SIST EN 303-7:2007

Heating boilers - Part 7: Gas-fired central heating boilers equipped with a forced draught burner of nominal heat output not exceeding 1 000 kW

This European Standard specifies the requirements and test methods for the construction, the safety and the rational energy usage for gas-fired central heating boilers equipped with a forced draught burner. These boilers are formed of the assembly of a boiler body and a forced draught gas burner achieved on the production site of the manufacturer, the whole being designed and marketed as a complete boiler. The boiler body shall be in accordance with EN 303-1. The construction of the forced draught gas burner shall be in accordance with EN 676.

Heizkessel - Teil 7 : Zentralheizkessel für gasförmige Brennstoffe mit einer Gebläsebrenner mit einer Nennwärmeleistung kleiner als oder gleich 1 000 kW

Diese Europäische Norm legt die Anforderungen und Prüfungen für die Konstruktion, die Sicherheit und den wirtschaftlichen Energieeinsatz von Standard- und Niedertemperatur-Zentralheizkesseln für gasförmige Brennstoffe fest, die mit einem Gebläsebrenner ausgerüstet sind.
Diese Heizungskessel werden in der Fertigung des Herstellers aus dem Zusammenbau eines Kesselkörpers und eines Gasgebläsebrenners gebildet, die als zusammengehörende Einheit angeboten werden.
Die vorliegende Norm behandelt nicht den Fall eines Zusammenbaus aus Kesselkörper und Gasgebläse¬brenner, die getrennt voneinander angeboten werden. In diesem Fall gilt die EN 303-3.
Diese Europäische Norm ist für Kessel vom Typ B23 mit einer Nennwärmeleistung bis 1000 kW und einer normalen Betriebstemperatur die 105 °C und einen wasserseitigen Maximaldruck von nicht über 8 bar anzuwenden.
Die vorliegende Norm beinhaltet nicht alle notwendigen Anforderungen für die:
   Kessel mit Brennwertnutzung und Kombikessel;
   Kessel, die zur Installation im Freien vorgesehen sind;
   Kessel, die permanent mit mehr als einem Abgasstutzen ausgerüstet sind;
   Kessel, die für den Anschluss an eine gemeinsame Abgasanlage mit mechanischer Absaugung vorgesehen sind;
   Kessel, die mit mehreren Feuerräumen ausgerüstet sind.
Die vorliegende Norm gilt nicht für Kessel zur Aufstellung in Wohnräumen (siehe 3.6).
Diese Norm umfasst ausschließlich die Typprüfung.

Chaudiere de chauffage - Partie 7 : Chaudieres de chauffage central équipées d'un bruleur a air soufflé utilisant les combustibles gazeux de puissance utile inférieure ou égale a 1 000 kW

La présente norme européenne spécifie les exigences et les méthodes d'essais relatives à la construction, la sécurité et l'utilisation rationnelle de l'énergie d'un assemblage ou d'une unité constitué d'un corps de chaudière conforme à la norme EN 303-1 et d'un brûleur à air soufflé utilisant les combustibles gazeux. Dans le cas d'un assemblage composé d'un corps de chaudière et d'un brûleur à gaz à air soufflé conçus séparément, dénommé ci-après "chaudière", le brûleur à gaz à air soufflé doit être conforme à l'EN 676.

Kotli za gretje - 7. del: Plinski kotli za centralno gretje z ventilatorskimi gorilniki z imensko grelno močjo do vključno 1000 kW

General Information

• Status: Published
• Publication Date: 31-Jan-2007
• ICS: 91.140.10 - Central heating systems
• Technical Committee: PLN - Gas appliances for domestic use
• Current Stage: 6060 - National Implementation/Publication (Adopted Project)
• Start Date: 01-Feb-2007
• Due Date: 01-Feb-2007
• Completion Date: 01-Feb-2007
• Directive: 2009/142/EC - DIRECTIVE 2009/142/EC OF THE EUROPEAN PARLIAMENT AND OF THE COUNCIL of 30 November 2009 relating to appliances burning gaseous fuels
• Directive: 2016/426 - 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: 90/396/EEC - Appliances burning gaseous fuels
• Directive: 92/42/EEC - Efficiency requirements for new hot-water boilers fired with liquid or gaseous fuels
• Mandate: M/066 - Standardization mandate to CEN concerning Efficiency requirements for boilers
• Mandate: M/BC/CEN/89/6 - Standardization request to CEN concerning appliances burning gaseous fuels
• Ref Project: EN 303-7:2006 - Heating boilers - Part 7: Gas-fired central heating boilers equipped with a forced draught burner of nominal heat output not exceeding 1 000 kW

