The starting point In winter, the oil lines frequently froze. Apart from that, the oil consumption was very high, making operation uneco- nomical, so the operator regarded renovation as inevitable. It was therefore decided to avoid these problems with a modern gas system. Liquid gas was already being used for cooking in the castle, and as there was no connection to the natural-gas mains, this was the obvious choice of fuel. In addition, a number of regulations for listed buildings had to be taken into account. The new system As part of the development of the casemate (a vault in the fortress wall) the administrators of the Castle of Hohenzollern decided to modernise the heating system with ELCO. The heart of the new heating solution is the TRIGON L. This is suitable for renovation projects or for use in commercial and public buildings. A high modulation ratio ensures an optimum stan- dard efficiency factor of 111 %. The TRIGON L has convenient, fully electronic, weather-dependent controls and a pre-mix burner. A tremendous advantage is its light weight, which made delivery and set-up quick and easy, even in this case with the unusual, historic interior. Equipment Boiler Total power Renovation: Castle of Hohenzollern From frozen oil lines to reliable gas condensing heating solution New system TRIGON L 19.7-96.3 kW 111.0 % 1:5 Equipment Boiler Rated power Standard efficiency factor Modulation Old system One 30-year-old oil-fired boiler with oil fan burner 160 kW