Vaillant 7kw hot water always beats heating for scop

[iapainter (Ian)]

Adam,

I’m assuming you mean the Vaillant reported COP in the MyVaillant App rather then an OEM calculated COP. If so have a look at this thread:

Why doesn't a low flow temp translate into a decent COP

I have a Vaillant Aerotherm Plus 10kW + 250L UniStor Cylinder with a designed flow of 40C @ -2.3C outside. The house is a modern 5 bed house, excellent insulation with UFH throughout over 3 floors. The system is an open loop system, weather compensated with no buffer. I’m able to monitor the system from the Vaillant App and the MyVaillant Integration with Home Assistant. I’ve had the heat pump installed for 4 months now. I’m able to keep the house warm at a constant 20C with a 0.35 Heating Curve…

and follow the instructions in this part for checking if your Vaillant flow and return sensors are mis-reporting

Why doesn't a low flow temp translate into a decent COP

You’ll need some moderate weather when the heat pump has to cycle because it cannot modulate low enough. The fans out the outside unit will turn off and the compressor stops for some time, while the water is still kept circulating, and that’s when you’ll want to look at the temperatures. Alternatively, you could temporarily set a significantly lower target temperature on your controller, e.g. 15°C instead of the typical 20°C. As your system is still running at the required flow temperature for t…

As the thread describes it’s a really common problem with Vaillant Aerotherm systems. That said in theory you should also see that on you hot water too. MyVaillant App is misreporting my COP by over 33% due to temp sensor issues

Ian