oSIST prEN 15420:2006

SLOVENSKI STANDARD
01-marec-2006
3OLQVNLNRWOL]DFHQWUDOQRJUHWMH7LSNRWORY&]LPHQVNRPRþMRQDGN:GR
YNOMXþQRN:
Gas-fired central heating boilers - Type C boilers of nominal heat input exceeding 70 kW,
but not exceeding 1000 kW
Heizkessel für gasförmige Brennstoffe - Heizkessel der Bauart C mit einer
Nennwärmebelastung größer als 70 kW aber nicht größer als 1 000 kW
Chaudieres de chauffage central utilisant les combustibles gazeux - Chaudieres de type
C dont le débit calorifique nominal est supérieur a 70 kW, mais inférieur ou égal a 1000
kW
Ta slovenski standard je istoveten z: prEN 15420
ICS:
91.140.10 Sistemi centralnega Central heating systems
ogrevanja
97.100.20 Plinski grelniki Gas heaters
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD
DRAFT
NORME EUROPÉENNE
EUROPÄISCHE NORM
January 2006
ICS
English Version
Gas-fired central heating boilers - Type C boilers of nominal heat
input exceeding 70 kW, but not exceeding 1000 kW
Chaudières de chauffage central utilisant les combustibles
gazeux - Chaudières de type C dont le débit calorifique
nominal est supérieur à 70 kW, mais inférieur ou égal à
1000 kW
This draft European Standard is submitted to CEN members for enquiry. It has been drawn up by the Technical Committee CEN/TC 109.
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 Management Centre has the same
status as the official versions.
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.
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
Management Centre: rue de Stassart, 36  B-1050 Brussels
© 2006 CEN All rights of exploitation in any form and by any means reserved Ref. No. prEN 15420:2006: E
worldwide for CEN national Members.

Contents
1 Scope. 7
2 Normative references . 7
3 Definitions. 9
3.1 Combustible gases . 9
3.2 Constituent parts of the boiler. 11
3.2.1 Gas supply. 11
3.2.2 Air supply and combustion products evacuation . 12
3.2.3 Adjusting, control and safety devices . 13
3.3 Operation of the boiler. 16
3.3.1 Gas rates. 16
3.3.2 Outputs. 17
4 Classification of boilers. 20
4.1 Gases and categories. 20
4.2 Mode of air supply and evacuation of the combustion products . 20
4.2.1 General. 20
4.2.2 Type of installation of the boiler. 21
4.2.3 Presence and position of a fan. 22
)
4.3 Classification according to operating conditions . 22
4.3.1 Standard boiler. 22
4.3.2 Low-temperature boiler . 22
4.3.3 Gas condensing boiler . 22
4.4 Modular boiler . 22
5 Constructional requirements. 22
5.1 General. 22
5.2 Conversion to different gases . 22
5.3 Materials and method of construction. 23
5.3.1 General. 23
5.3.2 Materials and thicknesses of walls or tubes under water pressure . 23
5.3.3 Thermal insulation . 32
5.4 Combustion products evacuation duct . 33
5.4.1 Stability under mechanical loading. 33
5.4.2 Stability under exposure to heat .33
5.4.3 Corrosion resistance . 33
5.4.4 Resistance to condensate and moisture under normal operating conditions. 33
5.5 Design . 33
5.5.1 General. 33
5.5.2 Modular boilers . 34
5.6 Use and servicing . 34
5.7 Connections to the gas and water pipes. 34
5.7.1 General. 34
5.7.2 Connections to the gas pipe. 34
5.7.3 Connections to the central heating circuit. 35
5.8 Soundness. 35
5.8.1 Soundness of the gas circuit. 35
5.8.2 Soundness of the combustion circuit. 35
5.9 Supply of combustion air and the evacuation of the combustion products . 36
5.9.1 General. 36
5.9.2 Air supply and combustion products evacuation duct. 36
5.9.3 Terminal . 36
5.9.4 Terminal guard . 36
5.9.5 Fitting piece . 37
