Thank you for your understanding. I was awake in the night so went over at 3am to see what it was doing, and woke up grumpy 😊 

The temperature in the house was better, but it was only 6° outside and I had some windows open. The outside unit was running when I arrived, but according to the controller the 'water tank sterilisation' cycle was running, so it could have coincidentally have been that.

I lowered the flow temp slightly again and on a whim reduced the WL2 settings to the same, although I sure it's set on WL1

Just went there now and it's far more comfortable (though windows are still open). I also played around with the settings but this time touch testing the pipes either side of the diverter valve (rather than rads). Everything seemed to be working as I would expect.

So I think the issue might be that it's operating as it should, but wildly overestimating expected heat loss. Then the sun comes in the south facing windows and makes things worse.

I guess I need a room stat or s

Oops... hit reply

I need some way to compensate for this better. I've also now reduced the controller setting by the maximum -5.

On which...

What does 'Outing mode' actually do? The instructions vaguely say "heating can operate at low temperature " but that's all. If this is on, does the domestic hot water still heat as normal? 

Posted by: @pooneil

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So I think the issue might be that it's operating as it should, but wildly overestimating expected heat loss. Then the sun comes in the south facing windows and makes things worse.

 

Good to hear this, sensible to set the WL2 curve the same as WL1 for now also, avoids any ambiguity.  Sun and south facing windows can be a mixed bag.  I have them and at this time of year the house overheats by 2-3 degrees during the day and then cools back down rapidly at night.  That was true also with gas, although the ASHP seems to perform better than the gas did.  In the height of summer I close the curtains!

Posted by: @pooneil

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I guess I need a room stat

The controller has a built in room stat.  It also has the ability (I think) to raise or lower the flow temperature by a few degrees without changing the WC curve.   Depending on how you set it up one or other of these is accessible in 'user' as opposed to 'installer' mode.  Although the Samsung controller isnt as user friendly as some, it still has the essentials, it beggars belief that installers put it in a cupboard unless they are also installing homely.

If you buy a separate room stat do not buy a clever one.  Some 'clever' ones attempt to pulse width modulate the boiler as they approach the set temperature.  Thats about the worst possible thing to do with an ashp.  You want a dumb one or the one in the controller. 

Personally id go for the latter.  If you get a stat you either have to wire it up, in which case you may as well move the controller and wire that, or you will get a wireless one which isn't necessarily reliable.  That said I dont know the layout of the house so it maybe that wireless is the only realistic option at this stage.

@jamespa 

I believe the water flow adjustment as user that you mentioned is what I've now reduced by the maximum of -5

To be fair to my installer, it was totally my fault that I didn't provide a cable for the controller. My electrician asked at 1st fix, I said I'd check, then I forgot,  and by the time we remembered the house was plastered.

Any idea about the "Outing mode"? 

I assume it does the same as reducing water flow as mentioned above, but with one quick button. I don't want to advise the tenant that this is an option if it turns dhw off as well. 

@pooneil Apparently you can set up a different water law for the outing mode. see this thread:

https://renewableheatinghub.co.uk/forums/renewable-heating-air-source-heap-pumps-ashps/samsung-ashp-scheduling-help

If thats the case and you can find what it is set to then that might give you the settings you are looking for as you said the temperature was comfortable when using it.