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Heating coming on when not required

 
Air Source Heat Pumps (ASHPs)
Last Post by JamesPa 1 year ago
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bontwoody
 bontwoody
(@bontwoody)
Noble Member Contributor
Joined: 4 years ago
Posts: 1055
Topic starter 04/07/2025 3:39 pm   [#2373]

Im probably having a brain fart, but for the life of me I cant think what is going on with my heating.

My Samsung Gen 6, keeps coming on intermittently to run the heating when the weather is warm. Im running it on weather compensation, but also have the control unit in my lounge to limit it when the lounge reaches temperature. At the moment I have the lounge stat set to 16C. As you can see in the first graph my room temperature never got below 20C, so by my logic the heating should be off.

Last night

The second graph shows how some days its on and others its not!

days

House-3 bed partial stone bungalow, 5kW Samsung Gen 6 ASHP (Self install)
6.9 kWp of PV
10kWh DC coupled battery
Blog: https://thegreeningofrosecottage.weebly.com/
Heatpump Stats: http://heatpumpmonitor.org/system/view?id=60


   
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Mars
 Mars
(@editor)
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Joined: 5 years ago
Posts: 4763
04/07/2025 4:15 pm  

So you're saying that nothing is calling for heat because all your indoor thermostats are below temperature?

Is it quite cold outside where you are? Below 16ºC?


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bontwoody
 bontwoody
(@bontwoody)
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Joined: 4 years ago
Posts: 1055
Topic starter 04/07/2025 5:09 pm  

@editor Thats correct. Its not particularly cold but the purple line in the first graph shows the outside temperature. Its shows that the heating came on at 9.30pm when the outside temperature was about 16C and the indoor temperature 21C.


House-3 bed partial stone bungalow, 5kW Samsung Gen 6 ASHP (Self install)
6.9 kWp of PV
10kWh DC coupled battery
Blog: https://thegreeningofrosecottage.weebly.com/
Heatpump Stats: http://heatpumpmonitor.org/system/view?id=60


   
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Mars
 Mars
(@editor)
Illustrious Member Admin
Joined: 5 years ago
Posts: 4763
04/07/2025 8:29 pm  

@bontwoody, his is one of those odd things Rob Berridge mentioned in one of my podcasts and it stuck with me. I assume your heating isn’t manually switched off, correct?

If I remember rightly, he said that some heat pumps have an in-built setting linked to a CIBSE guideline (I think it was around 15.5C, but don’t quote me) which can automatically trigger certain pre-configured heating systems to come on below that point, regardless of whether there’s an actual "call for heat".

After that episode, I asked the panel about it, and they all agreed it’s usually better to switch heating off entirely (keeping HW on) in the shoulder months and summer if you don’t need space heating at all.

Just wondering if that could be what’s happening in your case... might not be, but worth checking. Just thinking out loud!


New to heat pumps? Take the Heat Pump Fundamentals course and use INTRO50 at checkout for 50% off.
Rewritten and updated for 2027
📘 From Zero to Heat Pump Hero
🛠️ Bodge Buster
🎧 Prefer to listen? Heat Pumps Explained


   
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bontwoody
 bontwoody
(@bontwoody)
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Joined: 4 years ago
Posts: 1055
Topic starter 04/07/2025 8:37 pm  

@editor It may be that. I do remember setting up a max OAT at which the heating should turn off but can't remember where it was in the settings. I'm curious as to what I set it to now.


House-3 bed partial stone bungalow, 5kW Samsung Gen 6 ASHP (Self install)
6.9 kWp of PV
10kWh DC coupled battery
Blog: https://thegreeningofrosecottage.weebly.com/
Heatpump Stats: http://heatpumpmonitor.org/system/view?id=60


   
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JamesPa
 JamesPa
(@jamespa)
Illustrious Member Moderator
Joined: 3 years ago
Posts: 5200
04/07/2025 9:49 pm  

Posted by: @bontwoody
↑

@editor It may be that. I do remember setting up a max OAT at which the heating should turn off but can't remember where it was in the settings. I'm curious as to what I set it to now.

I played with a max heating temp but there is a world of difference between what you want it to do on a cool day in shoulder season and what you want it to do on a coolish summer night for example. 

So I reverted to simply switching heating off altogether for summer as I did with the boiler.  Sometimes simple is best!

Perhaps if it offered a setting that looked forward and averaged the next 24-48hrs before deciding whether to switch off altogether that might cut it, but realistically I can do that myself and I don't want my heating control to be dependent on the internet.

 

 


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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