Posted by: @stevet

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So are you suggesting I reduce the -2 to -4 (I have adjusted the 50C down to 48) Currently my settings are -2C -  48C and 15C and 30C

Yes, I would- based on what you have said with respect to your house being too warm, and furthermore you want your linear relationship between OAT and flow temp to extend beyond -2. Try 48 or 49 at -4 and see how you get on perhaps?

Regarding the data analysis-  the benefits of having the modbus connectivity, and indeed having this so easily accessible via the indoor control panel, becomes a real bonus and you'll soon forget about the useless native app. There are several options as cathoderay says. I use home assistant and use a couple of out of the box solutions which were quite simple to set up.

@benson 

I have now got -48C at -4C and 30C at 15C  - I am amazed at what appears to be very little heat at the RAD giving us 22C . Last night I nearly had to open bed room windows as felt like hot humid night in the summer! We very poor app is showing about 1Kw every other hour.  I have read about Home Assistant, aware this can be wired to the Midea Wall Unit.  My main focus currently is getting the system running as efficiently as possible while giving us a comfortable living temperature. Initially I was more focussed on using the low overnight tarriff, but understand a lot more now. Solar has generated 15KW today which is pretty good. My sons gaming PC draws almost as much electricity as the heat pump! I now remember to turn DHW and Heat after each modification. 

To expand on what @benson has said about the lower end of the WCC, thee key point is the curve flat lines either side of the end points:

T1SETH1 and T1SETH2 are the LWT (flow) temps we set, T4H1 and T4H2 the OAT. Either side of the slope, which sits between the end points we set, the 'curve' flat lines. If the OAT goes below T4H1, the LWT doesn't get any hotter. By moving T4H1 a bit lower, the LWT continues to rise to that lower point, and only then flat lines. I have at times set my T4H1 to -4, but it is currently -2°C.   

Posted by: @stevet

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I am amazed at what appears to be very little heat at the RAD giving us 22C

Find another bit of metal in the room and put the back of your hand on that, you will then appreciate the rad is warmer that you first thought! Plus it is mild at the moment, and a 30°C @ 15°C setting means that 15°C OAT, the rads will be, and are meant to to be, at less than blood temperature. They will get to blood temperature at about 10°C OAT with your WCC. They only need to reach these temps when it is mild outside, as the heat loss is much less. 

Posted by: @cathoderay

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Posted by: @stevet

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I am amazed at what appears to be very little heat at the RAD giving us 22C

Find another bit of metal in the room and put the back of your hand on that, you will then appreciate the rad is warmer that you first thought! Plus it is mild at the moment, and a 30°C @ 15°C setting means that 15°C OAT, the rads will be, and are meant to to be, at less than blood temperature. They will get to blood temperature at about 10°C OAT with your WCC. They only need to reach these temps when it is mild outside, as the heat loss is much less. 

You are right.  I think I would turn the system off a the moment and the house will hardly lose any heat. I will almost certainly getter a better perspective when we return to more normal winter weather.  I also probably have oversized rads now due to the over conservative heat loss calculations per room and design flow temperature. Personally I am not too concerned as it least gives me headroom and beong to hot is not a bad problem.  

We had some friends over for dinner and they experienced the nightmare scenario about 7 years ago with a complete novice builder using no design criteria installing a useless system only because the planning permission for a massive extension insisted in a heat pump. No heat loss, first heat pump installed by the builder. Result freezing house they have now sold. They have been put of heat pumps for life which is  a shame.