Thanks, will have a look.
BTW, do you know how to connect this PWM cable ? It has 3 wired but PWM terminal has only two screws. So I think I will connect BROWN cable to PWM signal and BLUE cable to Reference (GND) but where to connect the BLACK wire ?
one is a return signal I think which you don’t need. can’t remember which is which. plenty of info available if you get googling.
Yeah, seems BLACK is output signal from pump so i will keep this disconnected.
Or is it vice versa? Do I need to connect signal input to the MIM or Signal output ? 
@Ian_Calderbank Sorry for bother again but want to double check, if this is proper terminal to connect ? It’s a bit chaotically written in manual.
UPDATE:
OK, connected like this and seems working
I agree, it’s a shame the hysteresis is not adjustable. But I can’t see an option for this. 1C of hysteresis does not bother me, this makes for decent length runtimes.
Here’s my video about my heat pump:
Installation:
Performance:
Interesting, mine defiantly has a 1C hysteresis. It’s quite possible there are differences between different firmware versions. This is my indoor temperature as measured by the controller, I’m reading the modbus output.
Ian, could you please tell me what this settings mean exactly and what the difference between pump1 and pump2 and what means it there is no pump at all only on or off.
Michal you’ve hit on one of the more impenetrable parts of the manual, which hasn’t been updated reflect to the current controller firmware.
My interpretation (glad to be corrected) is that FSV 2091/2/3 settings refer to the way the circulating pump (CP) is controlled once the room reaches roomstat setpoint or LWT reaches Water Law setpoint. 2091/2 are used for 3rd party roomstats; 2093 when you use the MIM roomstat.
Values 0-4 (per the Table on p26 of the User Manual) seem to be 0 = do nothing, 1 = start/stop CP only from roomstat (i.e. ignore Water Law), 2 = start/stop CP from roomstat or stop CP one minute after LWT reaches WL setpont (restarts when LWT drops ~2degC below WL sepoint), 3 = as 2 except CP keeps going when LWT reaches WL setpoint (i.e. only stops when roomstat satisfied), 4 = as 2 except CP starts/stops on a 10-minute cycle once LWT reaches WL setpoint.
Confusingly, on the MIM display these are now called Pump1 for value 2, Pump2 for value 3, and Pump3 for value 4. One of the delightful mysteries of the MIM designers…
Sarah
we both have 1C hysteresis band, but you said yours, if you set it to 20, its off at 20 on at 19 right?
whereas mine set to 20 would be off at 21 on at 20. it runs like that on cold days at least.
actually on mild days like now that seems to be not true either. I get long stable burns with decent COP but switching off / on for unknown reason. Not LWT reaching RWT, not room temp stat satisfied either. still , its efficient so the mystery doesn’t have to be solved.
Hi Glyn, I will definitely take a look on your video.
No I’ve finally setup the PWM cable.
I’ve started the pump and set 22.5C on the indoor controller. I watched the temperatures. It startet both LWT, RWT at 28C… I’ve watched LWT started to increase, as well as RWT. Water pump was running at 100% speed which is around 15 lpm. The pump stopped at exactly when it reached set temperature of 22.5C. Is this correct ? Because Ian said he will set 21C and it will stop heating at +1C so I’m kind of confused. Now the HP is stopped finally for more than 3 minutes! Now it’s of for 25 minutes! Wow. This is first success I guess. I will see for how long it will be off but looks pretty promising.
Please explain to me that temperature graph. What temperature you had set on the controller ? Was it 20.5 ? So once reached HP stopped and then it waits until it goes down to 19.5 and then turn the compressor back on ? This looks like mine is doing but I have to observe this. In that case I could set target to 23C and let it down to 22C. This could be comfortable for me. I wis it allows to set 0.5 hysteresis.
Also could you tell me which setting shall I use for control by room temp sensor ? I can choose 4 options.
20931 - compressor can be turned off only by room temp sensor. not quite understand what’s the meaning here and how if differs from other options.
Can be turned of by room sensor OR according water law discharged water temp and here:
20932 - water pump is off once thermostat switch off the HP
20933 water pump is on all the time
20934 water pump is on for 7 minutes and then off for 3 minute
What setting do you think is best for my cycling issue ?
