EN 656:1999/A1:2006

SLOVENSKI STANDARD
01-september-2006
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Gas-fired central heating boilers - Type B boilers of nominal heat input exceeding 70 kW,
but not exceeding 300 kW
Heizkessel für gasförmige Brennstoffe - Heizkessel der Bauart B mit einer
Nennwärmebelastung größer als 70 kW aber gleich oder kleiner als 300 kW
Chaudieres de chauffage central utilisant les combustibles gazeux - Chaudieres de type
B dont le débit calorifique nominal est supérieur a 70 kW mais inférieur ou égal a 300 kW
Ta slovenski standard je istoveten z: EN 656:1999/A1:2006
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
EN 656:1999/A1
NORME EUROPÉENNE
EUROPÄISCHE NORM
July 2006
ICS 91.140.10
English Version
Gas-fired central heating boilers - Type B boilers of nominal heat
input exceeding 70 kW, but not exceeding 300 kW
Gas-fired central heating boilers - Type B boilers of nominal Heizkessel für gasförmige Brennstoffe - Heizkessel der
heat input exceeding 70 kW, but not exceeding 300 kW Bauart B mit einer Nennwärmebelastung größer als 70 kW
aber gleich oder kleiner als 300 kW
This amendment A1 modifies the European Standard EN 656:1999; it was approved by CEN on 20 March 2006.
CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for inclusion of this
amendment into the relevant national standard without any alteration. Up-to-date lists and bibliographical references concerning such
national standards may be obtained on application to the Central Secretariat or to any CEN member.
This amendment exists 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 Central Secretariat 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.
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. EN 656:1999/A1:2006: E
worldwide for CEN national Members.

Contents Page
Foreword 3
4 Classification of boilers 4
4.3 Type of technologies 4
5.3.1 General 5
5.4.1 General 5
5.8.5 Removal of condensate for low temperature boilers 5
5.16 Chemical composition of the condensate for low-temperature boilers 6
6.5.9 Condensate discharge blockage 6
6.7.1 Useful efficiency at the nominal heat input 6
6.7.2 Useful efficiency at part load 7
6.8 Non-condensation in the flue 7

6.9.1 General 7
6.12 Condensation in a standard boiler 7
7.1.1.3 Characteristics and choice of test gases 8
7.5.9 Condensate discharge blockage 8
7.6 Combustion 8
7.7.1 Useful efficiency at the nominal heat input 8
7.7.2.1 General 8
7.7.2.2 Direct method 9
7.7.2.2.1 General 9
7.7.2.2.2 Operating mode No. 1 9
7.7.2.2.3 Operating mode No. 2 9
7.7.2.3 Indirect method 9
7.7.2.3 Indirect method 10
7.7.2.3.1 Measurements 10
7.7.2.3.1.1 Useful efficiency at the nominal heat input at reduced water temperature 10
7.7.2.3.1.2 Efficiency at the minimum controlled rate 12

7.7.2.3.1.3 Standby loss 12
7.7.2.3.1.4 Pilot recovery factor 13
7.7.2.3.2 Calculation 13
7.8 Non-condensation in the flue 14
7.8 Criteria for condensation in the flue 14
7.8.1 Determination of the flue losses 14
7.8.2 Minimum temperature of the combustion products 14
7.12 Condensation in a standard boiler 14
8.1.3 Supplementary marking 14
8.2.1 Technical instructions for the installer 15
Annex ZA (informative) 15
Foreword
This document (EN 656:1999/A1:2006) has been prepared by Technical Committee CEN/TC109 “Central
heating boilers using gaseous fuels”, the secretariat of which is held by NEN.
This Amendment to the European Standard EN 656:1999 shall be given the status of a national standard, either
by publication of an identical text or by endorsement, at the latest by January 2007, and conflicting national
standards shall be withdrawn at the latest by January 2007.
This document has been prepared under a mandate given to CEN by the European Commission and the
European Free Trade Association, and supports essential requirements of EU Directive(s).
For relationship with EU Directive(s), see informative annex ZA, which is an integral part of this document.
With this amendment, the requirements and test methods for low temperature boilers and for standard boilers
possibly producing condensate in certain circumstances are introduced in EN 656:1999.
According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following
countries are bound to implement this European Standard: 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.
1 Scope
Add to the first list of indents:
 of the standard type possibly producing condensation in certain circumstances;
 of the low-temperature type;
Delete in the second list of indents:
 of the low-temperature type;
3 Definitions
Amend clause 3.3.1.5 as follows:
Change "Symbol: Q " to "Symbol Q "
i ign
Add:
3.2.5
condensate
liquid formed from the combustion products during the condensation process
4 Classification of boilers
Insert a new clause as follows:
4.3 Type of technologies
4.3.1
gas condensing boiler
boiler designed to condense permanently a large part of the water vapour contained in the combustion gases

4.3.2
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

4.3.3
standard boiler
boiler for which the average water temperature can be restricted by design
Add a footnote to the clause 4.1 as follows:
These definitions are in accordance with 92/42/EEC, however, in this standard, definition 4.1.2 is limited to gas
Add a footnote to the new clause 4.3.3 as follows:
Specific requirements and test methods for condensing boilers with heat inputs exceeding 70 kW will be the
scope of a new standard
5.3.1 General
At the end of the clause, add the following:
If there is a risk of condensation in the combustion products circuit, 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.
5.4.1 General
Replace the second and third paragraphs with the following:
For standard boilers that 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.
If condensation is produced at start-up, this shall not:
 affect the operational safety;
 drop outside the appliance.
Insert new clauses as follows:
5.8.5 Removal of condensate for low temperature boilers
For low temperature boilers a condensate discharge shall be provided if the condensate:
 impairs safety or correct operation;
 results in spillage from the appliance;
 causes deterioration of materials.
A pipe or pipes shall be used to discharge condensate when this is necessary. The internal diameter of the
outside connection of the condensate discharge system shall be at least 13 mm.
The disposal system, forming part of the boiler or supplied with the boiler, shall be such that:
 it can be easily inspected and cleaned in accordance with the manufacturer’s instructions;
 it cannot transmit combustion products into the room where the boiler is installed; this requirement is
satisfied if the disposal system incorporates a water trap;
 a water trap has a seal of at least 25 mm at the maximum pressure in the combustion chamber at the
maximum flue length specified by the manufacturer.

