3021: 55 (but I use Eco mode so it only heats to 45C)
I heat DWH on a schedule, I’ve got two schedules per day to topup water to about 40C - 45C. I’ve only got a small 150L tank and we use a lot of hot water. Kid has a bath every day and usually two showers plus washing machine and dish washing all uses hot water. Yes, the colder the tank the better the efficiency.
I use Eco mode to avoid the immersion being triggered, not an issue for you if it’s not connected.
I set 3023:30, which to my reading of the manual should mean don’t reheat unless temp <= 25. But what actually happens is that it reheats after only a small temperature drop if set to always on, so the only way to defeat that is with a timer. interesting that you ended up with a timer as well. In your setup testing did you find that changing the value of 3023 actually works?
also regarding your heating scheduling its interesting to me that I think you are effectively using WC mode to give you a fixed LWT system because your WC line is basically flat? So your system will govern your IAT by balancing system running or not, against target IAT. and you can achieve a higher IAT by running for longer.
whereas in my (and most) systems to achieve a higher temporary IAT, one needs to make it run a higher LWT, which with the system in WC mode can’t be done. I’ve been trying to work around this with fixed LWT mode with the LWT controlled by home assistant according to the WC line, plus/minus “boost” inputs, but not proving easy to get right / stable.
Sorry, I never tested this. I like having control over when the DHW cycles run. Are you sure your tank sensor is in the right place? Could your sensor be in a low pocket?
Yes, I’m not really using WC, pretty much a fixed flow temperature seems to work fine for my system with oversized radiators. What ever the temperature I don’t need higher than 35C flow, and I’ve found that running lower than 30-35C flow results in lower performance. Correct, the system switched on/off based on IAT, if I need higher IAT it runs longer.
I guess this works for me since my 5kW heatpump is about 30% oversized for my house, so even running 35C flow temperature is enough to re-heat the house from cold if needed.
I think the way most Samsung installs achieve this is by using a third party thermostat to control the IAT and running the Samsung controller in WC mode based on LWT rather than IAT. The Samsung controller then provides a display to increase or decrease LWT by a few degrees e.g
Agree, the Samsung controller is very simplistic. I’ve recently installed a Vailltant Arotherm+ system, it’s quite impressive how it can do parallel WC curve shifting to temporary increase LWT to achieve a higher ITA
I have sensor 1/3 up from bottom, but thats not the point. 3011=use hysterises, should mean that DHW would refuse to run unless tank sensor <= (3021-3023), but I find that value of 3023 isn’t having any effect. if you didn’t test , doesn’t matter, I’ll perhaps contact samsung tech support.
separate stat for the IAT, with the controller doing LWT WC, is how I am using it at the moment. The “separate stat” is actually a relay thats closed by home assistant / node red logic. But the LWT change is only do-able by pressing those buttons as per grahams video - unless you’ve found a modbus way to do it?
In my short experience FSV 3023 is actually only DHW setting that matters. All the other 302* values are mostly some kind of user interface limiting parameters.
Right now I have DHW set to 46°C and with 3023 Start temp at 7°C it means it starts reheating at (46 - 7) = 39C.
I tried both DHW ON and ON with hysteresis and haven’t noticed any significant difference. My temp sensor is close to top of the tank and once it shows 39C it gets lukewarm pretty quickly.
When the pump is heating DHW it looks like running full steam ahead no matter what setting I use.
When closing those 46C it is using 2kW with outlet temp 60C and inlet cca 57C. It takes around 30minutes and 1,1kWh to heat our 150l tank. That happens twice a day usually.
I don’t use DHW scheduler as I found it doesn’t take actual temp into account and started reheating even when water temp was near the set temp.
Last weekend i played with cables and rewired Shelly EM - two channel energy meter so it logs power consumption for DHW under first channel and space heating under second.
3 way valve signal is used with relay switching the meter clamp for corresponding channel so I have the consumption in two separate graphs.
We still don’t have cold enough here to use floor heating fully.
I am courious how the regulation of room temperature will work. While using Glyn’s settings (constant flow temp 33-34C and Samsung controler as room thermostat) i am wondering if it will not overheat the space as there is around two hour delay between warm water entering the floor and feeling it in the air.
Maybe i will need some thermostat based on outside temp? e.g. when there is under 10C outside and under 21C inside at 15:00 let the pump run for 1hour, when under 5C/21C run for 2hours and so on… I dont know if something like that exists. Lets hope it will work as is with Samsung wired controller
No, I don’t have a max flow temp set. The flow temp during DHW will raise until the tank sensor measures the designed temperature plus overshoot. The smaller the coil in tank the higher the flow temp will need to be to achieve a given tank temperature. Maybe check the position of your tank sensor? And the overshot FSV?
I have my DHW set to 40C (45C on Eco), this results in a max flow temperature of 50C.
Do you know the size of the coil in your tank, and how long is the pipe run?
Hi Lukas, I’m new to community so only just seen your post. I have an 8kW Samsung Mono Quiet so not identical but similar.
As Glyn observed, there is no ASHP flow temp constraint for DHW (unlike the WL settings for CH). So the ASHP winds itself up to a high temp (with consequent high power requirement) until the hot tank temp setpoint is reached. I’ve moaned to Samsung about this to no avail (“no consumer demand for adding such an FSV”). This may be because most folk have DHW on 24/7 and the few minute’s top up takes hardly any power.
Samsung advise at least 2m2 coil area (pref 3m2) for 8kW unit to limit this temp wind-up, so your 0.7m2 explains the high power you see. I have 0.9m2 (I retained my old tank) but as I only enable DHW 2 days per week I can’t justify a new tank/coil.
I mitigate the high power during DHW demand by splitting scheduled heating time (2 x 15min bursts with 15min in between). This drops peak power demand by ~50% by giving the tank chance to convect some heat.
You really need the tank temp sensor near the bottom, otherwise most of the tank will not be heated.
Unless I misunderstand your numbers, your DHW CoP is simply 29/12 = 2.4 (not the 3.4 you posted). But happy to be re-educated…
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 “tank needs to warm up” 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) I’m not much of a coder. so wasn’t getting very far very fast.
b) its got cold. I don’t 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 I’ve 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 don’t think there’s a way to set a Fixed Water Temp on my Samsung on DHW. I can’t even control ASHP compressor speed, so “Modbus control” is pretty meaningless. All I have is the Samsung weather compensator on CH. On DHW the ASHP let’s 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 tolerable…
I contacted Samsung (Customer Service Dept) last week about the MIM-B19N, and was advised that it doesn’t 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.
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. I’ve built all my monitoring around the MIM-B19N + one SDM120.
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 think… I only read the manual didn’t build it) , or via an analogue input (which I’ve no idea where it would connect) . If only setting FSV 5051 by itself , without also adding that input, I wouldn’t 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