Samsung Gen 6 water law - compressor stops always for 3 minutes no matter what

Hardware Heatpump
21

Yes Matt, this is correct. Seems that with my current setup I can’t use pure water law without extensive cycling at higher outdoor temperatures. This would be possible if Samsung’s control logic is more advanced which obviously is not.

In UK you have a product named Homely which is an intelligent controlling for heatpumps. It connects to modbus and then can manage the pump according weather, light sensor etc. and I believe this is much more intelligent that the Samsung default logic. It can learn how your house is consuming heat and can adjust pump parameters according this. So this could help indeed, unfortunately, it’s available only in UK an few other countries. I would order it from UK but their installer app is not available in my region.

So I’m thinking to install modbus and somehow play with it and see if I can figure out some better thermostatic control.

Installer knows nothing, they didn’t know they have to install external pump. I had to say them…

So the conclusion is that I have to use “indoor thermostat” mode and set curves at higher outlet temps - for now :slight_smile: Probably I will install external thermostat where I can set hysteresis of my own. This would fully solve my current issue with thermostatic controls.

For now I will simply set it that under 3C the system never reach the desired temperature (by setting the heating curve appropriately) - it will only approach it. This ensures that pump will be running constantly and this is not a problem for my radiators. Above 3C the higher outlet water will cause the thermostat to switch off and then it starts again only if temp decrease by 1C. Not perfect solution but I guess it’s the best option at the moment. Or maybe I connect external thermostat if I figure it out where to connect it :slight_smile: Saw some Chinese Wi-Fi thermostats which operates with 0.5C hysteresis. I still can’t believe Samsung did not incorporate this primitive settings into their wired controller.

Do you agree ?

22

You may be able to do something, I don’t know but it would not be my solution.

The hysteresis on the room temperature is much lower than Daikin give, ours is nearly 2c.

This is because you are trying to make a heat pump work like a gas boiler.

With the correct size/correct type of heat pump this should never be an issue.

Who chose the heat pump you have, you or the installer?

23

Yeah Marko, it will be something like this.

System is very easy, just main pipe from the HP (28mm), PWM pump, TF1 filter and then this pipe divides into 3 circuits which are 22m.

Max flow is low and I believe it’s because installers installed TF1 filter with 19mm valves on the main 28mm pipe… With a low power pump (25-40) you can imagine the disaster on max. flow. But this is mostly not culprit for this issue since it’s more like a problem in very cold weather.

I would say the amount of water volume is low. I swear I will release the water from the system and count buckets :slight_smile: But personally I think it can be something between 50 - 100L of water. Exactly as you said if there is 200L it would not fall so fast therefore I think buffer tank would make sense but seems guys here says otherwise. It would take longer to heat such high amount of water and would take much longer to drop enough bellow the temperature the pump kicks back in. Or am I missing something ? I don’t know what other drawback could buffer tank has ? It’s accumulating heat so this is only a good thing or ?

On this I would add that I would install this buffer tank as an “isulated” jar directly connected into the main pipe outlet or inlet. So the water pass through directly. Not sure if it’s possible something like this. But it would behave like another completely insulated “radiator” in a system.

It’s definitely being cycled fast but only because my radiators are not able to give the hear that fast. So let’s say target water temp is calculated at 35C but because there is not enough water if hats up quickly over this temp and pump switch off. And then I can see it cool down or drop to 32 in 3 minutes or so when the pump kicks back in… and you are in a circle… Radiators are balanced fine all open all the heat transfer is OK everywhere so I can’t get better here :slight_smile:

24

Wow, Daikin has 2C hysteresis ? Damn, I would get frozed at such big jump.

You are right, but it’s too late. And most importantly, when I was buying this 8KW heat pump I didn’t know that in reality this is 14KW unit. You know what Samsung did ? They’ve used the same compressor in all HTQueit pumps range so 8KW, 12KW and 14KW all have same compressor and the max. power output is limited in the software… OK, 12KW and 14KW have slightly better heatsink but that’s it! So I have basically 14KW unit. Of course this is written nowhere as they states only max. power output. 8KW HP would be great match for my house since my heat loses are around 7KW@-15C.

So this is not indeed my fault and I consider myself as not completely stupid. Yes, some things I’m still missing but I cannot become a HP specialist in one week research.

