What is viessmann f2?

As an AI language model, I cannot confirm an accurate answer to this question as there is no context provided in regards to viessmann f2.

However, if it refers to the Viessmann Vitodens 200-W F2, it is a gas condensing wall-mounted boiler made by the German manufacturer Viessmann. The boiler features 98% efficiency, compact design and low noise levels. It is suitable for both residential and commercial applications and has modulation range up to 1:17 that ensures lower energy consumption.