After doing almost every configuration of hardware and control, my happy spot was to strip back to Uber simple. My heat pump is twice the size it needs to be, and very little modulation. 

Big heat pumps can be run quite easily. Without lots of external control. You just need to step back and understand what your heat pump needs. Micro management is generally not it.

If your cycle times are too short you just need system volume or to run a higher temperature so you radiators can pump out the heat easily, then you just run a thermostat (ideally the one in the controller) that can be coupled with WC.

I think Grant just make the units normal plumber friendly. The Chofu controller may be one you refer to. Download a copy of Chofu operating install manual. You will be surprise what the old looking controller can do. Most functions are not included in the grant manual.

@johnmo, yarp I used the Chofu manual to map all the parameters and now have  good monitoring of the system, adding the thermistor to the tank has also helped (why is this not included as standard I don’t know, maybe it is and the cowboys left it out). I haven’t used any of the TOU tarrifs etc but i have set the pump to night mode and modulated it down but as we are now out of heating season I will have to wait till winter to see if any of this works. But in that time I am going to try to design options to better control the system so we can get up and running as soon as we can before it gets too cold.

@johnmo 

This is not too much about micro-management of the HP, but about getting more from it.

I have a Grant 13kw, two to three times larger than the house needs and rather than run it as per the HP I run it as per the house needs. This means it runs for a few hours only, during the day and is then switched off for 12 to 18hrs.

I don't like WC, as I don't care what the weather is like outside, just what the temp is inside, which is now 20 to 21°c, and feel the HP should respond to this temp only. Inorder to do this the HP runs around 30 to 27°c and its the length of time it's run which controls our heating. Our house can take about 6 to 12hrs to gain 1° in the fabric of the house and upto 12hrs to lose 1°c, so it's more about understanding and anticipation of your heat / loss requirements that will help.

But as the controller has limited number of settings, I have to use 2 to 3hr slots to make / force changes though rather than make adjustments in the flow temp, which would help maintain better workings of the HP

@uk_pete_2000 Yeah we get massive solar gain on half of our house but as soon as the wind changes it wicks away the warmth like no ones business, the trials and tribulations of living on a cliff top in Wales! I want to be able to eventually get to where the system predicts what it needs and just works and in order to do that I need to understand as much of the system as possible, which is why I started down this rabbit hole! 
All that said I would also like a diverter valve that actually diverts properly, pipework that doesn’t leak, and to not have to put my waders on every time I walk past the damn thing! At least the last one I can do something about!

And I also did a thing!!!!! In my quest to learn all the things I have created an AI agent that I will be adding to, that can search all things Chofu/Aerona3, ASHP, automation thermodynamics, space lasers and store that information with added context so it makes retrieval much better. I really have gone down a rabbit hole!!!!!

This is great work, @grantmethestrength; personally I'd like to see a modbus-capable integration for every heat pump on the market.

That said, in several ways I agree with @johnmo in that I have found heat pumps generally to be better left to their thing. I can certainly see what you mean about your knowledge of your circumstances making a case for tweaking the operation in a specific set of scenarios but in general I see what you've put together as far more important for its ability to monitor than control. I suspect you may find quite a following as time goes on.

Posted by: @Anonymous

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After my internet being off for a few days, home assistant is now banned from any core duties for the house. Heating being a core duty.

@Johnmo, I agree with the problems of kit being unmanageable without internet access - and would never buy Tesla kit for that reason amongst others - but any Home Assistant integration that uses modbus is surely therefore a good thing. I've had any number of times when Growatt has been unreachable (their issue, not mine) and yet my local modbus connection has allowed my Home Assistant to keep actively managing the inverter and battery as if nothing was wrong.

@majordennisbloodnok I deffo don’t disagree I would love for it to just chug along and I have got it working pretty well, the thermistor means I am not wasting energy heating the DHW once it has reached its set target it only took 30 mins to heat up the tank and jobs a goodun! 
I guess the real test will be next winter!