5.9.6 Special requirements for certain components of boilers with a fan . 37
5.9.7 Condensate discharge. 38
5.10 Checking the state of operation .38
5.11 Drainage. 38
5.12 Electrical equipment. 39
5.13 Operational safety in the event of failure of the auxiliary energy. 39
5.14 Adjusting, control and safety devices . 39
5.14.1 General. 39
5.14.2 Adjusters and range rating devices. 39
5.14.3 Gas circuit. 40
5.14.4 Gas pressure governor. 41
5.14.5 Ignition devices . 42
5.14.6 Flame supervision systems . 42
5.14.7 Thermostats and water temperature limiting devices. 43
5.15 Burners . 44
5.16 Pressure test points. 44
5.17 Chemical composition of the condensate. 44
6 Operational requirements . 45
6.1 General. 45
6.2 Soundness. 45
6.2.1 Soundness of the gas circuit. 45
6.2.2 Soundness of the combustion circuit. 45
6.2.3 Soundness of the water circuit. 46
6.3 Nominal, maximum and minimum heat inputs, and nominal output. 46
6.3.1 Nominal heat input or maximum and minimum heat inputs . 46
6.3.2 Adjustment of the heat input by the downstream pressure. 46
6.3.3 Ignition rate. 46
6.3.4 Nominal output. 46
6.3.5 Gas pressure governor. 47
6.4 Safety of operation. 47
6.4.1 Limiting temperatures . 47
6.4.2 lgnition – Cross-lighting – Flame stability. 48
6.4.3 Pre-purge . 49
6.4.4 Functioning of a permanent ignition burner when the fan stops during the
standby time . 50
6.5 Adjusting, control and safety devices . 50
6.5.1 General. 50
6.5.2 Ignition devices . 50
6.5.3 Flame supervision devices . 51
6.5.4 Ignition burner and ignition rates. 53
6.5.5 Air proving . 53
6.5.6 Gas pressure switches. 55
6.5.7 Control thermostat and safety temperature limiter . 55
6.5.8 Condensate discharge blockage. 56
6.6 Combustion . 56
6.6.1 Carbon monoxide. 56
6.6.2 Other pollutants . 57
6.7 Useful efficiencies. 57
6.7.1 Useful efficiency at the nominal heat input. 57
6.7.2 Useful efficiency at part load . 57
6.8 Criteria for condensation in the flue .58
6.9 Resistance of the materials to pressure. 58
6.9.1 General. 58
6.9.2 Boilers of sheet steel or non-ferrous metals . 58
6.9.3 Boilers of cast iron and cast materials. 58
6.10 Hydraulic resistance. 59
6.11 Condensation in the boiler. 59
7 Test methods. 59
7.1 General. 59
7.1.1 Characteristics of the reference and limit gases. 59
7.1.2 General test conditions . 65
7.2 Soundness. 68
7.2.1 Soundness of the gas circuit. 68
7.2.2 Soundness of the combustion circuit. 69
7.2.3 Soundness of the water circuit. 70
7.3 Nominal, maximum and minimum heat inputs and nominal output. 70
7.3.1 The nominal heat input or the maximum and minimum heat inputs. 70
7.3.2 Adjustment of the heat input by the downstream pressure. 71
7.3.3 Minimum ignition rate. 71
7.3.4 Nominal output. 72
7.3.5 Gas governor. 72
7.4 Safety of operation. 72
7.4.1 Limiting temperatures . 72
7.4.2 Ignition - Cross-lighting - Flame stability . 74
7.4.3 Pre-purge . 77
7.4.4 Functioning of a permanent ignition burner when the fan stops during standby
time. 78
7.5 Adjusting, control and safety devices . 78
7.5.1 General. 78
7.5.2 Ignition devices . 78
7.5.3 Flame supervision device . 79
7.5.4 Ignition burner and ignition rates. 81
7.5.5 Air proving device. 81
7.5.6 Gas pressure switches. 83
7.5.7 Control thermostat and safety temperature limiter . 83
7.5.8 Condensate discharge blockage. 84
7.6 Combustion . 85
7.6.1 Carbon monoxide. 85
7.6.2 Other pollutants . 89
7.7 Useful efficiencies. 92
7.7.1 Useful efficiency at the nominal heat input. 92
7.7.2 Useful efficiency at part load . 93
