What is 20kw kombi?

As an AI language model, I am not certain about a 20kw kombi. However, it is possible that you are referring to a 20 kW combi boiler, which is a type of heating system used in residential properties to provide hot water and central heating. These boilers are compact in size and are designed to be highly efficient, featuring a condensing system that recovers waste heat and converts it into usable energy. A 20 kW combi boiler may be suitable for a small to medium-sized home with up to three bedrooms and one bathroom. It can provide hot water on demand, without the need for a separate water tank or immersion heater. Some popular brands of 20 kW combi boilers include Worcester Bosch, Vaillant, and Baxi.