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

Michal_S · 4 February 2024 17:00

Jesus guys, so whom should I trust now Those are completely different statements…

But somehow I’m more towards this statements. It needs more time to heat and then it’s more time until it went cold so this must have impact on heating cycle or ? The only question how big it at which temperature. The max power output of this pump at 15C is I guess around 9KW or maybe even more.

Yeah, I would have the best temperature stability but with at least cycles as possible. I’m fine with 2 per hour at 15C but definitely not like 6 - 8.

matt-drummer · 4 February 2024 17:16

I would believe Marko.

He is an expert and I am not.

matt-drummer · 4 February 2024 17:43

Wouldn’t it be better to just increase radiator capacity?

He is talking about fitting a large amount of extra volume.

What does that do to efficiency?

When I had this problem it was not caused by short cycling, it was my poor COP that bothered me.

It looks like Michal has more radiators than I had with my 9kW Daikin and I never had a problem like this and my house is much smaller.

It seems like a reluctance to run at a low flow rate and high enough flow temperature.

Michal doesn’t want the heat that his heat pump will produce, I still don’t really see that any solution that involves the heat pump running for longer and producing more heat will solve his problem, it will just make it worse.

He wants to run on a wdc with no room influence, I just don’t think that is possible and I don’t think any tanks of any sort will solve that.

I could have explained what I think better about buffers and volumisers but Michal has been suffering this for some time.

Buying more stuff and complicating the system doesn’t seem right to me. it would be better to buy bigger radiators as he will get the benefit of those at all times.

But I will admit, that @marko knows better than me.

If Michal chooses a solution like this then I expect a lot of help will be required.

greentangerine · 4 February 2024 18:13

Mine was installed with a four pipe buffer.

I changed that to three pipe and it works really well now.

Michal_S · 4 February 2024 18:18

Thanks, Matt. I think both of you have something right on it. I’m just not sure how much this buffer tank would help.

Exchanging all the radiators would cost around 1500 eur if I will do it on my own. It’s not a problem but I fear exchanging from P+(Type 21) to K2 (Type 22) does not help that much volume wise. Because the water capacity I believe is the same for both P+ and K2 types. Correct me if I wrong.

So what I would achieve is slightly better heat dissipation by the 2nd convection thin but I’m really afraid this won’t be a big benefit at such low temperatures 35 and lower.

Also it won’t help with thermal stability. It will heat the room faster with lower flow temperature but still amount of the heat generated by mump will be the same and house can’t take it at higher outdoor temperature because I would cook myself up

So I guess to prolong cycles while I can’t absorb more heat is to store this is somewhere else (in this case in a buffer tank). Then when the pump will turn off, the heat from buffer tanks is consumed and the water temperature won’t decrease that fast so pump can stay longer off. And then when it starts it takes longer to heat all the water do target water temperature so in the end the cycle is longer. How much ? Twice or more ?

Actually efficiency will increase in warmer weather, in colder weather I guess it could decrease since it needs to heat more water. But probably not that much and maybe not at all.

I have 10 radiators P+ type. I have more and probably I have better insulation, there are so many factors. Keep in mind that Daking 9KW is 9KW in reality, My Samsung is in fact 14KW. Your Daikin was able to run at much lower input that my Samsung. I can’t go lower than 700-800W which results in 3 - 4 KW if there is hot outside.

I have Toshiba AC which is 5KW unit and this can go as low as 250W. This makes big difference on cycling.

Also my radiators can run at 35C and keep the house at 23C when there is 7C outside. Problem is that the pump generates more power and my radiators are not able to give it to air. But even I have bigger ones it won’t help me because I would have higher room temperature if I use the same flow.

The solution is to simply store energy somewhere and then use it when pump is stopped. Bigger radiators won’t help because the heat demand is less than the pump provides at given temperature.

But if you say buffer tank can’t alleviate the cycling then I really need to use only thermostat control or but I less power pump. But then I can have issues with very cold temps.