Since there is 9C outside I did not understand why the HP is trying to heat water that fast and use high compressor rotations. I saw 1.9KW. Shouldn’t it heat with less power ? At the other hand energy display showed 4/5 start so this is pretty good, it had to create really lot of energy. SCOP maybe 5 ? I don’t know.
BTW, does anyone knows what is exactly meaning of this energy efficiency monitoring ? I saw as low as 2/5 and as high as 4/5 while HP was running and not. I’ve never seen 1/5 or 5/5 so I’m curious… On 5/5 i really needs to run as optimally as possible.
Yes, this is also my interpretation I only don’t know the difference between 1 and other 3 modes. Does it mean that HP is not controlled by outlet water temperature ? Then probably it should not stop not matter what dT is ? Don’t understand. Also in mode 1 pump is running or not ?
But for 2093 there is no 0 value available. It’s either 1 (thermostat only) or 2 - 4 (thermostat + water law discharge temp)
@Ian_Calderbank yes, seems mine behaves same as Glyn’s. It turns of at set temperature and now I need to observe if it kick back in at 21.5C. But this will help with cycling dramatically I swear. Only wish the hysteresis can be changed to 0.5.
What’s the avarage COP on that picture ? and what was the temp outside ?
If your heat pump cannot get to 22.5C without cycling, your best choice would be to see if a lower set temperature works eg 18C. If it does, then you can try increasing the set temperature to see when cycling occurs. Hopefully your PWM will help. Also bigger radiators as others have said.
Edit - looks like your PWM may have sorted it.
You want the one that ends WP1 - the water pump will run for 1 minute after the compressor stops. WP3 means the water pump runs for 3 minutes and then off for 7 minutes and repeat. WP2 means the water pump keeps running.
Hey, 18 is to low lol
I have normally 22C or 23C. Well it’s not purely PWM I would say. I switched heating for an hour or so and since its +9C here the temperature decrease only a little bit but the water temperature was 28C.
The PWM definitely help to move water so the HP did not stop because too big dT difference. I wish I have higher flow than 15 - 16 liter per minute. Wish I have up to 25 but…
So then my thermostat kicked in since it reached the set temp of 22.5C so now I’m waiting until temperature drops under 21.5. The pump is still off Then I will observer what happened and if it will be able to het it back to 22.5. I’ve increased LWT to around 41. Before I had 36 or so so radiators could give more energy to heat space quickly.
This is pure science I have to say. I’m sorry for all those people who has HP since I’m sure 80% works non optimized.
UPDATE:
The HP started again after 40 minutes BUT the temperature is set to 22.5C and it is still 25.5 so I don’t understand why it has started ??? Could it be because I use 2093-4 mode ??? So it’s controlled by both roomstat thermometer and water law discharge temp ? I simply don’t understand this behavior yet…
Nevertheless, it has been running for 20 minutes and then it turned off. The temperature is still 22.5C so I don’t understand. I think it has turned odd because the flow is not ehough? I saw the outlet temp was 40 but inlet still 32. DO you think it has turned it off because of this ? But I don’t think so because the HP was not running at minumal compressor speed. So I’m totally lost now, really
At the end you can see it was even increasing ipnut power. WHY ?? Jesus this is nonsense. Temperature is satisfied on thermometer but problem is it did not drop a bit lol.
COP4.8 (bottom left corner), 11-12C (purple line).
ref 2093: 0 makes no sense to have, thats why its not there… you would not set the controller as thermostat then not set it as thermostat. 2091 is where you set whether its external thermostat or wired contoroller. manual page 28.
2094: 1 vs 2 vs 3. I was always recommended to use 3 by samsung docs and youtubes that I found, and thats what I run. but mikejh gets better with 1. No right answer here I think, just experiment.
the PWM will only start to slow down if the DT goes smaller than the target AND the system has been running for “a reasonable period”. on my system this is at least 30 mins from any restart.
I will try it. So I should set 20932 right? Then after thermostat will stop the compressor the pump is still running for 1 minute and then turns off ? But since I have small radiators isn’t it better if the water circulates so it can give most heat as possible ? I don’t know what is better.
I’m still not sure what exactly 909321 is doing.
Very nice COP.
You have meant 2093 right ? This has for option 1 - 4. Default is for. Do you know what setting 1 is good for ? I mean there is no water law involved ?
