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Air Source Heat Pumps (ASHPs)
Last Post by Derek M 4 years ago
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 adaml
(@adaml)
Trusted Member Member
Joined: 4 years ago
Posts: 42
Topic starter 01/12/2021 10:18 am  

Hello,

I have been browsing for a few days and thought it best to register to say Hi and see if I can get a bit more specific advice. Lots of useful information already and hoping with more specific guidance I can that I will be able to pass forward to some of my friends with identical setups.

 

We are in a 2020 new build with a Daikin, gas boiler module and outdoor ASHP unit. The ASHP unit is an EVLQ05CAV3. Our DHW is from the gas boiler. We are in a three bed house with 9 radiators. The installer had the DHW set at 60°C, and the weather dependent curve set at; 55°C flow at -5°C and 35°C flow at 20°C.

 

I have adjusted this to set the DHW at 50°C (still slightly too hot) and the weather dependent curve to 50°C flow at -5°C and 30°C flow at 20°C. The lower limit is set at 30° for the flow temp when adjusting the curve. I see people referencing lower values than this however perhaps this is with UFH or different units?

 

I have the thermostat/controller in the hall set to 21°C from 07:30 till 22:30 and to 17°C overnight.

 

I'd be really grateful for some pointers as to how best adjust and happy to provide any further info you may need?

 

Thanks,

 

Adam



   
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 batalto
(@batalto)
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Joined: 5 years ago
Posts: 1092
01/12/2021 10:37 am  

Is it a thermostat or the ASHP controller?


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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 adaml
(@adaml)
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Joined: 4 years ago
Posts: 42
Topic starter 01/12/2021 10:53 am  

@batalto The ASHP controller panel located in hall also functions as the room thermostat for the system. The radiators then have TRV's.



   
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 batalto
(@batalto)
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Joined: 5 years ago
Posts: 1092
01/12/2021 10:57 am  

@adaml ok well thats the thermostat issue solved!

Do you know how much the unit the cycling? If you want to experiment I would suggest just lowering the values on the weather compensation and see what happens, try 1 or 2 degrees and leave it for the day. The other option you have is to keep the numbers the same, just change the ambient down/up.

As example I have rads and my setting is 45@-1 and 25@18 degrees - I had to tweak this morning as the back room was 20 degrees and my wife moaned at me. I think you'll just had to do some trial and error and see what works for you.

Also, whack your TRVs up to 5 everywhere


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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 adaml
(@adaml)
Trusted Member Member
Joined: 4 years ago
Posts: 42
Topic starter 01/12/2021 11:34 am  

@batalto Thanks, that's great. I will put the TRV's to 5 and drop a couple of degrees on the curve and review.

 

It is strange that I can't bring the lower end of the curve down to below 30°C. I wonder what settings others with a Daikin are using due to this?

 

Any thoughts re running the system as it currently is with a reduced temp overnight vs running it 24/7 at say 21°C?

 



   
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 batalto
(@batalto)
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Posts: 1092
01/12/2021 11:48 am  

@adaml my lowest setting is 25. What you can do is just drop the temperature that it kicks in at 30 e.g. 30 at 15 degrees.

I am using mine 24/7 at 21 degrees, but my power at 00:30-04:30 is 5p/kw so its pretty advantageous for me to heat over that time. Do you have a smart meter? you could just do a test if there are two days of a similar temperature and what the impact is. Ultimately, you are going to have to put the heat you lose back into the house


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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 adaml
(@adaml)
Trusted Member Member
Joined: 4 years ago
Posts: 42
Topic starter 01/12/2021 1:17 pm  

@batalto Thanks for all your help so far!

 

Okay I understand I can drop the other value, that makes sense, I just didn't know if the value was absolute as in 30°C is the lowest?

 

I can see why it is in your interest to keep it on 24/7. I am trying to work out is it more expensive to make up the degrees heat lost between 22:30 and when the temp goes back up to 21°C at 07:30 or to maintain a constant temp? No smart meter unfortunately but can get a pen and paper out and give it a shot.

 

I would be keen to hear from any other Daikin users as well with rads? Also anyone any data for the 24/7 vs dropping the temp overnight? @Kev-M sorry for pulling you in but I noticed in your thread which is full of useful info that you may have looked at this - any advice would be really appreciated?



   
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 Kev M
(@kev-m)
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Posts: 1276
01/12/2021 2:29 pm  

@adaml 

I think @derek-m has done some more modelling on this.  Just to clarify; I'm looking at switching it off, not down, at night.  That's significantly diffferent.  I'll post some results/thoughts on my thread.   



   
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 adaml
(@adaml)
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Joined: 4 years ago
Posts: 42
Topic starter 01/12/2021 2:55 pm  

@kev-m Thank you!

 

I will have a look at my heat loss overnight as well, this will of course be heavily influenced by the outside temp. I am curious to get some data on it and see if a conclusion can be reached as the consensus seems to vary. @derek-m Please let me know if you have any pointers? I am happy to give it a shot if a couple of days of similar weather are due in the near future.

Would others be able to share their weather dependent curve or to what is extent is it just trial and error? I've adjusted the DHW to 45°C and the weather dependent curve to 45°C flow at -1°C and 30°C flow at 15°C to see how things go. All TRV's are now at 5 also.

 

Thanks for all your help so far!



   
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 Kev M
(@kev-m)
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Joined: 5 years ago
Posts: 1276
01/12/2021 5:55 pm  

@adaml 

it's really trial and error.  What you've suggested sounds OK;  see what happens. 



   
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 Derek M
(@derek-m)
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Joined: 5 years ago
Posts: 4425
01/12/2021 6:24 pm  
Posted by: @kev-m

@adaml 

I think @derek-m has done some more modelling on this.  Just to clarify; I'm looking at switching it off, not down, at night.  That's significantly diffferent.  I'll post some results/thoughts on my thread.   

Hi Adam,

I would suggest that you have a read through the manual, and see if there are parameters set, that limit the maximum and minimum water flow temperature that the ASHP can produce, if the minimum value is set too high it may be preventing you from lowering the weather compensation curve setting. If you have the Daikin indoor controller unit, it may be possible that this may automatically vary the water flow temperature for maximum efficiency, the manual should give more details on this.

I have attached a copy of the spreadsheet that I produced for Ecodan owners, whilst not for the Daikin it will still provide you with some idea of how the required water flow temperature varies with changes in ambient air temperature.

 

Ecodan 14kW ASHP Data.xlsx


   
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 adaml
(@adaml)
Trusted Member Member
Joined: 4 years ago
Posts: 42
Topic starter 01/12/2021 7:17 pm  

@derek-m Thanks that is brilliant, I shall have a look at this. Thank you.



   
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