7.8 Criteria for condensation in the flue .99
7.8.1 Determination of flue losses. 99
7.8.2 Minimum temperature of the combustion products. 100
7.9 Resistance of materials to pressure . 100
7.9.1 General. 100
7.9.2 Boilers of sheet steel or non-ferrous metals . 100
7.9.3 Boilers of cast iron and cast materials. 100
7.10 Hydraulic resistance. 101
7.11 Condensation in the boiler. 101
8 Marking and instructions . 101
8.1 Marking of the boiler. 101
8.1.1 General. 101
8.1.2 Data plate . 101
8.1.3 Supplementary marking . 103
8.1.4 Packaging . 105
8.1.5 Warnings on the boiler and on the packaging. 105
8.1.6 Other information. 105
8.2 Instructions. 105
8.2.1 Technical instructions for the installer. 105
8.2.2 For installation of the combustion circuit . 106
8.2.3 Use and maintenance instructions for the user . 107
8.2.4 Conversion instructions. 108
Annex A (informative) National situations . 123
Annex B (informative) Special national conditions. 129
Annex C (informative) A-deviations . 130
Annex D (informative) Classification of type C boilers. 131
Annex E (informative) Practical method of calibrating the test rig to enable the heat loss
D to be determined . 138
p
Annex F (informative) Main symbols and abbreviations used. 139
Annex G (informative) Compilation of test conditions . 140
Annex H (informative) Valving. 143
Annex I (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 . 150
Annex J (informative) Means of determining the ignition time at full rate. 151
Annex K (informative) Example of calculation of the weighting factors for a boiler with
several rates . 152
Annex L (informative) Calculation of conversions of NOx. 154
Annex M (normative) Test apparatus for type C boilers (see 7.4.2.3.3) . 155
Annex N (informative) Requirements and test methods for separate air supply and
combustion products evacuation ducts of type C boilers . 156
Annex O (informative) Use of test gases. 161
Annex ZA (informative) Clauses of this European Standard addressing essential
requirements or provisions of EU Directives. 162

Foreword
This document (prEN 15420:2005) has been prepared by Technical Committee CEN/TC 109 "Central
heating boilers using gaseous fuels", the secretariat of which is held by NEN.
This document is currently submitted to the CEN Enquiry.
It was established to deal with aspects related to:
 safety;
 rational use of energy;
 fitness for purpose.
Other types of boilers are dealt with in separate standards.
This draft European standard has been prepared under a mandate given to CEN by the European
Commission and the European Free Trade Association, and supports and supports Essential
Requirements of EU Directive(s).
For relationship with EU Directives 90/396/EEC "Approximation of the laws of Member States
concerning gas appliances" and 92/42/EEC "Efficiency requirements for new hot water boilers fired
with liquid or gaseous fuels" see informative annex ZA, which is an integral part of this standard.
This standard covers only type testing.
Matters related to quality assurance systems, tests during production and to certificates of conformity
to auxiliary devices are not dealt with in this standard.
It is impractical to use the full range of test gases to EN 437 for type testing since their availability, for
inputs over 300 kW, may present problems for test houses and manufacturers. Informative annex O
gives guidance on the use of gases for tests in order to ensure conformity with EU Directive
90/396/EEC “Approximation of the laws of Member States concerning gas appliances.