So yes I’ve chosen is but only because I had not idea this in in reality a 14KW unit. Contractor and installers have absolutely no idea anyway. A had one offering and the guy there were suggesting better to take bigger unit because 8KW seems to low for him… So what to say ?

So yes, unfortunately at temps higher than 5C I will have to run this as a gas boiler :slight_smile: Efficiency will probably suffer but I have no other opinion now. I can only warn people to not buy this for smaller houses because it’s much bigger than what is written on their page… 8KW my ass… for sure…

25

Yes, the indoor thermostat is probably your best bet.

When looking for a 3rd-party thermostat, avoid any “modulating” ones that use TPI, as they’re designed to cycle boilers on-and-off several times an hour. The Samsung thermostat is probably the better choice, tbqhwy.

The strategy I use with my system (not Samsung) is to monitor the room temperature, and when it reaches the setpoint I drop it by half-a-degree. This effectively reduces the hysteresis from 1° to 0.5°K. This might be achievable with Modbus if you can write some code for it.

Quite a few heat pump manufacturers do this.

1 Like
26

Yeah, this is good idea and I was also thinking about it but the drawback is you have to do it manually on the controller every time :slight_smile: Yeah using modbus I guess this could be programmed like you need to monitor the indoor temperature constantly and if you see it’s at SET_TEMP + 0.5 then you will simply set command to lower target temperature by 0.5C and then after a while you set it back. Genuine now only to have a knowledge about programming a mod bus lol :slight_smile: With +5C and more outside my room temperature decrease really very slowly so I can imagine hysteresis even 0.3C. The heat comfort would be much better imo. And for the colder temps you don’t need to to this at all and can rely on pure weather compensation curve.

Yeah, but why they don’t state this clearly ??? Just to sell more units or what? It’s not fair to be honest because knowing this before I would never buy practically 14KW unit… I was thinking how the hell they would be able to achieve 70C water outlet temperature with just 8KW unit… Well, this is the answer! I feel cheated a bit to be honest.

27

This is why it is a really good idea to use a decent installer that knows what they are installing and backs it up.

Of course, it probably costs more, but that is what you are paying for, to make sure you don’t end up in this situation, and if you do, it can be rectified.

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They were supposed to decent… This is a quite big company here dealing with heat pumps and AC systems. Installation was not cheap, around 2000 eur. I’ve set 5 inquires to 5 bigger or smaller companies but nowhere they were interested about heat losses, current system, etc. Maybe in UK you have such good companies but here in Slovakia seems we don’t have any. The only thing they care of are quick money and don’t bother. I swear it’s better to give this job to some enthusiast guy who know what he is doing, it’s his hobby and will tell you everything in details. I’m consider myself as a pretty advanced user so I can’t imagine how normal people can handle this. But I guess they even don’t have an idea how their pump work. They don’t know is inefficient, they don’t know it’s cycling 100x a day… You know what I mean. Well, we all learn on our own faults unfortunately. But next time I will be more educated…

29

2,000 Euros is really cheap compared to here!

30

You are missing nothing.

A tank plumbed in with two pipes acts as a “volumiser” to add capacity

Some folks plumb them in with 4 pipes as a “buffer” though which can, if not managed correctly, cause chaos.

It is also possible that the volume in the existing system is not being utilised effectively. If too much flow is “bypassing” through one radiator (or an auto bypass valve) then although there may be 100 litres in the system you might only “effectively” be heating the 20 litres that is short circuiting through an imbalanced radiator or an auto bypass valve.

2 Likes
31

There is nothing wrong with a heat pump cycling at part load if the cycles are long enough.

All heat pumps will need to do this at some point because minimum turndown will be below the heat demand of the house at some point.

The cycles should not be so short that startup/shutdown losses are high or compressor wear is high.

The power should not be so low that the heat pump is less efficient than it could be.

The cycles should not be so long that indoor temperature moves too much.

The better heat pumps manage this optimisation internally and can do so with a wide range of flow rates/water volumes etc.

The basic heat pumps have the intelligence of a rock and rely on the design of the heating system to present them with conditions that force them to work in an efficient way.

If you have enough in-use circulating volume on a Samsung unit it will not physically be able to short cycle.

