<b>Heating Systems</b> Living rooms and lounges, but also work rooms on ships must be heated which can be done by means of an air conditioning system. If an air conditioning system is not provided, the required temperatures must be generated in another way. In particular, the heat from the cooling water circuit of the main engine or the heat from the exhaust gas from the main engine can be used for heating purposes while driving. But hot water and the possibility of room heating must also be available during the lay times at anchor or at the pier. In addition, various types of heating systems are used, from normal hot water heating systems with an oil-fired boiler to electric heating, steam heating or warm air heating. Which system is chosen essentially depends on the overall electrical and heat balance of the ship. The heating systems can also be used to heat the domestic water required for washing and showering. All heat generators have one thing in common: they use the heat of an open flame or the waste heat from other systems to heat water. The flame is surrounded by a heat exchanger through which the water flows. The heat exchangers in the boiler should be as large as possible in relation to the combustion output (that is approximately the heat output of the flame). This ensures that the combustion air of the flame is very strongly cooled. Low exhaust gas temperatures ensure that the water in the exhaust gas condenses. The desired effect is called condensing technology.