The pump came on again early this morning. 

I took more pics but I can't see any clues apart from  "Thermostat 1" being "on" in Zone status info ?

ASHP ran on until outlet temp reached 64.

The lights on zone valve boxes above show neither were calling for heat.

@lenny The main Thing that comes to mind is that the heat pump is heating your domestic hot water tank. This is about the only time you would expect the flow temperature to reach 60° or more.

Thanks.

Heat pump does heat/maintain DHW but max temp is 55 (I wonder if it is running random disinfection cycle ? }

@lenny When you say the max temperature is 55 deg C, I presume you mean the max temperature that your DHW  is heated to. That is the default maximum. However the flow temperature from the heat pump (the water outlet temperature in your screenshot) will be at least 60 deg C to achieve the 55 deg C temperature of the domestic hot water. Otherwise, it wouldn't heat your hot water to 55 deg C.

@mike-h 

thanks again, yes, that is probably it. I'll wait till next time and look

@lenny If you have Solar PV, it would probably save you a lot of money to install a Solar iBoost or similar device. This will heat your hot water from the electricity produced by your solar PV for free for at least half the year. My Samsung doesn't get used at this time of year. Failing that, it is also probably cheaper to schedule when your heat pump heats your hot water. There is inevitable heat loss from the tank and pipe work, so unless you need piping hot water all the time, heating it once or twice a day is more economical.

Set DHW on a schedule and this AM it came on proving that it was just as you suggested 🙂 . not a "issue I couldn't find" just me not thinking sideways enough.

Also the iBoost suggestion, I have been thinking about that 

Thanks

I have the same pump as your self and a 4kw solar array. I would strongly advise you to get an Iboost. My iboost heats my water approx 9mths in the year. As I have nowhere else for my free energy to go I have the tanks set for 70C. I also have the HP coming on in the late afternoon so any "free" solar during the day is used to heat water, the HP is set to heat the hot water to 48c which is adequate for us as a back up to solar. The HP is only set for 1 hour which is long enough to heat to 48c and has never failed to achieve that. Limiting the schedule saves you money. 

thanks.........

The HP coming on via the iBoost or with the PV setting in the Gen6 controller ?

@mike-h - can you possibly point me towards any advice on how to install iBoost with a Samsung Gen 6 ashp? I have searched the forums, but can't find out whether to wire iBoost directly to the immersion, or disconnect immersion from Samsung, before connecting iBoost? Flumoxed (I have a qualified electrician trying to sort this for me). Thanks in advance 😁