oSIST prEN 26:2026

Gas-fired instantaneous water heaters for the production of domestic hot water

This document defines the specifications and test methods and also the classification, marking and energy labelling of gas-fired instantaneous water heaters for sanitary uses, hereafter called “water heaters”.
This document applies to water heaters:
-   of types A, B and C as described at the appropriated clauses;
NOTE   For more information on the configuration of the types of appliances, see EN 1749:2020.
-   using one or more combustible gases corresponding to the three gas families and at the pressures stated in accordance with EN 437:2021;
-   of nominal heat input not exceeding 77 kW based on the gross calorific value (GCV);
-   with an ignition burner or with direct ignition of the main burner.
In this document, the heat inputs are expressed in relation to the net calorific value (Hi).
This document does not contain all the requirements necessary for:
-   boiling water appliances;
-   appliances intended to be connected to a mechanical means of evacuating the combustion products;
-   appliances which fulfil a dual role of space heating and heating water for sanitary use.
This document only covers water heaters where the fan, if any, is an integral part of the appliance.
This document is not intended to cover appliances designed and constructed to burn gas containing toxic components.

Gasbeheizte Durchlauf-Wasserheizer für den sanitären Gebrauch

Dieses Dokument legt die Spezifikationen und Prüfverfahren sowie die Klassifizierung, Kennzeichnung und Energieeffizienzkennzeichnung von gasbeheizten Durchlauf-Wasserheizern für den sanitären Gebrauch, im Folgenden als "Wasserheizer" bezeichnet, fest.
Dieses Dokument ist anwendbar für Wasserheizer:
-   der Typen A, B und C, wie jeweils in den entsprechenden Abschnitten beschrieben;
ANMERKUNG   Für weitere Informationen zur Konfiguration der Gerätearten siehe EN 1749:2020.
-   die in Übereinstimmung mit EN 437:2021 ein oder mehrere brennbare Gase der drei Gasfamilien und die angegebenen Drücke verwenden;
-   mit einer Nennwärmebelastung bis höchstens 77 kW basierend auf dem Brennwert (GCV, en: gross calorific value);
-   mit einem Zündbrenner oder direkter Zündung des Hauptbrenners.
In diesem Dokument werden die Wärmebelastungen auf den Heizwert (Hi) bezogen.
Dieses Dokument umfasst nicht alle notwendigen Anforderungen an:
-   Kochwassergeräte;
-   Geräte, die für den Anschluss an eine mechanische Abführung der Abgase vorgesehen sind;
-   Geräte, die eine Doppelfunktion von Raumheizern und Warmwasserbereitung für den sanitären Gebrauch erfüllen.
Dieses Dokument behandelt nur Wasserheizer, bei denen, falls vorhanden, das Gebläse ein integraler Bestandteil des Gerätes ist.
Dieses Dokument ist nicht für die Abdeckung von Geräten vorgesehen, die dafür ausgelegt und gebaut wurden, Gas mit toxischen Komponenten zu verbrennen.

Appareils de production instantanée d'eau chaude pour usages sanitaires utilisant les combustibles gazeux

Le présent document définit les spécifications et méthodes d'essais, ainsi que la classification, le marquage et l'étiquetage énergétique des appareils de production instantanée d'eau chaude pour usages sanitaires utilisant les combustibles gazeux, désignés ci-après « chauffe-eau ».
Le présent document s'applique aux chauffe-eau:
-   de type A, B et C décrits aux articles appropriés;
NOTE   Pour plus d'informations sur la configuration de ces types d'appareils, voir l'EN 1749:2020.
-   utilisant un ou plusieurs combustibles gazeux correspondant aux trois familles de gaz et aux pressions indiquées conformément à l'EN 437:2021;
-   de débit calorifique nominal inférieur à 77 kW, sur la base du pouvoir calorifique supérieur (PCS);
-   avec brûleur d'allumage ou à allumage direct du brûleur principal.
Dans le présent document, les débits calorifiques sont exprimés par rapport au pouvoir calorifique inférieur (Hi).
Le présent document ne contient pas toutes les exigences nécessaires pour:
-   les appareils à eau bouillante;
-   les appareils destinés à être connectés à des moyens mécaniques d'évacuation des produits de combustion;
-   les appareils qui remplissent une double fonction de chauffage des locaux et de production d'eau chaude sanitaire.
Le présent document couvre uniquement les chauffe-eau où le ventilateur, le cas échéant, fait partie intégrante de l'appareil.
Le présent document n'a pas pour objet de couvrir les appareils conçus et construits pour brûler du gaz contenant des composants toxiques.

