CEN/TC 109/WG 1 - Domestic central heating boilers using gaseous fuels

This document specifies the requirements and tests methods concerning the construction, safety, fitness for purpose, and rational use of energy, as well as the classification and marking of hybrid units.
A hybrid unit is composed of:
-   a gas boiler as a heat generator which is able to supply the heat demand in all operating conditions;
-   an electrical air-to-water heat pump, as a heat generator, which does not have to meet the heat demand in all operating conditions;
-   a control unit (see definition 3.1.10).
A hybrid unit can include the facility to produce hot water, either by the instantaneous or storage principle, the whole being marketed as a single unit.
A gas boiler as part of a hybrid unit covered by this document is a gas-fired central heating boiler from the types C1 up to C9 and the types B2, B3 and B5, according to the classification in EN 1749:2020:
a)   that have a nominal heat input (on the basis of gross calorific value) not exceeding 400 kW;
b)   that use one or more combustible gases of the three gas families at the pressures stated in EN 437:2021;
c)   where the temperature of the heat transfer fluid does not exceed 105 °C during normal operation;
d)   where the maximum operating pressure in the water circuit does not exceed 6 bar;
e)   which are classified as a gas-fired central heating boiler;
f)   which are intended to be installed either indoors or outdoors in a partially protected place;
g)   which are designed for either sealed water systems or for open water systems.
This document provides requirements for boilers with known constructions.
NOTE 1   For boilers with any alternative constructions, which might not fully be covered by this document, the risk associated with this alternative construction needs to be assessed.
NOTE 2   An example of an assessment methodology, based upon risk assessment and which covers the essential requirements of the Gas Appliance Regulation UE/426/2016, is given in Clause 11.
This document does not cover all the requirements for:
aa)   appliances that are intended to be connected to gas grids where the quality of the distributed gas is likely to vary to a large extent over the lifetime of the appliance (see EN 15502-1:2021, Annex AB);
ab)   appliances using flue dampers;
ac)   appliances of the types B21, B31, B51, C21, C41, C51, C61, C71 and C81;
ad)   appliances incorporating flexible plastic flue liners;
ae)   appliances designed to become connected to a combined flue duct system.
af)   appliances of the types C(10),C(11), C(12) and C(13);
ag)   C7 appliances that have a nominal heat input (on the basis of net calorific value) exceeding 70 kW;
ah)   appliances intended to be connected to a flue having mechanical extraction;
ai)   surface temperatures of external parts particular to children and elderly people;
aj)   appliances that are intended to burn natural gases of the second family where hydrogen is added to the natural gas;
ak)   appliances equipped with an adaptive combustion control function (ACCF);
al)   boilers intended to be installed in areas accessible to elderly people and children.
This document specifies minimum operating requirements which ensure that the products are fit for the use designated by the technical instructions when used for space heating and/or DHW production.
This document is intended to be used in conjunction with:
ba)   the gas-fired boiler, the generic part EN 15502-1:2021 and specific parts FprEN 15502-2-1:2022 and FprEN 15502-2-2:2022;
bb)   the electrical heat pump, EN 14511-4:2018, EN 378-1:2016+A1:2020, EN 378-2:2016 and EN 14825:2022;
bc)   electrical safety, EN 60335-1:2012 , EN 60335-2-102:2016 and IEC 60335-2-40:2018;
bd)   for domestic hot water production, EN 13203-5:2022.

