Welcome. Firstly looking at individual days is essentially useless, houses have a 'memory' so you can really only make meaningful 'measurements' several days into a stable period or by taking readings over a substantial part of a season.
For max efficiency (or at least the soundest starting point from which to tweak) weather comp needs to be as low as possible consistent with getting the house warm with HP on 24*7 or thereabouts. There are various approaches to adjusting it but starting with ~ 25/15 at the high end then adjusting the low end is a good way to go. Drop the flow temperature back by a degree no more frequently than once per day, until it fails to reach temp, then put it back up by one degree.
Some heat pumps feature an adaptive/learning mode which starts with a fairly basic WC setting and does the rest for you. What make is yours?
@dinhp I have a 12kW Gen 6 Samsung and your weather compensation settings look fine. Mine are -5/50 and 10/30, so at 7C OAT our flow temperatures should be pretty similar - approx 33-35C, but my COP for space heating at this OAT is over 4. The good news is that your house is warm. There are a number of reasons why your reported COP is so low:
The Samsung may be reporting the consumption and production incorrectly. Is the reported consumption matching your electricity meter data?
If it is reporting correctly, can you document your COP for space heating compared with your COP for DHW heating? If there is a problem with your DHW cylinder, this could be skewing your results badly. My COP for DHW heating is occasionally around 1.3 for reasons unknown. If you are heating your DHW twice a day, it will be affecting your overall COP to a greater extent.
A delta T of 1 does not appear normal. How are you measuring this? Do you have a buffer tank/volumiser/low loss header? Do you have a bypass valve that could be active?Can you send us a photo of your wired remote controller and some figures for instantaneous power, LWT, RWT, flow rate, IAT, OAT taken during a period of stability?
@jamespa@mike-h thanks both for the replies, useful to know how to actually drop the temps. We are really happy with how it’s actually keeping us warm compared to the few electric radiators we had so now to hopefully improve the efficiency. Yesterday we used around 59kwh for 126kwh generated.
Ours is a Samsung 12KW Gen 6 also. I am tempted to use the same settings and see how that goes. We heat the water twice a day for 2 hours on eco mode which is giving us enough hot water but I don’t know if there is a more economical way of doing this. We don’t have a smart meter yet and didn’t think to take a meter reading before the heat pump was switched on but have done now so hopefully we can see if the Samsung readings are accurate.
The delta t I was guessing from this screen, not sure if that’s right. I’ll try to get some more to compare today as these were taken on Monday afternoon but it’s currently doing DHW so not accurate figures I assume. We don’t have a buffer tank or low loss header. I’m not sure in the bypass valve where would one usually be located? I’ve attached the photos of our cylinder set up. Thanks a lot
We heat the water twice a day for 2 hours on eco mode which is giving us enough hot water but I don’t know if there is a more economical way of doing this. We don’t have a smart meter yet and didn’t think to take a meter reading before the heat pump was switched on but have done now so hopefully we can see if the Samsung readings are accurate.
Unless you have a time of use tarriff/economy 7 then the most economical way to heat DHW is when its warmest outside, generally mid afternoon. However that might not suit your usage pattern (although the tank should be well insulated so not much heat should be lost)
The delta t I was guessing from this screen, not sure if that’s right. I’ll try to get some more to compare today as these were taken on Monday afternoon but it’s currently doing DHW so not accurate figures I assume. We don’t have a buffer tank or low loss header. I’m not sure in the bypass valve where would one usually be located? I’ve attached the photos of our cylinder set up. Thanks a lot
Looks like a deltaT of 3C, but as there are no decimal points in the figures it could be 1C either way. Dont worry too much about this, there is nothing 'magic' about 5C that is just a design value for sizing radiators and flow rates and will anyway vary with OAT unless your heat pump varies the flow rate to keep it constant (some do, some don't). If it was 10C or 1 C I would get worried, but as far as I know its not critical. Flow rate and flow temperature are the critical things, if these are OK everything downstream (provided its been tolerably well designed) should also be OK.
Thanks - some more up to date figures from today after running quite stable (as far as I know). The usage looks accurate compared to our electric meter. It’s currently relatively mild here at 9 degrees, house is 18-22 degrees with thermostat set to 24. I’m reluctant to turn the weather comp settings down further as the bedrooms/bathroom will drop further than I’d like as they have been fitted with smaller radiators (all fitted new K2). This is also why I’ve not set a set back temperature at night to save on costs that way as the bedrooms are already cooler because of the radiators and we have a little one - (I don’t even know if you can’t do a set back on the Samsung though). Still waiting on the installers input on it.
@dinhp Thanks for the extra info. Your COP of 2.49 for today is not great if OAT is 9C, although it was probably colder overnight. Does this include a DHW cycle? It would be good to see consumption and production without a DHW cycle. The delta T of 1 could be 0.1 to 1.9 as LWT and RWT are only displayed as integers. With a flow rate of 26.3 l/min and a delta T of 2, heat output should be 3.68 kW, which is very close to the minimum that a 12 kW Samsung can modulate down to, so I think we should use the higher figure for delta T. This would give you an instantaneous COP of 3.35, which is not great for OAT of 9 C and LWT of 31 C. At that minimum heat output, I would expect instantaneous power to be around 750 W (a COP of 4.9).[
Dont worry too much about this, there is nothing 'magic' about 5C
@jamespa may be right about this, but there are suggestions that controlling delta T is beneficial (eg comments by Brendon Uys on this forum). Some manufacturers use special PWM water pumps to adjust flow to control delta T. The default on your Samsung, should your pump be a PWM pump is to control to a delta T of 5 C. I doubt if your water pump has this facility, meaning that it runs with a fixed flow rate as mine does. However, it should have a means of turning it down - mine has options 1 - 3 equivalent to 6 - 8 metres of pump head. My flow rate is 16-20 l/min depending which of my two flow meters you believe. It would be worth a trial of a higher delta T by turning your flow rate down, especially when it is milder. Higher flow rates are required when it is much colder outside to obtain the higher heat outputs without delta T rising too high.
The other possibility that might explain poor efficiency when it is milder is that your compressor might be cycling very frequently. This is a common problem with Samsung. One way to prevent this is to set FSV 2091/2092 to 'Use(Signal only ON/OFF)' if you are using an external thermostat or set FSV 2093 to 'Room Temp. only ON/OFF' if you are using the wired remote controller. From your photos, your wired remote controller is not in a helpful place to use its thermostat, so I assume that you have a 3rd party thermostat. Changing these settings means that your compressor will only be turned off by your thermostat. At lower OATs, this makes no difference. At higher OATs, the LWT is lower and the emitters consequently emit less heat. If the heat output from the emiiters is less than the minimum heat output of the heat pump, then there cannot be a steady state at that LWT. What happens with 2091/2092 = 'Use(Signal only ON/OFF)' is that the LWT rises until the emitters can match the minimum ASHP heat output. In my experience, this doesn't seem to increase consumption by much if at all. The screenshot below was taken when target LWT was 25 C, but the minimum ASHP output was around 2.75 kW which could only be matched by my radiators by increasing LWT to 30 C. But despite the higher LWT compared with target LWT, the electricity consumption once in a steady state was only 700 W which is the minimum consumption that I have seen with my set up.
If FSV 2093 had been set to 2-4, then the compressor would have cycled repeatedly and COP would have been terrible. When my Samsung cycles it does so every 8 minutes - not good!
If you decide to make any of the changes suggested above, please keep an eye on your LWT and consumption in case my observations of how to improve my system don't carry over to yours!
@mike-h thanks so much for taking the time to go through this. I’ll work on making some adjustments.
Can I ask what your heat pump sounds like? It’s almost like a chugging sound. I have a video but I can’t upload so I don’t know if that’s not allowed. I’ve also noticed that some of the back of the heap pumps like metal is flattened down, I’m assuming either during transport or fitting - any idea if this will cause issues? Our installers are down playing our questions and issues so I don’t feel like I can get an answer out of them over what is acceptable.
@dinhp I will try and upload an audio file as it is difficult to describe how it sounds. The noise level will vary depending on how hard the heat pump is working. Regarding the flat spots on your evaporators, I am not qualified to make any comment apart from not being normal, but @editor might be able to ask one of his installer contacts.
I already had independent flow, temperature and electrical monitoring fitted to my system, but through this forum I have been able to add additional monitoring for under £40. It gives you the data from within Samsung, some that is visible on the controller and some that isn't like compressor frequency, RWT to one decimal place, instantaneous heat production etc. You can save the data and download it to a csv file to analyse it more easily, so it might be helpful to you if your issues don't get resolved soon.
