I have read a fair number of older posts where you've described much of the above (in detail, and in a way that's understandable, thanks) so I was already wondering if the compressor is reducing to it's minimum operating speed then having to stop to allow LWT to reduce. I'm not sure if I'm looking at the right parameter but do you know if code 016 (I think that is compressor frequency) will give a clue as to if it's running close to minimum (the couple of times I've checked in heating mode the number has been 36)? Indeed, is there any way of checking?
Appreciate what you say around the testing/graph times. AA seems to take a day or two to settle back down so I had to get the graphs at as near same indoor/outdoor temps as I could. Nominally, outdoor temps were 5c, indoor 18c.
Generally, it is only the 6kW unit (and the heat loss survey come up with 5.8kW heat loss estimates, so appears to be right sized) and it does seem to be providing the required heat with relative ease. I've been comparing my stats versus Heat Geeks graphs on their open monitor - I near matched their COP when temps were at or below zero, as soon as it gets much above that they race ahead (and that milder range is likely where the efficiencies save the most money).
I'm afraid that I don't have an Ecodan, so I basically have to try to interpret the information in the manual, along with my assessment of how I think that the heat pump should be operating. I don't remember seeing any specific details for the operating range of the compressor, though some of the forum members with Ecodan's may be able to throw more light on the subject.
ASHP's gather the majority of their energy supply from the outside air, with the remainder being provided by the electrical supply. Obviously as the outside air temperature falls, the amount of available energy is reduced, and this happens at the time when the energy demand is increasing. The net effect is the heat pump has to work harder, at lower efficiency and is therefore more expensive to run. As you state, higher efficiency will occur at higher outside air temperatures.
There are quite a number of operating parameters that it is possible to adjust within the Ecodan controller, not all of which, I suspect, have been fully explored. Some may improve efficiency during the Winter months, whilst other may be better in Spring and Autumn, only detailed testing may further unlock the secrets of Ecodan World.
If you system only requires a LWT of 36C at -3C, then that would indicate that you home is well insulated and that you have correctly sized heat emitters. Whilst that is good news in colder weather conditions, it of course can lead to cycling during milder weather.
Unfortunately the graphs don't include the indoor temperature and outside temperature, which makes like for like comparison more difficult.
The other thing that I noted was that the AA test was performed at 08:00, whilst the WC one was at 15:00. This can make quite a difference, even if the actual outside air temperature reading is the same. Overnight the fabric of your home will lose heat energy, because the outside air temperature often falls, and also because there is a lack of solar thermal energy to help warm the building fabric, or at least reduce the rate of heat loss. At 08:00, the external fabric can still be quite cold from the overnight temperature drop, which will present more heat loss to internals of the building. At 15:00, the external fabric of the building will probably be much warmer, even on cloudy days, so the probable heat loss will have reduced.
The two graphs show that your heat pump was producing more heat energy than that being lost from your home, so it can be expected that both the internal temperature, and that of the water flowing around your heating system, will start to increase. Under normal operating conditions the speed of the compressor would be controlled to regulate the LWT, and the speed of the water pump would be controlled to provide the required DeltaT between LWT and RWT.
It is difficult to be certain what is actually happening within your system. It could be that the controller has reduced the compressor to its minimum operating speed, and it can no longer prevent the LWT from increasing, it therefore reaches the setting when the controller stops the compressor, until the LWT falls to the lower setting and the compressor is once more started. If the settings of the WC curve are higher than required at the warmer end of the curve, this may also cause the heat supply to exceed the heat demand, and hence cause the heat pump to be stopped for a period of time.
Without closely monitoring the various parameters, over a period of time, it is difficult to identify the root cause. You could try lowering the WC curve and see if this makes any difference.
Firstly, thanks for the detailed response. Appreciated.
I have read a fair number of older posts where you've described much of the above (in detail, and in a way that's understandable, thanks) so I was already wondering if the compressor is reducing to it's minimum operating speed then having to stop to allow LWT to reduce. I'm not sure if I'm looking at the right parameter but do you know if code 016 (I think that is compressor frequency) will give a clue as to if it's running close to minimum (the couple of times I've checked in heating mode the number has been 36)? Indeed, is there any way of checking?
Appreciate what you say around the testing/graph times. AA seems to take a day or two to settle back down so I had to get the graphs at as near same indoor/outdoor temps as I could. Nominally, outdoor temps were 5c, indoor 18c.
Generally, it is only the 6kW unit (and the heat loss survey come up with 5.8kW heat loss estimates, so appears to be right sized) and it does seem to be providing the required heat with relative ease. I've been comparing my stats versus Heat Geeks graphs on their open monitor - I near matched their COP when temps were at or below zero, as soon as it gets much above that they race ahead (and that milder range is likely where the efficiencies save the most money).