Yeah, but what happen if the flow is 15 l/m and let say there is 10C outside and the water inlet and outlet temp is same let’s say 28C. Pump will start pump heat so the inlet temperature begin to raise. Don’t you think at this flow the outlet temperature will raise more than outlet temperature causing “overheating” and the pump switch off ? Would flow of 23 l/m help here somehow dramatically or not ?
Guys very strange thing happened. Look at this graph:
The pump was off for 1h. The indoor temperature did not changed and all it has started and after 3 minutes it shut down the damned compressor! What’s goind on here ???
Water inlet was 24C and outlet 32C… I just don’t undersand this.
Apologies, you’re totally right, mine has the same operation. It allows the temp to rise 1C above the set point then switches off once the temp drops back to the set point. I’ve added the set point to the graph. Sorry for the confusion, it’s a while since I looked at this in detail.
I use waterpump3, I’ve observed that this runs the pump for runs for 1min at the end of a cycle.
Yes, I’ve observed the same. The pump always runs at 100% for 30min at beginning of cycle and when doing DHW
getting a flow rate increase engineered (to whatever the system needs to support its spec) is pretty much always going to help. That and having enough emitters. I think I’ve said this enough times now! you’re tinkering on the edges with the PWM and the FSV settings, you might alleviate it a bit, but the core of this is about emitters and pipework.
Yeah you said that. I only don’t understand how mine is working now. I turned off the pump for one hour. set target temperature to 22.5 and it is still turning on! Any explanation? temp didn’t dropped a bit. then it starts cycle for 5 mins and turn off, why? It’s just weird.
Seems the pump cycle much less now. It’s 9C outside and this is the graph. It was running continuously from 5:30 - 8:30. But not impressed by COP yet - only around 3.1 
BUT, can anyone explain why once thermostat switched off the HP why the water pump is not running in 7/3 minute cycles ? So 7 min off, then 3 minutes off, then 7 minute on and 3 minutes off, etc until compressor start again ? Seems on mine it’s simply off all the time. And I am using 2093-4 mode selected.
Hi experts, @Ian_Calderbank @glyn.hudson @Robert.Wall @SarahH
I have two additional questions:
Question 1:
Today I did some tests - I have 5 radiators in the ground floor and 5 on the 1st floor. I’ve opened all and check the flow at 100% of water pump which gives 16.7 l/l. This is known, this is max flow I can get from this pump.
But then I’ve closed all the radiators at ground floor but flow dropped max only by 1 l/m so it was still around 15.3 l/s with all TRVs in the basement closed.
Then I’ve opened up all again and closed all the TRVs on the 1st flow. I was surprised to see that flow was still around 15 l/s and didn’t change much.
I haven’t try with all TRVs closed but I assume the max. flow still will be around 15 l/s no matter how much radiators are closes ? Only the water in circulation will be much less volume ? I had an impression the more radiators closed the lower flow I get. But maybe this was wrong. So what is a relation between overall flow rate and number of emitters (TRVs) closed ?
Question 2:
I have set the controlling of the pump by indoor controller thermostat + water low (pump3). Yesterday there was around +5C outside and the mump worked all days at minimum compressor power which is around 0.8KW. All good. This night was a little bit colder +3C but the pump was running at 1.1KW power input on average and cycled 3x during the night. I would expect it will run all day with lower power input. But maybe the pump decide to use higher RPMs of compressor because it is colder and would not be that efficient on lower speed ? I can’t say if the reason was that target temperature was fulfilled or simply water low kicked in. Seems I don’t understand this water low stuff - can someone explain me how it works ? I would expect that if there is too much heat produced by the pump the HP will lower compressor speed more and more and only if it is running at minimum speed and can’t get lower it switches off. But seems here indoor temp was not fulfilled but it still turned of the pump ff while power input was not minimal. There was a room to go lower but seems it does not work like this. Seems I’m missing something here. Seems it is running more stable on higher outside temp (+5C) than on lower outside temp (+3C).How can I tweak this ? I would be happy if the pump can run on lowest speed as long as possible.
A update Question 3:
This cycled even the indoor temp target was not fulfilled and pump was running on higher compressor speed so I don’t know why it didn’t reduced the power. I really don’t understand this Samsung heat pump and don’t like how it works. Detailed description in screenshot.
Thanks!
