ᐅ Upgrading Viessmann Vitolig 200 Wood Boiler with Solar Thermal System

Hello everyone,

In our purchased house, we have a Viessmann Vitolig 200 wood heating system with approximately a 2000-?? liter buffer tank; unfortunately, I cannot determine the exact capacity of the buffer.

I can’t find the information on the nameplate (or is it 750 liters (198 gallons)?) and Google isn’t helpful either. See the attached image of the nameplate.

The system is from 2006 and heats an uninsulated house (the roof insulation is now being added) built in 1909 with about 180 square meters (1940 square feet) of living space.

We want to install a solar thermal system to support and ease the heating operation. It should assist both the heating and hot water supply. The roof has a 45-degree south-west orientation with no shading.

We have come across the company Volkssolar, which offers a water-based system. To qualify for the maximum subsidy, they recommend 30 square meters (323 square feet) of solar collectors, which would cost us approximately €5500 (without installation).

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

Volkssolar? A company that names itself like that is only after one thing: your money. Go to the local plumber and heating technician. With an older house, you need a good customer relationship anyway. Preferably the one who installed the Viessmann system back in 2006… there’s probably a sticker from them somewhere. That’s how they do it. They mark their territory, like cats. Karsten

That would also be my preferred option, but I haven’t found anything yet. However, I now know that the maximum is 728 liters (193 gallons) per buffer. The company Citrin investigated. Good customer service.

On Monday, I will be at the house and continue searching. The roofer and local electrician will also be there, and they might have the name of the installer.

First, carefully assess the existing conditions, and as mentioned before, it’s best to consult with the person who originally installed the system.

Solar thermal for domestic hot water is usually not a big issue. In summer, you generally have so much hot water that you don’t know what to do with it. During transitional seasons, depending on the weather, it’s always a mix of both.

I would think twice about using solar for space heating. First, you need to have a good control system when integrated with your heating, and second, consider how much solar actually supports the heating system during winter.

Heating with solar energy is like using refrigerators in Alaska. If solar energy is effective, you don’t heat; you heat when solar energy barely provides anything. I also need hot water from April to September, during which time solar alone covers it. Our heating system has been off since around Easter. The water is almost too hot in midsummer.

Okay, then only for the domestic hot water. Would you connect it to the existing buffer tanks, or keep it completely separate?

Do you have experience with how long a buffer tank can retain heat? Our concern is to avoid having to fire up the heating just for a few hours in the morning and evening.