Nice lad called Rhys Simmons came (from Shrewsbury) to update the heatpump firmware - took all of 60 seconds after he got the side off. While he was here he had yet another update for the display and controller (now SO24.29 and SO24.24) though not obvious I got any new functions from that.
He was impressed by the install quality, pipework, groundwork, and bricklaying!
The heatpump firmware update now allows water pump standby / low / high settings (as PWM %), though standby won’t go below 25% or low below 30%, so low (2.5kW heatpump output) still runs at 15L/min, down from 21-23 at the previous fixed 50%. Have yet to see if it modulates nicely (or at all).
No drama, all back to running as before. I now have it set at WC 1.1, shift -4, ‘room influence’ (or whatever they call it) x factor of 10 (ie 1c over on the room stat means 10c drop in flow temp). Set to 21c daytime, 22c at night (though to do that you have to reverse day and night, negative setback not allowed!)
However I am fiddling the curve, to use actual weather station ‘feels like’ temperature (which accounts for wind, as well as having a sensibly placed sensor - not on a wall), to use median house temps (from multiple sensors, rather than just the one) and to apply a fixed offset at night - I use the result of MY calculation to adjust the -4 shift to get the circuit1 target where I think it ought be.
Water pump power is down by about 10W, and DT has increased slightly, but is still <3c at low power outputs.
Rhys hinted that more firmware updates for the pump may be on the way, and that OTA update may arrive one day. We can hope .. sending engineer out for a 1 minute job (requiring special equipment) has got to be dumb.