1 Scope
This standard specifies the requirements and test methods concerning, in particular the construction,
safety, fitness for purpose, and rational use of energy, as well as the classification and marking of
gas-fired central heating boilers that are fitted with atmospheric burners, fan assisted atmospheric
burners or fully premixed burners, and are hereafter referred to as "boilers".
This standard applies to boilers of type C, as listed in 4.2:
 that use one or more combustible gases of the three gas families at the pressures stated in
Tables 14 and 15;
 that have a nominal heat input (on the basis of net calorific value) exceeding 70 kW, but not
exceeding 1000 kW, including modular boilers;
 where the temperature of the heat transfer fluid does not exceed 105 °C during normal operation;
 where the maximum operating pressure in the water circuit does not exceed 6 bar;
 which can give rise to condensation under certain circumstances.
The standard applies to boilers designed for sealed water systems or for open water systems.
The standard does not contain all the requirements necessary for boilers:
 intended to be installed in the open or in living rooms;
 permanently fitted with more than one flue outlet;
 of the condensing type;
 intended to be connected to a common flue having mechanical extraction;
 type C ,C , C , C and C boilers;
41 51 61 7 81
 fitted with a forced draught burner in accordance with EN 676;
 producing hot water for domestic purposes.
This standard only covers type testing.
2 Normative references
This standard includes provisions from other publications, either by dated or undated reference.
These normative references are quoted in the appropriate places in the text and the publications are
listed below. For the dated references, amendments or revisions later than one or other of the
publications only apply to this standard if they were incorporated in it by amendment or revision. For
undated references, the last edition of the publication to which reference is made applies.
EN 88, Pressure governors for gas appliances for inlet pressures up to 200 mbar
EN 125, Specification for flame supervision devices for gas burning appliances — Thermoelectric
flame supervision devices
EN 126, Multi-functional controls for gas burning appliances
EN 257, Mechanical thermostats for gas burning appliances
EN 297, Gas-fired central heating boilers — Type B and B boilers fitted with atmospheric burners
11 11BS
of nominal heat input not exceeding 70 kW
EN 298, Automatic burner control systems for gas burners and gas burning appliances with or without
fans
EN 437, Test gases — Test pressures — Appliance categories
EN 1057, Copper and copper alloys — Seamless, round copper tubes for water and gas in sanitary
and heating applications
EN 1092-1, Flanges and their joints. Circular flanges for pipes, valves, fittings and accessories,
PN designated – Part 1: Steel flanges
EN 1092-2, Flanges and their joints. Circular flanges for pipes, valves, fittings and accessories,
PN designated – Part 2: Cast iron flanges
EN 1092-3, Flanges and their joints. Circular flanges for pipes, valves, fittings and accessories,
PN designated – Part 3: Copper alloy flanges
EN 1561, Founding — Grey cast irons
EN 1643, Valve proving systems for automatic shut off valves for gas burners and gas burning
appliances
EN 1854, Pressure sensing devices for gas burners and gas burning appliances
EN 10029, Hot rolled steel plate 3 mm thick or above — Tolerances on dimensions, shape and mass
EN 12067-1, Gas/air ratio controls for gas burners and gas burning appliances – Part 1: Pneumatic
types
EN 12067-2, Gas/air ratio controls for gas burners and gas burning appliances – Part 2: Electronic
types
EN 50165, Electrical equipment of non-electric heating appliances for household and similar purposes
- Safety requirements
EN 60335-1, Safety of household and similar electrical appliances — Part 1: General requirements
EN 60529, Degrees of protection provided by enclosures (IP code)
EN 60730-2-9, Automatic electrical controls for household and similar use — Part 2: Particular