Pretočni plinski grelniki vode za pripravo tople sanitarne vode

Ta dokument določa specifikacije in preskusne metode ter tudi razvrstitev, označevanje in energetsko označevanje plinskih pretočnih grelnikov vode za sanitarne namene, v nadaljevanju imenovanih "grelniki vode".
Ta dokument se nanaša na grelnike vode:
- tipov A, B in C, kot je opisano v ustreznih členih;
OPOMBA Za več informacij o konfiguraciji tipov naprav glejte EN 1749:2020.
- ki uporabljajo enega ali več gorljivih plinov, ki ustrezajo trem plinskim družinam in pri tlakih, določenih v skladu z EN 437:2021;
- z nazivno toplotno močjo, ki ne presega 77 kW na osnovi višje kurilne vrednosti (GCV);
- z vžigalnim gorilnikom ali z neposrednim vžigom glavnega gorilnika.
V tem dokumentu so toplotne moči izražene glede na nižjo kurilno vrednost (Hi).
Ta dokument ne vsebuje vseh zahtev, potrebnih za:
- naprave za kuhanje vode;
- naprave, namenjene priključitvi na mehansko sredstvo za odvajanje produktov zgorevanja;
- naprave, ki izpolnjujejo dvojno vlogo ogrevanja prostora in ogrevanja vode za sanitarno uporabo.
Ta dokument zajema le grelnike vode, kjer je ventilator, če obstaja, sestavni del naprave.
Ta dokument ni namenjen zajemanju naprav, zasnovanih in izdelanih za izgorevanje plina, ki vsebuje strupene komponente.

General Information

• Status: Not Published
• Public Enquiry End Date: 01-Jun-2026
• ICS: 91.140.65 - Water heating equipment
• ICS: 97.100.20 - Gas heaters
• Technical Committee: PLN - Gas appliances for domestic use
• Current Stage: 4020 - Public enquire (PE) (Adopted Project)
• Start Date: 08-Apr-2026
• Due Date: 26-Aug-2026
• Directive: Harmonized Standard2016/426 - 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
• Directive:

  ---

  Not Harmonized812/2013 - Commission Delegated Regulation (EU) No 812/2013 of 18 February 2013 supplementing Directive 2010/30/EU of the European Parliament and of the Council with regard to the energy labelling of water heaters, hot water storage tanks and packages of water heater and solar device
• Directive:

  ---

  Not Harmonized814/2013 - Commission Regulation (EU) No 814/2013 of 2 August 2013 implementing Directive 2009/125/EC of the European Parliament and of the Council with regard to ecodesign requirements for water heaters and hot water storage tanks
• Mandate: M/534 - [C(2015)2625] Standardisation request to the European standardisation organisations pursuant to Article 10(1) of Regulation (EU) No 1025/2012 of the European Parliament and of the Council in support of implementation of Commission Regulation (EU) No 814/2013 of 2 August 2013 implementing Directive 2009/125/EC of the European Parliament and of the Council with regard to ecodesign requirements for water heaters and hot water storage tanks and Commission Delegated Regulation (EU) No 812/2013 of 18 February 2013 supplementing Directive 2010/30/EU of the European Parliament and of the Council with regard to the energy labelling of water heaters, hot water storage tanks and packages of water heater and solar device
• Mandate: M/535 - [C(2016)2626) Standardisation request to the European standardisation organisations to draft harmonised European standards pursuant to Article 10(1) of Regulation (EU) No 1025/2012 of the European Parliament and of the Council in support of implementation of 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 eco-design requirements for space heaters and combination heaters and 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 heaters, temperature control and solar device and packages of combination heater, temperature control and solar device
• Mandate: M/595 - [C(2023)4789] - Commission Implementing Decision of 20.7.2023 on a standardisation reques as regards gas appliances and fittings in support of Regulation (EU) 2016/426 of the European Parliament and of the Council
• Ref Project: prEN 26 - Gas-fired instantaneous water heaters for the production of domestic hot water

