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Running ASHP efficiently, general thought process. (Low and slow)

 
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Air Source Heat Pumps (ASHPs)
Last Post by SUNandAIR 9 months ago
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 Boycey
(@boycey)
Trusted Member Member
Joined: 9 months ago
Posts: 37
Topic starter 27/12/2024 6:14 pm  

UFH and 5kw Mitsibushi ecodan system, weather comp in a modern 2 bed flat.  Am i thinking correctly  by setting my heating system (via weather comp and flow rates) so its calling for heat most of the time during the day and to not quite getting to the thermostat setting?  I've set it so the room temp it's sitting at is a comfortable 20.5deg and stats about 1deg higher, does this sound like the correct scenario for efficiently running the above? It's on this from 6am to 9pm then set back 1 deg. HW is on twice a day 1pm and 11pm for tank at 49C. 

Regards Boycey


This topic was modified 9 months ago by Mars

   
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Ecodan mitsibushi ashp
bontwoody
 bontwoody
(@bontwoody)
Noble Member Contributor
Joined: 4 years ago
Posts: 859
28/12/2024 1:22 pm  

Sounds perfect 🤩 


House-2 bed partial stone bungalow, 5kW Samsung Gen 6 ASHP (Self install)
6.9 kWp of PV
5kWh 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: 3443
28/12/2024 3:36 pm  

@boycey, welcome to the forums. It sounds like you’ve set everything up really well. Are the rooms feeling warm and cosy? If so, take a look at your SCOP to ensure you’re achieving this efficiently. Anything over 3 is a good indicator that you’re on track for efficient operation. Keep us updated.


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 JohnnyB
(@johnnyb)
Estimable Member Member
Joined: 9 months ago
Posts: 51
28/12/2024 4:54 pm  

I have a Samsung unit in a new build house and it seems to use more energy if I run it really low and slow. When it first went in, only about a month ago, I had the weather compensation was set so the water leaving temperature was around 25° most of the time with an indoor temperature of 20-21° 

Setting the weather compensation so the WLT is about 30-35° is more efficient for my system at the moment, but the temperature indoors isn't as consistent as the heating isn't on much, especially at the moment with it being warm for December.



   
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 Boycey
(@boycey)
Trusted Member Member
Joined: 9 months ago
Posts: 37
Topic starter 28/12/2024 4:57 pm  

@editor Hi Mars, on the ecodan FTC6 it shows consumed for Dec 148kwh delivered 388 kwh. So is that a COP or SCOP? Of 2.65? So not very good? How could I improve this. I think my delta T is low, (if that's the difference in flow temp and return) it's about 3. Only been with this system since Oct so lots of learning



   
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Toodles
 Toodles
(@toodles)
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Joined: 3 years ago
Posts: 2096
28/12/2024 5:30 pm  

@johnnyb Perhaps adjustments to the WC curve so as to raise the LWT to approx 30 degrees might be worth a try? It is a cat and mouse game of course due to all the variables but it sounds as though your original 25 degrees was just a little too low and the 35 too high? Regards, Toodles.


This post was modified 9 months ago by Toodles

Toodles, he heats his home with cold draughts and cooks his food with magnets.


   
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 Boycey
(@boycey)
Trusted Member Member
Joined: 9 months ago
Posts: 37
Topic starter 28/12/2024 6:19 pm  

@toodles hi, I think you may of mis understood my post, I'm happy with my temps atm, and I'm monitoring them as the oat getting nearer 0C and will tweak as needed. My post was, am I thinking right, aiming to keep the third party stats above the obtainable room temp so they are always calling for heat, ie so the loops are all open and flow temp is just right to keep rooms at, for example 20.5c or whatever the comfortable level is for any one using this thought process. If one can get the weather comp curve just right, the ufh will continually run just the right flow temp, ie low and slow.. is this the right way to try and run my heat pump.



   
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 JamesPa
(@jamespa)
Illustrious Member Moderator
Joined: 2 years ago
Posts: 2885
28/12/2024 6:47 pm  

Posted by: @boycey
↑

.. is this the right way to try and run my heat pump.

Basically yes!


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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 Judith
(@judith)
Prominent Member Member
Joined: 2 years ago
Posts: 389
28/12/2024 7:38 pm  

@boycey The only added wrinkle for your flat is that 5kW is a lot for a 2bed flat so your pump perhaps could be on for less time. UFH often has a “long time constant” so it will stay warm for a while after the heating switches off. Low and slow is certainly ideal, but you might be able to drop your overnight set back to less for example. 
What electric tariff are you one you might be able to use cheaper periods only as a further example?

Are you a newer build or a refurbished older building?


2kW + Growatt & 4kW +Sunnyboy PV on south-facing roof Solar thermal. 9.5kWh Givenergy battery with AC3. MVHR. Vaillant 7kW ASHP (very pleased with it) open system operating on WC


   
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 Boycey
(@boycey)
Trusted Member Member
Joined: 9 months ago
Posts: 37
Topic starter 28/12/2024 7:58 pm  

@judith ĥi, I managed to get on to Ovos limited trial for their heat pump tarrif, 15p  a unit for all heat pump consumption. It's a new build apartment.



   
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 JohnnyB
(@johnnyb)
Estimable Member Member
Joined: 9 months ago
Posts: 51
29/12/2024 12:35 am  

@toodles I have been trying different temperatures and trying to get a balance between comfort and efficiency, but haven't got there yet!

I commented as I have a similar situation, small heat pump in a new build with UFH, and I can run the flow temperatures very low because the heat loss is very low, but it seems that not all heat pumps are as efficient at really low temperatures so it may be worth experimenting with higher temperatures to see what works best. Most people seem to require a lot higher flow temperature to keep the house warm but if the floor holds the temperature for a long time and releases it slowly having the heating on for less hours per day, but still maintain a constant temperature, might work out more cost effective. It seems to be helping my electricity consumption, but it has also been a bit warmer and less windy the last week or two.



   
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Toodles
 Toodles
(@toodles)
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Joined: 3 years ago
Posts: 2096
29/12/2024 10:02 am  

@johnnyb Where is the ‘envious’ emoticon? Toodles.


Toodles, he heats his home with cold draughts and cooks his food with magnets.


   
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