requirements for heat-sensing controls
EN 60742, Isolating transformers and safety isolating transformers — Requirements
EN ISO 228-1, Pipe threads where pressure-tight joints are not made on the threads — Part 1:
Dimensions, tolerances and designation
EN ISO 3166-1, Codes for the representation of names of countries and their subdivisions — Part 1:
Country codes
EN ISO 4063, Welding and allied processes. Nomenclature of processes and reference numbers
ISO 7-1, Pipe threads where pressure-tight joints are made on the threads — Part 1: Designation,
dimensions and tolerances
ISO 857, Welding, brazing and soldering processes - Vocabulary — Bilingual edition
ISO 2553, Welded, brazed and soldered joints — Symbolic representation on drawings
CR 1404, Determination of emissions from appliances burning gaseous fuels during type testing
CR 1749, European scheme for the classification of gas appliances according to the method of
evacuation of the products of combustion (types)
3 Definitions
For the purposes of this standard, the following definitions apply:
3.1 Combustible gases
3.1.1
test gases
gases intended for the verification of the operational characteristics of appliances using combustible
gases. They consist of reference gases and limit gases
3.1.2
reference gases
test gases with which appliances operate under nominal conditions, when they are supplied at the
corresponding normal pressure
3.1.3
limit gases
test gases representative of the extreme variations in the characteristics of the gases for which
appliances have been designed
3.1.4
reference conditions
o
these correspond to 15 C , 1 013,25 mbar, unless otherwise specified
3.1.5
relative density
ratio of the masses of equal volumes of dry gas and dry air under the same conditions of temperature
and pressure: 15 °C or 0 °C and 1 013,25 mbar
Symbol: d
3.1.6
calorific value
quantity of heat produced by the complete combustion, at a constant pressure equal to
1 013,25 mbar, of a unit volume or mass of gas, the constituents of the combustible mixture being
taken at reference conditions and the products of combustion being brought back to the same
conditions
A distinction is made between:
 the gross calorific value : the water produced by combustion is assumed to be condensed
Symbol: H
s
 the net calorific value : the water produced by combustion is assumed to be in the vapour state
Symbol: H
i
Unit:
 either in megajoules per cubic metre (MJ/m ) of dry gas under the reference conditions;
 or in megajoules per kilogram (MJ/kg) of dry gas.
3.1.7
wobbe index
ratio of the calorific value of a gas per unit volume and the square root of its relative density under the
same reference conditions. The Wobbe index is said to be gross or net according to whether the
calorific value used is the gross or net calorific value
Symbols: gross Wobbe index: W
s
net Wobbe index: W
i
The Wobbe indices are expressed:
 either in megajoules per cubic metre (MJ/m ) of dry gas under the reference conditions;
 or in megajoules per kilogram (MJ/kg) of dry gas
3.1.8
gas pressure
static pressure of the moving gas, relative to the atmospheric pressure, measured at right angles to
the direction of flow of the gas
Symbol:  p
Unit:  millibar (mbar)
3.1.9
test pressures
gas pressures used to verify the operational characteristics of appliances using combustible gases.
They consist of normal and limit pressures.
[3.5 of EN 437:2003]
3.1.10
normal pressure
pressure under which the appliances operate in nominal conditions when they are supplied with the
corresponding reference gas
Symbol:  p
n
3.1.11
limit pressures
pressures representative of the extreme variations in the appliance supply conditions
Symbols: maximum pressure: p
max
minimum pressure: p
min
3.1.12
pressure couple
combination of two distinct gas distribution pressures applied by reason of the significant difference
existing between the Wobbe indices within a single family or group in which
 the higher pressure corresponds only to gases of low Wobbe index;
 the lower pressure corresponds to gases of high Wobbe index.