So maybe 2 pipe buffer could really help. I don’t know, experts needs to say.

@greentangerine do you have problems with often cycling ? what buffer size do you have ? What was the problem with 4 pipes buffer ? Wonder if 2 pipe could solve my issue and prolong cycles…

matt-drummer · 4 February 2024 18:26

Michal,

My 9kW Daikin is a 16kw heat pump, they make it in four sizes, 9, 11, 14 and 16, they all have the same compressor and enormous circulation pump.

My minimum input is 900w and I need to deal with 4kW of heat at a minimum.

It is worse than you have.

My heat loss at 23c indoors and -4 outside is just over 4kW

I do have some experience of this.

I can’t run water law like you are aiming to do, I have to reduce my flow temperature as it gets colder.

But I do run my heat pump successfully.

My house is 98m2 with a 15m2 all glass conservatory, but that does have special glass.

I used to run at over 42c all the time, now I am at around 35c and although I have the same heat it is much less noticeable and easier to manage.

You can see my data here

Emoncms - app view

markocoheat · 4 February 2024 18:37

I would believe the physics…everybody else must show their calculations…

Here is a spreadsheet for a friend:
Heat Pump Calcs.xlsx (2.1 MB)

In the “Heat pump” worksheet you can see the data for the heat pump. It shows the minimum / maximum outputs at various outside temperatures and flowrates.

In the “Emitters” worksheet you can see the radiators installed and how much heat they provide / how much water they contain / what the flowrates should be for a few different “scenarios”

These are:

Whole house at -2C (design temperature) with radiators at 45/40
Whole house at +12C (about the warmest you would ever have heating on) with radiators at 35/30
Part of the house at -2C (design temperature) with radiators at 45/40
Part of the house at 12C (about the warmest you would ever have heating on) with radiators at 35/30

The design condition for the house is 9 kW @ 45/40C at -2C outside in the condition it is today. Part of it is undergoing renovation at the moment (the newer part) which is why it is interesting to look at what happens when part of the house is heated.

In reality the radiator temperatures would be much lower when it is 12C…or you would decide to only use them at 35C for part of the the day (when electricity is cheaper etc)

The user can choose that strategy. Maybe the heat pump gets best performance runnign radiators at 25C 24 hours a day. Maybe the heat pump gets better performacne running them for 1 hour on / 1 hour off at 30C. Maybe it gets better performance running them for 1 hour on / 2 hours off at 35C etc. I don’t know and it doesn’t really matter. It is EASY (if the heat pump cas controls) to make it run on/off. What you can’t do is make it run continuously if it won’t turn down far enough.

The “Runtime” worksheet checks to see if the heat pump will cycle.

A “7 kW” Vaillant unit (actually 9 kW at 45/40C and -2C) will turn down to 3.5 kW at +12C and 35/30.

With the radiators sized to give out 9.6 kW at 45/40C; it will never cycle when running at 45/40C and -2C because the radiators can always emit the minium heat; and it will never cycle when running at 35/30C and +12C because the radiators can still emit the heat.

You could run it continuously at minimum output if you wanted to; although you would cook.

If we took the same heat pump and conencted it to only part of the house (simulating part of the house being renovated; or a heat pump that is too big being fitted to a house) then things change. Now we only have radiators for 6 kW@ at 45/40C.

Still it will never cycle when running at 45/40C and -2C because the radiators can always emit the minimum heat; but it will be forced to cycle when running at 35/30C and +12C because the radiators cannot emit the minimum output of the heat pump.

How long does it take to increase the water temperature 1 degC? That depends on how much water there is. With 0.8 kW too much power the 61 litres of water in the radiators (I ahve ignored the heat pump and the pipes and the metal of the radiators here so in pracitce the cycles would be longer) it would take 5 minutes for that temperature to change by 1 degC.

Add 100 litres of system volume and not it takes 15 minutes for the temperature to increase by 1 degC.

The extra volume increases the length of the cycle.