Overview

EN 303-7:2006 is a CEN (European) standard that specifies requirements and test methods for gas-fired central heating boilers equipped with a forced draught burner with a nominal heat output not exceeding 1 000 kW. The standard covers construction, safety and rational energy use for boilers supplied as a complete assembly (boiler body + forced draught gas burner) manufactured and marketed together. It applies to type B23 appliances (fan upstream of combustion chamber) and is intended for type testing rather than site installation rules.

Key Topics and Requirements

• Scope & applicability
  • Boilers assembled and marketed as a complete unit; separate sold components fall under EN 303-3.
  • Applies to boilers with normal water temperatures ≤ 105 °C and maximum water-side pressure ≤ 8 bar.
  • Excludes condensing boilers, open-air installations, boilers with multiple flue outlets, common mechanically extracted flues, multiple combustion chambers, and living-space dedicated boilers.
• Constructional requirements
  • Boiler body must conform to EN 303-1; forced draught burner construction per EN 676.
  • Low-temperature boiler materials and parts likely to contact condensate require specific treatment.
• Safety & control
  • Safety of operation, flame supervision, ignition and automatic shut-off requirements.
  • Control and safety equipment checks, ignition safety times, non-volatile lockout behavior, purge procedures.
• Test methods
  • Test suites include external gas-line tightness, heat input measurement, gas pressure governor performance, combustion characteristics (CO, NOx), useful efficiency, condensation behavior and operational endurance.
  • Annexes provide normative procedures (e.g., Annex E for combustion emissions; Annex F for burners complying with EN 676).
• Marking & instructions
  • Requirements for product marking, technical instructions and conformity documentation; Annex ZA links clauses to applicable EU Directives.

Applications and Who Uses It

• Manufacturers of gas-fired central heating boilers to design, test and CE-mark complete boiler units.
• Test laboratories conducting type testing, efficiency and safety verification.
• Certification bodies and national standards institutes for regulatory compliance and market access in CEN member states.
• Product designers and HVAC engineers specifying or selecting commercial and industrial central heating boilers.
• Installers and commissioning agents consulting test and safety criteria during selection and handover.

Related Standards

• EN 303-1 - Boiler body requirements and general testing
• EN 676 - Automatic forced draught burners for gaseous fuels
• EN 437 - Test gases, pressures, appliance categories
• EN 60335-1 - Electrical safety (household & similar appliances)
• CEN/TR 1749 - Classification by combustion product evacuation (types)

EN 303-7:2006 is an essential reference for ensuring safety, performance and regulatory compliance of non-condensing, forced-draught gas boilers up to 1 000 kW.

Standards Content (Sample)

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.Heating boilers - Part 7: Gas-fired central heating boilers equipped with a forced draught burner of nominal heat output not exceeding 1 000 kWChaudiere de chauffage - Partie 7 : Chaudieres de chauffage central équipées d'un bruleur a air soufflé utilisant les combustibles gazeux de puissance utile inférieure ou égale a 1 000 kWHeizkessel - Teil 7 : Zentralheizkessel für gasförmige Brennstoffe mit einer Gebläsebrenner mit einer Nennwärmeleistung kleiner als oder gleich 1 000 kWTa slovenski standard je istoveten z:EN 303-7:2006SIST EN 303-7:2007en,fr,de91.140.10ICS:SLOVENSKI
STANDARDSIST EN 303-7:200701-februar-2007

