Room temperature dip every afternoon Daikin 11kw

Hardware Heatpump
1

I’ve had a Dailin 11kw Altherma for about a year. Every day I go into my garage to the mmi to see things like LWT for the current outside temp and to get energy data to track COP.

I’ve got the WD curve set right (for me) and it ticks over at 19.5. with a 2 degree LWT setback overnight. The Madoka room stat is set to 22 in case I get a significant solar gain, so normally I wouldn’t expect it to cut in at all. Modulation is off.

However every afternoon about 3pm there is a dip in the room temperature of a degree or two which I cannot fathom.

DHW schedule is 12-14:00 every day with no reheat.

My questions are two fold:

  1. What on earth can I look for as to

    Screenshot_20260103-095407
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    the cause of the dip which occurs every day?

  2. What (minimum) additions can you suggest to assist me with the daily gathering of data and help to track down my issue.

1 Like
2

Have you tried rescheduling the DHW to see if this is a factor?

3

Good thinking. I’ll shift it by an hour

4

If you eyeball the preceeding hump out of the graph, the trend upwards continues and it isn’t a dip at all. So maybe the question should be: “what causes the hump before the dip”? Looks like it starts rising faster just after 11am. Does it happen every day or only on sunny days?

5

I think you are on to something there. I’ll monitor it over the next few days.

BTW, do you know /can you recommend a simple additional installation that would let me monitor LWT and figure from which I can derive COP without going to the mmi panel and entering a snapshot into a spreadsheet?

Martin

6

I’m using ESPAltherma which provides a low cost insight, albeit with a little config and setup required. There is an excellent guide here. You can then use Home Assistant to perform various calculations, amongst which is a rough CoP.

7

… or send the data to EmonCMS, either locally or the EmonCMS.org website - everything you want to know about your heat pump will be there with no need for HA. Also easy to add input energy monitoring and derive CoP yourself.