@bontwoody 

My plan is to run the flow temp at about 35 degrees by varying the return temp according to the outside weather, I will have to see what inbuilt weather compensation the ASHP has for this when it gets really cold. That way I can run the UFH and rads at 35 degrees and will vary each room via the lock shield (all TRV are set at fully open) if they are getting too warm. To be honest it would be nice to have the problem of having to turn the heat down as this is not an issue I have had over the last few years. We will have to wait and see how this winter pans out.

Regarding the NC valves I quite like that idea and then a single anti freeze valve on the lowest part (which is the return pipe). Would ordinary motorized zone valves work for that? My pressure within the system is about 0.8 bar.

Its what ive used. I know some people choose ones which dont constrict the pipework too much but mine are just honeywell. 

@polar-bear just done a bit of searching and it looks like this unit could probably be controlled via the Tuya Smart Life app. If you don’t have any manuals I have found some links but they are deffo badly translated from Chinese.

If you are interested in getting better control of the unit it may help to get photos of the controller, model number plate on the side of the unit, and if possible a picture of the PCB where the electric is plumbed into the outside unit.

@grantmethestrength 

That is kind

Attached are photos

First is of the control unit I have that is plugged in to the ack of the ASHP and the only variables I can control are return temp, time, timer, and run (on/off)

The second one is the diagrammatic electric input that I can access, I tried to wire SA/SA via volt free contacts to see if that would control the ASHP (ie switch on and off) but it didn't. A bnd B arent attached as I would have no idea how to connect it to the wifi. Only one used then is PC that runs the pumps.

Third one is photo of the plate on the outside of the ASHP

Well you certainly are a brave polar bear!  

A few comments:

1. I presume you have insulated the remainder of the pipe work, since you took the first photo?
2. The sheet you have built for the heat pump looks really nice.  I am just wondering whether it may reduce air flow and therefore reduce the efficiency of the system.
3. I imagine that your system must have a controller?  If so, you should be able to find the weather compensation settings.  At least some heat pumps have their own built in atmospheric thermometer, but a separate weather compensation thermometer would be more accurate.
4. If you want to monitor the performance more accurately, you could install:
   • A full heat pump monitor, but this would cost nearly as much as the heat pump!  See https://openenergymonitor.org  
   • A Shelly Pro EM-50 which will monitor two electric circuits.  It is available on Amazon for £75.
     https://www.amazon.co.uk/Shelly-Bluetooth-Measurement-Automation-Compatible/dp/B0CH1JW2CW/ref=sr_1_2?crid=3J4LY0SIMCD9R&dib=eyJ2IjoiMSJ9.eSNNVC0oq2d0utJqj_RrH0uqCPg-4VS_egWsEcopiDLDktanRl-FExcWLvxYr7raQJbbNhYhyEDAKR5XXO5zMapY9AWUdD8kQ-fTOxt3NMynZiZbfJnPjptJXTySC6n0gYBLTIn0oR3aOgiwntnCYiMbsEzZ5Qzf5P9WvfjsWvs.2GfkODUcBaEk3CSla3Ak0_e27VN3yXx2uq0f5KikbSY&dib_tag=se&keywords=shelly%2Bem-50%2Bpro&qid=1762515861&sprefix=shelly%2Bem-50%2Bpro%2Caps%2C103&sr=8-2&th=1
5. It's probably a bit late now, but you could include DHW in your heat pump design and switch to the immersion when the weather gets really cold.  That would reduce your running costs.  My 16kW heat pump runs for just 1.5 hours per day and provides enough hot water for two people.

Brave or stupid? I like a challenge and DIY so the thought of paying thousands to someone and then it doesn't work didn't appeal. At least if this doesn't work then I have no one else to blame.

Your queries

1. Yes , all fully insulated pipework now, the photo was taken just after finishing and checking for leaks.

2. It always surprises me that ASHP just sit out in all conditions. I thought a simple cover to keep the worst of the rain/snow off could only help, I had it on my old ones. The sides are slatted so I really don't think will impede airflow at all but I will monitor that. I may keep it on in summer and take the side off in winter when I need it most, it is only really there to hide it slightly from a patio area. On this point it always surprises me how close to walls the back of ASHP are, my instructions suggested 300mm and mine is actually 500mm from the wall. Many I have seen fitted however seem to be really close 100-200 mm away and that surely is where the majority of the airflow takes place. 

