I don't understand how temperature is regulated with my ASHP

Redlander

I have a Vaillant aroTherm Plus 5kW heat pump and a SensoComfort 720f thermostatic controller.

The SensoComfort has a control called a heat curve which determines my system's flow temperature for any given outside temperature.

But there is also a control to set the desired ambient temperature.

What I don't understand is the relationship between these two controls. I can see that the Heat Curve determines what the flow temperature will be, and I presume that the flow temperature determines the ambient temperature.

But if I desire a different ambient temperature, this surely requires a different flow temperature from the temperature specified by the Heat Curve. So it looks as if the Heat Curve is only true for one ambient temperature. Is that the case? 

Fatferds12

There's also a very helpful Facebook group for Vaillant air source heat pumps you may find useful
https://www.facebook.com/groups/488794632317506/

Netexporter

You might find this video helpful:

Just Set Your Heat Pump Curve to 40 Degrees!

Vitor

Your SensoComfort isn’t running two competing controls. The heat curve is the primary setting that tells the system what flow temperature to use for any outdoor temperature. The room-temperature set-point doesn’t override that curve, it only applies a small offset up or down. In practice you tune the heat curve so that, on continuous operation, the house naturally settles near your set indoor temperature. If it runs a bit cool, you raise the curve; if it overshoots, you lower it. The room setting then just trims things. Weather compensation works best when the curve does most of the work.

koru

What Vitor describes is correct assuming you have your heating set to "inactive". In this mode, the sensocomfort is not acting as a thermostat at all. The system is purely delivering heat based on the heat curve and the difference in temperature between the actual outdoor temperature and the target indoor temperature.

But if it is set to "active" or "expanded", then your sensoCOMFORT also acts as a thermostat, so it turns off the heat for a while if the indoor temperature is overshooting and turns it up if it is under shooting. This potentially keeps the actual indoor temperature closer to the target, which can be helpful if the heat loss of your home fluctuates significantly on the basis of factors other than outdoor temperature. For instance, solar gain or strong winds. This can be beneficial, but it comes at the cost of your heat pump cycling on and off more frequently, which is less efficient than if you can find the exact right heat curve so that it constantly matches the heat loss.

In expanded, the moderating effect of the thermostat is heavier than in active mode.