My 14kW Ecodan can modulate down to 30-35% of its nominal output. Mine will start to cycle at about 10 degrees ambient, sometimes a little more. As you have found, AA mode seems to reduce cycling at higher ambients. What was your design temp and at what room temp? You can work out (roughly) the ambient at which your ASHP will hit its minimum from the spreadsheet below.
I've not tried, in fact I've not considered trying, Auto Adaptation on my Ecodan 11.2 as I am not in the least bit tech minded. All tech instructions simply float over my head as I watch and become totally bemused.
That said, having read some of this thread and come to realise that AA might provide some efficiency gains and much needed financial savings, it is becoming clear that I must pay more attention and see if I can't get my head around this and switch from WC to AA. Oh no, I feel a headache coming on. 🤔
Retrofitted 11.2kw Mitsubishi Ecodan to new radiators commissioned November 2021.
14 x 500w Monocrystalline solar panels.
...I have trialed both and the conclusion I am coming to is that weather comp seems to be a bit more costly to run and the pump cycles a bit more frequently.
I've also been trailing room temp versus weather comp - so far my findings reflect yours. i.e. more cycling/energy consumption in weather comp mode at milder temperatures. Once ambient temps get to around zero the cycling stops and I get constant running (just a defrost cycle interrupts things).
Cycling will occur in milder weather conditions when the controller cannot lower the water pump speed any more. Cycling could also occur if the WC curve is set too high at the warmer end of the curve, what are the settings of your WC curve?
Hi. The curve was at 36c at -3 and 26c at +15 which was resulting in the attached at +5 degrees (4 cycles per hour
). Second attachment was also at +5 ambient temps but in AA mode (2 cycles per hour).
[Edit] the attachments got added in the wrong order.
This is great information from everyone. Thanks all. Just as a total aside and completely non technical. Has anyone suffered with flow rate problems, air lock blockage? We had no idea what our pump should deliver in terms of flow rate. But when we noticed a small slow down I opened the large debris sump nut on the outside shutoff valve. This is the isolation valve outside on the return pipe.
Caution: need to power down the heat pump first * then we shut the valve first to prevent draining down the system then unscrewed the large sump nut and cleaned it out.
When it was turned back on we had 40% more flow which stoped our 8.5 ecodan from cycling. We were then able to slow down the primary pump speed to its lowest setting and still achieve 15 LPM which we then restricted it with the valves down to 12 LPM. We then kept the CH pump fully unrestricted which dragged up the overall flow rate to 13 LPM (Theoretical Intention: to encourage more of the hotter primary flow to be drawn into the CH flow through our 4 pipe low loss header.)
We are now using AA for the first time and for the past 3 days our COP has been 3.17 using 29kw, 3.08 using 24kw and 3.75 using 16kw -but this last day was set at 19c daytime, 21c evening and 17c night setback.
I'm afraid that I don't have an Ecodan, so I basically have to try to interpret the information in the manual, along with my assessment of how I think that the heat pump should be operating. I don't remember seeing any specific details for the operating range of the compressor, though some of the forum members with Ecodan's may be able to throw more light on the subject.
Ah sorry, I didn't realise you don't have an Ecodan. From my research, running code 016 relates to compressor frequency and there seems to be some general consensus that the operating range is approx 30Hz all the way up to 255Hz (although some say the actual upper limit is nearer to 100-110Hz, most agreeing that 30Hz is the lower). I haven't got my timing right yet, but my unit does appear to be going off in the lower 30's.
This is great information from everyone. Thanks all. Just as a total aside and completely non technical. Has anyone suffered with flow rate problems, air lock blockage? We had no idea what our pump should deliver in terms of flow rate. But when we noticed a small slow down I opened the large debris sump nut on the outside shutoff valve. This is the isolation valve outside on the return pipe.
Caution: need to power down the heat pump first * then we shut the valve first to prevent draining down the system then unscrewed the large sump nut and cleaned it out.
When it was turned back on we had 40% more flow which stoped our 8.5 ecodan from cycling. We were then able to slow down the primary pump speed to its lowest setting and still achieve 15 LPM which we then restricted it with the valves down to 12 LPM. We then kept the CH pump fully unrestricted which dragged up the overall flow rate to 13 LPM (Theoretical Intention: to encourage more of the hotter primary flow to be drawn into the CH flow through our 4 pipe low loss header.
info: 4 bed house, 14 radiators, no UFHeating,
Interesting, thanks. Pretty sure I don't have that problem, but you've reminded me that flow rates and delta t are a rabbit hole I want to go down.
My 14kW Ecodan can modulate down to 30-35% of its nominal output. Mine will start to cycle at about 10 degrees ambient, sometimes a little more. As you have found, AA mode seems to reduce cycling at higher ambients. What was your design temp and at what room temp? You can work out (roughly) the ambient at which your ASHP will hit its minimum from the spreadsheet below.
