You can get a good estimate of flow rate if you know the exact kW heat output from the heat pump software and the delta-t (difference in flow and return temperature). As we know the specific heat capacity of water you can get a reasonable estimate of the flow. The systems I work on (different manufacturer, so can’t say for Ecodan) use this method to give a good indication of flow rates. Note, this method might be slightly off with inhibitor or glycol added for antifreeze protection as that changes the specific heat capacity and increases the “gloopiness” of the water, for want of a better term. Examples here:
Another possible way of measuring flow is to use an inline sensor, something a bit like this:
Note I have no idea how well this would integrate into OEM / heat pump monitor. Looks like this sensor has different options for output signalling too. Adding an inline sensor may also act as a flow restriction, so it might actually be better off not having it in circuit!
There is also another device useful for checking flow rates manually that can be installed, made by Taconova, either the Tacosetter:
with the restrictor opened fully for max flow or the TacoControl flow meter. With this, they are always in circuit (potentially adding a restriction to the system!) and require you to walk up and squeeze the red lever and read off the bottom of the float.
Just as a “rough n ready” rule of thumb, look at the difference between flow and return temperatures and ideally the difference between them in heating should be between 5k to 8k difference (5 to 8 degrees C difference). Too high a difference and that suggests poor flow rates. Good flow rates usually result in a happy heat pump