@cloudclear

Hi, I run my Samsung using pure weather compensation. I think the low end of my WC setting is about 33C. When I try to drop it any lower the radiators cant get rid of enough heat and the ASHP starts to cycle. My Samsung controller is in my living room and that's the one we keep warmest with two sizeable radiators. Its set to 22C.

I cant really say whats happening in your situation, but my system is well monitored and the temperature I set in the WC settings is the one I getting. Here is yesterdays graph. You can see Im bobbling along between 34 and 36 C which is exactly what I would expect at the outside temperature I was experiencing.

@bontwoody Thank you! I think you've confirmed that I need to invest in some data monitoring. What system do you have and would you recommend? Cheers

Posted by: @cloudclear

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Earlier this week when playing with those temps I could not get the flow temp below 34.8degrees resulting in the house continuing to warm as I lowered the curve lower and lower. I had a bit more success today and got the flow down to 32degrees and got closer to balance, but ultimately the temp kept increasing and would not stop even as I reduced the temp on the controller.

Has anyone else had problems dropping the flow temp to balance the temp on a samsung and any guidance on how to crack it?

Could you post a photo of your wired remote controller display please? It is not clear from your description just how you are trying to control the flow temperature as there are different ways of doing this.

If your current display allows you to set the desired room temperature then this means that you are using the thermostat in the wired remote controller. To alter your flow temperature you will be altering the appropriate FSVs in service mode. You should be able to set your expected flow temperature for a given outside air temperature down as low as 25C for example. 

Whether your heat pump delivers that flow temperature depends on the FSV 2093 setting. If it is set to  2-4 then as @bontwoody has described, the heat pump will run at a flow temperature of 25C for a certain length of time and then cycle off. This is because the emitters cannot emit sufficient heat at such a low flow temperature to match the Samsung’s minimum heat output. 

However if FSV 2093=1, The flow temperature will rise above 25C and keep rising until the emitters are matching the Samsung’s minimum heat output. The heat pump will not cycle off with this setting unless the thermostat turns it off. 

This might be what you are experiencing if you are operating your heat pump in the mode that I have described above. A photo of your display would clarify this and also what values are in FSV 2091, 2092 and 2093  

@cloudclear I have an open energy monitor system which Im very happy with. It certainly lets you get the best out of your system and is modular. It is however quite expensive if you go the whole hog and get a heat meter.

An alternate less accurate but cheaper way of monitoring is to get a MIM-B19N card and use modbus to interrogate it. There is a fair bit of information on the web how to do it

@bontwoody Thank you. I will take a look in to it

@mike-h Hi Mike

Thanks for your input. I have been in service mode a fair bit to edit the flow temps but not the other settings. Here is what I have (including the flow temps).

It appears I have in the setting 1. What you recommend that I change? or is it a case of trial and error?

Thank you

FSV as follows:

201* 15/-5

202* 30/47

203* 30/47

2091 Use (Signal On/off) or WL Interlink Off (WP1)

2092 Use (Signal On/off) or WL Interlink Off (WP1)

2093 Room Temp On/off or WL Interlink Off (WP1)

Front screen i Have as -3 with a flow of 30ish (lower than I have had before) but house still warming (slowly). Photo hopefully attached!

 @mike-h 

I believe the guys above have nailed it.

I have a similar 12kW Gen6 Samsung and observe exactly the same. The heat that the ASHP is producing has to go somewhere, and if the emitters are not big enough, the flow temp must increase in order for the radiators to emit the heat produced. If you set the WC curve too low, the heat pump will either cycle on/off or the flow temps will rise until the system reaches equilibrium whereby the heat produced can be emitted by the radiators. For me, that equilibrium is reached at around 32.5C flow temp, but it will depend primarily on the size of the radiators and the dT between flow temps and room temp. I started out setting the WC curve to 30C but my system simply cannot emit the heat produced when the flow temps are that low, so the LWT gradually rises until equilibrium is reached.

Once you have the equilibrium temperature, this is the minimum flow temp you can achieve (without adding more/larger radiators) and you can set this as the flow temp for the warm end of the WC curve (e.g at 15C ambient outside temp). Then you can try to establish the flow temps your property needs for the cold end of the curve, so wait until you get a day of 5C or 0C, and slowly adjust the flow temp to try to find the flow temp that will keep the house at the desired temperature. For me, that's looking like 32C @ 15C ambient and maybe 35C and 0C ambient, but I'm still waiting for some prolonged really cold weather to nail down the cold end of the WC curve.

