Upgrade Viessmann Vitolig 200 wood with solar thermal

Hello everyone,

In our purchased house, we have a Viessmann Vitolig 200 wood heating system with approximately 2000- ??buffer storage, I unfortunately cannot tell how many liters the buffers have.

I do not find the information on the nameplate (or is it 750l) and Google does not help either. See picture of the nameplate.

The system is from 2006 and heats an uninsulated house (the roof is now being insulated) from 1909 with approximately 180 sqm of living space.

We want to install a solar thermal system for support and to make work easier. It should support heating and hot water. The roof has a 45-degree south/west orientation and no shading.

We ended up with the company Volkssolar, which is water-based, and to get the maximum funding, they recommend (thanks to the large buffer) 30 sqm, which would cost us about €5500 without installation.

What do you think? Does that make sense? Which systems can you recommend?

Volkssolar? Whoever names their company like that only wants your best: money. Go to the plumber and heating engineer around the corner. With an old house, you need a customer relationship anyway. Best the one who installed the Viessmann. 2006... there is surely a sticker from him somewhere. That's how they do it. Territorial behavior, they are like cats. Karsten

That would be my preference as well, but I haven't found anything yet. However, I now know that the maximum is 728L per buffer. Company citrin has investigated. Good customer service. On Monday I will be at home and continue my search. Then the roofer and local electrician will also come; perhaps they have the name of the installer.

First, calmly take stock and as already mentioned, ideally with the person who originally installed the whole thing.

Solar for hot water is usually not a big deal. In summer, you simply have so much hot water that you don’t even know what to do with it. In the transitional season, depending on the weather, it’s always a combination of both.

I would think twice about heating with solar. First, you need to get a good control system in connection with the heating, and second, how much does solar really support the heating in winter?

Heating with solar is like refrigerators in Alaska. If solar does something, you don’t heat; you heat when solar hardly produces anything. I also need hot water from April to September; during that time, solar alone provides it. Our heating has been off since around Easter. The water is already almost too hot in midsummer.

okay, then only for the domestic hot water. Would you connect it to the existing buffer tanks, or run it completely separate? Do you have experience with how long a buffer can retain the heat? We wanted to avoid having to fire up the heating just for a couple of hours in the morning and evening.