Hot-water Boilers Directive Explained


This Directive, which comes under the SAVE programme concerning the promotion of energy efficiency in the Community, determines the efficiency requirements applicable to new hot-water boilers fired by liquid or gaseous fuels with a rated output of no less than 4 kW and no more than 400 kW, hereinafter called 'boilers'.


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.


1. The following shall be excluded from this Directive:

- hot-water boilers capable of being fired by different fuels including solid fuels,

- equipment for the instantaneous preparation of hot water,

- boilers designed to be fired by fuels the properties of which differ appreciably from the properties of the liquid and gaseous fuels commonly marketed (industrial waste gas, biogas, etc),

- cookers and appliances designed mainly to heat the premises in which they are installed and, as a subsidiary function, to supply hot water for central heating and sanitary hot water,

- appliances with rated outputs of less than 6 kW using gravity circulation and designed solely for the production of stored sanitary hot water,

- boilers manufactured on a one-off basis.


2. In the case of boilers with a dual function, that of heating premises and also providing sanitary hot water, the efficiency requirements referred to in Article 5 (1) concern the heating function only.