3. It does have a controller but the directions for it are next to useless, I contacted the company via whatsap and corresponded with an 'engineer' whose English was better than my Chinese  but lets just say details were lost in the conversation. I think it does have a built in weather compensation but I am going to have to monitor how things perform. Up till now I have return temp at 30 degrees and it seems to get the flow temp to about 34-36 and just hold it there but the weather has been so mild recently it is difficult to monitor.

4. I did look in to the monitor but you are right the price was in the £ hundreds and seemed to defeat the object. I think the real test rather than getting bogged down in minutiae of COP/ energy use is just to monitor the whole house electric compared to the whole house temperature and see if I am happy with that. I am not on mains gas so everything in the house is electric so I use quite a bit anyway but can monitor my usage daily/weekly/monthly. £ 75 isn't too bad though so I may look in to the Shelly.

5. The plumbing for the DHW is still there just closed off via zone valve so I can use it again if necessary. Problem is if flow water is only at 35 degrees then it is not going to heat the water much. As I said through the summer the Iboost produced all our hot water and now with Octopus EV tariff I am only having it on for 1 hour at night costing 21p so am happy with that at the moment. I will certainly keep an eye on it though. I also have a home made solar array that heats hot water on my roof that cost me £ 400 fifteen years ago so has paid for itself many times over. In summer it heats the water to 70 degrees plus and even in winter on a sunny day will get up to mid 30's. That feeds in to a water tank that is then the feed to my larger hot water tank so instead of water coming in to that at 15 degrees from the mains it is coming in at 35 in winter and up to 70 in summer.

If anyone is interested, I got the idea off the internet fifteen years ago. Very simple design as everything I do is very simple the theory being less to go wrong.

50 meters of 10mm black rubber industrial piping.

Make a wooden box and attach 22mm insulation on the back and then cover that with aluminium sheets.

Paint the whole thing black with heat resistant paint.

Attach the pipe in a serpentine manner with clips to the aluminium sheets.

Use plastic insulated sheeting to cover the front and black plastic guttering panels for the sides.

Get your builder at the time when scaffolding is up to put it on your roof and attach it via 2 brackets to the main roof support, remove a tile and run the pipe through the roof then replace tile and make sure is leak proof.

Attach 10mm piping to 10mm polypipe and via a central heating pump run in to a vented hot water tank.

Set the pump on a timer to come on for 4 hours in winter up to 12 hours in summer.

That way the tank now becomes a header tank for your primary hot water tank.

Worst case scenario is water comes in to the primary tank at 15 degrees direct from mains as it would anyway.

Best case scenario is on sunny winter days water feeds in the the primary tank at 30 degrees and in summer anything up to 70 degrees.

Cost fifteen years ago approximately £ 400.

2 photos attached, not great but hopefully give you an idea. The ghostly figure in the window is the wife who has no interest in anything I do as long as the water is hot and the house is warm.

This is awesome, I will take a look at how you can set up the app it will probably entail connecting to the wifi network access point of the heat pump and then adding your wifi credentials to connect. If all else fails it has a modbus connection so you could go down that route!!!! 

Posted by: @polar-bear

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So, I decided to do it myself, everything was there, it maybe just needed tweaking. I was lucky as I know an ASHP engineer who gave me some advice and my wife's cousin is a plumber who is now specialising in refits of botched ASHP installations, he also gave me advice. 

For your DIY install, what did you do about the whole building regs / certification side of things?

@temperature_gradient 

Building regs I had my initial ASHP system signed off when I had my extension built in 2010 so this is just a like for like replacement.

Certification I have not bothered with. I have not claimed any grants off anyone so nothing needs to be certified.

@polar-bear So I have a done a bit of late night shiraz fuelled internet sleuthing and it looks like the AIROSD ASHP’s are the same or very similar to the SPRSUN ones. There isn’t much on the AIROSDs (as they are an OEM and sell their units under different brands)but there are a few projects involving the SPRSUNs. 

Both are controlled by the Tuya based Huilian Smart App, you should be able to use the more widely used Smart Life app (generic Tuya based app) to achieve the same results. It is pretty easy to use and integrates with Home Assistant if that is your bag. The app won’t give you much more than the wall controller it just makes it that little bit easier. It uses the older 2.4ghz wi-fi so you will need to ensure that you have one available to connect to.

If you want more granular monitoring and control then modbus is the way ahead.