This European 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 and are hereafter referred to as boilers.
Where the word boiler is used, this is to be read as the boiler including its connecting ducts, ducts and terminals, if any.
This European Standard covers gas-fired central heating boilers type B11, B11BS, B12, B12BS, B13, B13BS according to the classification in CEN/TR 1749:2009:
a)   that have a nominal heat input (on the basis of net calorific value) not exceeding 70 kW;
b)   that use one or more combustible gases of the three gas families at the pressures stated in EN 437;
c)   where the temperature of the heat transfer fluid does not exceed 105 °C during normal operation;
d)   where the maximum operating pressure in the water circuit does not exceed 6 bar;
e)   which are declared in the technical instructions to be either a low temperature boiler or a standard boiler. If no declaration is given the boiler is to be considered a standard boiler;
f)   which are intended to be installed either indoors or in a partially protected place;
g)   which are either not intended to produce hot water, or are intended to produce hot water either by the instantaneous or storage principle, the whole being marketed as a single unit.
h)   which are designed for either sealed water systems or for open water systems.
This European Standard is to be used in conjunction with the General Requirements Standard EN 15502 1.
For applications within the scope of the PED further requirements may be necessary (e.g. situations where the maximum allowable temperature exceeds 110 °C, or where volume times maximum allowable pressure is over 50 bar x litres).
This standard provides requirements for boilers with known constructions. For boilers with any alternative constructions, which might not fully be covered by this standard, the risk associated with this alternative construction shall be assessed.
An example of an assessment methodology, based upon risk assessment and which covers the essential requirements of the Gas Appliance Directive, is given in Clause 11.
This standard does not cover all the requirements for:
i)   appliances that are intended to be connected to gas grids where the quality of the distributed gas is likely to vary to a large extent over the lifetime of the appliance (see Annex DD of EN 15502 2 1:2012);
j)   appliances using flue dampers;
k)   appliances that have a nominal heat input (on the basis of net calorific value) exceeding 70 kW;
l)   appliances of the types A, B14, B2, B3, B4, B5 and C;
m)   appliances intended to be connected to a (common) flue having mechanical extraction;
n)   appliances with gas/air ratio control;
o)   modular boilers;
p)   boilers which can give rise to condensation under certain circumstances;
q)   boilers intended to be installed in a room with a foreseeable negative pressure relative to the pressure in the flue system.
NOTE   Negative pressure relative to the pressure in the flue system can for example be caused by mechanical or thermal ventilation in airtight buildings.

This document specifies, the requirements and test methods concerning the classification and marking of gas-fired central heating boilers that are fitted with atmospheric burners, fan assisted atmospheric burners and are hereafter referred to as “boilers”.
Where the word boiler is used, this is intended to be read as the boiler including its connecting ducts, ducts and terminals, if any.
This document covers gas-fired central heating boilers type B11, B11BS, B12, B12BS, B13, B13BS:
NOTE 1   For further background information on appliance types see EN 1749:2020.
a)   that have a nominal heat input (on the basis of net calorific value) not exceeding 70 kW;
b)   that use one or more combustible gases of the three gas families at the pressures stated in EN 437:2021;
c)   where the temperature of the heat transfer fluid does not exceed 105 °C during normal operation;
d)   where the maximum operating pressure in the water circuit does not exceed 6 bar;
e)   which are declared in the technical instructions to be either a “low temperature boiler” or a “standard boiler”. If no declaration is given the boiler is to be considered a “standard boiler”;
f)   which are intended to be installed inside a building or in a partially protected place;
g)   which are intended to produce also hot water either by the instantaneous or storage principle, as a single unit;
h)   which are designed for either sealed water systems or for open water systems.
NOTE 2   This document provides requirements for boilers with known constructions. For boilers with any alternative constructions, which might not fully be covered by this document, the risk associated with this alternative construction needs to be assessed.
An example of an assessment methodology, based upon risk assessment, is given in Clause 11.
This document does not cover all the requirements for:
aa)   appliances that are intended to be connected to gas grids where the quality of the distributed gas is likely to vary to a large extent over the lifetime of the appliance (see Annex AB);
ab)   appliances using flue dampers;
ac)   appliances that have a nominal heat input (on the basis of net calorific value) exceeding 70 kW;
ad)   appliances of the types A, B14, B¬2, B3, B4, B5 and C;
ae)   appliances intended to be connected to a (common) flue having mechanical extraction;
af)   appliances with gas/air ratio control;
ag)   modular boilers;
ah)   boilers which can give rise to condensation under certain circumstances;
ai)   boilers intended to be installed in a room with a foreseeable negative pressure relative to the pressure in the flue system;
aj)   surface temperatures of external parts particular to children and elderly people;
ak)   appliances that are intended to burn natural gases of the second family where hydrogen is added to the natural gas;
al)   boilers intended to be installed in areas accessible to elderly people and children;
am)   boilers equipped with an adaptive combustion control function (ACCF).
NOTE   Negative pressure relative to the pressure in the flue system can for example be caused by mechanical or thermal ventilation in airtight buildings.

