Beelbeebub

When the heating comes on, does the flow pipe out of the HP get warm? You are saying that when the heating comes on, only 2 of your rads gets warm but then the HP shuts itself down even though there is a call for heat. That does sound alot like you're not getting the right flow on the heating circuit. Maybe try this First I assume you have a single 3 port valve that sends the water to the heating or DHW circuit. Remove the power head from the valve. This is easy, you need to isolate the supply then take the cover off thr case (single screw) once inside carefully undo the two screws on opposite corners thwt hold it down and it pops off. Replace the cover and leave safely tucked away. Use a pair of pliers or small spanner to old the shaft in the DHW position Set the system to heat the hot water, the HP should hum away merrily and the flow pipe should get hot and thecpipe to the cylinder. Once that's ticking along nicely use the spanner to switch the valve to heating. The pipe tonthrntqfiatoranshoukd start to get warm pretty quick. If the system then shuts down, your problem is some sort of flow restriction on the heating circuit. Maybe your rads have been turned down on the balancing vlaves. If it keeps running an all your rads get plenty hot, then yous system is hydraulicly OK and the issue might be with the controls, a parameter in the settings or an iffy connection. Alternatively get a local plumber to fit a visual flow indicator so you can see the flow rates.

Shocked, I tell you! SHOCKED!

This may be a case of not seeing the overall efficency wood for the (CoP) trees. At these mild temps the parasitic losses of the system (controls, valves, pumps) will be significant in comparison to the useful heat produced. October used around 200kwh for heat and DHW, which is about 275w continuously. That's a pretty low consumption given your standby consumption is likely to be in the 100w range. Maybe, in mild weather, some sort of scheduling where you turn the thing off might yield better results, but your finial gains are likely to be negligible.

https://www.carbonbrief.org/factcheck-18-misleading-myths-about-heat-pumps/

Is there an isolation valve(s) that was turned off during the building work? Sounds a bit like the heating circuit isn't able to dump enough heat and the HP is shutting down. If you could get a flow indicator fitted it would be helpful.

A2a has a theoretical advantage as the target temperature (and hence pressure) for the compressor to reach can be lower than with a water based system *for a given emitter surface area*. A2W can gain an advantage if it uses underfloor as the surface area can be huge. I think a2a has potential as it can usually be fitted alongside any existing heating system. This negates any fear of "will I be cold" or "will it cost more to run" as the owner can use whichever system is most appropriate at the time. They tend to be cheaper to install too.

The pumps aren't DC in any real sense. They are variable frequency AC, created by an inverter chopping up DC. Chopping up DC created from rectifying AC is no major problem. 240v AC is a a useful "universal" form of power - you power wall will output it efficiently, and your HP will accept it readily. Your electrician will be able to work with it and components like breakers, monitors, switches etc are easily availble. I doubt the efficency gains (if any) would be worth the extra hassle of a non standard setup.

Creativity isn't my problem. It's the restrictions. They, in turn add cost. I have a nice cladding system i am trialing on an out of the way building. No way I would be allowed to fit it to my main buildings because of planning restrictions combined with it's industrial look Personally,, I think there is a pint when how warm and cheap to run a building is for the occupants trumps how it looks for the passers by. But my view is very much in the minority, so solid walls and single glazed windows it is.

The thing is, I don't think it requires any creative or novel engineering. The major hurdles are finance and regulations (sound, visual etc)

That was the doc I was trying to remember. I think my error was I was focused on the older housing as that is where my professional interest lies as I manage rental properties, most of which are victorian or early 1900's vintage. My main interest in. HPs is because I can see I am goi g to have to deal with the upgrades in the future and am trying to work out how to approach it.

The house we just moved into is fairly well insulated and has good heat recovery system though it is stupidly big which pushes up the demand. My old self build had a demand of around 3kw at -5C and was stupidly easy to heat. I don't think the heating has come on yet (my parent now live there) Both are still on gas as the boilers are trucking along nicely and no point in chucking them out. My old house will be very easy to convert as I designed it to use a HP. The new one (my parents) will be a pig as the UFH has packed up and it's massive so the HP will cost more than ideal. Both will get swapped when they die.

I think the average is closer to 11kw, but yes a bare HP for a typical house can be had for as little as £2k but more likely £4k. But the point holds that a bigger unit will cost more than a smaller unit. Then you also have a higher likelihood of having to upgrade pipes, emitters etc. at extra cost.

Rocket launches are an example of a flashy high carbon thing that isnt actually a big % of the total. Each launch is 1,600 homes for a year. If we launched 2 a day, it would be just over 1. 1m homes for a year, which is about the number of homes in Wales (the standard SI tabloid unit) So 2 rocket launches a day worldwide, which is about 3 or 4x the current rate, would have the carbon emissions of one Wales. Measured against that are the benefits of space industry, primarily satellites, for navigation, earth observation, communication, science etc. Sadly, or fortunately depending on your POV, climate change will be fought with unsexy stuff that lots of people do. More efficient hearing and (more importantly) cooling. Lower carbon transport. Less transport (as in better planning of our cities and work patterns along with more public transport). Getting rid of high GWP refrigerants. Minimising or eliminating methane leaks. We'd probably get more benefit from abnnig SUVs in Europe and America than space flight.

I am all for heritage and tradition.... To a point. When it comes to cutting carbon emissions it's pretty urgent. Imagine the blitz and someone saying "you can't put blackout blinds up there! It will ruin in the look of those Georgian windows!" - 😁 But the solution then is to just install a bigger HPs If we (as a society) have accepted that keeping traditional buildings is going to be expensive, why baulk at the cost of a 20kw HP? We've already accepted that you have more for new windows or new doors or repainting or re-roofing. We need to get the capital cost of HPs (and associated stuff like fan coil rads) down and ideally adjust the balance of gas/elec prices to make hitting the break even (and hence saving money) easy.

I assume you have an unvented hot water cylinder. The grant system (assuming they have installed as per instructions) uses a totally seperate anti legionella system basically a timer and immersion you set to go off once a week. So you can set the hot water temp to as low as provides enough water at a hot enough temp for you. The next thing is to check if weather comp is active. It might not be if your installer was not on the ball. The easiest way to check is to feel the rads. Are they warm to the touch, and does that vary? Ie on a cold night are they warmer than a mild day? Do you have a single thermostat or one of each room?