Relations

• Revises: SIST EN 26:2024 - Gas-fired instantaneous water heaters for the production of domestic hot water
• Effective Date: 01-May-2026

Overview

oSIST prEN 26:2026:2026 is a draft European Standard developed by CEN/TC 48 for gas-fired instantaneous water heaters used for producing domestic hot water. The standard outlines specifications, classification, test methods, marking requirements, and energy labelling for gas-fired water heaters utilized in sanitary applications. It applies to appliances of types A, B, and C, according to their air supply and exhaust configurations, and for those running on various types of combustible gases as defined by the major gas families and relevant European standards.

The main aim of this standard is to promote the safety, reliability, and energy efficiency of gas-fired water heaters, supporting both regulatory compliance and consumer confidence across the European market.

Key Topics

• Product Scope:

  • Applies to gas-fired instantaneous water heaters with a nominal heat input up to 77 kW (GCV).
  • Covers appliances that feature either an ignition burner or direct ignition of the main burner.
  • Excludes devices designed for boiling water, space heating, or use with toxic gases.

• Classification and Appliance Types:

  • Appliance types A, B, and C are defined according to EN 1749, clarifying their combustion air supply and combustion product evacuation methods.
  • Covers water heaters configured for use with multiple gas families based on EN 437.

• Technical Specifications:

  • Construction requirements for materials, assembly, connection, maintenance, and safety devices.
  • Performance characteristics, such as soundness tests for gas, water, and combustion circuits, heat input, flame stability, and temperature requirements.

• Testing and Performance Verification:

  • Detailed operational and endurance test methods to ensure product reliability and compliance.
  • Emphasis on efficiency measurements, emissions (notably NOx), and sound power levels.

• Marking, Instructions, and Energy Labelling:

  • Requirements for product marking, data plates, warning notices, packaging, and user instructions.
  • Alignment with EU energy labelling and eco-design regulations for increased transparency and consumer information.

• Environmental and Regulatory Compliance:

  • Addresses links to the Gas Appliances Regulation (EU) No. 2016/426, EcoDesign requirements (EU No. 814/2013), and energy labelling (EU No. 812/2013).

Applications

• Domestic Hot Water Production:

  • Ensures safe, reliable, and energy-efficient operation of gas-fired water heaters in private homes and residential buildings.

• Product Certification and Market Access:

  • Acts as a reference point for manufacturers and regulatory bodies to demonstrate compliance with key EU directives and regulations.
  • Facilitates CE marking and enables smooth market entry across EU member states.

• Quality Assurance and Installer Guidance:

  • Offers detailed guidance for product selection, installation, commissioning, and servicing by professionals.
  • Enhances consumer protection by establishing minimum performance and safety thresholds.

• Supporting Sustainable Building Practices:

  • Promotes the rational use of energy and reduced emissions in water heating through standardization.

Related Standards

For comprehensive conformity and up-to-date practices, oSIST prEN 26:2026 should be used alongside relevant related standards, including:

• EN 437:2021 - Test gases, test pressures, and categories of appliances.
• EN 1749:2020 - Classification of gas appliances regarding the supply of combustion air and evacuation of combustion products.
• EN 13203-2:2022 - Efficiency and performance of domestic hot water production.
• EN 15502-1 Series - General requirements for gas-fired heating appliances.
• Commission Regulation (EU) No. 814/2013 - Ecodesign for water heaters and hot water storage tanks.
• Commission Delegated Regulation (EU) No. 812/2013 - Energy labelling for water heaters and tanks.
• Regulation (EU) 2016/426 - Gas Appliances Regulation (GAR).

By adhering to oSIST prEN 26:2026 and its related standards, stakeholders ensure high-quality, safe, and energy-efficient gas-fired water heaters for domestic hot water applications across Europe.

