Nice, but you still have zigzag pattern which is not optimal for compressor, it’s hunting. But I’ve came around this so you can maybe inspire even more.
FRC you need of course but alpha-omega is to not limit your flow temp. Not sure if you can achieve it with UFH (sorry forgot if you have radiators or floor heating), depends on the pump frequencies at given outside level, desired indoor temp and your heat looses. If on this chart of yours you are alredy at minimum compressor speed then you can’t do it but also means your system is very oversized. Seems you still running too high with compressor speed. For 35C water 1500W is pretty much. I think you can go lower. Think about it.
What I’ve done is to limit FRC to minimum up to -1C outside. From 2C outside above I use thermostat to control indoor temp since even at minimum compressor speed 22Hz the heat looses are lower for my target indoor temp so I cut out at 23.5C indoor… Then I have FRC zones that from -1 to -6C I’m using 27Hz, -6C to -11C 32Hz and so on you got the point. Thermostat is not used because heat loses are always slightly higher for target 23.5C. I have only emergency stop at 24C in case there is lot of sunshine for example and house overheats. This way it is heating as much as it can at given outside temperature so no hunting ever. I also lowering FRC if I’m coming close to target and I’m not at minimum FRC already.
Simply I did my own PID regulation and completely bypassed Samsung stupid and aggressive logic. For the moment it works very well, need to test with freezing temperatures and also above +5C. But Still if there is above +5C I hold min compressor speed which helps with dramatic water heating and then panicking like crazy. Maybe it can help you even more.
With DHW I didn’t notice any signific COP increase between 30Hz (min FRC) and 45Hz (100%). So I’ve set 356 for FRC when heating water.
This my chart from last day. You can see that max. flow temp at 1C outside is around 41C.
I have contacted samsung about it, no help, they say just look at the avg for COP. There is no control over the algorithm for it, they won’t share it eather, (If anyone has any more luck)
Not sure what you mean, its 1500W input for 7000W heating, I can’t go lower otherwise the house loses temp.
I have worked out the heat loss to be roughly 14.5kW at -2.5.
I can only limit my compressor to 40Hz with FC 50%. Wise there was a way to go less as the compressor can go down to 18-20Hz.
You can see the pump is still hunting to hold the target. Hunting is usually by oscillating at 7Hz up and down which is tragic control. With FRC you can go 10% lower with compressor speed and keep it like that it will slowly go up to max. possible output because pump is much more stable at current outdoor temperature. You need to set your weather curve flat and much higher above target… Just forget on Samsung’s two points weather curve it’s bullshit. This will eliminate hunting and you will see what max output temp you can get at that speed and outside conditions. You need to play with it and find your best compressor speed with outside temperature and desired flow temp. Of course there will be some temp fluctuation but for me it’s max. 5C and I always can add some offset to FRC when I see the power input is low. But this way you can eliminate this zigzag completely creating your own
What model do you have exactly ? That’s not possible you can go down only to 40Hz. Are you sure FRC works properly ? Of course this method will work only if you go lower at 22Hz, i know some pumps can go even lower like 14hz. But 40Hz sounds just too much and wonder why you can’t go lover ? If 40Hz is 50% then what is 100% and 150% for your pump ?
I see, then I’m afraid there is no way to prevent it. You could only write a hunting detection algorithm and turn off the pump for some minutes but not sure it’s worth of it. I don’t know how bad are these 7Hz oscillations every minute for a compressor. It’s unpleasant only if you stay next to the unit so from this point not a big deal but I’m more worried about lifespan because it’s not only about compressor frequency - with each such a big frequency change other components are stressed as well, pressures must establish etc. and if the pump fluctuates every minute… I don’t know.
Wow, just re-reading this thread and discovered this (thanks for sharing @mrsimonbennett)
I have a gen6 Samsung 12kW unit, and had used Quiet Mode for DHW runs to try and narrow the dT for my tank (i.e, give the tank more time to absorb the heat being produced).