As for monitoring I have installed the emoncms integration and which gives me long term logging I am toying with the idea of adding more monitoring kit such as a decent flow meter some more temperature probes and when we have the wiring redone some proper energy monitoring. But at the end of the day the only thing that really matters is! is the missus warm, am I comfortable and is it running as cheaply as possible! Ah we can dream!

Posted by: @grantmethestrength

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emoncms

Best this I added to my system, you can really see what does and doesn't work. I have a full heat meter and electric meter installation.

Posted by: @uk_pete_2000

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Our house can take about 6 to 12hrs to gain 1° in the fabric of the house and upto 12hrs to lose 1°c, so it's more about understanding and anticipation of your heat / loss requirements that will help

Our is similar, so you are on UFH?

I found when I was doing batch heating a very low hysterisis worked wonders. I also do hybrid heating when really cold and heat pump at all other times. Heat pump can use a +/-0.1 hysterisis thermostat, I end up getting about 0.3 overshoot about an hour after heat pump is switched off.

On the boiler I run at a fixed flow temp but that runs against a tighter hysterisis of +0 -0.1 thermostat. This gives me a house fluctuations of about 0.2 degs. Boiler min modulation is 8kW against a heat loss of no more than 3.5kW at -9. Boiler flow temp is set to run without stopping, so it starts it runs until thermostat satisfied.

Have also found from running pure WC the solar gain is seen by the heat pump as a the return temperature changes, so heat pump modulates down then stops the heat cycle, the circulation pump stays on distributes the water temp around other rooms. As soon as the solar gain reduces the heat pump starts again. It will not do this at elevated flow temperature but does in straight WC.

Have done similar to you, had sensors and relays everywhere, but simple wins the day.

Also see you have loads of solar. I have a shelly relay to activate when I have excess PV, this make the second set point active (6 degs hotter than normal) on heat pump, during Feb and March this did most of our heating. When you are getting solar gain floor output reduces to close to zero, floor mass holds back input heat until room temps decrease - basically a big storage heater.

@johnmo 

Yes, we have about 300m2 of UFH, over 3 manifolds. One manifold is then split to deal with radiators upstairs.

Our return temp is around 23°c, which seems to work, as long as we keep flow at 27°c or above. Anything lower and the HP will cycle. Also if we try to run 24/7 then the slab will heat to max, return temp increases and cycling starts. Another reason to turn the system off for a few hours.

We too suffer from solar gain which increases the room temp, but I feel it is a short gain as most lasting heat comes from the floor slab, so the last temp change is up to 22°c. 

This all seems to work and regardless the HP turns itself off at 15.55hrs and doesn't start till after 04.00hrs if the temp is too low.

How I envy you guys and your stupid warm feet!!!!!! When we eventually get around to tackling renovating the downstairs I am going to try and convince the missus the investment (and disruption) will be worth it!

Posted by: @uk_pete_2000

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return temp increases and cycling starts

Cycling is a normal activity of heat pumps and boilers. As long as it's not short cycling (1 to 2 minutes or less on off cycling) ideally it will cycling is about 3 or 4 time an hour or less, that is how they operate when below the minimum modulation.

The long run time is the heat pump slowly pushing heat into the floor. The cycling is the heat pump just topping up the energy in floor, basically applying just the right amount of energy to keep stable. WC just adds more or less energy based on heat loss to outside.

Your running costs will decrease if you embrace what the heat pump does normally. Basically the heat pump does a bit of work has a rest, your making it run a marathon each day, which is fine if you are a time if use tariff. If not WC wins every day.

I am currently cooling but the same rules apply. This is my last 24 hrs, just read in reverse to apply to heating. The purple line is outside temp and the spikes are the heat pump running. As it gets cooler the heat pump has less work to do so the cycling gets wider, heating is the opposite.

I think you have missed the point on weather compensation. It is about having a stable house temperature, that's it. If you aren't getting that, some fine tuning may be required. You have to change flow temperature as it's the only mechanism to change energy output from a radiator or UFH system as once installed you cannot change the area. WC just changes the flow temperature in line with the energy likely to be lost on lower temps outside.