Standards Content (Sample)

SLOVENSKI STANDARD
01-maj-2026
Pretočni plinski grelniki vode za pripravo tople sanitarne vode
Gas-fired instantaneous water heaters for the production of domestic hot water
Gasbeheizte Durchlauf-Wasserheizer für den sanitären Gebrauch
Appareils de production instantanée d'eau chaude pour usages sanitaires utilisant les
combustibles gazeux
Ta slovenski standard je istoveten z: prEN 26
ICS:
91.140.65 Oprema za ogrevanje vode Water heating equipment
97.100.20 Plinski grelniki Gas heaters
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

DRAFT
EUROPEAN STANDARD
NORME EUROPÉENNE
EUROPÄISCHE NORM
March 2026
ICS 91.140.65 Will supersede EN 26:2023
English Version
Gas-fired instantaneous water heaters for the production
of domestic hot water
Appareils de production instantanée d'eau chaude Gasbeheizte Durchlauf-Wasserheizer für den sanitären
pour usages sanitaires utilisant les combustibles Gebrauch
gazeux
This draft European Standard is submitted to CEN members for enquiry. It has been drawn up by the Technical Committee
CEN/TC 48.
If this draft becomes a European Standard, CEN members are bound to comply with the CEN/CENELEC Internal Regulations
which stipulate the conditions for giving this European Standard the status of a national standard without any alteration.

This draft European Standard was established by CEN in three official versions (English, French, German). A version in any other
language made by translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC
Management Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and
United Kingdom.
Recipients of this draft are invited to submit, with their comments, notification of any relevant patent rights of which they are
aware and to provide supporting documentation.

Warning : This document is not a European Standard. It is distributed for review and comments. It is subject to change without
notice and shall not be referred to as a European Standard.

EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2026 CEN All rights of exploitation in any form and by any means reserved Ref. No. prEN 26:2026 E
worldwide for CEN national Members.