You HAD to do this for old fixed speed units because they HAD to cycle to deliver an output that was smaller than the design heating power. You would use a combination of system volume AND controls to manage the cycling.

You don’t HAVE to do this for inverter units if they are about the right size. (that 7 kW Arotherm in the house above doesn’t need to cycle unless you cut off 30% of the house)

You MAY want to do it if the unit is oversized, has a poor turndown (high minimum output), and/or the heating system has a small volume.

Here’s how that unit is behaving with “part of a house” connected at approx +7-12C air temperature (average winter temperature in the UK / average heating season temperature is +7C)

The onwer chooses to run a “night setback” with it when the weather is mild (cooler temperatures at night/warmer during day) for comfort reasons.

It does briefly run maximum output (not the most efficient way of running) first thing in the mornign but then settles into a steady 3.5 kW just as you would expect from the datasheet.

The second day is a bit warmer and it is forced to cycle towards the end of the day.

The Vaillant controls use degree-minutes. It measures the difference between the target water temperature and the actual water temperature, and how long this has been happening for. By default once “60 degree minutes” have been counted the compressor is started.

Tricky to see from the graph but it stops at 19:55 and restarts at about 20:05; having waited for the water temperature to drop by 5 degC for 10 minutes (this integral would be 50 degree minutes)

The target water temperature is set by the weather-compensation curve (and modified by any load compensation). There is also compressor protection to prevent restart for X minutes after it stops. (no matter what the controls want to do)

I don’t know modern Samsung. I don’t know how the target water temperature is set or when it decides to start and stop the compressor. It’s either dumb as a rock - being a little oversized with small volume doesn’t help - or there’s something that needs configuring here.

The old Samsung units WERE dumb as a rock. They has “water law” to set the target temeprature based ou outdoor temperature. The compressor would start if the water was too cold and stop if it was too hot. You needed to be careful with your wet heating system design to make sure that it wasn’t being asked to start and stop too often.

They didn’t have any “load compensation” either; so that UK distributor’s trick would be to set a minimum water temperature of 35C and add an external hysteresis thermostat. Under part-load conditions the thermostat would switch the heat pump on and off. After the water needed to be hototer than 35C it would run continuously using the “water law” curve instead. (the thermostat would always be askign for heat but it would never quite reach the set temperature)

Here’s a manual for an old fashioned heat pump that explains [outdoor temperature / weather copensation] curves (Samsung call this water law); room influence (I don’t think Samsung units have room influence capability at the same time as water law); integral control (unclear how Samsung control compressor start/stop); and hysteresis (if somebody makes a sudden change to the settings then wipe the integral and start again so that you’re responsive)

I think most heat pumps that originate in central/northern europe use similar control logic to avoid excessive cycling / early restart of compressors:

Installation and Service.pdf (5.5 MB)

And some typical settings:

60 degree-minutes to start the compressor
minimum 20 minutes between compressor starts (even if the degree-minutes want it to start sooner)
600 degree-minutes to start the auxiliary heat

e

Michal_S · 4 February 2024 18:47

Ah really, didn’t know even Daikin is doing this…

This sounds exactly like mine. 800W and 4KW of heat so I wonder how possible it did not cycle at you every few minutes with higher outdoor temps.

But yeah, the explanation is that you were not able to run water low. And seems I can’t either for the very same reason.

Well I can run it with indoor temperature control fine as well (besides that hysteresis. How can you tolerate 2C temperature drop ? I can feel the cold once is 1C below 23C). It’s only water law which making troubles. I will it has some better logic if pump sees it’s cycling instead of constantly start and stop the pump. Some AI stuff you know. If it’s controlled by person then what you would do if it is cycling too often is that you keep it stopped not for 3 minutes but 6 and observer behavior.

But maybe I’m naive. In any case seems you have bigger heat losses considering your house is smaller. Not so much though.

I will check your data. So you were running flat at 42C water temperature all the time ? What are your minimal outdoor temperatures ? What I like on water law mode that you could easily change the curve from the controller just adding +1C or -1C. In indoor mode this is not possible and you have to go to service menu to change it.