EUROPEAN STANDARDNORME EUROPÉENNEEUROPÄISCHE NORMEN 303-7October 2006ICS 91.140.10 English VersionHeating boilers - Part 7: Gas-fired central heating boilersequipped with a forced draught burner of nominal heat outputnot exceeding 1 000 kWChaudière de chauffage - Partie 7 : Chaudières dechauffage central équipées d'un brûleur à air souffléutilisant les combustibles gazeux de puissance utileinférieure ou égale à 1 000 kWHeizkessel - Teil 7 : Zentralheizkessel für gasförmigeBrennstoffe mit einer Gebläsebrenner mit einerNennwärmeleistung kleiner als oder gleich 1 000 kWThis European Standard was approved by CEN on 14 December 2005.CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this EuropeanStandard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such nationalstandards may be obtained on application to the Central Secretariat or to any CEN member.This European Standard exists in three official versions (English, French, German). A version in any other language made by translationunder the responsibility of a CEN member into its own language and notified to the Central Secretariat has the same status as the officialversions.CEN members are the national standards bodies of Austria, Belgium, Cyprus, Czech Republic, Denmark, Estonia, Finland, France,Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania,Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.EUROPEAN COMMITTEE FOR STANDARDIZATIONCOMITÉ EUROPÉEN DE NORMALISATIONEUROPÄISCHES KOMITEE FÜR NORMUNGManagement Centre: rue de Stassart, 36
B-1050 Brussels© 2006 CENAll rights of exploitation in any form and by any means reservedworldwide for CEN national Members.Ref. No. EN 303-7:2006: E

Diameters of combustion products evacuation ducts marketed in the various countries.49 Annex B (informative)
Practical method of calibrating the test rig to enable determination of heat loss Dp.50 Annex C (informative)
Determination of the heat losses from the test rig of the indirect method and the contributions of the circulating pump of the test rig (see 5.8.2.3.1.3).51 Annex D (informative)
Determination of the operating time at full rate prior to modulation.52 Annex E (normative)
Determination of the combustion characteristics – Carbon monoxide and nitrogen oxides.53 Annex F (normative)
Case of a forced draught burner complying with EN 676.55 Annex G (informative)
Main symbols and abbreviations used.56 Annex H (informative)
A-deviations.57 Annex ZA (informative)
Clauses of this European Standard addressing essential requirements or
other provisions of EU Directives.58 Bibliography.61

1 Scope This European Standard specifies the requirements and test methods for the construction, the safety and the rational energy usage for gas-fired standard and low temperature central heating boilers equipped with a forced draught burner.
These boilers comprise a boiler body and a forced draught gas burner brought together at the producer's assembly facility, the whole being designed and marketed as a complete boiler. This standard does not apply to the case of the assembly of a boiler body and a forced draught gas burner designed and marketed separately. In this case, EN 303-3 applies. This European Standard applies to type B23 boilers with a nominal heat output not exceeding 1000 kW with a water temperature at normal operation not exceeding 105 °C and with a maximum water-side operating pressure not exceeding 8 bar. This European Standard does not contain all the necessary requirements for:  condensing boilers and combination boilers;  boilers intended to be installed in the open;  boilers permanently fitted with more than one flue outlet;  boilers intended to be connected to a common flue having mechanical extraction;  boilers equipped with several combustion chambers. This European Standard does not apply to living-space dedicated boilers (see 3.6). This European Standard only covers type testing. 2 Normative references The following referenced documents are indispensable for the application 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 303-1:1999, Heating boilers  Part 1: Heating boilers with forced draught burners  Terminology, general requirements, testing and marking EN 437, Test gases  Test pressures  Appliance categories EN 676, Automatic forced draught burners for gaseous fuels EN 60335-1:2002, Household and similar electrical appliances - Safety  Part 1: General requirements
(IEC 60335-1:2001, modified) EN ISO 3166-1, Codes for the representation of name of countries and their subdivisions  Part 1: Country codes (ISO 3166-1:1997) CEN/TR 1749, European scheme for the classification of gas appliances according to the method of evacuation of the combustion products (types)

Qn heat input stated by the manufacturer 3.3 Outputs 3.3.1 useful output P quantity of heat transmitted to the heat carrier in unit time NOTE Outputs are expressed in kilowatts (kW) 3.3.2 nominal output Pn useful output stated by the manufacturer 3.4 useful efficiency
ηηηηu ratio of the useful output to the heat input NOTE the useful efficiency is expressed in percent (%). 3.5 nominal voltage voltage or range of voltages stated by the manufacturer, at which the boiler can operate normally
1) Boilers fitted with a range-rating device operate at a nominal heat input between the maximum and minimum adjustable heat inputs. Modulating boilers operate between the nominal heat input and the minimum controlled heat input. The maximum heat input corresponds to the nominal output of the boiler in accordance with EN 303-1.