Contents Page
European foreword . 7
1 Scope . 8
2 Normative references . 8
3 Terms and definitions . 11
4 Classification . 27
4.1 Gases and appliance categories . 27
4.2 Mode of air supply and evacuation of the combustion products . 27
4.3 Water pressure . 27
5 Constructional requirements . 27
5.1 Conversion to different gases . 27
5.1.1 General . 27
5.1.2 Permissible operations for changing gases . 28
5.2 Materials . 28
5.2.1 General requirements related to the use of materials in water heaters . 28
5.2.2 Materials in contact with water for human consumption . 29
5.2.3 Durability against corrosion of combustion product evacuation duct . 30
5.2.4 Disassembly, recycling and disposal . 31
5.2.5 Design - Assembly - Strength . 32
5.2.6 Accessibility - Ease of maintenance - Fitting and removal . 32
5.2.7 Connection to gas and water pipes . 32
5.2.8 Soundness . 33
5.2.9 Supply of combustion air and evacuation of the combustion products . 34
5.2.10 Checking the state of operation . 38
5.2.11 Drainage . 38
5.2.12 Electrical and electromagnetic safety . 38
5.2.13 Operational safety in the event of failure of the auxiliary energy . 39
5.3 Adjusting, control and safety devices . 39
5.3.1 General . 39
5.3.2 Construction requirements . 40
5.3.3 Shut off valves and/or gas rate adjusters . 41
5.3.4 Preset gas rate adjusters . 42
5.3.5 Gas pressure regulator . 42
5.3.6 Pressure test points. 42
5.3.7 Automatic water-operated gas valve . 43
5.3.8 Ignition devices . 43
5.3.9 Flame supervision device . 44
5.3.10 Atmosphere sensing device for type A appliances . 45
AS
5.3.11 Combustion products discharge safety device for type B , B and B
11BS 12BS 13BS
appliances . 45
5.3.12 Protection against accidental overheating of thermostatic appliances . 45
5.3.13 Composition of the gas circuit . 46
5.3.14 Protection for appliances intended to be installed in a partially protected place . 46
5.4 Main burner . 47
5.5 Supplementary requirements for condensing water heaters . 47
5.5.1 Materials in contact with condensate . 47
5.5.2 Discharge of condensate . 47
5.5.3 Control of the combustion products temperature . 48
5.5.4 Chemical composition of the condensate . 48
6 Operational requirements . 48
6.1 General . 48
6.1.1 Introduction. 48
6.1.2 Characteristics of the test gases . 48
6.1.3 Requirements for preparation of the test gases . 48
6.1.4 Choice of test gases . 48
6.1.5 Test pressures . 48
6.1.6 General test conditions . 48
6.2 Soundness . 53
6.2.1 Soundness of the gas circuit . 53
6.2.2 Soundness of the combustion circuit and evacuation of the combustion products . 54
6.2.3 Soundness of the water circuit. 60
6.3 Heat inputs . 60
6.3.1 General . 60
6.3.2 Nominal heat input. 62
6.3.3 Minimum heat input . 63
6.4 Temperature of the control knobs . 63
6.4.1 Requirements . 63
6.4.2 Test . 63
6.5 Temperature of the adjusting, control and safety devices . 63
6.5.1 Requirement . 63
6.5.2 Test . 63
6.6 Temperature of the appliance casing, the surface on which it is installed and
adjacent surfaces and external temperature of the ducts . 63
6.6.1 Requirements . 63
6.6.2 Tests . 64
6.7 Ignition - Cross-lighting - Flame stability . 65
6.7.1 Operation in still air for all appliances . 65
6.7.2 Supplementary tests for appliances of types A and B except for B . 66
AS 1 14
6.7.3 Supplementary tests for type C appliances and outdoors and/or partially protected
appliances. 67
6.7.4 Supplementary tests for type C appliances . 69
6.7.5 Supplementary tests for appliances of types C , C , C , C , B and B . 69
12 13 32 33 4 5
6.7.6 Supplementary tests for type C and type C appliances . 70
42 43
6.7.7 Supplementary tests for type C and type C appliances . 70
52 53
6.7.8 Supplementary tests for type C appliances . 70
6.7.9 Supplementary tests for type C and type C appliances . 70
72 73
6.7.10 Supplementary tests for type C and type C appliances . 70
82 83
6.7.11 Functioning of a permanent ignition burner when the fan stops during the standby
time . 71
6.7.12 Air proving device for fan assisted water heaters . 71
6.7.13 Functioning of the fan of types C and C water heaters . 74
42 43
6.7.14 Protection against the accumulation of gas in the combustion circuit for water
heaters equipped with a fan . 74
6.7.15 Leakage of combustion products from type C7 water heaters . 75
, B and B water heaters . 75
6.7.16 Supplementary tests for type B14 2 3
6.8 Adjusting, control and safety devices . 76
6.8.1 General . 76
6.8.2 Control devices . 76
6.8.3 Closing mechanisms . 76
6.8.4 Ignition devices . 78
6.8.5 Safety times . 79
6.8.6 Gas pressure regulator . 81
6.8.7 Adjustment of the water rate - Maximum water temperature (all appliances) . 82
6.8.8 Overheating of the water . 82
6.8.9 Effectiveness of the protection against accidental overheating of thermostatic
appliances . 84
6.8.10 Atmosphere sensing device for type A appliances . 84
AS
6.8.11 Combustion products discharge safety device of type B appliances . 86
11BS
6.9 Combustion . 88
6.9.1 Requirements . 88
6.9.2 Test . 88
6.9.3 Nitrogen oxides emissions . 93
6.10 Soot deposition . 95
6.10.1 Requirement . 95
6.10.2 Test . 95