2 Likes
32

Thanks. How do I know I’m not using the water effectively. I have all rads fully open - that means no TRVs and lock shield valves fully open. 5 radiators on 1st floor, 5 in basement. All heating just fine and thermals are OK and equal. So I guess it is heating all the volume properly. I don’t know how much liters 1 radiator K1 1200*60 can hold and how much it can be in pipes but the house is not big so I guess not that much. So do you think this insulated volumizer in the cellar where my pipes are could help with this short cycling at higher temps ? Definitely installed on 1 pipe probably outlet ? But not sure what volume and what flow would be there since it could decrease flow or ?

Yeah but only if it is just few times per day… 6 - 8x per hour is insane…

Agree.

Agree but I would rather lose some efficiency than it is cycling so I’m fine if the pump drops to lower power input as possible while still gives heat to the house. This ensures the heating comfort and probably better efficiency and less wear than constant cycling. If there is too much heat thermostat will take care of it.

This again will be handled by thermostat so not a big deal.

This is considered better pump, the fact is the best pump Samsung has on the market but regulation in water law mode kinda sucks.

So as I’ve understood, this can be achieved by large buffer tank or as you called it “volumiser” ? I don’t know at the moment if there is a difference between volumizer and buffer tank but I simply need to add some 150L more of water into the system ? So question is what is the best way to do so ?

Just stumbled upon this. Which setup you think is better ? Do you think it needs some additioal pump or I will conect it between outlet and return pipes and that’s it ? I have PWM pump installed on outlet.

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Edit 2:

So found this, which configuration do you think is better for me ?

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33

DO NOT install a 4-pipe buffer. You will only make things worse.

You probably DO want a 2-pipe volumiser in series because the heat pump is so large compared to the heat load for the house.

Install as shown the first option here:

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I’m fitting an old 6 kW fixed speed ground source unit that is limited to 4 starts per hour. A 200 litre buffer should ensure no more than 2 starts per hour. (with radiators with not much volume)

You can make them calculations for fun time if you know the power, temperature, and system volume/output power.

I would not consider the Samsung HTQ a high quality unit.

The earlier units were basic/robust and capable of good performance if installed carefully. They were not “fancy” units though.

The new HTQ seems to have had troubles at the R&D stage. They rushed out a unit with R32 gas before releasing the R290 version soon after. I can’t see why you would do this unless you had trouble with the R290 design and were not ready in time for launch.

Time will tell how it performs. Samsung are more like ‘Opel’ than ‘Mercedes’ in the market for heating though I think.

Others disagree though!

34

Oh boy, don’t tell me this :slight_smile: I thought it’s a Mercedes :slight_smile: At least one thing is good, it’s super silent but don’t have much to compare with to be honest. What brand do you consider an Mercedes ? Mitshubisi, or Daikin? Something else ? I’ve saw quiet few heat pump like LG monoblocks or midea or inverted and there were incredibly loud. With this I’m satisfied and also performance is great, COP as well. Only the controlling seems not the best to me… It’s very powerful pump.

I also don’t understand I reason why they’ve rushed to R290 - maybe they want to be leader in eco solutions ? I don’t know to be honest. But I think R290 is same design only medium is different probably. At least it looks the same on pictures. Maybe I should have wait for it or simply I should have bough something else but now it’s too late. These things you can’t buy and return to Walmart sadly :slight_smile:

What troubles do you mean ? With R290 gass ? I guess it is still not out. I was looking on it but the release date was not clear. BTW, LG also introduced new therma unit very similar in design to Samsung with R290. I was not sure when it starts to sell.

Now the question how to make this thing running as best as possible ?

So you suggest this right ? Is OK for the primary pump be there as I draw it ? What size would you
recommend ? Is there any big pressure loss at that tank ? Looks like really simple connection. Thanks!

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EDIT: Found the water volume. They say for 8KW pump minimum is 30L so this I definitely have, but the problem is with cycling ofc.

35

The average single panel radiator (K1) will hold about 7 litres. So ten radiators will be 70-ish litres, plus whatever’s in the pipework. I’ve not been able to find any better estimates.

A double panel radiator (K2) with hold twice as much, so upgrading your rads will also increase the system volume.