(CEN/TR 1749) 3.9.1 type B appliance intended to be connected to a flue that evacuates the products of combustion to the outside of the room containing the appliance. The combustion air is drawn directly from the room 3.9.2 type B2 type B appliance without draught diverter 3.9.3 type B23 type B2 appliance incorporating a fan upstream of the combustion chamber/heat exchanger 3.10 forced draught burner burner in which the combustion air is introduced by means of a fan 3.11 automatic forced draught burner forced draught burner that is fitted with automatic ignition, flame monitoring and burner control devices. Ignition, flame monitoring and the on/off switching of the burner occur automatically. The heat input of the burner can be adjusted during operation either automatically or manually 3.12 total pre-mixed burner burner in which at least all the air theoretically required for complete combustion of the gas is mixed with the gas upstream of the mixture outlet ports 3.13 nozzle mixed burner burner in which part, or all, of the air theoretically
required for combustion of the gas is mixed with the gas at, or downstream of, the air and gas ports 3.14 start gas rate gas rate ignited by the ignition device during the start-up of the burner

(tSA) time that elapses between the order to open and the order to close the gas supply to the burner in the event of no flame being detected 3.30 extinction safety time
(tSE) time that elapses between extinction of the supervised flame and the order to shut off the gas supply to the burner 3.31 first safety time period between the ignition burner gas valve, the start gas valve or main gas valve(s), as applicable, being energized and the pilot gas valve, start gas valve or main gas valve(s), as applicable, being de-energized if the flame detector device signals the absence of a flame NOTE Where there is no second safety time, this is called the safety time. 3.32 second safety time where there is a first safety time applicable to either an ignition burner or start gas flame only, the second safety time is the period between the main gas valves being energized and the main gas valves being de-energized if the flame detector device signals the absence of a flame 3.33 total closing time period that starts with the signal that the flame has been extinguished and ends with the shut-off valves being closed 3.34 automatic recycling after loss of flame during operation, the gas supply is interrupted and the full start procedure is re-initiated automatically 3.35 non-volatile lock-out safety shut-down condition of the system, such that a restart can only be accomplished by a manual reset of the system and by no other means 3.36 condensate liquid formed from the combustion products during the condensation process 3.37 standard boiler boiler for which the average water temperature can be restricted by design 3.38 low-temperature boiler boiler which can work continuously with a water supply temperature of 35 °C to 40 °C, possibly producing condensation in certain circumstances

ratio of the real air volume (in m3) to the stœchiometric air volume (in m3) 4 Constructional and operational requirements 4.1 General principles The boiler body shall comply with the relevant requirements of EN 303-1. The construction and the equipment of the forced draught gas burner shall be in accordance with EN 676. The operational requirements of the forced draught burner shall be checked on the boiler. The corresponding requirements and tests are described in this standard. In the case where the forced draught burner complies with EN 676, only the tests defined in Annex F are necessary. For low-temperature boilers, all parts of the heat exchanger(s) and other parts of the boiler likely to come into contact with condensate shall be constructed of sufficiently corrosion resistant materials or materials protected by a suitable coating in order to ensure a reasonable life for a boiler that is installed, used and maintained in accordance with the manufacturer's instructions. Surfaces in contact with condensate (except purpose provided drains, water traps and siphons) shall be designed to prevent condensate retention. 4.2 Operational requirements The following requirements are checked on the boiler in accordance with the test conditions of 5.1 unless otherwise specified 4.2.1 General operational requirements A controlling device shall not override the operation of any safety device. 4.2.2 External tightness of the gas circuit When tested as specified in 5.2 the gas carrying parts of the burner, up to the last downstream shut-off device, shall be sound. 4.2.3 Heat input range Under the test conditions of 5.3 at the normal test pressure, the maximum and minimum heat inputs declared by the manufacturer shall be obtained to within ± 5 %. 4.2.4 Gas pressure governor The gas regulators shall be conform to the relevant clause of EN 676. The gas supply for operation and start up shall be controlled by a governor to ensure that the pressure at the burner head remains stable. Under the test conditions of 5.4, the heat input shall not vary by more than ± 5 % from the specified value, if the supply pressure changes in the limits of the minimum and maximum pressure.

