The aim of my diplom thesis is the design of heat source for residential house with use of condensing technology. The residential house is situated in city district of Bratislava -- Podunajské Biskupice. Property of the residential house consist of ten overground and two underground floors, in which are sheltered parking spaces. Heat source -- gas boiler of II. category is located on the first overground floor. In the boiler room are installed two condesing boilers and one low temperature boiler with total installed thermal input of 701 kW. Horizontal lines are ducted under ceiling of the first overground floor hidden in lower ceiling. The heater system consists of conventional heater blocks in temperature gradient 70/50 °C. Preparation of warm water is solved as combinated heater system. Due to the height of the building is preparation of warm water divided into two pressure zones. The first pressure zone supplies with hot water store tank with a capacity of 750 liters, which is located in the boiler room. The second pressure zone supplies with hot water store tank with a capacity of 300 liters, which is located in technical room on the 10th overground floor. Part of the diplom thesis is complete design of heat source with accessories including drawing documentation in form of implementation project.