Adjust your thermostat by 0.5C, and you’ll effectively have the hysteresis you could live with.
Although the latest firmware update for the MIM-E03EN/CN includes extra FSVs which allow you vary hysteresis (see #106* in the screenshot from the manual below), the minimum hysteresis is 1degC, so still no good for you.
But if a smaller hysteresis this is really important to you you can always install a 3rd party roomstat (requires you to switch from #2093 control to #2092, of course). If you go for a wireless roomstat, its TPI control can easily maintain +/- 0.2degC or better. (Wireless also offers the advantage of being easily relocatable in the ideal position for temperature sensing.)
Edit: But be aware that a small hysteresis can provoke more rapid heat pump cycling, which comes with consequences…
Hi Sarah, thanks. Yes I was using external thermostat but all these extras makes me not comfortable. I would like to have it vanilla 
You right that hysteresis setting in new firmware is ridiculous. I don’t understand why it is still 1 and Samsung won’t give possibility to go less if you want… 0.5C would be perfect but no, not possible because they will hardcode it in UI. That’s Samsung
I found a way how to trick it using HA and modbus integration. I simply modify target room temperature as I need. Not perfect but it will work also in case something happen to home assistant
One thing I don’t like, and again, this is Samsung, why if I use remote controller as a roomstat I can’t modify water law target +/- 5C ??? If I enable external thermostat this is possible…
And you maybe know my struggle with anti-freezing protection stealing heat from DHW tank in case pump is off and it’s 5C or less outside… Over a night there can be 6 or 7 of these and each cycle steal 2C from the water so in the morning you can start to heat again even though in the evening you had tank full of warm water. This is something so stupid I can’t understand.
I had to do a stupid bypass with some shelly and HA automation so the FCU circuit stays open during DHW operation but again this is dependent on HA and it’s functionality. So a bit risky. And it would be such easy to fix to just give one stupid FSV switch - take heat from DHW or FCU. Problem solved… But no… they decided to steal heat from DHW circuit if the DHW is installed. It’s funny that before I’ve installed DHW it was no problem to use FCU circuit for AF cycles…
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Hi again, @Michal_S.
Did you explore the above NASA Protocol link any further? I noticed that there is another discussion group at omerfaruk-aran/esphome_samsung_hvac_bus · Discussions · GitHub, linked via the “Implementations” section at the end of the Protocol page.
Some of those contributors appear to have awesome knowledge of tricking the Samsung controller into doing things that aren’t in the manual (via the NASA/Modbus registers).
I know nothing of C++/GitHub/Modbus/Python/RS485 etc., and at my age don’t plan to learn, but you seem to know enough to at least ask sensible questions on this forum - who knows they may have already cracked your problems.
Good luck…
I have the ability to change this on my phone or laptop using ESPHome- see Sarah’s link to GitHub. It involves connecting a Esp32 to F1 and F2 and then flashing it with the correct YAML.
However, some users have discovered Auto mode, which also allows you to change water law +/- 5C. I haven’t been able to access this mode yet (it is visible but greyed out), so I don’t know if it removes other functionality, but I understand that it works for users who are just using the wired remote controller internal thermostat. If you can get auto mode to work this may resolve another one of your frustrations with Samsung!
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Hi Sarah, thanks I will probably drop them a message. Thing is when I use wired remote controller as thermostat it will only allow you to change temperature (Indoor settings). When I click of indoor it says there are no other options. Same for if I click on heat also no options. So with up and down arrows I can change only target temperature. I guess it’s because this controller lacks additional buttons but it is very stupid design because my wife is not able to change water law in field settings and is pretty inconvenient. Image is pretty cold and windy and you want temporarily increase water temperature. With external thermostat no problem but with wired controller this is not possible.
Hi Mike, yes I can also do this via Modbus but tell my wife 
I’m freezing.. Well connect to home assistant and change it there No way, with external thermostat this works directly on wired controller to change water temp by +/- 5C but once you use it as thermostat you may only change temperature. Who programmed this. At least if there would be some switch or something but nothing…
On Roomstat it says heating on the bottom left and I can’t change it. On right it shows indoor and I also can’t change it. Auto I had available only if I had external thermostat connected. With internal I think it’s not possible? Can you give me some hints what did you do or the users did to enable this auto mode ? I mean where ? What they’ve enabled ?
Thx.
This is the link to the post where Auto mode was described. However I wasn’t able to access it and I’m waiting till I get back from holiday to try again. It looks promising if only I could get it to work.
Thanks. Yes I can also have it like that on the picture but then I can’t set thermostat temperature! It’s either indoor temperature OR weather law offset temperature/outlet temperature.
I was just playing with it and for me it works as follows (not satisfactory).
The options what you have on bottom left corner depends on some settings. In service mode you have “Indoor Zone Options”. First Item is colling/heating where you can select Colling&heating and heating only. If you select heating only you will have only one item “Heating” in bottom left corner and you can’t change it. If you select heating&cooling then you will see 3 option in bottom left corder. “Heating”, “Cooling” and “Auto”. But if it is greyed out or not depends on another setting called “Standar Temperature”. And this is the catch. There are two options “Indoor” and “Water outlet”. If you select Indoor then in right bottom corner you see “Indoor” only and you can’t change it. But if you select “Water outlet” then you have “Auto” available!
But the big problem is that then in Heating mode you can change only water outlet temperature so water law is ignored completely and in Auto mode you can offset weather curve by +/-5C…
This is also what I don’t need. I would need 3rd option to set a thermostat temperature but this is not available… Again Samsung or I missing something
UPDATE: I wonder one thing. When I switch to AUTO and Water Law… How the pump know if it should start heating or stop heating when there is no thermostat target temp visible anymore ??? Will it stay at the last set value or how it works ?? Really Can’t understand this…
If so it will remember so if I set 22C before as a target temperature and in Water Law mode it will start heating at 22C and stops at 23C - only as a security point then I would be fine with that because I don’t need to touch target room temperature. I always have constant temp.
Havn’t read all the posts but a dedicated pump anti seize feature normally runs the pump (every 24 hrs, if no usage) for around 5 SECONDS, at least thats what my 15 year old thermal solar circ pump does, its just a kick.
I would expect it to use the last set target temperature, so this should work for you. I cannot test this until I return from holiday, so will be interested to know how you get on. I would also expect any weekly schedules that have been set to still work, but will have to wait and see. Thanks for the tip about standard temperature- that probably explains why Auto was greyed out on my system.
Welcome, thanks as well. I will try it and let you know. If it would be like that then it would be great. This way you can use weather compensation with adjustable offset all the time and have a thermostat like an emergency stop, for example if there is plenty of sun outside and house is being overheated in warmer climate. Still I find this ridiculous you don’t have access to target temperature control… But I’m a bit afraid that maybe it will not use indoor target temp at all and will simply follow weather compensation and never turn off the pump.
I wonder how it is with scheduling if you have water law mode selected. Will it still allow to set indoor target temperature or will it let you schedule offset ? This I have to try as well.