7511 Gas fired boilers (3) Gas fired boilers supplying heat, using oil, steam or hot water as the heating medium 7512 Oil fired boilers (3) Oil fired boilers, supplying heat using oil, steam or hot water as the heating medium 7513 Gas and oil fired boilers (1) Boilers designed to use dual fuels as the heat source, using oil, steam or hot water as the heating medium 7514 Coal fired boilers (1) Coal fired boilers supplying heat, using oil, steam or hot water as the heating medium 7515 Electrode boilers (0) Electrode boilers supplying heat using oil, steam or hot water as the heating medium 7516 Wood fired boilers (1) Wood fired boilers supplying heat, using oil, steam or hot water as the heating medium 7517 Alternative fuel boilers (2) Boilers designed to burn peat, straw, waste or similar fuels, supplying heat, using oil, steam or hot water as the heating medium 7518 Packaged steam generators (0) Packaged steam generators providing heat to user points by means of a heat distribution system, using a selected type of energy source