I have the 6kw unit as well and I have seen something similar to this a few times.
I think that the compressor stops because the LWT target is exceeded. In this circumstance the circulating pump stays on and the water circulates until it cools down enough that the compressor decides to turn back on.
The LWT rising and then the compressor stopping and then restarting all makes sense. The question is why does the unit increase the power to the compressor all of sudden, without obvious reason. The few times I have managed to look at the MMI while it is happening the LWT target (based on WD curve + Madoka) is unchanged, there is just an increase in compressor power, heat is produced, and the LWT quickly overshoots.
No, it is quite different. The input power increases and the output power increases in what looks like lockstep. It could be related in that it is an obvious step change in behaviour following steady-state running, without obvious cause or rationale. So perhaps a result of the control logic either getting it wrong or attempting to achieve something that is not obvious to us.
The rise in temperature is preceded by a drop in LWT. At about 18:47 the LWT begins to drop, with a falling heat output against slightly rising input power. At 18:56 the input power begins to rise dramatically and this raises the LWT again. During this time the flow rate is steady.
The section between 18:47 and 18:56 is similar to the unexplained drop in heating output that @matt-drummer is experiencing. @Chris_Hill system appears to be responding to it in a different way though and the drop in performance is more steady rather than falling off a cliff.
Firstly, it is so erratic despite me running in the purest way possible, fixed lwt at 31c and a fixed flow rate as a consequence of me selecting an unattainable dT
The second thing I notice is how long it takes to get up to speed in terms of efficiency, it actually takes hours.
I am sure all of this is connected to some lack of control of the flow of refrigerant, whether it is software, hardware or a combination of both, I don’t know.
My heat pump performs well on the face of it but I am sure it could be better.
It is always more efficient when it is stable but the flow temperature and electrical input is often erratic.
It has unpredictable `episodes’
And it takes ages, hours, to get into its stride and settle down to what it should be from the start of a cycle.
None of it is the end of the world, but the issue I first noticed in September has helped me understand more about why these heat pumps don’t work as well as they could.
It’s also interesting in @Chris_Hill data yesterday that the rise in lwt didn’t increase the return at all, it actually dropped slightly.
Something made the compressor stop but not the heating cycle and Daikins always try and restart asap if lwt upper limit is breached or return gets too high.
They don’t wait 25 minutes, I have never seen this.
Note how the power drawn by the compressor dips a little, followed by a matching dip of the flow temperature. I doubt that the controller has given any signal to the inverter to do this, so it might be little bit of refrigerant leaking into a different part of the circuit and dropping the pressure before recovering.
I’m seeing something very similar happening on a Samsung 7 in another topic, so it may be common behaviour amongst certain types of compressors
Yes, I don’t think that this is something unique to Daikin.
I think we have to remember where this started in September. With a pretty dramatic large consumption of electricity with very little heat output.
I think we know what is happening, and thankfully, I haven’t seen much of it for a while.
The COP/SCOP is really great and I have no complaints about the overall result.
Although, like many things, the way in which it is delivered is not so great.
For me, I think my issue is that it is always there waiting to pounce, you can’t really trust it.
But, it’s not the end of the world, and I am lucky (or perhaps unlucky?) that I can keep an eye on it,
I just wanted to understand and explain it, for my own peace of mind if nothing else.
It is disappointing that Daikin are dismissive of the fact that it even happens and it is a shame that their heat pump isn’t quite as good as it could have been(?)
I wish it is at least as good as Daikin Seems Daikin is erratic only occasionally. Mine is doing this all the time. This Samsung frequency control is really horrible. Today there were 400W jumps alternating every couple of minutes. This can’t be good for compressor in a long run. Maybe a bad unit I don’t know. Samsung seems don’t care.
I think this is a way for the producer to maintein proper COP of the system. For me the siquence is: lower % of modulation command to the compressor for a minute, resulting in lower energy production and this way lowering the suppy temperature. After a minute controller give command for higher modulation % and higher energy production restoring the supply temperature. A possible reason for this is adjusting the proper EEV position by constantly changing the work mode of the system…I don`t know really…Could be an oil issue also for proper lubrication at lower rpm of the compressor…
Twice today so far. I couldn’t stop the first one at 09.00 using the app and I missed the second one at 16.30 until it was too late, but stopped it with the app and restarted back to normal.
They stick out like a sore thumb, pretty annoying.
Seems Daikin is erratic only occasionally. Mine is doing this all the time. This Samsung frequency control is really horrible. Today there were 400W jumps alternating every couple of minutes. This can’t be good for compressor in a long run. Maybe a bad unit I don’t know. Samsung seems don’t care.
