ᐅ Heating During Transition Periods, Wood / Solar Thermal / Domestic Hot Water Supply

Hello everyone,
in 2012 we built a KW house with 120 sqm (1,292 sq ft) of living space.
It is heated by a water-bearing 10 kW fireplace (air/water 40:60) and has a collector area of 10.5 sqm (113 sq ft). The water storage tank holds 1000 l (264 gallons).
In autumn, we experienced a situation where, due to the insulation and the ventilation system, the room temperature was kept at a comfortable level, but the solar energy was no longer sufficient to meet our hot water demand.
Heating with the fireplace then caused such a high room temperature throughout the house that we were basically forced to keep the windows open all day, which is obviously not ideal.
Installing an electric heating element in the water storage tank is not an option, as this would compromise the KW55 standard.

Does anyone have a tip or a technical solution for our problem? 😕 😕 😕

Greetings from the coast

Hello house manager,

Do I understand correctly that you have no other heat source besides the wood stove and the solar thermal system?
A solar thermal system is a heat source that cannot be controlled. When the sun is shining, thermal energy is produced; when it is not (or if the collectors are covered with snow), no energy is generated.
The wood stove is a heat source for air heating – the heating of water is just a byproduct. So regarding the hot water, it is not really controllable either...

In my opinion, you will have to add another heat source that can be regulated according to the hot water demand.
Which type of heat source makes sense in your case, I cannot judge. But it definitely needs to be controllable...

Sorry, but this is a planning mistake that would have been obvious to any heating specialist (no matter how little experience they might have)...
Who planned this system?

Regards
Micha 😎

Hello Micha,
we are already at that point! 🙂
It is actually true that the heating installer told me last autumn that the system cannot work as it is. He informed the builder about this, but as a client of the builder, he was unable to do anything.
The builder has since gone bankrupt, but all the companies involved in the construction have been keen to protect their good reputation and helped wherever they could.
The manufacturer of the fireplace calculated that we would have to run it at full capacity for about 9 hours daily to heat 1000 liters (264 gallons) of water to 60°C (140°F). At that rate, we could practically open a public sauna here.
We have basically decided to replace the fireplace with a pellet stove, but that would involve high costs.
So I am hoping someone here might have a clever idea to avoid that. 😕
Greetings from the coast

Hmm, I’m also just an amateur, but perhaps a small heat pump dedicated to domestic hot water heating could help in this case?

A small heat pump that heats an additional 200L (53 gallons) tank, which is responsible for domestic hot water and is hydraulically connected to the larger one. However, you will quickly spend several thousand euros. The heat pump does not heat the 1000L (264 gallons) tank "cheaply."

Hello!

I haven’t quite understood the purpose of the 1000 l (264 gallon) tank yet – basically, I would have recommended replacing the tank with a smaller one of 200 liters (53 gallons). However, that doesn’t really help when there is no sun and the apartment is already warm.

In theory, you could add an instantaneous water heater after the tank – whether that is practically feasible, though…

Best regards,
TomTom1