Ian,
I think one of your issues causing the cycling is the fact that you are only heating one room, with the remaining TRVs switched off. The heat pump wont be able to modulate low enough and this is causing the cycling when the room is up to temperature and the TRV starts closing.
Colin
Hi Colin,
My Samsung was initially very unstable , cycling repeatedly when the outside Temperature was 15 C.
The Cycling was then attributed to the Heat Pump operating , as you say , at the minimum , 25% power rating.
A 50 litre Volumising tank was installed to smooth out these Oscillations.
The Volumising tank probably smooths out the Radiator Temperature Cycling .
However , the Hot Water System is still Oscillating.
The Volumiser tank also consumes more Energy , and lowers the Efficiency .
The System is already inefficient with the “designer” having no knowledge of the Heat Exchanger.
The analogy between Water and electronics is Truly remarkable.
ian
Hi Trystan and Tim,
When using Weather Compensation my Samsung is using TWO Thermostats.
The Room thermostat, a simple Honeywell Thermostat.
the Electronic Water Law Thermostat using the Air Thermistor outside, on the outdoor unit.
To limit excessive energy consumption , The Room Thermostat is AND ed with the Weather Compensation Thermostat.
Any Thermostat is prone to excessive switching caused on approaching the set temperature.
Both of these Thermostats are therefore prone to this Noise .
The Samsung Water Law Thermostat has Variable Hysteresis to limit the effects of noise.
The Honeywell Room Thermostat has a fixed Hysteresis.
The Effects of this noise are shown in the following power Graph.
Notice the Oscillations when the room Temperature falls in response to a drop in demand.
The smaller amplitude Oscillations appear to be caused by the Pump motors
The larger appear to be calls for the outdoor compressor to Run and the Pump motors…
The system is prone to oscillations caused by the Switching "noise " on BOTH Thermostats.
To reduce the effects of this dual Thermostat noise i Could
One other graph shows the absolute Radiator Temperature
The Radiator Temperature is slightly higher than the Water Flow Temperature.
I will now look at the absolute Temperature of the Radiators themselves.
ian
.
Hi Trystan,
THE REAL COP
I am returning to my comments about the Real Efficiency measurement of Heat Pumps.
Currently , COP is defined as
**COP = Energy Generated/Energy Consumed in generation**
However ,Neither
** Energy Generated **
** NOR**
** Energy Consumed **
** includes ALL the energy used by the Heat Pump itself!**
Absolute Energy Generated should be
. Absolute Energy Generated = Energy Generated - Energy consumed by the Heat Pump Itself.
The COP presented does NOT include ALL of the energy used by the Heat Pump itself.
For, Example, The Heat Pump can enter de-icing using Heat from the Hot Water tank.
The Energy used to heat the Hot Water in the first place , for de-icing , is regarded as part of the load., and NOT used in the COP Calculation…
ian
Hi Trystan, Tim,
I have measured the Real COP and compared with the Standard definition of COP.
From my energy consumption Graph
I get the Energy Consumption to be 11 kwh for 4-5 Feb
From the Samsung Heat Pump I get a generated total of 29 Kwh.
The REAL COP is therefore
** REAL COP = 29/11 = 2.6 **
The Samsung computed COP with a consumption of 8.8 Kwh is
** SAMSUNG COP = 29/8.8 = 3.3**
The COP Presented by SAMSUNG is , at least Questionable ?
ian
What was the reason to not use the samsung display/controller itself? Can you relocate that to your living room? That may provide the most significant improvement over using the 3rd party thermostat.
It may not be included by the samsung calculation, im not sure, but it should be included in wider boundary calculations as you say. It is included on mine, so is all other heat pump related consumption e.g the central heating pump, diverter valve and indoor controller of my unit. I also include any top up from the immersion heater in my monthly/annual summary calculations.
Interesting yes questionable, but I’m actually surprised that it would over-estimate the COP. It turns out that for Glyn’s it actually under-estimates the COP significantly due to taking pipe surface temperature measurements of flow and return to calculate heat output. Did the heat pump come installed with a separate electricity meter from which you could read kwh readings? If not I would suggest installing a class 1 SDM120 modbus output electricity meter if you get the chance to do so in future.
Thanks I will take a closer look at this later.