36

Yeah thanks, it makes sense so probably how I’ve estimated up to 100L of water. But sec K1 is single panel ? Ah, my apologies, I’ve screwed it. Not familiar with UK typing. It’s P+ or Type 21 here. It’s a 2 panel radiator with 1 set of convection fins. Ah, sorry…

But look at this graph. You can see the issue with cycling in water law mode… Simply for some unknown reason this pump stops only for 3 minutes - aways. I think this is defined a minimum time the pump needs to stop. Seems my temperature in system decrease from 35C water temperature to like 32 in these 3 minutes so pump decide to start. I’ve switched to temp control and from 11 to 16 the temperature dropped only by 0.9C so the pump is still not running. Now it will start soon and continue until the target temp is achieved again. So I guess low heating performance of radiators together with small amount of water in a system. SO do you think this buffer tank could help here? I guess so, however, question is to what degree.

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37

Why wouldn’t the heat pump start again as soon as it was able to?

You have asked it to flow water continuously at 35c

It stops when it can no longer do it and then starts again as soon as it is able to.

It is exactly what you are asking it to do.

I don’t understand why you expect it to wait?

It doesn’t know that your house is hot enough, it doesn’t know that it is producing more heat than your house/radiators can cope with.

How long do you think it should wait?

What you think is the correct time might not be the correct time for another owner.

As far as I can see the heat pump is doing exactly what you have asked it to and Samsung have ensured that you have to wait no longer than absolutely necessary for their product to continue to do what you have asked.

If you want it to do something else then you do it with the room temperature controller.

A buffer tank won’t help in my opinion, or a volumiser.

Volumisers are fitted to aid in defrosting.

Buffer tanks are used for hydraulic separation where different flow rates are required in different zones.

A volumiser doesn’t lose heat, your water will still return too hot as you don’t run at a high enough flow temperature in relation the the size of your radiators.

Any solution you find must involve the heat pump delivering the heat it produces to your house, otherwise the short cycling will continue.

Any solution will mean that more heat gets delivered to your home than you want at times, the heat pump will have to run in shorter cycles if you can’t accommodate the heat produced.

It’s really simple and it has been explained to you many times by lots of people.

You can’t limit the heat output from the pump any lower than you have, if you don’t provide somewhere for the heat to go then the pump stops.

If you only want it to heat the house to a certain temperature then use the room temperature control.

If you want the pump to run continuously in longer cycles then buy bigger radiators or run at a higher flow temperature.

They are your only options other than buying a more suitable heat pump.

1 Like
38

Sorry, but that’s utter nonsense.

Adding volume is not only for the scenario where the system volume is insufficient for defrost.

Adding volume also extends the runtime needed to achieve a flow temperature AND the time needed for it to fall again.

This extends cycle times for a given set of control inputs.

I’ll share a spreadsheet example that includes the working later.

There are also dumb ways to control the time-average temperatures and more sophisticated ways.

I’ll try dig out an example of the degree-minute logic that also avoids unnecessary cycling and can be used to trade-off cycling Vs temperature variation.

39

That is simply not true. See response above.

40

I understand all your points. Seems the only option is to control it by thermostat then. Granted. So now only to find a way how to decrease hysteresis to more like 0.5C :slight_smile:

And yes, I simply can’t deliver more heat to the house because it would be too warm inside. It can work continuously until around and +3C and bellow. Above this I have too much heat so water law is not possible to apply without extensive cycling. And the higher temp outside the worse the cycling is. Can’t image how it would behave at 15C outside heh :slight_smile: But I believe every pump would have problems at 15C with radiator heating or ? If I’d buy 5KW pump I would have issues above -10C. There is simply no win win strategy with these damn radiators. Btw, I have P+, not K1, I’ve screwed the types.

So seems the best option for me is just keep it heating with indoor thermostat controlled. I guess then the pump will not switch until target temp is desired no matter what the water temperature is set on the heating curve and will probably run on the minimal compressor speed and lowest water temperature it is able to maintain. Is that right assumption ? Or am I wrong ? I assume this because when I set indoor temp control it didn’t stop once and I’ve set water temperature pretty low and always saw it running at 37-38 while target was 35 or so.

Guess I will test it this evening. Will switch to indoor control and set the curve very low at high outdoor temperatures. Now it’s 9C so will se it like 32C and see what happens :slight_smile: