Hi @JPB,
I’m not sure TBH and you don’t say whether this is a one-off event or happens a lot. (Also, I don’t monitor, so I’m not sure of your colour scheme - I assume red is LWT, green is RWT), but for background information…
- The controller runs a wintersation cycle if the circulating pump hasn’t run for a while (per Samsung R32 ASHPs - when is a defrost not a defrost?) but this takes heat from the DHW tank, it doesn’t inject it.
- The controller exercises the circulating pump every so often if it hasn’t been used (I think it’s once per day, but this was discussed in a recent thread). This is most unlikely at this time of year of course, but if it does run it will move move a little heat around, possibly via the DHW tank if your 3-way valve is set up with DHW as default.
- On which subject, it may be possible that if you have FSV#3071 set to “DHW” the 3-way sits in that position until the controller demands space heating. You could always reset #3071 as a trial.
- The event at 04.50 looks like a classic defrost cycle.