Scope of CEN/TS 15502-3-1
EN 15502-2-1:2022, Clause 1 applies with the following modifications:
Add after k):
l) which are fully premixed appliances equipped with an Adaptive Combustion Control Function (ACCF) that are intended to be connected to gas grids where the quality of the distributed gas is likely to vary to a large extent over the lifetime of the appliance including gas grids for natural gases of the second family where up to 20% hydrogen volume is added to the natural gas (H2NG-Y20).
m) which are fully premixed appliances equipped with a Pneumatic Gas Air Ratio controller (PGAR) that are intended to be connected to gas grids for natural gases of the second family where up to 20% hydrogen volume is added to the natural gas (H2NG-Y20), where the quality of the distributed gas without adding the hydrogen is not likely to vary to a large extent over the lifetime of the appliance.
Replace ab) and ak) and al) by the following:
ab) appliances that are intended to be connected to gas grids where the quality of the distributed gas is likely to vary to a large extent over the lifetime of the appliance (see Annex AB of EN 15502-1:2021), except for fully premixed appliances with a ACCF, as ACCF appliances are designed to adapt to variations in gas quality.
ak) appliances that are intended to burn natural gases of the second family where hydrogen is added to the natural gas, except for fully premixed appliances with a ACCF or PGAR (which are covered by this document);
al) Partially premixed appliances equipped with an adaptive combustion control function (ACCF).

Amendment for the addition of ecodesign requirements (Regulation No 813/2013)
and energy labelling requirements (Regulation No 811/2013)
This European Standard specifies the common requirements and test methods concerning, in particular the construction, safety, fitness for purpose, and rational use of energy, as well as the classification, marking and energy labelling 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 European Standard is to be used in conjunction with the specific Parts 2 (Part 2-1 and following ones).
This European Standard applies to boilers of types B and C, according to CEN/TR 1749:2014:
a)   that use one or more combustible gases of the three gas families at the pressures stated in EN 437;
b)   where the temperature of the heat transfer fluid does not exceed 105 °C during normal operation;
c)   where the maximum operating pressure in the water circuit does not exceed 6 bar;
d)   which can give rise to condensation under certain circumstances;
e)   which are declared in the installation instructions to be either a “condensing” boiler or a "low temperature boiler" or a “standard boiler”. If no declaration is given the boiler is to be considered a “standard boiler”
f)   which are intended to be installed inside a building or in a partially protected place;
g)   which are intended to produce hot water either by the instantaneous or storage principle, the whole being marketed as a single unit.
This European Standard applies to boilers designed for sealed water systems or for open water systems.
This general standard and the specific standards (see Part 2) provide requirements for boilers with known constructions. For boilers with any alternative constructions, which might not fully be covered by this standard or a specific standard, the risk associated with this alternative construction will need to be assessed.
An example of an assessment methodology, based upon risk assessment, is given in Clause 11.
This European Standard is not intended to cover appliances intended for connection to gas grids where the quality of the distributed gas is likely to vary to a large extent over the lifetime of the appliance.

When final draft in CCMC - Double check that a decision (to submit to FV) is taken both by CEN/TC 166 and CEN/TC 109 - See CEN/BT Decision 72/2014

