@benson In the case of Daikin, the ASHP varies the pump speed to maintain the chosen Delta T, in my own case, this means it starts up at ~28 lpm, settles to ~14 lpm after a few minutes then drops to ~7 lpm where it then sits for hour sometimes. This is actually a fairly recent thing as it used to run at ~14 lpm most of the time; I have yet to find out whether this is due to a firmware update or something else.

As to the LSV’s and the Thermostats on the radiators, usually the starting point is with the TRV’s fully open and gradually adjust the LSV’s this will help reduce the number of variables too! Toodles.

@benson — I had a rather unusual, or maybe it is not, situation. I have a TRV (all fully open, achieved by taking their heads off) on one end of the rad and lock shield on the other. In my attempts to balance the rads, in particular to get better flow to two end of the run rads, I had so turned down all the other lock shields such that they seriously restricted flow. This in turn meant less heat delivery. Being in this state is not obvious, apart from the fact that overall energy out, and so heat delivered, is capped. It took a very clever forum member to spot this state of affairs (the clue was the heat was not getting across my plate heat exchanger as it should, because the secondary circuit circulation was too sluggish, and suggest the obvious solution, open up all the lock shield valves fully. The effect on output was immediate and very visible. hence 'big bang'. As I normally have all doors in the house open, air movement between rooms is enough to keep most of the house at around the same temperature. 

Posted by: @benson

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What I have only recently realised is that the pump speed will be set by the ashp to achieve the correct delta T.

I am not sure this is the case with Midea and Midea clone units. My primary flow rate is usually either ~1.4m^3/h (most of the time) or ~1.0m^3/h (the rest of the time). See if you have flow rate in your data, and if so whether you can add it to a chart for a while. Failing that, the wired controller shows it as one of the Operational Parameters, check it from time to time to see if it varies much.

This is my version of such a chart, and seriously over-crowded it is too, which is why I don't normally include the extra variables. You can see the flow rate in mid-blue, multiplied by 10 to get it to display better on the chart. You can also see what the compressor is doing, and the amps in. I'm still not sure what sets the delta t...  

Posted by: @cathoderay

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I am not sure this is the case with Midea and Midea clone units. My primary flow rate is usually either ~1.4m^3/h (most of the time) or ~1.0m^3/h (the rest of the time). See if you have flow rate in your data, and if so whether you can add it to a chart for a while. Failing that, the wired controller shows it as one of the Operational Parameters, check it from time to time to see if it varies much.

Here's what mine typically looks like.

Hence why I assumed it was varying flow rate to achieve the correct temp drop...which is always around 4 or 5 degrees C.

@benson — your flow rate still shows a step pattern, albeit more exaggerated than mine, with what look like set points, with the highs and lows at the same value. This does not look like a continuously variable modulation of flow to me.

It would be interesting to see the same chart with the LWT and RWT added, zoomed in to say half a dozen cycles, to see how the flow rate changes during each cycle. Meanwhile taking your earlier chart, there are some things that don't really make sense to me, notably the almost instantaneous changes in LWT (zooming in as above will help clarify how instantaneous), and the change from a gradual (and more credible) rise in LWT/RWT delta t on the left to the sudden (and less credible) rises seen on the right:

I think this is well worth looking at in detail, as it may give us more insight into how Midea and Midea clone units modulate their output. It may also be worth looking in detail at how your charts get plotted, including the data point intervals. Mine use 'minute data' ie there is a data point every minute, which is a high enough resolution to make small changes visible. Exactly the same data plotted with hourly data points would look very different, even though it is from the same data set.

Posted by: @toodles

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As to the LSV’s and the Thermostats on the radiators, usually the starting point is with the TRV’s fully open and gradually adjust the LSV’s this will help reduce the number of variables too!

Very true, that is the standard method (and the one I used) but there is that trap that I fell into. Both the upstairs and the downstairs last radiators on the respective pipe runs were cooler than I wanted, and I ended up screwing down all the other lock shields to the point where the total system resistance restricted overall flow, which in turn restricted total heat output. The heat pump never managed to achieve its rated output. Once I opened up all the lock shield valves ('big bang') the heat pump showed a step increase in output: 

As well as noting the step increase, also note the overall output pattern before and after 'big bang'. For sure, some of the increased output after 'big bang' is down to lower OATs, but if you look at periods when the OAT is the same or very similar, output is generally higher after 'big bang' than before.