during the pre-purge or after a controlled shut-down; d) the air flow proving device has been proved to be functioning correctly. Under the conditions of 5.5.5, no excessive pressure fluctuation or flame pulsation shall take place in the boiler. 4.2.5.6 Ignition and flame stability a) Under the test conditions of 5.5.6, ignition shall be effected correctly, rapidly and without any pulsation. The flames shall be stable and shall not create any disturbing noise. A slight tendency to lift at the moment of ignition is permissible, but the flames shall be stable thereafter. For boilers fitted with a range-rating device, these requirements shall be satisfied in the range of the maximum and minimum heat inputs declared by the manufacturer. b) The ignition of the boiler at reduced pressure before the action of the low pressure gas switch or the flame supervision device shall not lead to a dangerous situation for the user or damage to the boiler. 4.2.5.7 Resistance of the burner to over-heating Under the test conditions of 5.5.7 the various parts of the burner shall not suffer any deterioration other than the superficial alterations inherent in combustion. 4.2.5.8 Pre-purge Before energising the ignition device the combustion chamber shall be purged. The duration of the pre-purge shall be either: a) at least 20 s at the full combustion air rate corresponding to the maximum nominal heat input or b) where the air rate is reduced, a time period increased by an amount inversely proportional to the reduced air rate. EXAMPLE 100% air rate – at least 20 s pre-purge time;
50% air rate – at least 40 s pre-purge time;
33% air rate (minimum permitted) – at least 60 s pre-purge time. This reduced air flow rate shall not be less than 33 % of the full combustion air rate. If the purge air flow falls below the required rate at any time during the purge either a) the boiler shall proceed to safety shut-down, or b) the purge shall be continued upon restoration of the required air rate provided that the air flow does not fall below 33 % of the required air rate and that the total purge time at the required air rate is not reduced.

fitted with either two class A safety shut-off valves in series, or with two class B safety shut-off valves in series plus a valve proving
system; b) boilers of heat input greater than 70 kW fitted with two class A safety shut-off valves in series plus a valve proving system. A pre-purge shall be carried out at any restart after every safety shut-down. 4.2.6 Control and safety equipments 4.2.6.1 Start-up heat input Boilers with a nominal heat input up to and including 120 kW may be ignited directly. For burners with a nominal heat input exceeding 120 kW, the start gas rate shall not exceed 120 kW or the value given by the equation
tSA × Qs
≤ 100 or tSA x QS ≤ 150 where appropriate (see Table 1); where:
tSA is the ignition safety time in seconds (s);
Qs is the maximum start gas rate expressed as a percentage of the main gas rate. The tests shall be carried out under the conditions of 5.6.1. 4.2.6.2 Start-up The start-up gas valves shall not be energised before the ignition spark (or other means of ignition) is energized. However, where a hot surface ignition system is used, the ignition system shall be so energised that the ignition source is capable of igniting incoming gas before the start gas valve(s) are opened. The start gas flame proving period shall establish that the flame is stable on its own. In the case of a flame failure, the requirements of 4.2.6.5 apply. Where the gas line is designed such that the gas supply to the ignition burner is taken from between the two main burner gas valves, it is checked under the test conditions of 5.5.6 that it is not possible for a hazardous situation to arise in the event of defective closure of the gas valve immediately upstream of the main burner when the ignition burner is lit. Where the start gas rate is controlled by a start gas rate position contained within the downstream main safety shut-off valve any means of adjustment of the start gas rate shall be capable of being pre-set and sealed. The tests shall be carried out under the conditions of 5.5.6. 4.2.6.3 Main burner ignition 4.2.6.3.1 Establishment by means of a start gas flame If the start gas flame has been ignited at a separate ignition burner and proved the second safety time shall be not more than the safety time mentioned in Table 1 at the end of which time sensing of the main flame shall begin. If the main flame is not detected at the end of this period, the requirements of 4.2.6.5 apply.

