prEN 303-2

Heating boilers - Part 2: Heating boilers with forced draught burners - Special requirements for boilers with atomizing oil burners

This document is applicable to boilers used for central heating in accordance with EN 303-1 up to a nominal heat output of 1 000 kW and EN 303-4 up to a nominal heat output of 70 kW with forced draught burners in accordance with EN 267 that are designed for operating with liquid fuels.
The performance requirements of this document apply to type testing to heating boilers (standard, low temperature and condensing boilers) which are tested on a test rig in accordance with the test code given in EN 304.
This document applies also to room sealed boilers as defined in EN 15035 regarding efficiency and emissions.
This document can also be used as the basis for evaluation of boiler-/burner units.

Heizkessel - Teil 2: Heizkessel mit Gebläsebrennern - Spezielle Anforderungen an Heizkessel mit Ölzerstäubungsbrennern

Dieses Dokument gilt für Kessel von Zentralheizungen nach EN 303-1:2017 bis zu einer Nennwärmeleistung von 1 000 kW und nach EN 303-4:1999 bis zu einer Nennwärmeleistung von 70 kW mit Gebläsebrennern nach EN 267:2020, die für den Betrieb mit flüssigen Brennstoffen konzipiert wurden.
Die Leistungsanforderungen dieses Dokuments gelten für die Typ-Prüfung von Heizkesseln (Standard-, Niedertemperatur- und Brennwertkessel), die auf einem Prüfstand nach den Prüfregeln in EN 304:2017 geprüft werden.
Dieses Dokument gilt auch für raumluftunabhängige Kessel nach EN 15035 in Bezug auf Wirkungsgrad und Emissionen.
Dieses Dokument kann auch als Grundlage für die Bewertung von Heizkessel-Brenner-Einheiten dienen.

Chaudières de chauffage - Partie 2 : Chaudières avec brûleurs à air soufflé - Prescriptions spéciales pour chaudières avec brûleurs fioul à pulvérisation

Le présent document s'applique aux chaudières de chauffage central conformes à l'EN 303-1:2017 jusqu'à une puissance utile nominale de 1 000 kW et à l'EN 303-4:1999 jusqu'à une puissance utile nominale de 70 kW, pourvues de brûleurs à air soufflé conformes à l'EN 267:2020 et conçues pour fonctionner avec des combustibles liquides.
Les exigences de performance du présent document s'appliquent aux essais de type de chaudières de chauffage (chaudières standard, à basse température et à condensation) soumises à essai sur un banc d'essai conformément aux règles d'essai de l'EN 304:2017.
Le présent document s'applique également aux chaudières étanches définies dans l'EN 15035, pour ce qui concerne le rendement et les émissions.
Le présent document peut aussi servir de base pour l'évaluation des assemblages de chaudière/brûleur.

Kotli za ogrevanje - 2. del: Kotli za ogrevanje z ventilatorskimi gorilniki - Posebne zahteve za kotle z razprševalnimi oljnimi gorilniki

General Information

• Status: Not Published
• Publication Date: 02-Jun-2025
• ICS: 91.140.10 - Central heating systems
• Technical Committee: CEN/TC 57 - Central heating boilers
• Drafting Committee: CEN/TC 57/WG 2 - Test method for the determination of efficiency at a partial load of 30%
• Current Stage: 4020 - Submission to enquiry - Enquiry
• Start Date: 16-Mar-2023
• Due Date: 18-Jul-2023
• Completion Date: 16-Mar-2023
• Directive: 811/2013 - 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
• Directive: 813/2013 - 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
• 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
• Ref Project: oSIST prEN 303-2:2023 - Heating boilers - Part 2: Heating boilers with forced draught burners - Special requirements for boilers with atomizing oil burners

Relations

• Revises: EN 303-2:2017 - Heating boilers - Part 2: Heating boilers with forced draught burners - Special requirements for boilers with atomizing oil burners
• Effective Date: 19-Jan-2023

Standards Content (Sample)

SLOVENSKI STANDARD
oSIST prEN 303-2:2023
01-marec-2023

Kotli za ogrevanje - 2. del: Kotli za ogrevanje z ventilatorskimi gorilniki - Posebne

zahteve za kotle z razprševalnimi oljnimi gorilniki
Heating boilers - Part 2: Heating boilers with forced draught burners - Special
requirements for boilers with atomizing oil burners
Heizkessel - Heizkessel mit Gebläsebrennern - Teil 2: Spezielle Anforderungen an
Heizkessel mit Ölzerstäubungsbrennern
Chaudières de chauffage - Chaudières avec brûleurs à air soufflé - Partie 2 :
Prescriptions spéciales pour chaudières avec brûleurs fioul à pulvérisation
Ta slovenski standard je istoveten z: prEN 303-2
ICS:
27.060.10 Gorilniki na tekoče in trdo Liquid and solid fuel burners
gorivo
91.140.10 Sistemi centralnega Central heating systems
ogrevanja
97.100.40 Grelniki na tekoče gorivo Liquid fuel heaters
oSIST prEN 303-2:2023 en,fr,de

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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oSIST prEN 303-2:2023
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oSIST prEN 303-2:2023
DRAFT
EUROPEAN STANDARD
prEN 303-2
NORME EUROPÉENNE
EUROPÄISCHE NORM
March 2023
ICS 91.140.10 Will supersede EN 303-2:2017
English Version
Heating boilers - Part 2: Heating boilers with forced
draught burners - Special requirements for boilers with
atomizing oil burners

Chaudières de chauffage - Chaudières avec brûleurs à Heizkessel - Heizkessel mit Gebläsebrennern - Teil 2:

air soufflé - Partie 2 : Prescriptions spéciales pour Spezielle Anforderungen an Heizkessel mit

chaudières avec brûleurs fioul à pulvérisation Ölzerstäubungsbrennern

This draft European Standard is submitted to CEN members for enquiry. It has been drawn up by the Technical Committee

CEN/TC 57.

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

© 2023 CEN All rights of exploitation in any form and by any means reserved Ref. No. prEN 303-2:2023 E

worldwide for CEN national Members.
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oSIST prEN 303-2:2023
prEN 303-2:2023 (E)
Contents Page

European foreword ....................................................................................................................................................... 4

1 Scope .................................................................................................................................................................... 5

2 Normative references .................................................................................................................................... 5

3 Terms and definitions ................................................................................................................................... 5

3.1 General terms and definitions .................................................................................................................... 5

3.2 Terms and definitions relevant to eco-design and labelling regulations terms ...................... 6

4 Performance requirements ......................................................................................................................... 6

4.1 General ................................................................................................................................................................ 6

4.2 Boiler efficiency ............................................................................................................................................... 6

4.2.1 Air ratio for efficiency measurement ....................................................................................................... 6

4.2.2 Boilers of heat output ≤ 70 kW ................................................................................................................... 6

4.2.3 Boilers of heat output > 70 kW and ≤ 400 kW ...................................................................................... 6

4.2.4 Boilers of heat output > 400 kW and ≤ 1 000 kW ................................................................................ 7

4.3 Draught requirements and gas side resistance.................................................................................... 7

4.4 Emission values ............................................................................................................................................... 7

4.5 Standby heat loss ............................................................................................................................................. 7

4.6 Auxiliary electricity consumption ............................................................................................................ 8

4.7 Sound power level ........................................................................................................................................... 8

4.8 Samples for testing ......................................................................................................................................... 8

5 Material performance .................................................................................................................................... 8

5.1 General ................................................................................................................................................................ 8

5.2 Test specimen and test duration ............................................................................................................... 8

5.3 Adjustment values for the test.................................................................................................................... 9

6 Marking and instructions .......................................................................................................................... 10

6.1 Information for disassembly, recycling and disposal ..................................................................... 10

6.2 Annual energy consumption .................................................................................................................... 10

6.2.1 Rated heat output (P and P ) ....................................................................................................... 10

rated 4

6.2.2 Calculation of the annual energy consumption for space heating (Q ) (GCV) .................... 11

6.2.3 Water heating energy efficiency and energy consumption of combination boilers for

water heating mode..................................................................................................................................... 11

6.2.4 Ignition burner power consumption (GCV) (P ) .......................................................................... 12

ign

Annex AA (informative) Product Information related to Eco-design Regulation and Labelling

Regulation ....................................................................................................................................................... 13

⁠⁠AA.1 Product information – technical parameters required by the ErP Regulation

(813/2013) ..................................................................................................................................................... 13

⁠⁠⁠AA.2 Product information – technical parameters required by the Labelling Regulation

(811/2013) ..................................................................................................................................................... 15

Annex A (normative) Assembly criteria ............................................................................................................. 17

Annex B (informative) Example of test evaluation for a 3-months duration test ................................ 19

Annex ZA (informative) Relationship between this European Standard and the ecodesign

requirements of Commission Regulation (EU) No [813/2013] aimed to be covered ......... 21

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Annex ZB (informative) Relationship between this European Standard and the energy

labelling requirements of Commission Delegated Regulation (EU) No 811/2013

aimed to be covered ..................................................................................................................................... 22

Bibliography ................................................................................................................................................................. 25

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oSIST prEN 303-2:2023
prEN 303-2:2023 (E)
European foreword

This document (prEN 303-2:2023) has been prepared by Technical Committee CEN/TC 57 “Central

heating boilers”, the secretariat of which is held by DIN.

This document has been prepared under a Standardization Request given to CEN by the European

Commission and the European Free Trade Association, and supports essential requirements of EU

Directive(s) / Regulation(s).

For relationship with EU Directive(s) / Regulation(s), see informative Annexes ZA and ZB, which is an

integral part of this document.
This document supersedes EN 303-2:2017.
The main technical changes compared to EN 303-2:2017 are the following:
a) new Annex AA for information in regard to the labelling was added;
b) new clause marking and instructions was added;

c) technical and editorial changes related to ecotest were introduced in order to bring in more clarity

and less deviations of test results;
d) updated references;
e) updated normative references.
The following structure is intended for the standards for heating boilers:

— EN 303-1, Heating boilers — Part 1: Heating boilers with forced draught burners — Terminology,

general requirements, testing and marking

— EN 303-2, Heating boilers — Part 2: Heating boilers with forced draught burners — Special

requirements for boilers with atomizing oil burners

— EN 303-3, Heating boilers — Part 3: Gas fired central heating boilers — Assembly comprising a boiler

body and a forced draught burner

— EN 303-4, Heating boilers — Part 4: Heating boilers with forced draught burners — Special

requirements for boilers with forced draught oil burners with outputs up to 70 kW and a maximum

operating pressure of 3 bar — Terminology, special requirements, testing and marking

— EN 303-5, Heating boilers — Part 5: Heating boilers for solid fuels, manually and automatically stoked,

— nominal heat output of up to 500 kW - Terminology, requirements, testing and marking

— EN 304, Heating boilers — Test code for heating boilers for atomizing oil burners

— EN 303-6, Heating boilers — Part 6: Heating boilers with forced draught burners; specific requirements

for the domestic hot water operation of combination boilers with atomizing oil burners of nominal heat

input not exceeding 70 kW
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oSIST prEN 303-2:2023
prEN 303-2:2023 (E)
1 Scope

This document is applicable to boilers used for central heating in accordance with EN 303-1:2017 up to

a nominal heat output of 1 000 kW and EN 303-4:1999 up to a nominal heat output of 70 kW with forced

draught burners in accordance with EN 267:2020 that are designed for operating with liquid fuels.

The performance requirements of this document apply to type testing to heating boilers (standard, low

temperature and condensing boilers) which are tested on a test rig in accordance with the test code given

in EN 304:2017.

This document applies also to room sealed boilers as defined in EN 15035 regarding efficiency and

emissions.

This document can also be used as the basis for evaluation of boiler-/burner units.

2 Normative references

The following documents, in whole or in part, are normatively referenced in this document and are

indispensable for its application. For dated references, only the edition cited applies. For undated

references, the latest edition of the referenced document (including any amendments) applies.

EN 267:2020, Forced draught burners for liquid fuels

EN 303-1:2017, Heating boilers — Part 1: Heating boilers with forced draught burners - Terminology,

general requirements, testing and marking

EN 304:2017, Heating boilers — Test code for heating boilers for atomizing oil burners

EN 15036-1:2006, Heating boilers — Test regulations for airborne noise emissions from heat generators —

Part 1: Airborne noise emissions from heat generators

EN 15316-4-1:2017, Energy performance of buildings — Method for calculation of system energy

requirements and system efficiencies — Part 4-1: Space heating and DHW generation systems, combustion

systems (boilers, biomass), Module M3-8-1, M8-8-1
3 Terms and definitions

For the purposes of this document, the terms and definitions given in EN 303-1:2017 and the following

apply.
3.1 General terms and definitions
3.1.1
range rated boiler
appliance where the heat output is fixed in a given range
3.1.2
modulating boiler
appliance where the heat output is varying in a given range automatically
3.1.3
standby heat loss
stby

heat loss of a boiler space heater, boiler combination heater in operating mode without heat demand,

expressed in kW
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3.1.4
combination boiler (combi boiler)

boiler designed both for central heating and for the production of domestic hot water

Note 1 to entry: Depending on its type of domestic hot water production, the combination boiler is classified in

accordance with the manufacturer's declaration as instantaneous type or storage type.

3.2 Terms and definitions relevant to eco-design and labelling regulations terms
3.2.1
sound power level
A-weighted sound power level, indoors, expressed in dB(A)
3.2.2
package

unit of boilers or combination boilers, temperature control and/or solar devices means a package offered

to the end-user containing one or more boilers or combination boilers combined with one or more

temperature controls and/or one or more solar devices

Note 1 to entry: Definition based on Labelling Regulation 811/2013 Article 2 - (19) and (20).

Note 2 to entry: Informative Annex AA (and its Tables AA.1 and AA.2) provides a copy of table 1 of Annex II of

COMMISSION REGULATION (EU) No 813/2013 that uses many of the definitions given in this document.

4 Performance requirements
4.1 General

All the following performance tests are carried out using an oil forced draught burner in accordance with

EN 267:2020.

Multi-stage or modulating burners shall operate within the output range of the boiler.

If the boiler was already tested with a forced draught burner for gaseous fuels in accordance with

EN 303-1:2017 and EN 303-3:2006, the tests described in 4.2 and 4.6 need not be performed.

For assembly criteria see Annex A.
4.2 Boiler efficiency
4.2.1 Air ratio for efficiency measurement
The air ratio λ for the efficiency measurement shall comply with the following:

— less than 100 kW: with the requirements of Figure 1 in the tolerance ± 10 % of λ;

— from 100 kW up to 1 000 kW: 1,18 ≤ λ ≤ 1,22.
4.2.2 Boilers of heat output ≤ 70 kW

The seasonal space heating energy efficiency (η ) shall not fall below 86 % based on GCV.

4.2.3 Boilers of heat output > 70 kW and ≤ 400 kW

The useful efficiency at nominal heat output (η ) shall not fall below 86 % based on GCV, and the useful

efficiency at 30 % of the nominal heat output (η ) shall not fall below 94 % based on GCV.