I need 40C at 0C to cover heat losses at 23C indoor. And 50C at -10 or -12. Didn’t try it yet. So I need to set the curve around this and then user thermostatic control. But that means that at 10C it would be bellow 35 in water law and this would not work.

So you have changed your radiators so you could drop WL from 42C to 35 C ?? What type you had and what you’ve installed ? Not sure if change for P+ to K2 would make a big difference since they have maybe +30% output ? Is it worth it in your opinion ?

matt-drummer · 4 February 2024 18:56

Hi Michal,

My heat pump will run continuously 24 hours a day. Daikin cycle it every 6 hours whatever. The only other times it stops is to defrost.

Of course, I turn it off when I don’t want it.

My heat loss is my heat loss, it doesn’t matter how big the house is, the heat pump has no idea how big my house is.

I have about 45kW of radiators in my 113m2 house, that is at dT50c.

I can run even lower than 35c if I wanted to.

The reason I don’t is because of the minimum electrical input. My heat pump will run at about 38c at the minimum electrical input.

When it was -4c here I reduced the flow temperature to 32c as it gave enough heat and the least electricity use possible.

This is what I mean about not using water law, it doesn’t work in my circumstances, I need a reverse curve to get the best efficiency.

So I just play with it to see what it could do.

Now I have settled at 34c and just leave it alone.

But because I went with a big installer, they are replacing it in two weeks for a smaller unit.

The one I have is just too big.

As far as radiators go, I increased my capacity so I now have about 2.5 times what I had originally.

markocoheat · 4 February 2024 19:02

My reply was quite long.

I will try a shorter version:

The average tempeature of the radiators needs to match the heat loss of the building
You can calculate the heat output from the radiators at a number of temperatures by using the “derating factor”
You can work out the “excess heat” as the difference between the minimum heat pump output and the radiator output
If there is “excess” heat then the heat pump MUST cycle to avoid overheating the house

You can control this cycling in a few ways:

The more water in teh system the longer it will take from the initial compressor start for the radiator temperatures to become too high. This sets the “basic” cycling rate and does not impact comfort (because the heat ourput remains stable)
If the heat pump has proper controls, you will also be able to tell the heat pump how long to wait (best case degree minutes; worst case just minutes) before restarting the compressor to control the cycling. This does impact comfort (you get the “heat spikes” that the volumiser screengrab I shared earlier refers to)
You can also add external controls if the heat pump doesn’t do what you need it to (e.g. using a combination of a fairly high minimum flow tempeature plus an air temperature hysteresis thermostat to force it to switch off for a period before restarting)

What works best will be dictated by the heat pump.

If the heat pump is the right size for the property, has a decent modulating range, and has decent controls it should “just work” out of the box.

This Samsung HTQ seems to be a bit of a dog compared with the older versions when it comes to turndown (the new scroll compressor equipped units don’t appear to turn down anywhere near as far as the old rotary compressor units on R410A/R32)
It also seems to be too big for your property in general

How is it performing though? Apart from it breaking…is the COP what it says on the tin?

Michal_S · 4 February 2024 19:03

Hey, this is a very nice elaboration and exactly from what I’m observing on my unit. It will takes some time for me to read those charts but what I can say it works exactly like this.

Also I would say this Samsung “modern” unit is dumb as its predecessors in terms of water law controlling. Really dumbass. It has a very nice design, it’s quiet but the software is the same shit. It does not think. Simply follows the water low ignoring the heating capacity is maybe too much for such high outdoor temperature lol.

So this is exactly what I said earlier and what is my strategy. Seems that at least I start to understand this problematic. Also my thinking of using external thermostat with my own hysteresis seems to be reasonable. Of course, only when there is +5C outside. Bellow it would work strictly by water low. Only in case there is a very sunny day thermostat can kick in but I’m totally fine with that.

