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Air source heat pump performance

 
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Air Source Heat Pumps (ASHPs)
Last Post by batalto 4 years ago
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 Derek M
(@derek-m)
Illustrious Member Member
Joined: 5 years ago
Posts: 4425
15/11/2021 9:30 am  

@dant 

Good morning Dan,

I suggest that you download the following manual and confirm that it matches your equipment before we proceed any further.

ThermaV owners manual Monobloc



   
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 Derek M
(@derek-m)
Illustrious Member Member
Joined: 5 years ago
Posts: 4425
22/11/2021 1:25 pm  

Bad news I'm afraid, my radiators have started to feel warm to the touch. 😥 



   
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Morgan
 Morgan
(@morgan)
Noble Member Member
Joined: 5 years ago
Posts: 697
22/11/2021 4:56 pm  

@derek-m 

EE8CF195 FECE 4C26 AA18 1EAA81CBBA3A

 


Retrofitted 11.2kw Mitsubishi Ecodan to new radiators commissioned November 2021.
14 x 500w Monocrystalline solar panels.

2 ESS Smile G3 10.1 batteries.
ESS Smile G3 5kw inverter.


   
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 Derek M
(@derek-m)
Illustrious Member Member
Joined: 5 years ago
Posts: 4425
22/11/2021 6:08 pm  
Posted by: @morgan

@derek-m 

EE8CF195 FECE 4C26 AA18 1EAA81CBBA3A

 

I knew I had heard that somewhere. 😎 



   
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 Hr_3
(@hr_3)
Active Member Member
Joined: 4 years ago
Posts: 16
23/11/2021 6:40 am  

Hi all

Has anyone adjusted their flow temperature as I hear it can produce decent savings on electricity usage?

Also, how often do others ASHP defrost cycle, particularly at night? 



   
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Mars
 Mars
(@editor)
Illustrious Member Admin
Joined: 5 years ago
Posts: 4351
Topic starter 23/11/2021 7:37 am  

@hr_3, we dropped ours from 45C to 40C in November. Our previous COP was 2.7 and it’s now over 3, which is good. Depending on how well insulated you are, and if you’ve got UFH or big rads, you could get away with 35C. 

As for defrosts, we’ll easily do 8-10 when temperatures drop. Humid evenings with temperatures in the 1-3C range are worst for us. Sub-zero temperatures don’t lead to as many defrosts for us because there’s typically less moisture in the air.


Get a copy of The Ultimate Guide to Heat Pumps

Subscribe and follow our YouTube channel!


   
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 DanT
(@dant)
Trusted Member Member
Joined: 5 years ago
Posts: 35
23/11/2021 8:42 am  

I asked my installers about switching to weather compensation mode

This was their feedback:

"When we have rads and UFH working together we tend to find using the weather compensation curve is not particularly effective. It can mean that there’s low temperature water in a convective radiator panel which doesn’t provide sufficient output. Our customers with similar set ups are far happier to hit a set flow temp of 50/55 which ensures the panels convect warm air into the rooms.

You can experiment with using the weather compensation mode to see if it suits, but we would recommend just to keep the set flow temperature. Ultimately the thermostat will turn off once it’s hit the set temp so the heat pump will be operating for a shorter period of time at a slightly higher flow temperature and  you’ll find little difference in the ultimate efficiency. You could try adjusting the set back temperature by a few degrees which would mean the temperature in the house is maintained.

Hope that makes sense and do come back to me if there are any further issues re. upstairs heating."

 



   
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 Kev M
(@kev-m)
Noble Member Member
Joined: 5 years ago
Posts: 1276
23/11/2021 9:47 am  

@dant,

I thought on a dual rad/ufh system the ASHP heated water to a single temperature; the rads got fed this directly and the ufh got it mixed with cold water because it didn't need such a high temperature?  Would your supplier still be saying go for a set 50/55 if you didn't have ufh?  A flow temp of 50 is right at the upper end.  



   
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 witchcraft
(@witchcraft)
Estimable Member Contributor
Joined: 5 years ago
Posts: 91
23/11/2021 10:56 am  

@kev-m The installer (since sacked) who commissioned our rad only installation set flow temps to 55.  I have set it down now to 40 and still the house remains comfortable.



   
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 Kev M
(@kev-m)
Noble Member Member
Joined: 5 years ago
Posts: 1276
23/11/2021 11:11 am  

@witchcraft,

I remember seeing an article or video where the installer said they set the radiators at 50C because otherwise the customers complained the heating wasn't working.  



   
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 Hr_3
(@hr_3)
Active Member Member
Joined: 4 years ago
Posts: 16
23/11/2021 3:32 pm  
Posted by: @editor

@hr_3, we dropped ours from 45C to 40C in November. Our previous COP was 2.7 and it’s now over 3, which is good. Depending on how well insulated you are, and if you’ve got UFH or big rads, you could get away with 35C. 

As for defrosts, we’ll easily do 8-10 when temperatures drop. Humid evenings with temperatures in the 1-3C range are worst for us. Sub-zero temperatures don’t lead to as many defrosts for us because there’s typically less moisture in the air.

Hi Mars

Thanks, OK I think my ASHP (steibel eltron wpl17) is in line with your cop there (about 2.7)at the moment at 45c flow

I may drop to 35/40c and see outcome.

We have large k2 double convector rads, no ufh but system was installed from scratch, not retrofit so mainly 22mm pipe everywhere. System gets up to 20c no issues which for us is too hot and temperature seems to only drop below 19c after 11-12hours (on the recent colder days at 5c)



   
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Mars
 Mars
(@editor)
Illustrious Member Admin
Joined: 5 years ago
Posts: 4351
Topic starter 23/11/2021 4:49 pm  

@hr_3, give it a bash - you should get a feel for temperature and efficiency within a few days.


Get a copy of The Ultimate Guide to Heat Pumps

Subscribe and follow our YouTube channel!


   
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