This document specifies the requirements and test methods, 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 document is intended to be used in conjunction with EN 15502-1:2021.
This document covers gas-fired central heating boilers from the types C1 up to C(11) and the types B2, B3 and B5:
NOTE 1   For further background information on appliance types see EN 1749:2020.
a)   that have a nominal heat input (on the basis of net calorific value) not exceeding 1 000 kW;
b)   that use one or more combustible gases of the three gas families at the pressures stated in EN 437:2021;
c)   where the temperature of the heat transfer fluid does not exceed 105 °C during normal operation;
d)   where the maximum operating pressure in the water circuit does not exceed 6 bar;
e)   which can give rise to condensation under certain circumstances;
f)   which are declared in the instructions for installation to be either a "condensing" boiler or a "low temperature boiler" or a "standard boiler"; if no declaration is given the boiler is to be considered a "standard boiler";
g)   which are intended to be installed inside a building or in a partially protected place;
h)   which are intended to produce also hot water either by the instantaneous or storage principle as a single unit;
i)   which are designed for either sealed water systems or for open water systems;
j)   which are either modular boilers, or non-modular boilers.
k)   which are from the types C(10) that are equipped with a gas-air ratio control and that have a ∆pmax, saf(min) of 25 Pa, and C(11) that have condensing boiler modules that are equipped with a gas-air ratio control and that have a ∆pmax, saf(min) of 25 Pa.
NOTE 2   This document provides requirements for boilers with known constructions. For boilers with any alternative constructions, which might not fully be covered by this standard, the risk associated with this alternative construction needs to be assessed.
An example of an assessment methodology, based upon risk assessment, is given in Clause 11.
This document does not cover all the requirements for:
aa)   appliances above 1 000 kW;
ab)   appliances that are intended to be connected to gas grids where the quality of the distributed gas is likely to vary to a large extent over the lifetime of the appliance (see Annex AB of EN 15502-1:2021);
ac)   appliances using flue dampers;
ad)   appliances of the types B21, B31, B51, C21, C41, C51, C61, C71, C81, C(12) and C(13);
ae)   C7 appliances that have a nominal heat input (on the basis of net calorific value) exceeding 70 kW;
af)   appliances incorporating flexible plastic flue liners;
ag)   C(10) boilers:
1)   without a gas-air ratio control, or
2)   which are non-condensing appliances, or
3)   which have a maximum safety pressure difference at minimum heat input not equal to 25 Pa (∆pmax, saf(min));
ah)   C(11) boilers that have boiler modules:
1)   without a gas-air ratio control, or
2)   which are non-condensing appliances, or
3)   which have a maximum safety pressure difference at minimum heat input not equal to 25 Pa (∆pmax, saf(min));
ai)   appliances intended to be connected to a flue having mechanical extraction;
aj)   surface temperatures of external parts particular to children and elderly people;
ak)   appliances that are intended to burn natural gases of the second family where hydrogen is added to the natural gas;
al)   appliances equipped with an adaptive combustion control function (ACCF);
am)   boilers intended to be installed in areas accessible to elderly people and children.

This European Standard specifies the common requirements and test methods, as well as the classification, marking and energy labelling 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 European Standard is to be used in conjunction with the specific Parts 2 (Part 2-1 and following ones).
This European Standard applies to boilers of types B and C.
NOTE For further background information on appliance types see CEN/TR 1749:2014 [1].
a) that use one or more combustible gases of the three gas families at the pressures stated in EN 437;
b) where the temperature of the water is below or above 105 °C during normal operation;
c) where the maximum operating pressure in the water circuit does not exceed 6 bar;
d) which can give rise to condensation under certain circumstances;
e) which are declared in the instructions for installation to be either a "condensing" boiler or a "low temperature boiler" or a "standard boiler" or an "other boiler". If no declaration is given the boiler is to be considered both a "standard boiler" and an "other boiler";
NOTE The Ecodesign Directive defines "other boilers", "low temperature boilers" and "condensing boilers". The Boiler Efficiency Directive defines "standard boilers", "low temperature boilers" and "condensing boilers". Depending on the legislation applied, a boiler can be both "a standard boiler" and an "other boiler"."
f) which are intended to be installed inside a building or in a partially protected place;
g) which are intended to produce also hot water either by the instantaneous or storage principle as a single unit.
This European Standard applies to boilers designed for sealed water systems or for open water systems.
NOTE This general standard and the specific standards (see Part 2) provide requirements for boilers with known constructions. For boilers with any alternative constructions, which might not fully be covered by this standard or a specific standard, the risk associated with this alternative construction will need to be assessed.
An example of an assessment methodology, based upon risk assessment, is given in Clause 11.
This European Standard is not intended to cover appliances intended for connection to gas grids where the quality of the distributed gas is likely to vary to a large extent over the lifetime of the appliance (see Annex EE).
This European Standard is not intended to cover appliances designed and constructed to burn gas containing toxic components.

