First of all let me apologise for the mistakes in Y Axis titles on some of my graphs.
The Power on the Y Axis should have been in Watts not kW, also, the DS18B20 sensors are wrongly multiplied by 10.
Sorry, a typical primary School error.
THE ELEPHANT IN THE ROOM
My Hot Water tank and Buffer contain 250 litres or 250Kg of weight on my kitchen floor.
The Hot water Tank is very inefficient with the hot water tank continuously, and wastefully , switching between Hot water and Room heating.
I know how to alter the priority between Hot water heating and Room heating but it is , yet again , a compromise.
I see other on-line comments about these Hot water tanks , often saying that an On-Demand Electric Heater would be better suited to a small hot water user.
Do I replace the Hot water tank with an "under sink" electric water heater and an Electric bathroom shower?
The "Designed" Flow temperatures provided by three different "installers " were:
1) MP Group , Warm flow Heat pump , first estimate 50 C
2) MP Group , Samsung 5Kw Heat Pump , second estimate , 50 C
3) MP Group , Samsung 5Kw Heat Pump , third estimate, 50 C
4) CMS Group, Midea 7.3 kW , first estimate , 55 C
5) Quarterion, Mitsubishi 8kW , estimate , 50 C
The NIC engineer with two other "engineers" from my "installer" attempted, unsuccessfully , in setting the flow temperature to 35 C on my Heat Pump when the flow temperature was controlled by the Water Law Thermostat resulting in Heat Pump failure.
The NIC "Engineer " then discovered that "he needed some fresh air" disappearing into my garden leaving the pair of "engineers" from my "installer" trying , again unsuccessfully, to repair the Heat Pump.
My "Installer" was STRUCK_OFF again after this demonstration.
The Primary Heat Exchanger Temperatures.
Please find the Primary Heat Exchanger Temperatures in the following graphs of the Input , output and difference Temperatures across the Heat Exchanger on 6th Feb 2024
-- Attachment is not available -- -- Attachment is not available -- -- Attachment is not available --
The DS18B20 sensors, being high speed serial devices are plainly sensitive to noise!
I do not have DS18B20 fitted to the PHE output ports but the Sharky Water meter is nearby giving a more accurate, if confusing picture:
-- Attachment is not available --
-- Attachment is not available -- -- Attachment is not available --
The Sharky In-Water Sensors are here relatively noise insensitive.
The Temperatures are here altered by Modulating the Pulse Width Modulation motor ports on BOTH Motors.
The PWM Modulation is here controlled by the Delta_T across the Primary ports of the Heat Exchanger.
ian
Noted re flow temperatures. Thats quite high and means that any losses/inefficiencies will have greater effect.
Regarding the heat exchanger Im not absolutely which ports you are comparing but if its input and output on the flow side (ie flow FROM HP and TO emitters) then it looks like a 3C difference which is worth at order 10% loss of efficiency (probably higher given the quite high flow temperature
Regarding your question about replacing the DHW tank with an inline heater, etc, any CH system with weather compensation MUST be set up so that it heats either DHW or space at any one time. This is not unique to heat pumps and its because the two applications require different flow temperatures. With a 250l tank you should be able to set it up to heat to say 48C once per day (not 'constant switching', and there will be enough hot water to supply you for the rest of the day, unless you are a very heavy user. Thats the way to do it. Many (including me) do DHW heating overnight when you would otherwise have the space heating on setback anyway. My suspicion, based on what you have said, is that the HP is constantly topping up the DHW tank (the 'safe' setting for installer - it guarantees that there is always a full tank of hot water) rather than batch heating as it should. If you have a very long run from your DHW tank to sink it may reduce the effective COP below 1 in which case yes, an inline heater would be cheaper.
I think my previous post stands, you are almost certainly going to need to make several changes to fix the problems you are seeing (I listed the ones most likely to have an impact, but with only partial details of your system and settings the list could be wrong or incomplete). However, as @Derek-M says, you should do these step by step monitoring the results each time. Also I would do them in a way that is reversible if possible.
Its really up to you whether you 'grasp the nettle' and take the risk, or put up with the system as it is.
4kW peak of solar PV since 2011; EV and a 1930s house which has been partially renovated to improve its efficiency. 7kW Vaillant heat pump.
The "Designed" Flow temperatures provided by three different "installers " were:
1) MP Group , Warm flow Heat pump , first estimate 50 C
2) MP Group , Samsung 5Kw Heat Pump , second estimate , 50 C
3) MP Group , Samsung 5Kw Heat Pump , third estimate, 50 C
4) CMS Group, Midea 7.3 kW , first estimate , 55 C
5) Quarterion, Mitsubishi 8kW , estimate , 50 C
The NIC engineer with two other "engineers" from my "installer" attempted, unsuccessfully , in setting the flow temperature to 35 C on my Heat Pump when the flow temperature was controlled by the Water Law Thermostat resulting in Heat Pump failure.
The NIC "Engineer " then discovered that "he needed some fresh air" disappearing into my garden leaving the pair of "engineers" from my "installer" trying , again unsuccessfully, to repair the Heat Pump.
My "Installer" was STRUCK_OFF again after this demonstration.
The Primary Heat Exchanger Temperatures.