I have quite a small tank (Joule slimline 160L), and although the tank supposedly has a high power coil, I would see LWTs typically ~10C higher than the DHW tank set point (e.g, 55C LWT for 45C DHW set point). Turning on Quiet mode reduces this to around 7-8C, and now enabling #5051, which reduces power output further, brings down my dT to ~5C presumably making my DHW runs more efficient.
@mrsimonbennett do you have any data runs for similar showing lower energy usage / increased COP? I’m sorry, but I don’t have any monitoring so mine are observational only.
I don’t have a good side by side compairson of COP as hard to get two situlations the same
The best example I have in the data. I feel its way better, the flow temp is greatly reduced givening the heat exchange process more time to happen. The trade off is the time it takes, given the size of my head pump 40% is still alot of power. When heating at 16kW it takes no time at all!
I’ve done some testing with the requency response control over the last few days.
Firstly, I just turned 5051 on, with no voltage input or modbus contol, limiting the compressor frequency to 50%. I also switched off quiet mode at the same time, as I used to have this on permanently. (recently changing from quiet mode level 3, to level 1 on the outdoor unit) This seems to have give really good results over the last few days.
Findings (50% cap):
Much longer DHW runs, that when running quiet mode level 1, but similar to when running quiet mode level 3, suggesting that the frequency cap on quiet mode level 3 for DHW is also 50%. It seems to now take longer than 90 minutes to do a DHW run, (250L tank) which is the longest it will do when both heat and DHW demand are ON, before switching back to heating for a while and then back to DHW for up to another 90 mins. I had to adjust my schedule and DHW setting because of this. It could complete it within 2 x 90 min runs, and with the min space heating time (3024) now set to 20min, and max space heating time (3026) set to 30 mins I had to have my DHW schedule on for at least 210mins (90+30+90) to ensure it would reach target temperature. Previously it was only on for 2 hours.
Zero defrosts, even with the temperature sneaking down to 1-2 degrees a couple of times. Compared to defrosting sometimes every 50-60 minutes at time, even at temperatures as high as 4 degrees. Quiet mode reduces the fan speed, which reduces the amount of “warm” air passing over the cool to keep the condensation from freezing. So with quiet mode off, and with limiting the compressor frequency, and OAT not yet getting below freezing) it hasn’t had to defrost at all.
Decreased heat output. On my 8kW unit, by heat output seemed to be limited to around 4-4.5kW.
Improvement to COP for both DHW and CH when compared against days with similar OAT before the change.
My concern was, that with my heat output limited to 4kW (or potentially less when below freezing & defrosting) that it wouldn’t be able to keep the house warm at design OAT, as the heat loss is around 4.3-4.5kW.
Next change was trying to get the frequency limit up from 50% using the voltage control. Yesterday, I tried a variable resistor pot, but it was just 1 I had lying around and was a bit iffy and the voltage was jumping around, so I took this out and ordered a voltage simulator off ebay.
Today, I got even more inventive as there’s going to be a cold snap coming in the next few days (before my voltage simulator is due to arrive) so needed a way of capping the frequency at higher than 50%. I think (guess) a 60% cap would be suitable for me so needed a 1-2v input on the controller. I decided to use an AA battery to do this as they’re 1.6V. I went with just taping wires to the ends of the battery for now, a battery holder with leads would have been the best. It’s only temporary. There should be much draw from the battery, if any, as it’s a high impedance circuit. It only needs to see the voltage, not draw power from it. I put a connector between the battery and the controller so that I can quickly disconnect it if I need to.
Early findings (60% cap):
I am now getting 5.1kW output. Hopefully this will give me that little bit extra to keep the house warmer over the cold snap, even if output reduces at colder OATs, and if it does start to defrost below freezing. The danger zone for defrosts seems to be around -2 to +5 degrees, where you should get the most frost. So the fact I’ve got down to +1 to +2 without any is a good sign.
Maybe slightly improved COP again. But it’s still very early.
I debated this, at the moment I have turned off the limits, ive needed the full 16kW.
I am intrested on the theory of the fan speed, in my mind the higher fan speed would help more than hurt. The Samsung pretty much always goes to full speed on mine