column 4, Figure 10);  ignition of the main burner by means of an independent ignition burner; (see Table 1, column 5, Figure 11). Higher start gas rates than those specified in Table 1 may be achieved at the end of the safety time provided that it is proved that the total amount of energy released in the combustion chamber during the safety time is not greater than the energy release calculated by multiplying the values of maximum start gas heat input and safety time given by Table 1. When the electrical supply voltage UN is varied between 85 % of the minimum nominal voltage and 110 % of the maximum nominal voltage declared by the manufacturer, the safety times declared by the manufacturer shall not be exceeded. The safety times given in Table 1 are absolute maxima. The tests shall be carried out under the conditions of 5.6.2.1.

burner ignition at nominal rate Direct main burner ignition at reduced rate Direct main burner ignition at reduced rate with indepen-dent start gas supply Main burner ignition with independent ignition burner
Ignition burner ignition Main burner ignition Rate Qn kW Rate Qs kW Safety time s Rate Qs kW Safety time s Rate Qs kW Safety time s Rate Qs kW First Safety Time s Rate Qs kW Second safety time s ≤ 70 Qn 5 Qn 5 Qn 5 ≤ 0,1Qn 5 Qn 5 > 70 ≤120 Qn 3 Qn
3 Qn 3 ≤ 0,1Qn 5 Qn
3 > 120 not permitted 120 kW or tSA x
Qs ≤ 100 ( max. tSA = 3 s ) ≤ 0,1Qn 3 120 kW or tSA x
Qs ≤ 150 ( max.tSA = 5 s ) Qn = maximum burner heat input in kilowatts Qs = maximum start gas heat input expressed as a percentage of Qn
tSA = safety time in seconds
4.2.6.4.2 Extinction safety time In the test conditions of 5.6.2.2, the extinction safety time shall not exceed 1 s. 4.2.6.4.3 Total closing time In the test conditions of 5.6.2.3, the total closing time shall not exceed 2 s. The two valves shall close simultaneously, but where a valve proving system is used there may be a delay for the second valve of up to 2 s. 4.2.6.5 Failure to ignite For boilers with a heat input up to and including 120 kW, failure to ignite shall lead to either a) a single attempt at recycling, followed by non-volatile lock-out if this attempt fails, or b) non-volatile lock-out. For boilers with heat input greater than 120 kW failure to ignite shall lead to non-volatile lock-out. The test shall be carried out under the conditions of 5.6.2.4.

b) The CO concentration of the dry, air-free combustion products shall not exceed 0,2 % when the boiler operates at 85 % of the nominal voltage with the reference gas of the family or the group for which it is designed, or with a gas actually distributed for boilers of heat input higher than 300 kW. c) The CO concentration of the dry, air-free combustion products shall not exceed 0,2 % when the boiler operates under the nominal voltage with the incomplete combustion gas of the family or the group for which it is designed, or with an overload of 9 % in comparison with the nominal heat input. d) The boiler shall be designed such that if the voltage input becomes lower than 85 % of the nominal value, either the boiler continues to operate safely with a CO concentration in the products of combustion below 1% by volume or it shall go to a safety shut down.

The limit values are given for second family gases. For third family gases, the limit values of these classes are multiplied by a factor of 1,30. For boilers intended to use propane only, the limit values of these classes are multiplied by a factor of 1,20. 4.2.7.2.3 Weighting For multistage and modulating boilers the NOx concentration is equal to the arithmetic average of the values of NOx measured at the different stages or at the maximum and minimum heat input of the modulating boiler. None of the individual measured values shall exceed the value of the class immediately above the class in which the average value calculated belongs. Moreover none of the measured values shall exceed the value of the class 1 as specified in 4.2.7.2.2 for the gas concerned. 4.2.8 Useful efficiencies 4.2.8.1 Useful efficiency at the maximum nominal heat input
Under the conditions of 5.8.1, the useful efficiency, expressed in percent, shall be at least equal to the values derived from Table 3:

4 kW ≤ Pn ≤ 400 kW
≥ n10log284P+ for standard boilers
≥ n10log5,15,87P+ for low temperature boilers
400 kW < Pn ≤ 1 000 kW
≥ 89,2 for standard boilers ≥ 91,4 for low temperature boilers
1) Pn is the maximum nominal output, expressed in kilowatts (kW).
4.2.8.2 Useful efficiency at part load
Under the conditions of 5.8.2, the useful efficiency for a load corresponding to 30 % of the maximum nominal heat input, expressed in percent, shall be at least equal to the values derived from Table 4: Table 4 — Useful efficiency requirement at part load Ranges of nominal output Efficiency requirement expressed at
part load % 4 kW ≤ Pn ≤ 400 kW
≥ 80 + 3 log10 Pn for standard boilers ≥ 87,5 + 1,5 log10 Pn for low temperature boilers
400 kW < Pn ≤ 1 000 kW ≥ 87,8 for standard boilers ≥ 91,4 for low temperature boilers 1) Pn
is the maximum nominal output, expressed in kilowatts (kW).
4.2.9 Condensation For standard boilers which are designed not to give rise to condensation, there shall be no indication of condensation at the operating temperatures provided by the controls. Low temperature boilers are considered to be designed to give rise to condensation. This condensation shall not impair operation of low temperature boiler. The tests shall be carried out under the conditions of 5.9.

5.1 General principles The following test conditions are applied unless otherwise specified in particular paragraphs. 5.1.1 Test performance The boiler supplied by the reference gas of the category (or another gas distributed in the network for boilers of a heat input higher than 300 kW) is adjusted in accordance to the indications given by the manufacturer. Unless otherwise specified, the tests are performed at the maximum nominal heat input. 5.1.2 General conditions for the tests 5.1.2.1 Test room The boiler is installed in a well ventilated, draught-free room, which has an ambient temperature of about 20 °C; the boiler is protected from direct solar radiation. The ambient temperature is measured at a height of 1,50 m above the floor and at a minimum distance of 3 m from the boiler, with a temperature sensor protected against radiation from the test installation.

0,1 % beyond 1 h; 8) auxiliary electrical energy ± 2 %; 9) temperatures:  ambient ± 1 K ;

± 2 K ;  combustion products
± 5 K ;  gas
± 0,5 K ;  surface
± 5 K ; 10) CO, CO2 and O2, for the calculation of flue losses ± 6 % full scale; 11) gas calorific value ± 1 % ; 12) gas density ± 0,5 % ; 13) mass ± 0,05 %. The full range of the measuring apparatus is chosen to be suitable for the maximum anticipated value. The measurement uncertainties indicated concern individual measurements. For measurements requiring a combination of individual measurements (for example: efficiency measurements), lower uncertainties associated with individual measurements may be necessary to attain the total required uncertainty. 5.1.2.7 Adjustment of the heat input The heat input Q, in kilowatts (kW), obtained during a test is given by one of the two following expressions:  If the volumetric rate is measured:
Q = 0,278 × Vr ×
Hi ;  if the mass rate is measured: Q = 0,278 × Mr × Hi ; where:
Hi
is the net calorific value of the gas used for the test (dry, 15 °C, 1 013,25 mbar), in megajoules per cubic metre (MJ/m3) on the volume basis, or in megajoules per kilogram (MJ/kg) on the mass basis, as appropriate;
Vr is the volumetric rate measured in cubic metres per hour (m3/h) of dry gas under reference conditions (15 °C, 1 013,25 mbar), where: Vr = gsga1527315288251013tpppV+−+⋅,,, where:
ps is the saturated vapour pressure of water at tg, in millibars (mbar); for the meaning of the other symbols
see clause 6.
Mr is the mass rate measured in kilograms per hour (kg/h) of dry gas.

5.2 External tightness of the gas line The tests are carried at ambient temperature, using air or gas at a pressure of 150 mbar or 1,5 times the manufacturer's declared maximum supply pressure, whichever is the higher, in the direction of gas flow. An air or a gas supply is connected to the inlet of the burner gas line. The safety shut-off valves are maintained in the open position e
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