What you can set on Samsung is you can change some pump control settings like:

application
target dT
form factor

But I don’t have an idea what these means, especially form factor and if it has any impact on cycling. Do you know maybe ?

Still do you think this buffer tank could prolong these 3 minutes stop cycles ? Wonder if it’s worth it because as you said, maybe it would be better to run this at higher water temp and get better efficiency.

Michal_S · 4 February 2024 19:17

Can you explain ? It’s running all the time and cycle every 6 hours so how long it is stopped ? I quite don’t understand how it is not cycling when your heat demand is less than pump output power until you turn it of manually ??? We are still discussing water law mode or ? In this mode it would cycle like crazy when 10C outside even for you… We already agreed that in indoor temp mode this is not an issue since it heats until thermostat turns off.

Well you said your heat loss is 4KW at -4C. What I wanted to say is that your house has probably worse insulation than my house. Of course pump does not matter. If you insulate your house better you will even bigger issues with this pump so better don’t do it

What radiator types are those ? Those radiators are efficient at 32C at -4C ? This sounds strange to me, how they can handle it ? I need to have around 40C at 0C…

Yes, no water law at current stage for us but as @markocoheat said using some buffer tank could you help running water law mode with less cycling.

Thing is you know your heat losses at let’s say 10C. Let’s say it’s 2KW. You know it’s more than pump can provide but you you know that you need 32C water outlet to maintain 2KW heat loss with radiators. If you don’t have this buffer tank the pump will cycle because it heats quickly and also get cold quickly. If you user 100 or 200L additional water buffer it takes much longer to heat to 32C and also it takes much longer until this get cold.

Results? You will effectively reduce the pump cycles. It will still cycle but much less. The question is how much this is able to prolong the time when the pump is stopped. For me it’s now 3 minutes. If it is 15 minutes at 15C I could live with this because let’s say it will run for 20 minutes and 15 minutes stops. This is maybe one cycle or two cycles per hours which is OK for the pump.

Not sure if it makes sense but would say it’s a physics.

Michal_S · 4 February 2024 19:31

I don’t know if old models used the same compressor in alle the ranges like this one but this 8KW is basically 14KW. So it is big for my house? It depends. I need it can deliver at least 7KW of power at -15C since sometimes, not very often we have these temps for couple of days in a year. Decade ago it was very normal, but you know, global warming which does not exist, right… ?

So I need this. Problem is that minimal input is around 800W of this one so I believe if older Samsung HP were able to go down, they’ve modulated better. It is how it is, I can’t do anything with that and simply over +3C the minimal output f the pump is higher then my hat losses. So cycling is inevitable I only didn’t thing it’s that stupid how it is…

So seems cheapest would be to use external thermostat with hysteresis I can define + pure weather compensation at +3C and below. This would be best for the comfort and best for lowering cycling as much as possible.

It performs very good if we consider I have only P+ radiators. At 40C/35C it runs at 0C outside at minimum power so the efficiency is not the best but still it gives around COP 3. +7C around COP 4 and it’s only because of this stupid cycling the efficiency at +7 goes closer to what I have at 0C. I only can say this is stupid controlling.

And of course what was my priority is the noise and man, this is really quiet. I can hear only the fan and it’s very faint. 5 meters from it it’s barely heard. No vibrations in my house. My 2 AC units oh boy, this is night and day difference.

Of course Samsung gives only max heating capacity (integrated values) so at lower power COP will be lower but I have to live with that. I don’t understand why they don’t provide nominal and lowest heating capacities. This should be mandatory. Other cheap brands provides this information.

matt-drummer · 4 February 2024 19:33

I can leave my heat pump running as long as I want, it will never stop apart from what I said.

My house is very well insulated, heat loss is about 3kW at 23c indoors and -4c outside.

It is just the all glass conservatory that complicates things, it loses maybe 1.2kw at these temperatures.

It can run because of the radiators, they are very big.

That means I can run at low flow temperatures if I want to.

