ONORM EN 297 : 2006

Foreword
1 General
1.1 Field of application
1.2 Normative references
1.3 Definitions
1.3.1 Reference conditions
1.3.2 Combustible gases
1.3.3 Constituent parts of the boiler
1.3.4 Operation of the boiler
1.4 Classification
1.4.1 Classification of gases
1.4.2 Classification of boilers
2 Constructional requirements
2.1 General
2.1.1 Conversion to different gases
2.1.2 Materials and methods of construction
2.1.3 Design
2.1.4 Use and servicing
2.1.5 Connections to the gas and water pipes
2.1.6 Soundness
2.1.7 Supply of combustion air and evacuation of the
        combustion products
2.1.8 Checking the state of operation
2.1.9 Drainage
2.1.10 Electrical equipment
2.1.11 Operational safety in the event of failure of
        the auxiliary energy
2.2 Requirements for adjusting, control and safety
        devices
2.2.1 General
2.2.2 Adjuster and range-rating device
2.2.3 Gas circuit
2.2.4 Gas governor
2.2.5 Ignition devices
2.2.6 Flame supervision devices
2.2.7 Thermostats and water temperature limiting devices
2.2.8 Remote control
2.2.9 Expansion vessel and pressure gauge
2.2.10 Combustion products discharge safety device
2.3 Burners
2.4 Pressure test points
2.5 Chemical composition of the condensate
3 Operational requirements
3.1 General
3.2 Soundness
3.2.1 Soundness of the gas circuit
3.2.2 Soundness of the combustion circuit
3.2.3 Soundness of the water circuit
3.3 Nominal, maximum and minimum heat inputs and
        nominal output
3.3.1 General
3.3.2 Nominal heat input
3.3.3 Maximum and minimum heat input
3.3.4 Minimum heat input for ignition
3.3.5 Nominal output
3.4 Safety of operation
3.4.1 Limiting temperatures
3.4.2 Ignition - Cross lighting - Flame stability
3.5 Adjusting, control and safety devices
3.5.1 General
3.5.2 Control devices
3.5.3 Automatic valves
3.5.4 Ignition devices
3.5.5 Flame supervision devices
3.5.6 Gas governor
3.5.7 Thermostats and water temperature limiting
        devices
3.5.8 Combustion products discharge safety device
3.6 Combustion
3.6.1 Carbon monoxide
3.6.2 Other pollutants
3.7 Useful efficiencies
3.7.1 Useful efficiencies at the nominal heat input
3.7.2 Useful efficiencies at part load
3.8 Condensation in the flue
3.9 Resistance of the materials to pressure
3.9.1 General
3.9.2 Boilers of pressure class 1
3.9.3 Boilers of pressure class 2
3.9.4 Boilers of pressure class 3
3.10 Hydraulic resistance
3.11 Condensation in the boiler
4 Test methods
4.1 General
4.1.1 Characteristics of the reference and limit gases
4.1.2 Requirements for the preparation of test gases
4.1.3 Carrying out the tests
4.1.4 Test pressures
4.1.5 Conduct of the tests
4.1.6 General test conditions
4.1.7 Summary of the test conditions
4.2 Soundness
4.2.1 Soundness of the gas circuit
4.2.2 Soundness of the combustion circuit
4.2.3 Soundness of the water circuit
4.3 Nominal, maximum and minimum heat inputs and
        nominal output
4.3.1 General
4.3.2 Nominal heat input
4.3.3 Maximum and minimum heat input
4.3.4 Minimum heat input for ignition
4.3.5 Nominal output
4.4 Safety of operation
4.4.1 Limiting temperatures
4.4.2 Ignition - Cross lighting - Flame stability
4.5 Adjusting, control and safety devices
4.5.1 General
4.5.2 Control devices
4.5.3 Automatic valves
4.5.4 Ignition devices
4.5.5 Flame supervision devices
4.5.6 Gas governor
4.5.7 Thermostats and water temperature limiting
        devices
4.5.8 Combustion products discharge safety device
4.6 Combustion
4.6.1 Carbon monoxide
4.6.2 Other pollutants
4.7 Useful efficiencies
4.7.1 Useful efficiency at the nominal heat input
4.7.2 Useful efficiency at part load
4.8 Criteria for condensation in the flue
4.8.1 Determination of flue losses
4.8.2 Minimum temperature of the combustion products
4.9 Resistance of the materials to pressure
4.10 Hydraulic resistance
5 Marking and instructions
5.1 Marking of the boiler
5.2 Instructions
Tables
1 Classification of gases
2 Mechanical properties and chemical compositions
        of carbon and stainless steels
3 Minimum requirements for cast iron
4 Parts cast in aluminium and aluminium alloys
5 Parts cast in copper or copper alloys
6 Minimum thickness for rolled parts
7 Nominal minimum thicknesses of boiler sections
        of cast materials under water pressure
8 Weld joints and welding processes
9a Characteristics of the test gases
9b Calorific values of the third family test gases
9c Reference gas characteristics at 0 deg C
10 Test gases corresponding to the boiler categories
11a Test pressures when there is no pressure couple
11b Test pressures when there is a pressure couple
12 Calculation of the useful part load efficiency
13 Symbols and quantities needed to calculate the
        efficiency at part load
G.1 Table identifying conformity with the essential
G.2 Table identifying conformity with the relevant
        articles of the efficiency directive
L.1
L.2
M.1 Conversion of the emission value of NOx for
        first family gases
M.2 Conversion of the emission value of NOx for second
        family gases
M.3 Conversion of the emission value of NOx for third
        family gases
Annexes
A (informative) National situations
A.3 Flue connections in the various countries
A.4 Gas connections conditions in common use in the
        various countries
B (informative) Particular national conditions
B.1 Gases distributed locally
B.2 Special categories marketed nationally or locally
B.3 Particular conditions
C (informative) Practical method of calibrating
        the test rig to enable the heat loss Dp to be
        determined
D (informative) Main symbols and abbreviations used
E (informative) Summary of the test conditions
E.1 First family
E.2 Second family
E.3 Third family
F (informative) Composition of the gas circuit
G (informative) Table identifying conformity with
        the essential requirements of the gas appliance
        directive
H (informative) Deviation A for Switzerland
Figures
1a Test rig with direct recirculation
1b Test rig with heat exchanger
2 Sampling probe for flue diameters greater than DN 100
3 Sampling probe for flue diameters not greater
    than DN 100
4 Test of a boiler under special draught conditions
5 Connections to the 5 m flue
6 Device for checking the soundness of the gas circuit
7 Soundness test for components (pressure loss method)
8 Determination of the hydraulic resistance
9 Test rig for the combustion products discharge
    safety device
10 Test rig for determination of efficiency
11 Test installation to determine the heat emissions of the
    boiler when the burner is off

Specifies the requirements and test methods for the construction, safety, fitness for purpose, rational use of energy, classification and marking of gas fired central heating boilers.