Changing the topic a bit. I decided that if I was to really make sense of your setup and @thedawnbefore’s system which also has a heat exchanger, I needed to get my head around heat exchanger maths. The effectiveness NTU method is a particularly useful way to calculate temperature drops etc across a given heat exchanger. There’s a nice python library that can be used for heat exchanger calculations here that implements this method https://github.com/CalebBell/ht.
I’ve ported the calculation for a counterflow heat exchanger from this library into a little javascript web tool calculator that combines a heat pump, heat exchanger and radiator system. It calculates the system temperatures required to give a certain heat output from the radiator system (with all parameters adjustable). Here it is: https://openenergymonitor.org/heatexchanger/2.html
The code for this is all here: https://github.com/TrystanLea/heatexchanger
A couple of interesting results:
The COP penalty from introducing the heat exchanger is not as large as I would have thought, it appears to be around a 0.1-0.2 drop in COP. Maybe at most a 6% drop. This doesn’t take into account additional pumping electricity consumption from requiring two pumps but assuming low energy pumps the penalty for an additional 20W of pumping power is only a further 1% drop in COP, so maybe not that significant.
Varying the secondary flow rate on the heat exchanger has less effect on COP than I would have thought , which is probably the point! the heat exchanger allows for a greater range of conditions on the heat emitter side.
The variation of expected specific heat values (3800-4200) for the primary and secondary fluids have relatively little impact on the COP.
If you drive the same radiator system directly rather than through the heat exchanger at the same flow temperatures used to obtain a given heat output with the heat exchanger you can get ~20% more heat output (mean water temperature is higher). You can alternatively get a 20% boost in heat output by increasing the flow temperature and decreasing the COP by 0.1-0.2 as above.
Caveats are of course that this is theoretical steady state calculation. It doest take into account the buffer or cycling or anything that dynamically varies like that but hopefully an informative theoretical background on which to expand the science experiment! 
Hi Trystan,
Again , to yourself , and all the others , many thanks.
Trying to improve efficiency of my Heat Pump along with the several different oscillation frequencies takes my mind off the seemingly unending struggle to get someone to trust.
The Tank manufacturer has now said that he “does not have the drawings or the test performance for my Heat Pump”.
The Manufacturer now says that they “do not keep the drawings , specifications or test results for old Heat Pumps.”.
My "old Heat Pump was manufactured in 2021.
Whilst it is possible that the original drawings, Specifications and Test results were NOT kept, I feel it is unlikely, and far too convenient for the manufacturer .
The Manufacturer further denies any responsibility for the design , saying that Samsung Designed it , Talk to them. The manufacturer also says that “we recommend 50 litre buffers on all our units, but , talk to Samsung !”.
As we say in Scotland, “it wis’nae me it wis the Big boy doon the road”.
Returning to the specific problems I have with the Heat Pump I have found one of the Oscillations to have a period of 14 minutes. A fourteen minute corresponds to the period of the pump sequence used by field setting 2091, 2092 and 2093 option 4.
I have reset the 2091 and 2093 options to option 3 and reinstated the Volumising tank.
The results , so far are gratifying.
The 2091 option 4 was changed to 2091 option 3 at 1900 along with reinstating the Volumising tank at 1900.
As usual I will wait another day before changing another variable.
The Energy for the same period is
Again , notice the excessive amount of energy used during the oscillations.
The Heat was supplied with TWO Electricity consumption meters, never fitted by my then “installer”.
These meters were amongst the other five major components missing from the original “installation”.
I have used my home made , and, so far as I can see accurate Consumption meter using an Arduino attached to a CT transformer.
I will however, have to install a Calibrated consumption meter on BOTH the Outdoor unit and the indoor unit.
ian
Hi Trystan,
One of many problems with the Heat Pump is the provision of an adequate Thermostat.
None of the Thermostats I have seen have
I have been considering making my own Thermostat with inputs from
The Output would be a relay connected to the B22,B23 Thermostat inputs on my Samsung.
ian
Hi Trystan,
A Real COP
Returning to my original suggestion for a redefinition of COP , could I suggest
Real COP = Total usable energy per day / Total Energy consumed per day.
with
Total Daily Available Usable energy that available to the end user…
and
Total Daily Energy consumed including all consumed by the Heat Pump itself.
The energy consumed would be measured by a calibrated Energy Meter.
The Energy available would be
Daily Energy Available = Output Water Temperature ( C) x Output Flow rate (l/sec) X Specific heat of Water.x 24x60x60.
