This standard applies to the application design and installation of electrical equipment, control circuits and protective systems for furnaces which are operated with solid, liquid or gaseous fuels and their ancillary equipment. It specifies requirements to meet the operating conditions of furnaces, to reduce the hazards of combustion and to protect the heated systems from damage e.g. by overheating. Such furnaces and the electrical equipment may be part of the following plants for example: a) Water heating systems b) Steam boiler installations (steam and hot-water boilers) and heat recovery steam boilers