I can run much lower but the heat pump doesn’t like it, I just match my flow temperature to the electricity consumption.

It gives me the best COP and I like that because we just do!

My heat pump only turns off when I turn it off from the app on my phone.

I control it completely manually.

It gets too hot here, so I suffer it a bit and then turn it off. When I want more heat I turn it back on again.

It is all I can do really, I can use a room temperature control but I don’t like the other things it does, that is a Daikin thing, and I could use water law but it makes no difference and I want it to work backwards anyway.

So it is just a fixed flow of 34c with an allowable overshoot of 4c, another Daikin thing.

I have a target dT of 8c but I never get it at those flow temperatures because my flow rate is too high, the minimum on my heat pump 9it’s a monobloc) is 10lpm.

That is it and you can look for yourself.

Michal_S · 4 February 2024 19:48

So 3KW or 4KW ? This is a big difference.

Also what radiator types do you have ??? K2 or K3 ? This is also a big difference… Please specify.

I still think you have to control it differently because it is not possible that your pump will be able to run 24/7 when there is 5 or 10C outside when your heat loss is 3KW@-4C. This is maybe 1KW needed at 10C. Your pump minimum output is around 4KW. So how you can run this 24/7? Where those 3KW of heat goes ? Size of the radiators won’t have impact on this since you still deliver much more heat than your property needs for a target 23C indoor temp. So please explain this…

matt-drummer · 4 February 2024 20:04

4kW.

You were saying my house is poorly insulated, it isn’t as the 4kW includes a 15m2 all glass conservatory that I heat to the same temperature as the rest of the house. The house itself is about 3kw and the conservatory 1.2kW so 4.2kW in total.

The conservatory is a problem as the heat loss per m2 is much higher than the rest of the house.

I have K3 in the main but this isn’t the difference, radiator type is irrelevant, it is the output that matters.

I could have K2 or P+ instead, I would just need more or bigger.

You keep asking where the heat goes?

My house gets hotter or I open windows, but I haven’t done that this year as I am no longer looking for the best COP.

My house just gets hotter and hotter until I turn the heat pump off.

The difference between my house and yours is that my radiators keep delivering the heat because they are big enough to do it.

My returning water temperature doesn’t rise so the heat pump keeps going, it has no reason to stop as I haven’t asked it to.

This is what your Samsung is trying to do but can’t.

If you look at my data you will see when it is quite warm outside my flow and returns rise but the heat pump keeps going.

Right now I will leave it on until we good to bed, turn it off and then turn it back on again when I get up tomorrow for my wife when she gets up.

It is currently 12c here, the heat pump is producing 4.8kW of heat and it is 25c indoors.

I could have turned it off earlier really.

You really don’t understand radiators.

My radiators have an impact because even at a dT between room and radiator of 8c they can still put out 4.8kW of heat. If they were smaller they wouldn’t be able to do this.

I am not saying that anybody needs to go to my size of radiators but this is the difference they make.

I also have fan assistance on all of the downstairs radiators in the form of Speed Comfort fans.

matt-drummer · 4 February 2024 20:21

Here is the worst day, average -1.9c and -4.4c at the lowest on that day. It was actually a little colder in reality as the outside temperature is not actual but comes from the Met Office.

DHW was about 4.5kWh so the house took 4.25kW in heat on average

This is a day where I was trying to maximise COP to see what it could do. You will notice the flow temperature is higher even though it was 12.7c on average outside with a high of 14.0c.

The house took more heat that day as it got hotter and I opened windows and doors to get the most out of the heat pump.

It runs for six hours at a time in heating, only stopping to do DHW and because Daikin force it to stop once every six hours as routine. It starts straight back up again.

Michal_S · 4 February 2024 20:50

Ah, then OK I did not consider this glass conservatory. But then let’s say your house demands pretty much heat then. At the other hand this glass conservatory is your benefit on sunny days…

But I see your point now. So your heat losses without conservatory is around 0.11KW/1C. Mine is 0.19KW/C. This is 42% difference. My house around 160m2 yours 98m2 this is 38% difference so seems your is little bit better insulated, sorry. Do you have bungalow or storey house ?

