what you say and I shall think about it: thank you for tussling with this. But where you say "I think the latter results prove that the saving in the former is really attributable to the reduced temperature of the inhabited rooms, not to the setback in the uninhabited ones!" taken literally and simplistically is untrue: it is a simple matter of physics that all internal spaces that are at a lower temperature than they otherwise would be lose heat to outside more slowly than they otherwise would, and thus reduce heat demand, and where WC is in use that reduces electricity demand and thus cost. Note that the initial HG claim being countered was that reduced heat demand could cause increased electricity demand, which is again simply not true with use of plain open loop WC. Whether that arrangement is acceptable for other reasons, some of which we have discussed in this thread, is a separate issue.

FWIW my own live-ish TRV percentage-open chart (for most of the rads): and call for space heat: Note that there is currently a problem with this system and it hasn't been fully commissioned (or paid for!) yet, and I am continuing to tweak as householder and researcher. So have a good laugh! B^>

I agree, which is why I'm doing my research, to see if there are any wheels that I can find to grease...

"Eating your own dogfood" is a standard term in the start up world and beyond, meaning that you actually use (and understand and stand by) your own product, which is IMHO the right thing to do. Far from petulant. I estimate ~100M rads in UK homes, ~1B in European homes, and about the same again in commercial properties. There are ways of misusing all tools. Most UK home heating systems are vastly oversized and fairly poorly installed and understood and used I believe. The minimum power output of my gas combi was more than double the maximum heating demand on the coldest days, so it spent all its time cycling regardless of TRVs. And the expansion vessel failure rate was only beaten by the diverter valve. My new heat pump seems somewhat better matched to heat demand, though was the smallest one that Octopus could do AFAIK.

AND if you are running open loop weather compensation yes. But I also point out that a small degree of feedback and loop closing may retain the electricity savings that you'd expect from the heat savings, and mitigate sag somewhat - I did not attempt to calculate how much.

I say in the paper that I spent a decade inventing a smart TRV (and bringing a commercial version to market). There are now ~500k Radbots out there. I have views on TRVs, and I am eating my own dogfood at home, but I have no commerical involvement with Radbot any more. AND I am hoping during my PhD to fill some (huge) gaps in the academic literature about TRVs and in particular interactions with heat pumps, and some of that research may be funded by manufacturers because everyone would really like to know! My aim and thesis working title is "Improving UK home heating decarbonisation". I suspect that that will involve TRVs for reasons that I have laboured in this thread and elsewhere, but if TRVs aren't part of the answer then no problem. I shall find out what else is. My PhD research plans: https://www.earth.org.uk/img/research/20240917-PhD-confirmation/confirmation.pdf

I calculate the grid CO2 intensity and log it here: https://www.earth.org.uk/data/FUELINST/log/live/ and then combine it with exports/imports for each hour to compute the total. See the end of the page.

Yearly CO2 calcs for electricity and gas, about +225kgCO2 for the year. I now hope to see this drift back to slightly negative as the grid gets greener, etc. https://www.earth.org.uk/saving-electricity-2024.html