3.2 Constituent parts of the boiler
3.2.1 Gas supply
3.2.1.1
gas inlet connection
part of the boiler intended to be connected to the gas supply
3.2.1.2
gas circuit
assembly of parts of the boiler that carry or contain the combustible gas between the boiler gas inlet
connection and the point at which air is admitted
3.2.1.3
restrictor
device with one or more orifices, which is placed in the gas circuit so as to create a pressure drop and
thus bring the gas pressure at the burner to a predetermined value for a given supply pressure and
given rate
3.2.1.4
injector
a component that admits gas into the burner
3.2.1.5
gas rate adjuster
component allowing the gas rate of the burner to be brought to a predetermined value according to
the supply conditions
The action of operating this component is called "adjustment of the gas rate"
3.2.1.6
range rating device
component on the boiler intended to be used by the installer to adjust the heat input of the boiler,
within the range of maximum and minimum heat inputs stated by the manufacturer, to suit the actual
heat requirements of the installation
3.2.1.7
primary aeration adjuster
device enabling the primary aeration of a burner to be set to the desired value according to the supply
conditions
3.2.1.8
sealing an adjuster or a control
arrangements made to make evident any attempt to change its adjustment (e.g. breakage of a device
or of a sealing material)
A control or adjuster which is sealed is considered to be non-existent.
3.2.1.9
putting an adjuster or a control out of service
action intended to put an adjuster or control (rate, pressure, etc.) out of service
3.2.1.10 Burners
3.2.1.10.1
main burner
a burner that is intended to assure the thermal function of the boiler and is generally called "the
burner"
3.2.1.10.2
premixed burner
burner in which the gas and a quantity of air at least equal to that theoretically necessary for complete
combustion are mixed before the flame ports
3.2.1.10.3
ignition device
any means (flame, electrical ignition device or other device) used to ignite the gas at the ignition
burner or at the main burner
3.2.1.10.4
manual ignition device
device by means of which the burner is ignited following manual intervention
3.2.1.10.5
automatic ignition device
automatic device which ignites the ignition burner or the main burner directly
3.2.1.10.6
ignition burner
burner intended to ignite a main burner
3.2.1.10.7
permanent ignition burner
ignition burner that operates continuously throughout the whole period that the boiler is in use
3.2.1.10.8
intermittent ignition burner
ignition burner that is ignited before and extinguished at the same time as the main burner
3.2.1.10.9
alternating ignition burner
ignition burner which is extinguished as soon as ignition of the main burner is effected. It re-ignites at
the main burner flame just before the latter goes out
3.2.1.10.10
interrupted ignition burner
ignition burner which operates only during the ignition sequence
3.2.2 Air supply and combustion products evacuation
3.2.2.1
combustion circuit
circuit including the air supply duct, the combustion chamber, the heat exchanger, the combustion
products evacuation duct and either the fitting piece or the connection to the terminal, if any
3.2.2.2
combustion products circuit
circuit including the combustion chamber, the heat exchanger and the circuit permitting evacuation of
the combustion products to the flue, up to and including the flue outlet
3.2.2.3
combustion chamber
enclosure inside which combustion of the air-gas mixture takes place
3.2.2.4
flue outlet
part of the boiler through which the combustion products are evacuated to the flue system
3.2.2.5
air supply and combustion products evacuation ducts
means for transporting combustion air to the burner and combustion products to the terminal or fitting
piece
It is necessary to distinguish between:
 completely surrounded ducts:
the combustion products evacuation duct is surrounded by combustion air throughout its length
 separate ducts:
the combustion products evacuation duct and the combustion air supply duct are neither
concentric nor completely surrounded ducts
3.2.2.6
terminal
device fitted to the outside of the building, to which are connected:
 the air supply and combustion products evacuation ducts for type C and C boilers (one or two
1 3
devices;
 the air supply duct on the one hand and the combustion products evacuation duct on the other
hand for type C boilers (two devices);
 the air supply duct for type C boilers (one device
3.2.2.7
terminal guard
device that protects the terminal from mechanical damage from outside influences
3.2.2.8
fitting piece
device which allows the fitting of:
 the air supply and combustion products evacuation ducts to a single shared duct for type
C boilers;
 the air supply and combustion products evacuation ducts to two ducts of a shared duct
...