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4.2.4 Boilers of heat output > 400 kW and ≤ 1 000 kW
Table 1 — Efficiency requirements for boilers above 400 kW
a a b
Full load efficiency (%) Part load efficiency (%)
η η
4 1
Type of boiler NCV GCV NCV GCV
Standard 89,2 84,2 87,8 82,8
Low temperature 91,4 86,2 91,4 86,2
Condensing 93,6 88,3 96,6 91,1

The efficiency based on GCV is equal to the efficiency based on NCV divided by 1,06.

Part load efficiency is measured at 30 % of the nominal heat output
4.3 Draught requirements and gas side resistance

The gas side resistance and draught shall be determined during the efficiency performance test at

nominal load.

For boilers which operate with negative pressure in the combustion chamber, the values of draught

requirements shown in Figure 2 shall be met or the corresponding technical documentation and/or

manual shall be made available.

For boilers which are operated with positive pressure in the combustion chamber, the values for the flue

gas resistance shown in Figure 3 shall be met or the corresponding technical documentation and/or

manual shall be made available.
4.4 Emission values
The emission values in this clause are taken from EN 267:2020.

During the tests in accordance with 4.2 (at nominal heat output) the smoke number shall not exceed 1.

The concentration of unburnt hydrocarbons in the flue gases shall not exceed 10 ppm, except during the

first 20 s after release of the fuel. The measurement shall be carried out by a flame ionization detector

(FID).

The emissions of CO while operating the boiler at minimum continuous output and nominal output, shall

not exceed 60 mg/kWh on NCV or 56 mg/kWh on GCV.

The emissions of nitrogen oxides, expressed in nitrogen dioxide, shall not exceed:

— for boilers with P ≤ 400 kW: 120 mg/kWh fuel input in terms of GCV;
— for boilers with P > 400 kW: 250 mg/kWh fuel input in terms of NCV.
4.5 Standby heat loss

If the default value of EN 15316-4-1:2017 is not used the standby heat loss for boilers shall be measured

in accordance with EN 304:2017.

NOTE For boilers up to 70 kW, the value is used in the calculation of the seasonal space heating energy

efficiency.
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4.6 Auxiliary electricity consumption

If the default values of EN 15316-4-1:2017 are not used the auxiliary electricity consumption for boilers

shall be measured in accordance with EN 304:2017.

The auxiliary electricity consumption at nominal heat output (el ), the auxiliary electricity

max

consumption at 30 % part load (el ) and auxiliary electricity consumption in standby mode (P ) shall

min SB
be measured according EN 304:2017.
4.7 Sound power level

The sound power level L shall be measured at nominal heat output according to EN 15036-1:2006.

4.8 Samples for testing

The type test determines whether the individual boilers sizes of a type or range meet the requirements

laid down in this document. During the type test the boiler shall be representative of production in its

design and equipment.

For boilers in a product range which has the same constructional design it is sufficient to test only the

smallest and largest boiler provided the ratio in heat output of the smallest to the largest boiler is less

than or equal to 1:2. If, however, within the same product range, this ratio is larger than 1:2 then so many

intermediate sizes shall be tested so that the ratio of 1:2 is not exceeded.

The characteristics according to this document for non-tested boilers are determined by linear

interpolation based on the nominal heat output.
5 Material performance
5.1 General

— Material according to EN 303-1:2017, 4.1.1.3.3 have sufficient resistance regarding corrosion

resistance, heat resistance and mechanical stability for non-condensing boilers.

— Materials classified as corrosion resistant in Table 2 of EN 303-1:2017 are sufficient resistant as state

of the art for low temperature or condensing boilers. Materials not listed as corrosion resistant in

Table 2 of EN 303-1:2017 or materials with coating may be tested regarding corrosion resistance

according to Annex B (Table B.1, Figure B.1 and B.2) and 5.2 and 5.3.
5.2 Test specimen and test duration

At least two serial-production test specimens with the intended minimum equipment are to be selected

from the boiler series to be tested and subjected to fatigue tests according to the following provisions.

Before beginning the test, the test specimens shall be subje
...