Write your own control algorithm to control the LWT . so that the HP responds to your heating needs. basically write your own weather compensation + add other features if you wish! Load compensation being the obvious for a samsung.
put your own relay(s) in place to control your DHW/CH diverter valve(s), rather than giving the heat pump direct control of it(them). again linked to your control s/w.
monitor the temperature of your tank with your control software .
When s/w decides ātank needs to warm upā then
activate relay(s) to move diverter to DHW
send a LWT target increase to the HP via modbus. you have control of this value. you can wind it up slowly if you want, you can decide how high to go.
monitor the tank temp until satisfied, then move relay back and set LWT back into control of your heating loop.
I was having a bit of a play around with this but
a) Iām not much of a coder. so wasnāt getting very far very fast.
b) its got cold. I donāt want to poke around with system control whilst its cold. I just want it to run
c) I have a 3m2 coil in a 300L tank, and Iāve found that if I make sure I run DHW cycle only when the middle and bottom of the tank (where the coil is) are properly cool, then efficiency is good, so negating the need to try to optimise around this.
Thanks Ian, but unhappily I donāt think thereās a way to set a Fixed Water Temp on my Samsung on DHW. I canāt even control ASHP compressor speed, so āModbus controlā is pretty meaningless. All I have is the Samsung weather compensator on CH. On DHW the ASHP letās rip and can quickly get to 60degC LWT (so an awful CoP ).
Luckily I only heat DHW twice a week so 8kWh/week for my DHW is reasonably tolerableā¦
hi sarah
what I meant was, you can install the MIM-19 modbus module and take control of certain aspects of the heat pump via modbus protocol. If thatās something you want to do of course.
Thanks Ian.
I contacted Samsung (Customer Service Dept) last week about the MIM-B19N, and was advised that it doesnāt access all the parameters I wanted (e.g. ASHP power consumption, ambient temp) and that I should consider 3rd party hardware/software .
My conclusion: cost & effort of digital monitoring not justified (I speak as a part-time machine code programmer back in the day, so coding not insurmountable), in my case better to rely on empirical data for optimisation.
cust services are probably not the right people. try [email protected].
power consumption I agree, not provided by the MIM-B19N, but its easy, just need an SDM120M wired inline on the electrical supply to the outdoor unit. you read it via modbus.
outside temperature is provided by the outdoor unit and is readable via modbus using the MIM-B19N.
along with that you get the flow and return temperatures and the flow rate, multiplication gives you the heat output.
in short, everything you need to get your performance data for optimising your heat pump. Iāve built all my monitoring around the MIM-B19N + one SDM120.
Ian
There were two options I hoped that could slow down DHW heating for us with small coil exchangers: a)to bring down flow rate or b)to activate fsv 5051 - Pump frequency control.
I briefly tried both yesterday and found out 5051 had no effect on DHW and decreased flow rate made things worse, flowT increased even more.
So the next attempt would be something like Ian suggested, just not in so sophisticated way.
My plan is to disable DHW mode in controller and disconnect control wire from 3way valve. Then to schedule space heating with high flow temperature .e.g 50C from 14:00 to 16:00 and in the same schedule to divert 3way valve into DHW with suitable smart switch.
Not sure if it will work out or it will bring any benefits over standard Samsung DHW mode. Just out of curiosity, maybe it will be more efficient at least in summer time. Now when i am logging data into emoncms, will have an option to compare it.
I have read, that @glyn.hudson just did some high T space heating test on the same pump and i think it might work for DHW as well.
as per my PM but for the wider audience - I think FSV 5051 tells the system you will be sending it a value that (as I interpret that bit of the documentation) will attempt to control the compressor freq. with the means of sending that input value being either via modbus register 88 (I thinkā¦ I only read the manual didnāt build it) , or via an analogue input (which Iāve no idea where it would connect) . If only setting FSV 5051 by itself , without also adding that input, I wouldnāt expect it to do anything.
if you want schedule space heating flow temperature target changes using only the samsung controller, then you will have to put your system in to fixed water temperature mode driven by the controller, not sure if that is what you want?
According to manual just enabling FSV 5051 and bringing 0v to green FR control connector should limit compressor frequency to 50%. I tried it but heating DHW cycle looked the same as before.
Yes, i would consider switching samsung controller to water temperature mode and driving it with some external room thermostat or with my own raspberry pi programmed logic.
Samsung controller as a room thermostat doesnt work for me. If i set it to 21,5C it starts heating and wont stop until 22,5C. After that the energy from floor is still being released and my small insulated house gets overheated to 23,5C, with sunny weather even more. WL is set to 32C flat.
Now i am running it in scheduled blocks of 3hours heating and 2hours not operating. If the temp is ok after first heating block those successive will usually not activate the pump at all.
So now i am just happily monitoring it and will wait with other experiments until spring hopefully
You can use the SmartThings integration to connect the Samsung WiFi to Home Assistant. However, the integration is very poor, only DHW on/off controls are available. I donāt really use it.
But I have some problem with this f*** pump. This happened now absolutely no idea what is going on here. The pump was off for 2 hours or so so finally temperature reached the lower limit and the pump started. Well greatā¦ But what happened ? It switched it off after 4 minutes!!! Water temperature was 20C in pipesā¦ While it has switched it switched the pump off as well despite the fact Iāve set FSV 2093 to water pump 2 so it should not stop. I absolutely not understand this HP. Why it has switched off???
Iāve just noticed theyāve installed Grundfos 25-40 !!! Not 25-60 as Iāve thoughtā¦ I think thatās why I have such poor flow rate. What do you think Ian? I donāt know why I thought itās 25-60.