Working out COP from the FTC numbers is not always reliable and the match with reality gets a lot worse at low consumption.
BTW I'm doing some comparisons with AA mode vs WC and will post results soon.
Thanks. Design flow temp is 50c, most rooms target temp is 18c at -3. We are easily achieving the room targets at a much lower flow temp (highest was 41c in the recent -5/6 cold spell). Yes, I had previously read the thread you note, it's caused me to check a few things..
I've been keeping a daily log since installation (sad but true). I know it's not a fair comparison but I am finding the Heat Geek open data useful as a benchmark as such, up until now I was just comparing my daily COP versus theirs, you have prompted me to add consumed kWh as a comparison and it looks to be highlighting a bunch of stuff.
(see attached) firstly, look at the first two days (which were installer settings) my energy consumption was double that of Heat Geeks. I lasted two days before starting to edit the curve etc, what a marked change on 08/01/2023!
It get's even more interesting (again, sad but true) from 15/01/2023 (as the weather turned colder) my COPs come in-line with Heat Geeks, but look at the kWh consumed (I'm now 'outperforming' Heat Geek significantly). Looking back at my change log (highlights the need to log your config changes so you can refer back to them) I decreased circulation pump speed from 19lpm to 11lpm late on 14/01/2023, additionally on 17/01/2023 I configured 'Quiet Mode' in an attempt to reduce output. Now I've added kWh as a comparison, these changes are clear to see (my energy use has dropped well below Heat Geek as a reference).
Also note the increase in kWh consumed on 27-28/01/2023 (when I changed from AA back to weather curve as a test). I also upped the pump speed as a test on 27th as well (reminder to self - don't make more than one change until the effects of the previous are known). Pump speed and deltas are something I'd like to discuss, enough for now though (information overload).
My understanding is that when operating in WC mode, the controller compares the outside air temperature to the WC curve and calculates the required LWT.
When operating in Auto Adaptation (AA) mode, it still calculates the LWT using the above method, but then slightly modifies the actual required LWT if the 'room' temperatures has varied from the setpoint.
That does not match my understanding of the description of Auto Adaptation mode that Mitsubishi sent you in https://renewableheatinghub.co.uk/forums/postid/13354 — that reads to me as if the curve may be used for initial values, but then it uses a function (or extrapolates a table) to convert outside temperatures and required room temperature changes to target flow temperatures and then adapts that based on its experiences about whether the chosen flow temperature changed the room temperature sufficiently.
It's not clear to me if/how curve is used after adaptation begins. Maybe changing the curve reinitialises the learning, maybe it's used to adapt the curve, or maybe it's ignored. Another possible experiment for the brave!
It's not clear to me if/how curve is used after adaptation begins. Maybe changing the curve reinitialises the learning, maybe it's used to adapt the curve, or maybe it's ignored. Another possible experiment for the brave!
I'm not clear either. This Mitsubishi video does mention auto adaptation (around 2:05) where he does state it uses the weather comp curve in the background. From my tests so far it does appear to be doing this, then diverging as it learns over the next day or so. Like you say, I've no idea if that relationship gets broken at any point. I was considering changing the curve to a silly number to see if AA followed, I may still do so one day.
Hello can enybody tell me what 0.9 MPS actually stands for in this heat geek cheat
sheet. I thought it was Metres per second but that seems too big a scale. TIA
It is metres per second, and it is a measurement of velocity, just as we measure the velocity of a vehicle in miles per hour.
Most flowmeters measure the velocity of a gas or liquid, so to calculate the quantity, it is necessary to know the area of the pipe. The attached table displays the quantity of heat energy that can be transported by different diameter pipes, the larger the pipe, the more heat energy it can transport, under the specified operating conditions of a temperature difference of 5C and 7C, with a water flow velocity of 0.9 metres per second.
By calculating the volume of a section of pipe 0.9 metres in length, it is possible to quantify the volume of water in litres per minute.
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<img src="https://renewableheatinghub.co.uk/wp-content/uploads/wpforo/attachments/5029/thumbnail/2615-MelcloudChartat5degreesinRoomTempModeLessCycling.jpg" style="max-width: 400px; max-height: 300px;" alt="MelcloudChartat5degreesinRoomTempMode LessCycling" title="MelcloudChartat5degreesinRoomTempMode LessCycling" />
<img src="https://renewableheatinghub.co.uk/wp-content/uploads/wpforo/attachments/5029/thumbnail/2616-MelcloudChartat5degreesinWeatherCompModeCycling.jpg" style="max-width: 400px; max-height: 300px;" alt="MelcloudChartat5degreesinWeatherCompMode Cycling" title="MelcloudChartat5degreesinWeatherCompMode Cycling" />
