Heat pump is not compatible with a water-bearing fireplace

I am a layman and will try to explain. Please don’t take it too seriously. I don’t know much about heat pumps.

You have a buffer tank with a heating element, a supply and return for the fireplace, a supply and return for the heat pump.

You take your hot water from part of the buffer tank. The hot water should be at least 55, preferably 65 degrees.

When do you heat the fireplace? Surely not at 20 degrees outside temperature. What if, like today, there is no sun and the photovoltaic yield is almost zero.

Theoretically, everything sounds good. I would have installed the hot water generation and the heat pump separately. Technically, your hot water production works like a flow heater. So today your hot water is generated electrically. I suppose the heat pump tries to generate the hot water as well.

I think there are problems here with the control, priority switching, etc.

Your buffer tank consists of 3 parts: the heating water storage, the solar heat exchanger, and the domestic hot water heat exchanger.

It is surprising that your domestic hot water heat exchanger only has a volume of 56 liters. The solar heat exchanger only has a capacity of 17 liters. There should be two heating elements installed, each with 9 kW. So if your hot water is heated on demand, the electricity meter runs at 18 kW. You probably have a cheap electricity provider. Or you shower little.

The fireplace only heats into the heating circuit. The heat pump supply will always keep the water at 35 degrees supply temperature. And you have 250 sqm of living space. The water will cool down by more than just 5 degrees. When I heat with 50 degrees supply, about 20 degrees return comes to the oil heating. The heat in the house has to come from somewhere, and underfloor heating is only a big heat exchanger.

8 kW heating capacity of the fireplace is very little with water heating as well.

At least you were clever enough to have a fireplace installed. Many don’t have that. When I come home frozen from skiing in winter, I want to sit by a warm fireplace or at least a hot radiator and not in a minimally tempered house. People get old, I am old enough and can very well decide how I heat. I don’t need green moral preachers telling me that you can fly somewhere for 50 euros but I have to save the world’s climate with my heating. No thanks.

Can you imagine it more easily if you simply take 5x 5 degrees from the storage? So in principle, with each complete pass through the screed, 5 degrees are missing in the storage. Of course, this is not stepwise but a continuous process, but heat is transferred from the storage to the screed continuously. 1t water storage to 30t screed. That means approximately (simplified), if I cool the storage by 30 degrees, the screed has only warmed up by one degree.

That is certainly too high consumption. Basically, combining it with a fireplace in a new build is rather questionable (due to far too high heat output). Having water-based heating makes things more complicated, as now two heat sources operate at different ends of the spectrum. The error is certainly to be found in a control system here.

Thank you for the clear explanation. I understood that. So you mean everything is running correctly with us?

And we are supposed to be satisfied with a power consumption by the heating in winter averaging 65 kW per day despite firing the stove with 10 m3 of wood in the season? Is that normal? Well, I don't know...