That’s right output matters. I have to calculate mine so we can compare it but I guess I have much lower output since I have only P+.

Yes but if you not open windows and not turn of the pump you would get cooked at 10C outside or ?

We still not understand each other. I’m talking about continuous run. 24/7. This is not possible. You may run lower temperature but the house will heat in a same way and same time as mine if I run it on higher temperature. Of course you will have better efficiency but that’s it and result is the same - if we won’t switch it manually or thermostat it will overheat

But yeah, you can do it like this but I would cook at 25C lol. I could do it as well with higher flow temperatures but this is nothing for me. My max. is 23.5 I was talking about continuous operation and this we can’t both achieve.

This buffer tank could help to alleviate the cycling a little bit but it is unknown to which degree and if it’s worth it. Bigger radiators (K2) won’t help me much neither. The only possibility for me is to control by thermostat and by water law combination.

But thanks for insights, again I’ve understand a lot.

You can be sure I understand it very well now but probably we don’t understand each other. I’m talking about 24/7 operation and very short cycling and you are talking about overheating your home and cooking yourself. Then you let your house to cool down overnight and repeat the process. No offence but it’s like it is. My intention is not to output 4.8KW at 10C outside. Really I don’t. Instead, I would like to “store” or accumulate this heat and slowly release when the pump is off.

Seems you still don’t understand this principle, it’s quiet easy. Check the graph @markocoheat posted. And the bigger buffer tank the more heat you can store and the longer the pump can run so you effectively prolong its cycle

They would but at a tad higher outlet temperature and though much lower efficiency. And this fan assistance makes you even a better effectivity so congrats, your COP needs to be great. But I don’t aim at COP but more to temperature stability as much as possible.

What are those stops every 2h ?? I would expect to run this continuously at such cold temperature.

BTW, what setup do you use for monitoring ? emonHP Level 3 ? Or something else ? I like this COP stats.

Granted, if I let the system to cool down, then I can run ah hour or two at 33C as well. But keep it running for more than 6h. Besides you would cook yourself it would start to cycle.

I’ve started mine at 8PM, target temp according water law 33C and it is now still running at 34C with high effectivity:

Now around 35C I would need to turn it off for another hour or two and then start again so I can get as best efficiency as possible with a little bit lower comfort.

This 6h routine at Daikin is strange. Are you sure it’s intended ? Because mine does not do this. It can run 24h a day without any stop.

matt-drummer · 4 February 2024 20:55

I can do continuous 24 hours at 13c outside, I posted it above.

Look at my post it is there!

Here it is again though, all day, only stops once every six hours at 13c outside

I put in more heat on a 13c day at a higher flow temperature than I did on a -2c day at a lower flow temperature.

The stops every so often on the cold day is defrosting.

When it is colder here it is usually humid too, it causes the evaporator to freeze.

The heat pump has to take warm water from the house to remove the ice, it runs in reverse using a special valve.

I have a 20l volumiser to assist with this although I don’t really need it now with my bigger radiators.

I have OpenEnergyMonitor system with heat and electricity meters.

I do understand about the buffer tank.

I don’t have one as I don’t need or want one.

All of the four heat pumps in this Daikin range run for six hours maximum and then cycle, I assume it is a safety feature of some sort. They are very conservative about defrosting.

Michal_S · 4 February 2024 21:14

BUT, You can do this with all the windows open sorry. I can see throughout a day your pump deliver constantly more than 4KW of heat to your house !!! And your room temperature is steady from 0:00 until 14:00. How if your heat losses are 3KW at -4C ??? Your heat losses at 12C must be somewhere around 1KW!! So you pump 3KW more het every hour than your house need to maintain 23C indoors. This makes no sense, sorry… To satisfy this chart your heat loss would need to be 4KW at 12C. Would you mind to explain ?