Article 2
For the purposes of this Directive: - boiler: the combined boiler body-burner unit, designed to transmit to water the heat released from burning, - appliance: - the boiler body designed to have a burner fitted, - the burner designed to be fitted to a boiler body, - effective rated output (expressed in kW): the maximum calorific output laid down and guaranteed by the manufacturer as being deliverable during continuous operation while complying with the useful efficiency indicated by the manufacturer, - useful efficiency (expressed in %): the ratio between the heat output transmitted to the boiler water and the product of the net calorific value at constant fuel pressure and the consumption expressed as a quantity of fuel per unit time, - part load (expressed in %): the ratio between the effective output of a boiler operating intermittently or at an output lower than the effective rated output and the same effective rated output; - average temperature of the boiler water: the average of the water temperatures at the entry and exit of the boiler, - standard boiler: a boiler for which the average water temperature can be restricted by design, - back-boiler: a boiler designed to supply a central-heating system and to be installed in a fireplace recess as part of a back boiler/gas fire combination, - low-temperature boiler: a boiler which can work continuously with a water supply temperature of 35 to 40o C, possibly producing condensation in certain circumstances, including condensing boilers using liquid fuel, - gas condensing boiler: a boiler designed to condense permanently a large part of the water vapour contained in the combustion gases, - boiler to be installed in the living space: a boiler with an effective rated output of less than 37 kW, designed to provide heat to the part of the living space in which it is installed by means of the emission of heat from the casing having an open expansion chamber, supplying hot water using gravity circulation; such boilers shall bear on their casings the explicit indication that they must be installed in living space.