This European 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.
Where the word boiler is used, it needs to be read as the boiler including its connecting ducts, ducts and terminals, if any.
This European Standard covers gas-fired central heating boilers from the types C1 up to C9 and the types B2, B3 and B5:
NOTE   For further background information on appliance types see CEN/TR 1749:2014.
a)   that have a nominal heat input (on the basis of net calorific value) not exceeding 1 000 kW;
b)   that use one or more combustible gases of the three gas families at the pressures stated in EN 437;
c)   where the temperature of the heat transfer fluid does not exceed 105 °C during normal operation;
d)   where the maximum operating pressure in the water circuit does not exceed 6 bar;
e)   which may or may not give rise to condensation under certain circumstances;
f)   which are declared in the installation instructions to be either a condensing boiler or a "low temperature boiler" or a standard boiler; if no declaration is given the boiler is to be considered a standard boiler;
g)   which are intended to be installed either indoors or outdoors in a partially protected place;
h)   which may include the facility to produce hot water, either by the instantaneous or storage principle, the whole being marketed as a single unit;
i)   which are designed for either sealed water systems or for open water systems;
j)   which are either modular boilers, or non- modular boilers.
This European Standard also covers gas-fired condensing central heating boilers from the types C(10) that are equipped with a gas-air ratio control and that have a ∆pmax, saf(min) of 25 Pa, ).and C(11) boilers that have condensing boiler modules that are equipped with a gas-air ratio control and that have a ∆pmax, saf(min) of 25 Pa.
This European Standard provides requirements for boilers with known constructions. For boilers with any alternative constructions, which might not fully be covered by this standard, the risk associated with this alternative construction needs to be assessed.
An example of an assessment methodology, based upon risk assessment and which covers the essential requirements of the Gas Appliance Directive, is given in Clause 11.
This European Standard does not cover all the requirements for:
k)   Appliances that are intended to be connected to gas grids where the quality of the distributed gas is likely to vary to a large extent over the lifetime of the appliance (see Annex XC);
l)   Appliances using flue dampers;
m)   Appliances of the types B21, B31, B51, C21, C41, C51, C61, C71, C81 ,C(12) and C(13);
n)   C7 appliances that have a nominal heat input (on the basis of net calorific value) exceeding 70 kW;
o)   Appliances incorporating flexible plastic flue liners;
p)   C(10) boilers:
1)    without a gas-air ratio control, or
2)    which are non-condensing appliances, or
3)    which have a maximum safety pressure difference at minimum heat input not equal to 25 Pa (∆pmax, saf(min)), - ;
q)   C(11) boilers that have boiler modules:
1)    without a gas-air ratio control, or
2)    which are non-condensing appliances, or
3)    which have a maximum safety pressure difference at minimum heat input not equal to 25 Pa (∆pmax, saf(min));
r)   Appliances intended to be connected to a (common) flue having mechanical extraction.

This European Standard specifies the common requirements and test methods concerning, in particular the construction, safety, fitness for purpose, and rational use of energy, as well as the classification, marking and energy labelling 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 European Standard is to be used in conjunction with the specific Parts 2 (Part 2-1 and following ones).
This European Standard applies to boilers of types B and C, according to CEN/TR 1749:2014
a)   that use one or more combustible gases of the three gas families at the pressures stated in EN 437 ;
b)   where the temperature of the heat transfer fluid does not exceed 105 °C during normal operation;
c)   where the maximum operating pressure in the water circuit does not exceed 6 bar;
d)   which can give rise to condensation under certain circumstances;
e)   !which are declared in the installation instructions to be either a "condensing" boiler or a "low temperature boiler" or a "standard boiler" or an "other boiler". If no declaration is given the boiler is to be considered both a "standard boiler" and an "other boiler";
NOTE   The Ecodesign Directive defines "other boilers", "low temperature boilers" and "condensing boilers". The Boiler Efficiency Directive defines "standard boilers", "low temperature boilers" and "condensing boilers". Depending on the legislation applied, a boiler can be both "a standard boiler" and an "other boiler"."
f)   which are intended to be installed inside a building or in a partially protected place;
g)   which are intended to produce hot water either by the instantaneous or storage principle, the whole being marketed as a single unit.
This European Standard applies to boilers designed for sealed water systems or for open water systems.
This general standard and the specific standards (see Part 2) provide requirements for boilers with known constructions. For boilers with any alternative constructions, which might not fully be covered by this standard or a specific standard, the risk associated with this alternative construction will need to be assessed.
An example of an assessment methodology, based upon risk assessment, is given in Clause 11.
This European Standard is not intended to cover appliances intended for connection to gas grids where the quality of the distributed gas is likely to vary to a large extent over the lifetime of the appliance.

