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Air Source Heat Pumps (ASHPs)
Last Post by batalto 3 years ago
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 Kev M
(@kev-m)
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Joined: 5 years ago
Posts: 1276
06/11/2021 7:19 am  

@batalto, your latest weather comp settings sound about the same as ours now and I'm thinking of knocking it down a bit.  I agree about the water; I'm all for saving a few quid but not at the expense of comfort. We have electric showers for now so not an issue for us.  

Hopefully you'll stay warm with the latest adjustments.



   
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 batalto
(@batalto)
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Posts: 1092
Topic starter 06/11/2021 7:24 am  

@kev-m we'll see. I'll note that last night we used 11kw and delivered 42 in heat - COP 3.88. and the night is the coldest time...

Yesterday as a whole we used 36kw and delivered 110kw in heat - COP 3.05


12kW Midea ASHP - 8.4kw solar - 29kWh batteries
262m2 house in Hampshire
Current weather compensation: 47@-2 and 31@17
My current performance can be found - HERE
Heat pump calculator spreadsheet - HERE


   
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 Kev M
(@kev-m)
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Posts: 1276
06/11/2021 7:43 am  

@batalto, my corresponding numbers are 30.6 and 4.6.  I turn the room temps down during the day and through the night (something I'm going to experiment with).  My delivered energy has stopped recording so I don't know COP.  



   
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 batalto
(@batalto)
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Topic starter 06/11/2021 8:36 am  

@kev-m I'm confused, what are those numbers then?


12kW Midea ASHP - 8.4kw solar - 29kWh batteries
262m2 house in Hampshire
Current weather compensation: 47@-2 and 31@17
My current performance can be found - HERE
Heat pump calculator spreadsheet - HERE


   
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 Kev M
(@kev-m)
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Joined: 5 years ago
Posts: 1276
06/11/2021 9:05 am  
Posted by: @batalto

@kev-m I'm confused, what are those numbers then?

30.6 kWh used yesterday 5/11/21 and 4.6 kWh used from midnight to now.



   
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 batalto
(@batalto)
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Posts: 1092
Topic starter 06/11/2021 9:09 am  

@kev-m ah ok. That makes sense now


12kW Midea ASHP - 8.4kw solar - 29kWh batteries
262m2 house in Hampshire
Current weather compensation: 47@-2 and 31@17
My current performance can be found - HERE
Heat pump calculator spreadsheet - HERE


   
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 batalto
(@batalto)
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Posts: 1092
Topic starter 06/11/2021 7:53 pm  

Some feedback for everyone in two charts. As a note, I've created my own measure of efficiency beyond COP. At the moment its called COP-A (or COP per degree ambient). I'll explain my reasoning below.

This graph shows the impact of radiator balancing and weather compensation adjustment down. I started looking at the balance on the 2nd of November, which you can see coincides with a big drop in COP as we had a cold night. On the 3rd I adjusted them further and reduced my weather comp to 55 degrees at -2 and 33 at 16 degrees. You can see the COP easing upwards. However I find the graph very clunky to draw any conclusions. 

image

The solution (in my view) is to link ambient temperature and COP; as these are the two most critical to performance. What I've done is take the COP and divide it by the ambient temperature. This gives me COP per degree ambient. The lower the number, the worse the performance of your system.

image

As you can see, there is a much clearer outcome from this. Even with a falling ambient (or rising) you can see how efficient your system really is. If you maintain your COP but your ambient drops your COP-A has risen. I have no idea how this metric might perform over time, but at least it delivers an insight beyond COP.


12kW Midea ASHP - 8.4kw solar - 29kWh batteries
262m2 house in Hampshire
Current weather compensation: 47@-2 and 31@17
My current performance can be found - HERE
Heat pump calculator spreadsheet - HERE


   
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 Kev M
(@kev-m)
Famed Member Member
Joined: 5 years ago
Posts: 1276
07/11/2021 7:36 am  

@batalto, not sure I understand. Are you using degrees Celcius?  I see what you're trying to do but what happens when ambient temp gets to, or close to, or lower than, zero? 

 



   
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 Brendon Uys
(@heacol)
Noble Member Contributor
Joined: 5 years ago
Posts: 415
07/11/2021 9:05 am  

@batalto Nice indication of the implacations of flow temperature, try to drop your curve even further and disable all you other levels of control by turning them up fill (except your bedrooms). Control your internal temperature by adjusting the curve. You will find a huge differance and when you find the sweetspot for your house you wil need no furter control.



   
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 batalto
(@batalto)
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Posts: 1092
Topic starter 07/11/2021 9:30 am  

@kev-m that's an issue to cross when I get there lol. But it's more about trying to take cop out of the theoretical and ground it in reality so you can compare day to day. If today is warmer you can easily compare using this factor


12kW Midea ASHP - 8.4kw solar - 29kWh batteries
262m2 house in Hampshire
Current weather compensation: 47@-2 and 31@17
My current performance can be found - HERE
Heat pump calculator spreadsheet - HERE


   
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 batalto
(@batalto)
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Joined: 5 years ago
Posts: 1092
Topic starter 07/11/2021 7:41 pm  

Another day, another filter clean. Barely anything in there today


12kW Midea ASHP - 8.4kw solar - 29kWh batteries
262m2 house in Hampshire
Current weather compensation: 47@-2 and 31@17
My current performance can be found - HERE
Heat pump calculator spreadsheet - HERE


   
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2
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 batalto
(@batalto)
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Joined: 5 years ago
Posts: 1092
Topic starter 08/11/2021 9:16 am  

Curve adjusted down again last night -  we are now at;

Max: 50 @ -4 degrees

Min: 25 @ 15 degrees

I might leave these alone now and track for the next week. I've made quite a few changes recently and I need to see the impacts


12kW Midea ASHP - 8.4kw solar - 29kWh batteries
262m2 house in Hampshire
Current weather compensation: 47@-2 and 31@17
My current performance can be found - HERE
Heat pump calculator spreadsheet - HERE


   
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4
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