@old_scientist Thank you for your observations of your Samsung 12KW.

Yesterday I had the HP reasonably consistently operating around 30-32 and keeping the house warm. I suspect it can't go lower than that so I will use my 3rd party thermostats as limiters, but likely to come in to play more frequently than I would have hoped for.

Do you know if you can set back the WC over night on the samsung? My wife likes a cool bedroom overnight.

My plan of attack:

1) Get some sort of monitoring set up so I know what is actually going on

2) Learn about and play with 2093 settings - based @mike-h's comments I suspect they may not be right.

3) Hopefully use the coming weeks cold weather I can find the right upper limit of my curve.

Thanks!

@cloudclear sounds like a good plan. I do not have any monitoring, so am simply collecting data and recording through studious observations.

FSV #2091-2093 describe how the ASHP controls cycling when the system gets up to temp.

I run my system with a separate add-on 3rd party room thermostat which acts as an on/off switch to call for heat.

I have #2091 set to  Use (Signal On/off) only. My WL weather compensation curve is set to 32C flat for now (until it gets colder and I can collect more data for cold days).

When set this way, assuming the room stat is set high to force heating to stay on (say 25C), the heat pump will run continuously until the room temp is (ever) satisfied. The system will ramp up the LWT until the set point is reached (32C in my case is met). At this point the compressor will modulate down to minimum output (drawing around 8-900W in my case). If the radiators are large enough to emit the amount of heat being produced at this flow temp, the system should sit steady at the LWT flow temps as set in the WC curve. But if the radiators are not large enough to dissipate the heat being produced, the return water temp will be too high (as the heat isn't being dissipated) which will cause the LWT to continue to rise as 900W x COP of energy is still being applied to the flow of water. With #2091 set to Use (Signal On/off) only, I refer to this as running in continuous mode as the ASHP cannot cycle itself.

With #2091 set to Use (Signal On/off) or WL Interlink Off (WP1) as you have above, once the flow temp reaches the WC set point (or WL as Samsung call it), the ASHP will either stabilise at that flow temp or will cycle on and off rather than the flow temp rising higher if it is unable to dissipate the heat being produced. Occasional cycling is OK, but you don't want it constantly turning on/off every 5-10 mins as this is bad for the compressor.

The theory is that you will fine tune the WC flow temps to exactly match the heat loss of your house for any given outside ambient temps, then the system can run continuously and maintain a steady temperature. For my system, I am unlikely to be able to achieve this until the outside ambient temp drops below 5C, so for now the room stat kicks in and out at a room temp of 20C turning the heat pump on and off as required, and that has been working reasonable well over autumn so far.

Regarding overnight set backs - you have a couple choices:

1. Turn off the heating overnight and back on in the morning - works fine in mild weather if the temps don't drop too low and the system is able to warm the house again reasonable quickly in the morning. We have certainly been doing this during Sept and Oct.

2. Control the room temp / house temp with a room thermostat that you can turn down overnight - we have the option to do this, and can turn back the room stat to 18C overnight, which will turn the heat pump on and off as required to maintain that temp (exactly the same as you would have done with an old gas boiler).

3. You can also control the LWT / WC set point on the Samsung controller, as shown in your picture above. In the left hand pane, you can use the up / down arrows to adjust the LWT flow temp by +/-5C. So if the WC curve was calling for a 35C flow temp, and you manually set this to -3C overnight, the flow temps would drop back to 32C overnight and you could set it back to 0C (no correction/adjustment to the WC curve) in the morning. The reduced flow temps will mean less heat is output such that the system is now only able to maintain a lower temperature as the heat loss has remained constant but you are now putting less heat into the property so the temp will fall as a result. This is harder to fine tune in terms of a target room temp of say 18C, but running at a lower flow temp overnight is maybe more efficient than a higher flow temp and cycling on and off to maintain a lower room temp. If you are going to use this method, you will need to make adjustments and then allow the system time to settle to understand the effects.

@old_scientist thank you for this. It sounds like we have the same set up. Only difference is that I have two zones - one for UFH in extension and another for rest of the house.

Given that. I have changed my 2091, 2092 and 2093 to the same setting you have to see what happens!

Without additional monitoring, how do you know if the ASHP is cycling or not?