This European 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".
Where the word boiler is used, it needs to be read as the boiler including its connecting ducts, ducts and terminals, if any.
This European Standard covers gas-fired central heating boilers from the types C1 up to C9 and the types B2, B3 and B5, according to the classification in CEN/TR 1749:
a)   that have a nominal heat input (on the basis of net calorific value) not exceeding 1 000 kW;
b)   that use one or more combustible gases of the three gas families at the pressures stated in EN 437;
c)   where the temperature of the heat transfer fluid does not exceed 105 °C during normal operation;
d)   where the maximum operating pressure in the water circuit does not exceed 6 bar;
e)   which may or may not give rise to condensation under certain circumstances;
f)   which are declared in the installation instructions to be either a "condensing" boiler or a "low temperature boiler" or a "standard boiler"; if no declaration is given the boiler is to be considered a "standard boiler";
g)   which are intended to be installed either indoors or outdoors in a partially protected place;
h)   which may include the facility to produce hot water, either by the instantaneous or storage principle, the whole being marketed as a single unit;
i)   which are designed for either sealed water systems or for open water systems;
j)   which are either modular boilers, or non- modular boilers.
This European Standard will be used in conjunction with the General Requirements Standard EN 15502-1.
This European Standard provides requirements for boilers with known constructions. For boilers with any alternative constructions, which might not fully be covered by this standard, the risk associated with this alternative construction needs to be assessed.
An example of an assessment methodology, based upon risk assessment and which covers the essential requirements of the Gas Appliance Directive, is given in Clause 11.
This European Standard does not cover all the requirements for:
k)   Appliances that are intended to be connected to gas grids where the quality of the distributed gas is likely to vary to a large extent over the lifetime of the appliance (see Annex DD);
l)   Appliances using flue dampers;
m)   Appliances of the types B21, B31, B51, C21, C41, C51, C61, C71 and C81;
n)   C7 appliances that have a nominal heat input (on the basis of net calorific value) exceeding 70 kW;
o)   Appliances incorporating flexible plastic flue liners;
p)   Appliances designed to become connected to a combined flue duct system that is designed to operate under overpressure (for example Ca));
q)   Appliances incorporating a combined combustion products circuit that is designed to operate under overpressure (for example Cb));
r)   Appliances intended to be connected to a (common) flue having mechanical extraction.

This European Standard specifies, the common 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 European Standard is to be used in conjunction with the specific Parts 2 (Part 2-1 and following ones).
This European Standard applies to boilers of types B and C, according to CEN/TR 1749:
a)   that use one or more combustible gases of the three gas families at the pressures stated in EN 437;
b)   where the temperature of the heat transfer fluid does not exceed 105 °C during normal operation;
c)   where the maximum operating pressure in the water circuit does not exceed 6 bar;
d)   which can give rise to condensation under certain circumstances;
e)   which are declared in the installation instructions to be either a “condensing” boiler or a "low temperature boiler" or a “standard boiler”. If no declaration is given the boiler is to be considered a “standard boiler”
f)   which are intended to be installed in a partially protected place;
g)   which are intended to produce hot water either by the instantaneous or storage principle, the whole being marketed as a single unit.
This European Standard applies to boilers designed for sealed water systems or for open water systems.
For applications within the scope of the PED further requirements may be necessary (e.g. situations where the maximum allowable temperature exceeds 110 °C, or where volume times maximum allowable pressure is over 50 bar r litres).
This general standard and the specific standards (see Part 2) provide requirements for boilers with known constructions. For boilers with any alternative constructions, which might not fully be covered by this standard or a specific standard, the risk associated with this alternative construction shall be assessed.
An example of an assessment methodology, based upon risk assessment and which covers the essential requirements of the Gas Appliance Directive, is given in Clause 11.
This European Standard is not intended to cover appliances intended to being connected to gas grids where the quality of the distributed gas is likely to vary to a large extend over the lifetime of the appliance.