6.11 Frost protection system for appliances intended to be installed in a partially
protected place . 95
6.12 Protection against ingress of rain for appliances intended to be installed in a
partially protected place . 96
6.13 Condensing water heaters . 96
6.13.1 Formation of condensate . 96
6.13.2 Temperature of combustion products . 97
6.14 Electrical power measurements . 97
6.14.1 General . 97
6.14.2 Nominal and minimal conditions . 97
6.14.3 Standby . 97
6.15 Measurement of standby heat losses . 97
7 Rational use of energy . 97
7.1 General . 97
7.2 Heat input of ignition burners . 98
7.2.1 Requirement . 98
7.2.2 Test . 98
7.3 Efficiency . 98
7.3.1 Requirement . 98
7.3.2 Test . 98
8 Fitness for purpose . 99
8.1 General . 99
8.2 Constructional characteristics . 99
8.2.1 Preset water rate adjuster . 99
8.2.2 Temperature selector and summer-winter switch. 100
8.2.3 Designation and measurement of reference temperatures of flue systems . 100
8.2.4 Mechanical resistance and stability of ducts, terminal and fitting pieces . 100
8.3 Requirements for plastic in the combustion product evacuation ducts, terminals and
fitting pieces for appliances . 102
8.3.1 Thermal resistance . 102
8.3.2 Materials . 102
8.4 Requirements for elastomeric seals and elastomeric sealants in the combustion
product evacuation ducts, terminals and fitting pieces . 108
8.4.1 Characterization . 108
8.4.2 Long-term resistance to thermal load . 108
8.4.3 Long-term resistance to condensate exposure . 109
8.4.4 Cyclic condensate resistance test . 110
8.4.5 Relaxation behaviour . 111
8.4.6 Compression set . 111
8.4.7 Low temperature resistance . 111
8.4.8 Joints in elastomeric seals . 111
8.5 Operational characteristics . 112
8.5.1 Minimum heat input . 112
8.5.2 Nominal and minimum useful outputs . 112
8.5.3 Ignition of permanent ignition burners by a spark generator . 112
8.5.4 Ignition opening time (T ) . 112
IA
8.5.5 Automatic water-operated gas valve . 113
8.5.6 Adjustment of the water rate - Water temperature . 113
8.5.7 Heating-up time . 119
8.5.8 Specific rate . 119
8.6 Limiting surface temperatures . 119
8.6.1 Requirements . 119
8.6.2 Test conditions . 120
8.6.3 Limiting surface temperatures, consideration of children and the elderly . 120
8.6.4 Surface temperature mitigation . 120
8.6.5 Limiting temperature of the test panels . 121
9 It is checked that the above requirements are met.Marking and instructions . 121
9.1 Water heater marking . 121
9.1.1 Data plate . 121
9.1.2 Markings related to the state of adjustment . 123
9.1.3 Packaging . 123
9.1.4 Warnings notices on the water heater and the packaging . 123
9.1.5 Other information . 124
9.2 Instructions . 125
9.2.1 Instructions for installation . 125
9.2.2 Instructions for use and servicing . 131
9.2.3 Conversion instructions . 132
9.3 Presentation . 133
10 Nitrogen oxides emissions . 133
11 Sound power level (L ) . 133
WA
12 Figures referenced in this standard . 134
Annex A (informative) National situations . 146
A.1 General . 146
A.2 Gas connections in common use in the various countries . 146
A.3 Flue pipe diameters in force in the various countries . 149
Annex B (normative) Test apparatus for type C , C , B and B water heaters (see 6.7.3.2) . 150
1 3 4 5
Annex C (normative) Test apparatus for type C appliances (see 6.7.4.2) . 154
Annex D (normative) Description of the sealed room for the tests of type A appliances
AS
(see 6.8.10.1.2.1) . 155
D.1 Configuration of the sealed room . 155
D.2 Soundness of the room . 155
D.3 Effectiveness of mixing . 155
D.4 Equipment of the room . 155
Annex E (informative) Soundness of the gas circuit test - Volumetric method . 156
E.1 Equipment . 156
E.2 Test method . 156
Annex F (informative) Principal symbols and abbreviations used . 157
Annex G (informative) Guidelines for extension to other appliances categories . 159
Annex H (informative) Lists of materials currently used for the construction of the gas
water heaters . 160
H.1 General . 160
H.2 Special types of steel . 160
H.3 Copper and copper alloys . 160
H.4 Plastic materials . 161
Annex I (normative) Test methods to determine the effects of to long-term thermal load,
long-term condensate exposure, condensing/ non-condensing cycling and resistance
to UV radiation . 162
conversion calculation . 163
Annex J (informative) NOx
Annex K (normative) Parts in copper or copper alloys . 165
Annex L (informative) Compilation of the test conditions for the various gas families . 166
Annex ZA (informative) Relationship between this European Standard and the Essential
Requirements of the Commission Regulation (UE) 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 aimed to be covered . 168
Annex ZB (informative) Relationship between this European Standard and the ecodesign
requirements of Commission Regulation (EU) n°814/2013 [OJEU L239 of 6
September 2013] aimed to be covered . 176
Annex ZC (informative) Relationship between this European Standard and the energy
labelling requirements of Commission Delegated Regulation (EU) No 812/2013
[OJEU L239 of 6 September 2013] aimed to be covered . 177
Bibliography . 178