Please find the Primary Heat Exchanger Temperatures in the following graphs of the Input , output and difference Temperatures across the Heat Exchanger on 6th Feb 2024
The DS18B20 sensors, being high speed serial devices are plainly sensitive to noise!
I do not have DS18B20 fitted to the PHE output ports but the Sharky Water meter is nearby giving a more accurate, if confusing picture:
The Sharky In-Water Sensors are here relatively noise insensitive.
The Temperatures are here altered by Modulating the Pulse Width Modulation motor ports on BOTH Motors.
The PWM Modulation is here controlled by the Delta_T across the Primary ports of the Heat Exchanger.
ian
Could you confirm the location of sensors T2 and T3 and if the charts are correctly labelled, since what would appear to be the return temperature to the heat pump appears to be higher than the flow temperature.
It would be much better if you could combine all the various readings onto one chart.
As you can , doubtless, sense, With £14K having been spent , by various parties, including myself , I must be sceptical and careful.
Yet more Pipe hacking, Pipe insulation is, as you say , risky.
My trade off is between Hypothermia and bankruptcy.
Inverter Power Operating point?
1: The power , kW , of my Heat Pump is 5kW.
2: The Maximum power of my Heat Pump is therefore 5kW.
3: The minimum power is circa 0.25 times the maximum power , or 1.25 kW.
4: When operating below 1.25 kW the heat pump will Cycle .
5: The Resulting Average Measured Cycle time, at the minimum power of 1.25 kW is about 11 mins.
6: My Heat Pump is operating with a Inverter power perilously close to the Minimum operating power , 1.25 kW.
7: My heat Pump is "Short Cycling " with a period 0f 11mnutes because it's power operating point is very close to 1.25 kW when the outside temperature is greater than 8 C.
8: The close proximity of the operating point to the minimum power can be overcome by raising the operating point power by increasing the power setting operating point using the Weather compensation ( Samsung's Water Law ).
Conclusion
9: The increased operating point power will limit , or stop, "short cycling but at the cost of efficiency , COP .
10: Efficiency, COP,REAL-COP is in a trade OFF with "Short Cycling".
11: A "in Series", as against the parallel Buffer tank is required.
12: A mathematical model of the thermal dynamics of the system , providing greater confidence, is required.
Rather than providing answers to questions that have not yet been asked, it would probably be more productive if you were to answers the questions that have been asked.
Do you have any thermostats and TRV's and if so what is their make, model and settings.
The way you are operating your system does not appear to be the most efficient, so before suggesting any physical changes I would suggest ensuring that the method of operation is not adding to your problems. Obviously if you do not wish to work with us in trying to find the root cause of possible problems then that is your choice.
I would appreciate confirmation that you wish to proceed in a co-operative manner.
Sorry about my graphs Derek, I started temperature recording with a Quad K type Chinese Temperature data logger, later adding three Arduinos' and finally a "Sharky" Water Power meter.
All of these system use different software, time bases and cannot easily be reconciled into one graph.
Sensors
The Chinese Data logger uses K type temperature clamps, the power Sensor a CT Transformer, the T2 and T3 sensors are DS18B20 Digital sensors linked to an Arduino while the "Sharky" uses Diode Analogue sensors.
Each type of sensor has advantages and disadvantages, some are more noisy, whilst others are more accurate.
Again Derek, Sorry but I certainly do appreciate your help.
TRV's
The TRV's were installed by yet another plumber/installer who left no information.
I have tried to adjust , and balance, the TRV's without success. My Bedrooms never achieving 19 C.
Samsung Settings:
I have tried , and returned to the factory settings, all of the 50 odd controls within the Samsung .
Samsung Thermostats
The Samsung internal Water Law Thermostats are controlled by a plethora of settings.
These settings control thermostat cycling and Hysteresis, but, as the French Samsung Engineer said " appear very insensitive". These clearly work , and modify the cycling , but poorly in my case. The French "engineer" commenting that "only the Germans Really understand the PWM system".
Inverter or Switching ?
The Samsung has options to control the Power using the Inverter AND Pulse Width Modulation or the Inverter AND motor Switching.
The Motor Pulse width modulation control does not work on my Samsung with the Inverter AND Motor switching option used on my Samsung.
Sorry If I have given unintentional offence........
To be able to help locate the root cause of any problems I have to try to build a mental picture of the system and how it is functioning. To do so I rely upon the answers to the questions that I ask, which may at times appear irrelevant.
All TRV's, except possibly ones in bedrooms, should be fully open, with the room temperatures being balanced by means of the lockshield valves.
When I refer to thermostats I mean third party on - off type.
All of these system use different software, time bases and cannot easily be reconciled into one graph.
If you can log the data to csv files (eg using python), then you can plot the data any which way using any spreadsheet. You can also use python plotting modules for prettier graphs.
Reconciling different time bases is more tricky, but can be done using sql type 'left joins' using something called 'q - text as data' which lets you do sql type queries on csv files. I can elaborate if you want to try this.
Midea 14kW (for now...) ASHP heating both building and DHW
I will be going into town very soon so will reply later.
It would be useful if you could record the readings from the Samsung controller with the heat pump operating in a stable manner. Things like LWT, RWT, flowrate etc.
Thinking about installing a heat pump but unsure where to start? Already have one but it’s not performing as expected? Or are you locked in a frustrating dispute with an installer or manufacturer? We’re here to help.
