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Daikin Altherma 3 / HomeAssistant

Air Source Heat Pumps (ASHPs)

Last Post by JamesPa 3 weeks ago

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Ubert767

(@ubert767)

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Topic starter 30/10/2025 3:14 pm

Any "HomeAssistant" Boffins out there?

Can the frequency of compressor starts (short cycling) be determined from the data returned to "HomeAssistant" from my heat pump connected via the Daikin A.P.I.

If not then how??

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Majordennisbloodnok

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30/10/2025 7:46 pm

@ubert767, it’s a little unclear from your post, so forgive me if the questions seem a bit obvious to you.

Do you mean that you have Home Assistant running and already have the Daikin integration that uses their API already installed, but can’t find anything related to compressor starts? Or do you mean that you haven’t set up HA (or at least the Daikin integration) and are deciding whether it’s worth doing so?

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DCSH

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30/10/2025 8:05 pm

I think the data available in Home Assistant is limited to what Daikin exposes via their API, which is substantially less than can be seen with the indoor units display. I’ve had a look and can’t see anything explicitly about compressor stats, but you can see leaving watch temperature which I suppose could be used as a proxy to determine when heating is occurring with a custom sensor in HA.

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Majordennisbloodnok

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30/10/2025 8:17 pm

@dcsh, that’s a similar approach to what @jamespa was suggesting here ( https://renewableheatinghub.co.uk/forums/postid/51593/). Seems like a good approach if Daikin’s API isn’t as comprehensive as @ubert767 might want.

"Semper in excretia; sumus solum profundum variat"

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Ubert767

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Topic starter 30/10/2025 8:55 pm

Apologies for the lack of clarity in my question, yes I have HomeAssistant running and access to the Daikin via their API (after a bit of a struggle!!). I also have installed a Shelly EM on the supply to the heat pump which gives me a fair bit of electrical data but I'm not confident in interpreting the plots in order to determine wether the HP is short cycling. Are the energy plots showing compressor starts or is it showing the results of inverter control?

Any enlightenment is very welcome.

Rob

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DCSH

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30/10/2025 10:50 pm

I don’t have a Shelly EM on my heatpump, so only see the energy usage as part of the total home consumption via my GivEnergy inverter so it’s less detailed. I would guess that the series of power peaks within a few minutes are one cycle and those half an hour or so later are another, but maybe looking at the graphed leaving temperature would help identify this? Presumably the heatpump it set to with the emitters as underfloor with I believe sets the delta between leaving and returning which I assume would influence the cycle length?!?

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Majordennisbloodnok

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31/10/2025 9:07 am

@ubert767, thanks for the screenshots. Unfortunately, many of the tiles are too small to see the names of the entities they are reporting, but no matter.

If you go to you Developer Tools page…

…and then go to the States tab…

HA Dev Tools page with States highlighted

…you’ll be able to see and filter on every entity set up on HA including, of course, all the Daikin ones. If the integration has exposed compressor starts (or anything that could be used as a proxy for such) you’ll be able to find it here. If it isn’t here then it is still possible the Daikin API has it but the integration isn’t making use of it.

Does that help at all?

"Semper in excretia; sumus solum profundum variat"

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Ubert767

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Topic starter 31/10/2025 9:42 am

@majordennisbloodnok

Thanks for your input.

This is the resultant display, does the power factor act as a proxy for compressor start frequencies?

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Majordennisbloodnok

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31/10/2025 10:36 am

Hmm. That I don’t know. I would’ve thought power was a more likely candidate than power factor. In the thread I linked to in an earlier post, @jamespa was talking about either flow temperature or power as suitable proxies and @dcsh made another suggestion above. Worth looking at the history of each of those entities and seeing what they are suggesting.

"Semper in excretia; sumus solum profundum variat"

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JamesPa

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31/10/2025 11:57 am

Posted by: @majordennisbloodnok

↑

Hmm. That I don’t know. I would’ve thought power was a more likely candidate than power factor. In the thread I linked to in an earlier post, @jamespa was talking about either flow temperature or power as suitable proxies and @dcsh made another suggestion above. Worth looking at the history of each of those entities and seeing what they are suggesting.

I would have thought that (instantaneous) power is a fair proxy for compressor modulation. I haven't actually tried to compare though because I cant monitor the latter other than with the MK1 eyeball and, for the most part, don't particularly care what the modulation is. Flow temp is not a suitable proxy for this IMHO, but the first derivative of flow temp would presumably be at least indicative, although the scaling factor will be dependent on variables such as OAT. I cant comment on power factor, I simply dont know enough about the characteristics of electric motors!

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