EN 15502-2-3:2023

Gas-fired central heating boilers - Part 2-3: Specific standard for hybrid units combining a gas-fired boiler and an electrical heat pump in a product EN 15502-2-3:2023

Publication date:   Dec 14, 2023

General information

60.60 Standard published   Sep 14, 2023


CEN/TC 109 Central heating boilers using gaseous fuels

European Norm

27.060.30   Boilers and heat exchangers | 91.140.10   Central heating systems



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This document specifies the requirements and tests methods concerning the construction, safety, fitness for purpose, and rational use of energy, as well as the classification and marking of hybrid units.
A hybrid unit is composed of:
- a gas boiler as a heat generator which is able to supply the heat demand in all operating conditions;
- an electrical air-to-water heat pump, as a heat generator, which does not have to meet the heat demand in all operating conditions;
- a control unit (see definition 3.1.10).
A hybrid unit can include the facility to produce hot water, either by the instantaneous or storage principle, the whole being marketed as a single unit.
A gas boiler as part of a hybrid unit covered by this document is a gas-fired central heating boiler from the types C1 up to C9 and the types B2, B3 and B5, according to the classification in EN 1749:2020:
a) that have a nominal heat input (on the basis of gross calorific value) not exceeding 400 kW;
b) that use one or more combustible gases of the three gas families at the pressures stated in EN 437:2021;
c) where the temperature of the heat transfer fluid does not exceed 105 °C during normal operation;
d) where the maximum operating pressure in the water circuit does not exceed 6 bar;
e) which are classified as a gas-fired central heating boiler;
f) which are intended to be installed either indoors or outdoors in a partially protected place;
g) which are designed for either sealed water systems or for open water systems.
This document provides requirements for boilers with known constructions.
NOTE 1 For boilers with any alternative constructions, which might not fully be covered by this document, the risk associated with this alternative construction needs to be assessed.
NOTE 2 An example of an assessment methodology, based upon risk assessment and which covers the essential requirements of the Gas Appliance Regulation UE/426/2016, is given in Clause 11.
This document does not cover all the requirements for:
aa) appliances that are intended to be connected to gas grids where the quality of the distributed gas is likely to vary to a large extent over the lifetime of the appliance (see EN 15502-1:2021, Annex AB);
ab) appliances using flue dampers;
ac) appliances of the types B21, B31, B51, C21, C41, C51, C61, C71 and C81;
ad) appliances incorporating flexible plastic flue liners;
ae) appliances designed to become connected to a combined flue duct system.
af) appliances of the types C(10),C(11), C(12) and C(13);
ag) C7 appliances that have a nominal heat input (on the basis of net calorific value) exceeding 70 kW;
ah) appliances intended to be connected to a flue having mechanical extraction;
ai) surface temperatures of external parts particular to children and elderly people;
aj) appliances that are intended to burn natural gases of the second family where hydrogen is added to the natural gas;
ak) appliances equipped with an adaptive combustion control function (ACCF);
al) boilers intended to be installed in areas accessible to elderly people and children.
This document specifies minimum operating requirements which ensure that the products are fit for the use designated by the technical instructions when used for space heating and/or DHW production.
This document is intended to be used in conjunction with:
ba) the gas-fired boiler, the generic part EN 15502-1:2021 and specific parts FprEN 15502-2-1:2022 and FprEN 15502-2-2:2022;
bb) the electrical heat pump, EN 14511-4:2018, EN 378-1:2016+A1:2020, EN 378-2:2016 and EN 14825:2022;
bc) electrical safety, EN 60335-1:2012 , EN 60335-2-102:2016 and IEC 60335-2-40:2018;
bd) for domestic hot water production, EN 13203-5:2022.

Related legislation

Legislation related to this standard


Efficiency requirements for new hot-water boilers fired with liquid or gaseous fuels


Commission Delegated Regulation (EU) No 811/2013 of 18 February 2013 supplementing Directive 2010/30/EU of the European Parliament and of the Council with regard to the energy labelling of space heaters, combination heaters, packages of space heater, temperature control and solar device and packages of combination heater, temperature control and solar device


Commission Regulation (EU) No 813/2013 of 2 August 2013 implementing Directive 2009/125/EC of the European Parliament and of the Council with regard to ecodesign requirements for space heaters and combination heaters


REGULATION (EU) 2016/426 OF THE EUROPEAN PARLIAMENT AND OF THE COUNCIL of 9 March 2016 on appliances burning gaseous fuels and repealing Directive 2009/142/EC

Life cycle


EN 15502-2-3:2023
60.60 Standard published
Sep 14, 2023