With Hot Water accounted as that Energy consumed by the Heat Pump itself.
A Kwh meter input, a Water Temperature and Flow meter out.
ian
Hi Trystan,
Real COP ?
In Comparing my use of a Gas boiler last year with my Heat Pump this year , I have come to the conclusion that while the Heat Pump is undoubtedly more efficient than the Gas Boiler, the Heat Pump is continuously feeding energy into the HOT Water tank , whereas the Gas Hot Water was only used intermittently for less than 10 minutes each day.
So, the Heat Pump wins for efficiency but consumes much more energy in Water Heating than the Gas Boiler.
The Difference in the Definition of efficiency between the Heat Pump and the Gas boiler is critical.
The REAL COP.
So, I need to switch OFF the Water Heater on the Heat Pimp.
However, the Heat Pump uses the Energy stored within the Hot Water tank to De-icing.
When switched OFF , Field bit 3011 OFF, the Heat pump still calls for Hot Water from the Hot Water tank.
The Hot water tank is then filled with heat but runs completely out of Control sitting at a Water Temperature of 65 C.
Question?
How do I switch the Hot Water tank OFF and still have Hot Water for De-icing?
ian
There is standard for comparing the different system boundaries of heat pump seasonal performance factors (SPF’s). This digram from the Energy Saving Trust report illustrates this quite well
The boundary you are talking about is one further still, which is measuring the heat output from the hot water tank, they define that as the overall system efficiency:
The detailed analysis report is quite informative on these different boundaries https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/225825/analysis_data_second_phase_est_heat_pump_field_trials.pdf
Defining which boundary we are talking about is something we need to get better at in terms of our heat pump monitoring activities here.
Talking to Glyn again about this it seems that I was mistaken and his heat pump does take heat from the space heating system for defrosts if that’s what the heat pump was doing before going into defrost. It takes heat from whatever it was doing before the defrost.
There is a separate anti-freeze function that is different from defrosts, apparently that just runs the pump for a few minutes and that does pull heat from the cylinder but only if the pipes get below a certain temperature threshold. There’s probably a way of disabling the hot water cylinder but Im not sure how that’s done with a Samsung. Probably a question for Samsung technical support?
Hi Trystan,
Where did you get this knowledge about Heat Pumps?
Who stimulated your interest and expertise? A schoolteacher, or a lecturer ?
The Hot water system on the Samsung is controlled by setting the lowest acceptable Hot Water Temperature. I have now set this to 25 C .
The highest possible Hot Water temperature has now been set to 48 C.
I have selected Hysteresis for the Hot Water Thermostat operating between the Lowest and Highest possible temperatures.
Hopefully this should greatly reduce Heat Pump energy consumption while still allowing the de-icing to operate.
The Volumising tank has been correctly fitted to the input Heat Exchanger ports for removing oscillations.
However, the Volumising tank should have been fitted to the input to the Hot Water coil for de-icing!
My next move will involve some plumbing !
ian
I think my interest in heat pumps began after reading the late David MacKay FRS’s Sustainable Energy without the hot air in 2008 https://www.withouthotair.com. Then it was meeting @johncantor and seeing the data from his heat pump that convinced me to install one at home rather rather than going down the biomass heat route.
That’s quite a large range but certainly worth testing. Have you explored setting a hot water timer so that the hot water is heated in longer batches? e.g once at 2am another at 2pm… Or perhaps even a single heat up, if that’s sufficient for your hot water requirements.
I just had a look at what my system does when defrosting, and it doesn’t use hot water from the tank at all, it circulates the water from the heating system. During this 5 minutes, it consumed between 311W and 1451W, but mostly around 1000W, 0.065kWh total.
This reduced the flow temperature from 39.8 to 26.3, and the temperature of a radiator I’m monitoring went down from 33.6 to 29.3. It then took 17 minutes running the heat pump to get the radiator back to 33.6.
I don’t know the answer to your question but I think it may be cheaper overall for you to use water from the heating circuit than hotter water from DHW, to do your defrosts.
Hi Christian,Trystan , Glyn,Tim et al
Many thanks,
My Heat Pump, manufactured in 2021 , was later fitted with a Buffer tank under instructions from Samsung.
The Specific reason that Samsung asked for the fitting of a Buffer tank was de-icing.
