Many of the heat pump manufacturers allow the weather compensation curve to be tailored to a particular home, but Vaillant are one of the manufacturers that use predefined heat curves.

Weather compensation was developed to adjust the water flow temperature, in an attempt to keep the indoor air temperature reasonably constant, with changing outdoor air temperature. The degree by which the water flow temperature needs to be changed for each 1C change in outdoor air temperature is dependent upon the rate at which the heat energy leaks out of your home. This can vary under different weather conditions, sunny days increasing the indoor air temperature in some rooms due to solar gain, windy and/or rainy days causing additional heat loss. So plotting indoor air temperature and outdoor air temperature against water flow temperature will not necessarily produce a repeatable graph, but it should give some idea of how effective the selected heat curve is at maintaining the indoor air temperature at the desired value.

If your controller is located within the main living area, once you have achieved reasonably accurate control using solely weather compensation, the next step would be to enable adaptive control, which fine tunes the required water flow temperature to maintain the indoor air temperature at the desired setting. Even if the outdoor air temperature remains constant, if the indoor air temperature starts to increase, then the water flow temperature would be lowered slightly. The reverse action would take effect if the indoor air temperature started to reduce.

By all means collect the data and produce the graph, which I feel certain many, including myself, would be interested to see.

Hi Derek, just a wee query. Since I have Flow temperatures and outside temperatures at 2 min intervals, if I plot these  on a graph, if the weather compensation is working properly and the internal temperature is either 21 or setback 18, should the resulting graph map onto the 0.80 heat curve the system is set to?

Hi Newbie,

I don't seem to be able to access the private message that you sent yesterday evening, and for some reason I am not being notified of their existence. Can send your message again and remind me how your system is set to operate at the moment.

@derek-m thank you sorry again for being such a pain.

Hi Duncan,

You are not being a pain.

I have spent most of my career problem solving, which I find most enjoyable. 😀 

@derek-m sorry I cant seem to see the attachment you mentioned

Hi Duncan,

That's because I forgot to attach it. 🙄 

@derek-m Would the COP be lower if the radiator pipework running through a cold area doesn't have enough insulation ?

Hi Newbie,

It depends if the pipework is within the internal area of the building and hence helping to provide heat energy, or if it is say underneath the downstairs floorboards or in the loft, then it may create additional heat demand. The greater the heat demand, the harder the heat pump has to work, and the lower that the overall COP will be.