Now Iāve started it and Iāve got Error 911 for some reason. Do you have an idea what it could be ? What does it mean ? I donāt understand from manual.
Thanks.
UPDATE:
Guys tell me if Iām dreaming or what. So by accident Iāve found out that if you go to self-test settings to e.g. watch your LWT and RWT then guess what? The PUMP will shut down!!! (because it automatically set pump to OFF) So then I can wonder why the pump shuts down after a while! OMG. Who implemented this ? Once you go out from self test menu, it start working again but this means you canāt watch inlet and outlet temperatures! Well you can switch pump āONā in self test menu but this will put your PWM pump on MAX. SPEED, resp. the last fixed value which has been set on the pump. So monitoring temperatures makes no sense. Jeeeeesus Christ, tell me this is not a truth.
Sorry guys, I know Iām a bit boring but Iām really out of ideas.
It seems that PWM regulation does not work a bit. Now the HP is able to turn off the pump off and on but seems that speed control does not work at all. If you look at these two pictures you can see that HP requested to lower the speed but pump completely ignores it. At 77% is bigger than it was at 93%. All circuits are fully open. Do you know if I need to setup besides just connecting the PWM cable from pump to HP ?
Seems now it decreased the speed but only if inverter pump was below 70% or so. Now it is at 58% and shows 13.9 l/s flow rate. Do you know how the pump determine maximum and minimum speed of the pump when it is only sending signals and not receive ? Donāt understand if HP does not have a terminal for output signal from the pump. I thought that it will somehow determine the max. flow when it is on 100% and then decrease to 0 where 0% is no flow of pump. If anyone can explain how this PWM works exactly I would be glad. Now it is at 54% showing 13.3l/s so seems itās doing something. Dos it mean that 1% is minimum flow rate of the pump which is 7 l/s ?
Also another question. Now itās 10C outside. The HP show energy efficiency 3/5 only and it runs on 800W right now. The output water temperature is 37.5C. Can someone explain why it show such low efficiency of 3/5 and not 4/5 ??? It is because my heat exchange is slow (because of small radiators) which are not able to expel the heat more quickly so the compressor needs to run on low RPMās where it is not that sufficient ? If so, would it help to increase WLT to e.g. 45C even there is 10C outside so it can expel more heat? Will this be more efficient that running at lower flow temperatures ? Iāve checked stats for today and input energy is 30.5KW and output 9.1 which gives COP 3.4 only. According tech sheet it should deliver COP 4.4. Even for 50C water it gives much better COP@7C = 3.6. So make it sense to just set the temperature curve to almost linear ? e.g. 15C@45 and -15C@50. Does it makes sense to get better COP ?
thats actually good news. that means the system is running only about 3.2m head at the moment. So , if you get a normal 8m head pump (something 25-80) that should be able to get the flow rate you need. you need a curve with at least 6.1m head at 1.4m3/h (thats 24 l/min).
I completely ignore the efficiency number on the system status so I donāt know what mine usually says or the meaning of that number.
you were asking about home assistant monitoring : I have installed the modbus module in the outdoor unit, I connect a wifi ESP to the modbus cable , and then pull data via the ESP into home assistant. and then upload the data to emoncms.org which is where all the nice graphs we all keep showing you get generated. there is plenty of discussion about this , on this forum in other threads, and on renewable heating hub. Please read those first.
donāt worry about exactly what the PWM % number says. if its varying the flow rate, its working. you can alter the target DT which affects target flow rate but given the pump and emitter issues on your system I wouldnāt mess with that value yet.
At these low power levels, your system will have a minimum electrical power that it wonāt run less than. Plenty of people have seen this , not just on these units. just ask @matt-drummer about his daikin!
You can turn down the WT and get less energy out, but you wonāt be able to put less energy in, so once you are at that point your COP will keep getting worse if you keep lowering the WT. So you may as well keep the WT up a bit higher and have the energy. then your system should turn off on the room stat.
I would say if its stable at 800W , everyone seems to think that its got same engine room as the bigger units, then thats as low as you are going to get and you should be happy. FYI 800W is pretty much the low point on my 16kw unit. you just need to find a WT thats stable and that youāre comfortable with. more emitters will help!
Yeah, still lot to learn. I will deff look into it.
PWM works but seems it starts lower down only from 75% and below. Donāt know why. Do you know what is the control factor in pump settings ? I have set it to 2.
But now I guess the main problem is the weak water pump. Theyāve installed 25-40 and not 25-60. So characteristic +/- match. 16L at 3.3m which is height of my radiators on the 2nd floor.
Much higher flow at that height. What do you think ? Not sure what exact issues this will solve but I know that the HP always asks for more flow when I start it since it shows 100% at 16 l/m. How much more I have no idea but could be easily over 20. That way it could heat more efficiently since it takes some time until water in the system gets to the temperature.
I also have this tiny radiator closed in a room where I donāt need to heat and that room is pretty cold. Do you think opening it full could help with stability of a system and despite more heat is wasted the system can get better COP at the end ?
please, its getting a little bit frustrating. I did say all these things before:
height of radiators is irrelevant.
you need about 6.1m pump head meaning at least an 80 pump will be required. I thought before you needed something like a 120 (because you said you have 60) but now that you said you have a 40, then the maths tells me an 80 is enough (as per previous message). 60 will not be enough, it only has 4.5m head at 24l/min, you can see it in the graph you copied above.
control factor is a PWM/DT tuning. donāt mess with PWM / DT tuning until the pump is sorted,
if you can get more flow and achieve the flow rate that your HP needs, 100% flow will be a larger litre/min number. system will startup faster, it will be able to achieve full power output.
yes in general you should open all radiators. If not done already, try to balance them using the lockshield valve as well, so that all are warm.
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