As now configured my Heat Pump is filling the Hot Water system with energy during a 2 to 4 hour period in the early morning.
The Hot Water burst in the morning consumes upward of 2 KWh of energy.
******************************* BUFFER TANKS OR HEAT EXCHANGERS *****************
Buffer tanks or Heat Exchangers have been installed for three different reasons.
If a Heat has only one pipe circuit , containing a Heat Pump , a water pump and a series of Radiators , the Heat Pump would have it’s Water flow cut OFF should the user switch OFF ALL of the radiators.
To protect the Heat Pump either a Buffer is used or a Heat Exchanger can be used.
A) Heat Pumps protected by Buffers
A buffer tank is inserted across the Radiators to present a Volume of water that the Heat Pump can supply if the all of the Radiators are shut.
Kensa have produced an excellent description of this kind of tank
B) Heat Pumps protected by a Heat Exchanger.
A heat Exchanger is inserted into the water circuit , cutting the single Water circuit in two.
The Heat pump is totally protected from the Radiator circuit by the Heat Exchanger…
2) Heat Pumps fitted with buffers for Cycling reduction
If a Heat Pump is heating a small volume of water , the Heat stored in the water will quickly dissipate, causing the Heat Pump Thermostat to be asked to produce more energy .
The Period of time taken to dissipate the stored energy is called the Cycle time.
The Larger the Volume of water , the larger the Cycle Time.
To increase the cycle time a Volumising tank is installed.
A Volumising tank is only a buffer with a different purpose.
MCS have produced a good article on the size of tank for this kind of “Volumising Buffer tank”
3) Heat Pumps fitted with Buffers to store energy for De-icing.
During DE-icing the Heat Pump requires a source of energy to DE-ice the Fins on the Heat Pump itself.
The Heat Pump can demand energy from the Hot Water Tank, The Radiator circuit OR a direct Electrical heater fitted to the Heat Pump fins themselves.
When demanding DE-icing Energy from the Hot Water Tank a storage buffer May be fitted .
Your comments are welcome
ian
I like the sound of the Kensa recommendation to use 2 rather than 4 connections to the buffer tank, will talk to my installer about it.
Hi Christian, Trystan ,Glyn, Tim et al
I missed the elephant in the room !
Reducing the Hot Water by reducing the Hot Water Starting point Field bit 3023
AND / OR
reducing the Hot Water Stopping point Field bit 3022
still consumes lots of energy!
Stopping the Hot Water system using Field bit 3011 interferes with Energy storage during De-icing.
**To Switch the Hot Water System OFF, switch the front panel control OFF.
This will greatly improve the real efficiency .
ian
Yes, ours is always off but switched on for 30 minutes a day by the schedule.
Conversely, the heating is always on on the control panel but doesn’t run unless the smart thermostat calls for heat.
Hi Christian, Trystan, et al
The ultimate error !
I have only now discovered why my Samsung heat Pump fails to produce enough energy during the Winter.
My “installer” installed a 5 KW Samsung when the MCS calculations show a 8KW heat pump was required.
I received three quantitations to install the heat pump
Quotation no 1 from the "installer " whom I chose to install the Heat Pump specified a **
** Warmflow A501-R32 with a power specification of 8 KW.
** My “installer” installed a 5 KW Samsung.**
Quotation No 2 was designed using the MCS design sheet for a Medea MHC-V8 8 KW Heat Pump.
Quotation No 3 was designed for a Mitsubishi Daikin with a MCS specified power of 8 KW.
I have a 5 kW heat Pump installed to meet a 8 kw demand.!
My “installer” , on asked why the heat Pump was made available so quickly , commented that the Samsung had been made available by their supplier .
No one will accept responsibility for this fiasco .!
All of the “regulators” , MCS,NIC and RECC advise Legal action.
Legal action is Impossible, “I would win the case but would be made Bankrupt in the process”.
{ a retired ,former QC at the Court of session , Edinburgh }
Incompetent Installers , YES!
Incompetent Regulation , YES!
ian
You need to check what your Invoice/receipt says. If you paid for an 8 kW unit and got a 5 kW, it looks like fraud to me. If you were quoted an 8 kW unit and were invoiced and paid for a 5 kW, you should have checked when it was installed.
If you are a victim of a fraud, then it might be worth a call to your insurance company to see if you’re covered.
