3 ms·

"Modern A/C systems can pump heat at 500%+ efficiency even with very cold outside temperatures, no pre-heating needed." Name a source please.

pedrocr 6y ago
Here's a current R32 system by Daikin: https://www.daikin.co.uk/content/dam/dauk/document-library/data-sheet/ac/R32/r32_split/FTXA-AB%20(WSTB)%20RXA-AB_Datasheet_1067.pdf https://www.daikin.co.uk/content/dam/dauk/document-library/d... SCOP is at 5.15 and that's a seasonally adjusted value. So over the entirety of the winter the unit is expected to deliver 5.15 units of heat for each unit of energy. The unadjusted COP is 6.27. For this unit operational limits are listed at -15C/5F and I think there are units that go quite a bit lower. I haven't looked at that much as -15C is plenty for us. And this is with air to air. With air to ground much higher efficiencies are possible. For cooling it's even better, with the equivalent SEER at 8.75. The improvements have been so good that the efficiency scale is already at A+++ because the A standard has been so exceeded.
- Haemm0r 6y ago
  If you do not have temps below 0-5°C that might be true. Below the freezing point efficiency drops quite a bit.
  - pedrocr 6y ago
    "Name a source please" :) Keeping 5x over the entire winter includes some pretty cold nights. And ground source systems can improve even this by quite a bit.
    - Haemm0r 6y ago
      Nicely played :) Here we go: https://industrialheatpumps.nl/en/how_it_works/cop_heat_pump/ https://industrialheatpumps.nl/en/how_it_works/cop_heat_pump... or better this pic: https://www.researchgate.net/figure/Performance-map-of-the-heat-pump-showing-the-COP-as-a-function-of-ambient-temperature_fig2_261259472 https://www.researchgate.net/figure/Performance-map-of-the-h...
      - pedrocr 6y ago
        That seems to be for a 2006 Daikin model: > The heat pump model is based on linear interpolation in a performance map retrieved from manufacturer data (Daikin Europe N.V., 2006). And that model is half as good as the modern one I linked: > The nominal coefficient of performance (COP) is 3.17 at 2/35ºC and 2.44 at 2/45ºC test conditions (i.e. air/water temperature) for full load operation. And even then it gets a COP of 2 at -15C. So modern systems getting to at least 4 at -15C seems likely. This claims there are low ambient mini splits that maintain 100% efficiency down to -15C: https://www.ecomfort.com/stories/1341-Keeping-Your-Mini-Split-Working-Through-the-Winter.html https://www.ecomfort.com/stories/1341-Keeping-Your-Mini-Spli... That should cover most places but for really cold climates ground source heat pumps seem ideal. From what I've seen there are simple solutions where a single vertical hole is drilled with common well drilling machines and a single tube that has the loop inside is driven down. Makes it easier to retrofit and implement in small properties.

pedrocr 6y ago

Here's a current R32 system by Daikin: https://www.daikin.co.uk/content/dam/dauk/document-library/data-sheet/ac/R32/r32_split/FTXA-AB%20(WSTB)%20RXA-AB_Datasheet_1067.pdf https://www.daikin.co.uk/content/dam/dauk/document-library/d... SCOP is at 5.15 and that's a seasonally adjusted value. So over the entirety of the winter the unit is expected to deliver 5.15 units of heat for each unit of energy. The unadjusted COP is 6.27. For this unit operational limits are listed at -15C/5F and I think there are units that go quite a bit lower. I haven't looked at that much as -15C is plenty for us. And this is with air to air. With air to ground much higher efficiencies are possible. For cooling it's even better, with the equivalent SEER at 8.75. The improvements have been so good that the efficiency scale is already at A+++ because the A standard has been so exceeded.

Haemm0r 6y ago
If you do not have temps below 0-5°C that might be true. Below the freezing point efficiency drops quite a bit.
- pedrocr 6y ago
  "Name a source please" :) Keeping 5x over the entire winter includes some pretty cold nights. And ground source systems can improve even this by quite a bit.
  - Haemm0r 6y ago
    Nicely played :) Here we go: https://industrialheatpumps.nl/en/how_it_works/cop_heat_pump/ https://industrialheatpumps.nl/en/how_it_works/cop_heat_pump... or better this pic: https://www.researchgate.net/figure/Performance-map-of-the-heat-pump-showing-the-COP-as-a-function-of-ambient-temperature_fig2_261259472 https://www.researchgate.net/figure/Performance-map-of-the-h...
    - pedrocr 6y ago
      That seems to be for a 2006 Daikin model: > The heat pump model is based on linear interpolation in a performance map retrieved from manufacturer data (Daikin Europe N.V., 2006). And that model is half as good as the modern one I linked: > The nominal coefficient of performance (COP) is 3.17 at 2/35ºC and 2.44 at 2/45ºC test conditions (i.e. air/water temperature) for full load operation. And even then it gets a COP of 2 at -15C. So modern systems getting to at least 4 at -15C seems likely. This claims there are low ambient mini splits that maintain 100% efficiency down to -15C: https://www.ecomfort.com/stories/1341-Keeping-Your-Mini-Split-Working-Through-the-Winter.html https://www.ecomfort.com/stories/1341-Keeping-Your-Mini-Spli... That should cover most places but for really cold climates ground source heat pumps seem ideal. From what I've seen there are simple solutions where a single vertical hole is drilled with common well drilling machines and a single tube that has the loop inside is driven down. Makes it easier to retrofit and implement in small properties.