Daikin Atherma ASHP Cycling 6 Times an Hour?

Air Source Heat Pumps (ASHPs)

Last Post by John Marshall 11 hours ago

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John Marshall

(@john-marshall)

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Topic starter 06/01/2026 12:00 pm

I have a Daikin Atherma EDLQ07CAV unit and I've come here to the forum as I've contacted Daikin but they are not interested in giving me information on system set up apart from sending an engineer out, which at present I can't afford. And the enquiry is about the Ashp cycling 6 times an hour, which seems high.

The system was installed around 2017 and has been running fine until one of the motorised valves got stuck on and the house got rather warm! So, I changed the MV and works fine now. But, it got me thinking about my ashp and to see If I could get it more efficient, particularly after watching lots of videos on YT and from this channel!

Anyway, was never aware of weather comp and was using room stats but now have stats full on (as a test period) and just using weather comp. I will be buying new room stats(upstairs&down) digital, as the mech Sunvic s are inaccurate, but will then use as a limit say 1° above target temp.

I have got the WC fairly close to keeping house at around 20° but needs fine tuning. WC previously set limits at -10 to 15 35-25, -3 to 12 34-25, then 33-25, today trying 32-25.

My 2 bed house is very well insulated so as temps outside been around 5 to 0° the actual lwt has varied from around lwt 28 to 31-ish. Before I set WC it was set on 45-30 with room stats cutting in and out(so I used to whack them up, get house warm then switch off heating- house temp when outside say 2° drops 0.4° an hour)

So now using WC without interfering room stats its cycling 6 times an hour. As I've changed the WC settings, it seems consistent at 6 an hour. Even when I turned off downstairs rads I overnight, still about 6 or slightly under.

The system seems consistent and works well apart from this short cycling. So it makes me wonder if the 7kw ashp is oversized for this well insulated house?

I've checked various settings and am now taking daily readings, comp starts, pump hours etc. Electric too, eg, seems to be using around 450watts an hour for heating when it's around, 0,1,2,3,4° outside.

As the system seems to run ok apart from cycling it makes me think that it's just a control issue, ie, the calibration/balance of compressor, pump, running speeds interplay etc (unless if ashp oversized this can't be addressed?)

Perhaps this is where a Daikin or other engineer is needed to re calibrate the system? Though if there's anything I can adjust myself or try without mucking the system up, Il certainly have a go. Daikin weren't helpful. And I can at least reset to what works even if cycling too much!

Il be interested to hear from anyone any ideas of what, if anything I can try on the settings. And I'll continue to experiment with WC, maybe that's all I can do.

Thanks.

This topic was modified 1 day ago by Mars

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Mars

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Joined: 5 years ago

Posts: 3886

06/01/2026 10:01 pm

From what you describe, it sounds like you’ve done a solid job troubleshooting so far, especially replacing the motorised valve and experimenting with weather compensation settings. The short cycling (about six times an hour) does seem quite frequent, and it’s understandable you want to optimise efficiency without the immediate option of an engineer visit.

Given your well-insulated two-bedroom home and the 7kW ASHP size, it’s quite possible the heat pump is oversized for your current heat demand.

Your approach to using weather compensation as the primary control method is spot on, especially for smooth modulation of flow temperatures based on outdoor conditions. Fine-tuning the curve is key, and your gradual adjustments from 45-30 down to around 32-25 show you’re on the right track IMO. The fact that the low water temperature varies between 28 and 31C at outdoor temps around 0 to 5C suggests the system is running relatively low-temperature flow, which is good for efficiency.

Since you’re seeing consistent cycling, it points to the system’s overall heat output being more than the house needs at times. One thing you might try is slightly flattening the weather compensation curve further to reduce the flow temperature a bit more, which can extend run times and reduce cycling. Also, ensuring your pump speeds and compressor modulation settings are optimised can help, but these often require specialist tools or engineer input.

If you’re comfortable experimenting, keep monitoring daily data like compressor starts, pump hours and power consumption as you are. This info can help you spot patterns and understand how changes affect cycling.

Ultimately, while some tweaking can be done by yourself, certain calibrations (like adjusting compressor modulation parameters or pump speeds) usually need an engineer with the right diagnostic tools. If Daikin support isn’t forthcoming, you might consider a heating engineer experienced with Daikin ASHPs or similar systems who can do a proper system balance and calibration.

Keep tracking your data and adjusting carefully, and hopefully you’ll find a sweet spot that reduces cycling and keeps your home comfortable efficiently.

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John Marshall

(@john-marshall)

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Topic starter 07/01/2026 8:44 am

Thanks for your reply. Yes that's a good idea to try and flatten curve more. And from looking at compressor behaviour and pump switch ons, and how they're interacting (they don't seem balanced properly as some erratic behaviour) does point to probably an engineers diagnostics on the system, as you say, I can only adjust so many parameters. At least it runs and the heating works. I wouldn't be surprised if the Daikin control unit was never configured properly in the first place, all those years ago! So, I may check out and see if there are any local Daikin engineers near me. Do you think I should go with a Daikin experienced engineer or another company, say, heat geek? Also the last engineer (not Daikin) did a service and never mentioned to me about using weather compensation or anything about the fact the 2 room stats would have been interfering with that side of it. So I'll try and find someone who knows what they're doing around north Cornwall.

Thanks

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