I wonder if your ability to keep room temperature at +/- 0.3C is because you have got your water law settings perfectly set rather than feedback from the controller.

I did a little experiment last night and changed my water law setting to a flat 37C (WL-1) to verify if the controller configured as the thermostat still used this water law or calculated its own water temperatures based on the outside temperatures. It appears that the controller still uses the water law set in WL-1 in my case. The pump continuously runs due to the On /Off only setting in #2093 but the water outlet temperature basically stabilised at 37C for an outside temperature of 6.5C (should be around 44Cish).

In my case @mike-h your assumption is correct and my water law is set about right and is still being used.

This is not the behaviour implied in the video I posted in an earlier posting which indicates the pump "looks at the outside temperature and decides the required temperature to set your radiators to to achieve the indoor temperature set point. When the temperature is reached the pump is reduced to maintain the internal temperature set point" (not verbatim). The radiator temperature seems to still be based on the water law settings for the Gen 6 not some implied clever internal feature.

Apologies for misleading anyone :-)

Here is my firmware version info

Just to clarify, if you go to the Zone screen you should have the target room or water temp on the left and "Water Outlet" and "Indoor" temperatures on the right. These indicate the actual temperatures the system is seeing

Regards

Please make sure #2091 and #2092 are set to "not use" and any external third party thermostats are disconnected.

I did get an error myself but it looked like a flow interruption if I remember correctly. I think it is caused by the change in mode, I just pressed OK and it cleared then everything was running ok. The error for me was "Indoor (200000) / E121" for your info.

Regards

Once it reaches the room temp the flow temperature is backed off a little and the power consumption does go down compared to my previous consumption. If you monitor the controller it does vary the flow temperatures accordingly, to maintain the room temperature quite accurately in my case (+/- 0.3C on average) when the desired temperature has been reached.

You may have a different model from me - mine is a Gen 6 12kW Samsung - but on mine there is no feedback from the controller on LWT when room temperature target is approached. Basically, when the indoor temperature reaches target temperature plus one degree (eg 21C if target is 20C), then the heat pump is switched off and will come back on when the room temperature drops to 20C. The heat output does drop as room temperature rises, but this is due to the emitters emitting less heat as the temperature difference between emitter and room falls. I wonder if your ability to keep room temperature at +/- 0.3C is because you have got your water law settings perfectly set rather than feedback from the controller.

Because I wasn't aware of the setback scheduling option I've been using Home Assistant with the excellent ESP32 RS485 solution from @morh and a Home Assistant climate scheduler, which gives me control over the internet.

I do think your setup would be the simplest way to achieve local control without having to become a heat pump expert, providing that the MIM-E03 controller is installed in a good place for the thermostat within the building.

I opted for the room temperature control option due to my property having old 1970's radiators, which are unknown regards specifications in the system. Trying to calculate and tweak what flow temperatures are required to achieve 21C room temperature was a pain so I now let the heat pump do that for me.

I also confirmed it was working because some days the pump happily runs continuously producing water temperatures of  around 34C. When I was running on my manually configured WC I could not set the flow temperature to less than 37C before the compressor started cycling etc.  In addition, during the cold snap here of +2C, the pump increased the flow temperature to +48C and then varied the temperature between +45C and +48C to maintain the room temperature.

I am very pleased with the performance so far because the system used to take all day to recover from my setbacks with the old third party thermostat but now it takes approximately 4 - 5 hours in my case. This means I can start the pump during cheap electricity times when the samsung controller works the pump a little harder (I believe but not witnessed it so far) and the house is relatively warm when we get up in the morning. Once it reaches the room temp the flow temperature is backed off a little and the power consumption does go down compared to my previous consumption. If you monitor the controller it does vary the flow temperatures accordingly, to maintain the room temperature quite accurately in my case (+/- 0.3C on average) when the desired temperature has been reached.

As I have a bivalent system, my SCOP figure is based on an outside temperature of +2C and above. Since the beginning of January when I made the change, I am currently getting a COP of 3.95 for January and February compared to the previous 3.7 for November and December. I will need to run this new arrangement a full year to get an accurate SCOP figure but it is looking good to me so far