European foreword
This document (prEN 26:2026) has been prepared by Technical Committee CEN/TC 48 “Domestic gaz-
fired water heaters”, the secretariat of which is held by AFNOR.
This document is currently submitted to the CEN Enquiry.
This document will supersede EN 26:2023.
The main technical changes compared to EN 26:2023 are the following:
a) technical addition related to ecodesign and energy labelling for appliances < = 400 kW:
1) review of Annex ZA;
2) addition of Annex ZB and Annex ZC;
b) new or generally reworded requirements:
1) separation between requirements and test methods in to different clauses;
2) update of normative references;
3) alignment with clauses from EN 15502-1 series when relevant and applicable (e.g. requirements
and tests on controls, …);
c) updating of the Annex ZA by referring to the Gas Appliances Regulation 426/2016/UE. This
document has been prepared under the mandate M/595 given to CEN by the European Commission
and the European Free Trade Association and supports essential requirements of EU Directive(s).
This document has been prepared under a standardization request addressed to CEN by the European
Commission. The Standing Committee of the EFTA States subsequently approves these requests for its
Member States.
For relationship with EU Legislations, see informative Annex ZA, Annex ZB or Annex ZC, which are
integral parts of this document.
EN 13203-2:2022 provides a means of conforming to the Commission Delegated Regulation (EU) No
812/2013 of 18 February 2013 supplementing Directive 2010/30/UE of the European Parliament and of
the Council with regard to energy labelling of water heaters, hot water storage tanks and packages of
water heaters and solar service, except on Sound power level (L ) covered by the present standard, see
WA
Clause 11.
EN 13203-2:2022 provides a means of conforming to the Commission Regulation (EU) No 814/2013 of 2
August 2013 supplementing Directive 2009/125/EC of the European Parliament and of the Council with
regard to eco design requirements for water heaters and hot water storage tanks, except on nitrogen
oxides emissions (NO ) covered by the present standard, see Clause 10.
X
1 Scope
This document defines the specifications and test methods and also the classification, marking and energy
labelling of gas-fired instantaneous water heaters for sanitary uses, hereafter called “water heaters”.
This document applies to water heaters:
— of types A B and C as described at the appropriated clauses;
,
NOTE For more information on the configuration of the types of appliances, see EN 1749:2020.
— using one or more combustible gases corresponding to the three gas families and at the pressures
stated in accordance with EN 437:2021;
— of nominal heat input not exceeding 77 kW based on the gross calorific value (GCV);
— with an ignition burner or with direct ignition of the main burner.
In this document, the heat inputs are expressed in relation to the net calorific value (Hi).
This document does not contain all the requirements necessary for:
— boiling water appliances;
— appliances intended to be connected to a mechanical means of evacuating the combustion products;
— appliances which fulfil a dual role of space heating and heating water for sanitary use.
This document only covers water heaters where the fan, if any, is an integral part of the appliance.
This document is not intended to cover appliances designed and constructed to burn gas containing toxic
components.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
EN 88-1:2022+A1:2023, Pressure regulators and associated safety devices for gas appliances — Part 1:
Pressure regulators for inlet pressures up to and including 50 kPa
EN 125:2022+A1:2024, Flame supervision devices for gas burning appliances — Thermoelectric flame
supervision devices
EN 126:2025, Multifunctional controls for gas burning appliances
EN 161:2022+A1:2025, Automatic shut-off valves for gas burners and gas appliances
EN 298:2022, Automatic burner control systems for burners and appliances burning gaseous or liquid fuels
EN 437:2021, Test gases - Test pressures - Appliance categories
EN 513:2018, Plastics - Poly(vinyl chloride) (PVC) based profiles - Determination of the resistance to
artificial weathering
EN 573-1:2004, Aluminium and aluminium alloys - Chemical composition and form of wrought products -
Part 1: Numerical designation system
EN 1057:2006+A1:2010, Copper and copper alloys - Seamless, round copper tubes for water and gas in
sanitary and heating applications
EN 1092-1:2018, Flanges and their joints - Circular flanges for pipes, valves, fittings and accessories, PN
designated - Part 1: Steel flanges
EN 1092-2:2023, Flanges and their joints - Circular flanges for pipes, valves, fittings and accessories, PN
designated - Part 2: Cast iron flanges
EN 1092-3:2003, Flanges and their joints - Circular flanges for pipes, valves, fittings and accessories, PN
designated - Part 3: Copper alloy flanges
EN 1092-4:2002, Flanges and their joints - Circular flanges for pipes, valves, fittings and accessories, PN
designated - Part 4: Aluminium alloy flanges
EN 1749:2020, Classification of gas appliances according to the method of supplying combustion air and of
evacuation of the combustion products (types)
EN 1856-1:2009, Chimneys - Requirements for metal chimneys - Part 1: System chimney products
EN 1856-2:2009, Chimneys - Requirements for metal chimneys - Part 2: Metal flue liners and connecting
flue pipes
EN 1859:2009+A1:2013, Chimneys - Metal chimneys - Test methods
EN 10088-1:2023, Stainless steels — Part 1: List of stainless steels
EN 10226-1:2004, Pipe threads where pressure tight joints are made on the threads - Part 1: Taper external
threads and parallel internal threads - Dimensions, tolerances and designation
EN 12067-2:2022, Safety and control devices for burners and appliances burning gaseous or liquid fuels -
Control functions in electronic systems - Part 2: Fuel/air ratio control/supervision of the electronic type
EN 13203-1:2025, Gas fired domestic appliances producing hot water - Part 1: Assessment of performance
of hot water deliveries
EN 13216-1:2019, Chimneys — Test methods for system chimneys — Part 1: General test methods
EN 13501-1:2018, Fire classification of construction products and building elements — Part 1:
Classification using data from reaction to fire tests
EN 13611:2019, Safety and control devices for burners and appliances burning gaseous and/or liquid fuels
- General requirements
EN 14241-1:2013, Chimneys - Elastomeric seals and elastomeric sealants - Material requirements and test
methods - Part 1: Seals in flue liners

