Most Efficient Use of ASHP

[PeterW]

1 hour ago, joe90 said:

generally warmer (more heat available in the air?) but was told the difference in night and day air temps did not affect efficiency. Was/is this correct?

it is per K not °C above zero so the difference between 4°C and 8°C for example isn’t 100% more it is the difference between 277°K and 281°K which is 1.5%... 

 

The key is load shifting and being able to “store” the heat. UFH is good at this, radiators and building fabric less so due to heat capacity of air vs heat capacity of concrete etc. 

[J1mbo]

3 hours ago, PeterW said:

it is per K not °C above zero so the difference between 4°C and 8°C for example isn’t 100% more it is the difference between 277°K and 281°K which is 1.5%... 

 

The key is load shifting and being able to “store” the heat. UFH is good at this, radiators and building fabric less so due to heat capacity of air vs heat capacity of concrete etc. 

 

Surely it would be relative to the evaporation temperature, e.g. about -40*C for R290 IIRC. So 44 and 48, or 10% in that case.

[SteamyTea]

4 minutes ago, J1mbo said:

 

Surely it would be relative to the evaporation temperature, e.g. about -40*C for R290 IIRC. So 44 and 48, or 10% in that case.

It is a combination of all the factors. It is why CoP is used, it is more useful as an overall measure.