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Help me keep the faith with my air source heat pump installation

AdamK · 2025-03-29T13:05:20Z

i knew when setting out on this road it would be a challenge i just didnt know how much of one it would be. after having many quotes some i couldnt fathom why they were so high i thought id sorted an installer. problem is they are 72miles away so first issue was doing a remote heat loss which has been back and forth several times to get it more or less correct, but still have one room thats 2m2 smaller than what i measured. anyway the next issue was getting the 28mm primaries in before the new kitchen ceiling goes in. they sent a plumber that proceeded to bugger the job up as the wall sleeve kit hadnt been supplied to him. so sent him on his way. was promised the sleeve kit the next day and i said my plumber could fit it to save them sending an engineer. next day no kit. add to this all the mods im having to do to pipe work to maximise efficiency and im seeing why the take up is tiny in the UK. im not naming the company as they are a recommended one and have apparently done good work else where but maybe thats in there local area. i know living in Boston creates its own issues being miles from any proper trades so if someone asked me would i recommend getting a heat pump in my area id have to say no. theres just not enough skilled trades where i live.

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Air Source Heat Pumps (ASHPs)

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AdamK

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Topic starter 20/11/2025 9:38 am

ok now i had some cold days i think i can safely say i have an issue with either the heat pump or the install.

im getting as low as 2.4 scop for heating while getting maybe 2.8 for hot water.

this has been an issue since install. the hot water cycles always beat the heating.

i cant see any massive cycling going on ive tried dropping the wc curve and it seems to have very little effect on the scop. last setting i had which it seemed to struggle with was 0.4.

ive now let Havenwise have a go at sorting it.

all the rads are getting warm and the hot water gets upto temp. what i have noticed before letting Havenwise control it was the flow temp would rarely get above 33c yet bad scop.

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JamesPa

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20/11/2025 9:48 am

Posted by: @adamk

↑

ok now i had some cold days i think i can safely say i have an issue with either the heat pump or the install.

im getting as low as 2.4 scop for heating while getting maybe 2.8 for hot water.

this has been an issue since install. the hot water cycles always beat the heating.

i cant see any massive cycling going on ive tried dropping the wc curve and it seems to have very little effect on the scop. last setting i had which it seemed to struggle with was 0.4.

ive now let Havenwise have a go at sorting it.

all the rads are getting warm and the hot water gets upto temp. what i have noticed before letting Havenwise control it was the flow temp would rarely get above 33c yet bad scop.

Are you able to post any graphs?

Unless its cycling or defrosting it should be achieving (at the heat pump) a COP close to spec. Defrost can cripple COP if it happens too frequently or goes too deep, and looking at the graph of FT might reveal whats happening. My current 24hr COP as reported by the heat pump is 3.2 (and falling, not surprisingly, it will go sub 3 I suspect), its defrosting irregularly but not more than every couple of hours

This post was modified 3 months ago 2 times by JamesPa

4kW peak of solar PV since 2011; EV and a 1930s house which has been partially renovated to improve its efficiency. 7kW Vaillant heat pump.

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AdamK

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Topic starter 20/11/2025 10:28 am

I might try a wipe and re install of Home Assistant to see if I can get the power info to show. Was going to put it on a RPI 3B I have but it won't work as too old.

I've got an old laptop I could use. Is there a bare metal install I could use maybe? Or some decent places I can get support on it. I've asked on a couple of HA Facebook groups but silence. I can see the values in the states page in the firmware version right hand box, which seems odd, but doesn't let me add it as a history or tab.

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JamesPa

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20/11/2025 10:42 am

Posted by: @adamk

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Was going to put it on a RPI 3B I have but it won't work as too old.

Mine is running on a 3B, albeit one with the official power supply.

The power info is currently flaky (known issue with the integration) but you can learn almost everything from flow temp which is solid. Defrost should be visible and cycling too in the ft data.

I don't know about bare metal ha on a laptop tbh. You would need to check the site.

As a quick check - in the app, status, arotherm plus what are the running hours and on off cycles?

This post was modified 3 months ago 4 times by JamesPa

4kW peak of solar PV since 2011; EV and a 1930s house which has been partially renovated to improve its efficiency. 7kW Vaillant heat pump.

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AdamK

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Topic starter 20/11/2025 1:10 pm

@jamespa there is data for hrs and on/off cycles. But since switching to Havenwise that Vaillant app status page doesn't seem to be updating. Until around Monday it was about 600hrs and 800 on off .

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JamesPa

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20/11/2025 1:19 pm

Not great. Average run time < 1 hour. Suggests cycling on thermostat or due to oversize. However not that many hours either, when was it fitted?

It really would be good to look at an ft plot if it's still available, but it maybe havenwise highjack the feed.

This post was modified 3 months ago by JamesPa

4kW peak of solar PV since 2011; EV and a 1930s house which has been partially renovated to improve its efficiency. 7kW Vaillant heat pump.

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JamesPa

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20/11/2025 1:19 pm

Posted by: @jamespa

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Not great. Average run time < 1 hour. Suggests cycling on thermostat or due to oversize. However not that many hours either when was it fitted?

It really would be good to look at an ft plot if it's still available, but it maybe havenwise highjack the feed.

4kW peak of solar PV since 2011; EV and a 1930s house which has been partially renovated to improve its efficiency. 7kW Vaillant heat pump.

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AdamK

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Topic starter 20/11/2025 4:48 pm

@jamespa ive just pulled the flow temp from the Havenwise data, as im at work so cant spin up Home Assistant. its only a few days and the first few days were where it was in its learning phase. it certainly likes higher flow temps. still getting the same scop more or less, which is what i dont get, if im running effectively a higher curve it should lower the scop not keep it nearly the same.

This post was modified 3 months ago 2 times by AdamK

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AdamK

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Topic starter 20/11/2025 4:55 pm

@jamespa this is a graph with both flow and return on. seems to be keeping a 2.5c gap between them.

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AdamK

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Topic starter 20/11/2025 5:05 pm

@jamespa i seem to remember someone when i was digging for info on rad balancing saying they were having trouble as the Vaillant seems to want to control to Delta of 2.5 not 5. im guessing its doing this by controlling the circulation pump speed up and down.

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AdamK

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Topic starter 20/11/2025 5:15 pm

@jamespa just saw this massive spike on energy consumed which is sat in between two hot water heating mode on status. maybe a defrost?

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JamesPa

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20/11/2025 6:06 pm

Posted by: @adamk

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@jamespa i seem to remember someone when i was digging for info on rad balancing saying they were having trouble as the Vaillant seems to want to control to Delta of 2.5 not 5. im guessing its doing this by controlling the circulation pump speed up and down.

Possibly. I haven't yet worked out what Vaillant do with water pump speed as I can't monitor it and don't have a reason to care. Why is it a 'problem'

Yes I expect the spike is recovering from defrost. Mine seems to go to 100% compressor modulation for 5-10mins after defrost.

4kW peak of solar PV since 2011; EV and a 1930s house which has been partially renovated to improve its efficiency. 7kW Vaillant heat pump.

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