As impacted by EN 13611:2019/AC:2021.
EN 14459:2021, Safety and control devices for burners and appliances burning gaseous or liquid fuels -
Control functions in electronic systems - Methods for classification and assessment
EN 14471:2013+A1:2015, Chimneys — System chimneys with plastic flue liners — Requirements and test
methods
EN 15036-1:2006, Heating boilers - Test regulations for airborne noise emissions from heat generators -
Part 1: Airborne noise emissions from heat generators
EN 60335-1:2012, Household and similar electrical appliances - Safety — Part 1: General requirements
(IEC 60335-1:2010)
EN 60529:1991, Degrees of protection provided by enclosures (IP code) (IEC 60529:1989)
EN ISO 178:2019, Plastics — Determination of flexural properties (ISO 178:2019)
EN ISO 179-1:2023, Plastics — Determination of Charpy impact properties — Part 1: Non-instrumented
impact test (ISO 179-1:2023)
EN ISO 228-1:2003, Pipe threads where pressure-tight joints are not made on the threads - Part 1:
Dimensions, tolerances and designation (ISO 228-1:2000)
EN ISO 527-1:2019, Plastics — Determination of tensile properties — Part 1: General principles (ISO 527-
1:2019)
EN ISO 527-2:2025, Plastics — Determination of tensile properties — Part 2: Test conditions for moulding
and extrusion plastics (ISO 527-2:2025)
EN ISO 1183
...