5.16 Chemical composition of the condensate for low-temperature boilers
The manufacturer shall communicate the probable chemical composition of the condensate (pH, heavy metals,
etc.) if the composition is required by national regulations.
Amend clause 6.5.3.3.1 c) as follows:
In the line starting "for Q …" change the formula "T ≤ 5 Q / Q s ;" to "T ≤ 5 Q /Q s"
n SA,max n i SA,max n ign
In the line starting "for 150 kW." change the formula " T ≤5 x 150/ Q s" to " T ≤ 5 x 150/ Q s"
SA,max i SA,max ign
Change "where Q is the ignition rate" to "where Q is the ignition rate.
i ign
Insert a new clause as follows:
6.5.9 Condensate discharge blockage
Under the test conditions of clause 7.5.9, the formation of condensate shall not impair the correct operation of
the boiler.
By choice of the manufacturer, the boiler shall meet one of the following requirements:
a) when the condensate discharge is blocked, the gas supply shall be shut off before the CO concentration
exceeds 0,20 %; or
b) when the condensate discharge is blocked, causing a restriction in the flow of combustion products or air for
combustion, resulting in a CO concentration equal to or greater than 0,10 % at equilibrium, restart shall not
be possible from cold.
In either case, there shall be no spillage of condensate from the boiler.
6.7.1 Useful efficiency at the nominal heat input
Replace this clause by the following text:
Under the test conditions of 7.7.1 the useful efficiency at the nominal heat input shall be in accordance with
Table 10.
Table 10
Boiler type Efficiency at nominal output
%
a)
Standard ≥ 84 + 2 log P
10 n
Low-temperature
1)
≥ 87,5 + 1,5 log P
10 n
a)
P is the nominal output expressed in kilowatt (kW).
n
6.7.2 Useful efficiency at part load
Replace with the following text:
Under the test conditions of 7.7.2, the useful efficiency for a load corresponding to 30 % of the nominal heat
input shall be in accordance with Table 11.
Table 11
Boiler type Efficiency at 30 % nominal output
%
a)
Standard ≥ 80 + 3 log P
10 n
a)
Low-temperature
≥ 87,5 + 1,5 log P
10 n
a)
P is the nominal output expressed in kilowatts (kW).
n
6.8 Non-condensation in the flue
Replace this clause with the following text:
6.8 Criteria for condensation in the flue for standard boilers
For standard boilers it is determined whether condensation occurs in the flue. Condensation may occur when
one of the following criteria, depending on the manufacturer’s choice is met:
a) flue losses are less than 8 % under the test condition of 7.8.1;
b) temperature of the combustion products is less than 80 °C under the test conditions of 7.8.2.
6.9.1 General
At the end of the clause, add the following:
Corrosion resistant coatings shall show no sign of damage after the pressure tests described in 7.9.
Add a new clause as follows:
6.12 Condensation in a standard boiler
If condensation occurs in the flue of a standard boiler, according to one of the criteria of 6.8, additional tests are
carried out to determine whether condensation also occurs in the boiler.
Under the test conditions of 7.12, it is checked whether formation of condensate occurs in the boiler.
If there is condensation in the boiler, the appropriate requirements for low-temperature boilers in 5.3.1, 5.8.5,
5.16, 6.5.9, 6.9.1, 7.5.9, and 8.2.1 shall be met.

7.1.1.3 Characteristics and choice of test gases
Renumber tables as follows:
Tables 10, 11, 12, 13, 14, & 15 to be renumbered tables 12, 13, 14, 15, 16, & 17.
Insert a new clause as follows:
7.5.9 Condensate discharge blockage
The boiler is installed as stated in 7.1.2. The boiler is supplied with one of the reference gases for the category to
which it belongs.
The condensate discharge is blocked.
The boiler is operated with the temperature and heat input conditions specified for the low-temperature boilers in
either 7.7.2.2.2 or 7.7.2.2.3 at the manufacturer's choice.
By choice of the manufacturer one of the following tests is conducted:
 Boiler is operated, producing condensate, until the boiler goes to safety shutdown or lockout. The CO
concentration of the flue gas is determined at the point of shutdown;
 It is checked that the conditions of 6.5.9.a) are satisfied.
 Boiler is operated, producing condensate, until the CO concentration of the flue gas reaches the value of
0,10 % at which point the boiler is switched off and allowed to cool to ambient temperature.
The boiler is manually switched on and restart shall not occur. The condensate is allowed to drain from the boiler
to the point at which restart occurs. Further drainage of condensate is stopped. The CO concentration is
measured.
It is checked that the conditions of 6.5.9 b) are satisfied.
NOTE Artificially filling the condensate discharge system with water may shorten the test.
7.6 Combustion
Renumber tables as follows:
Tables 16 & 17 to be renumbered tables 18 & 19.
7.7.1 Useful efficiency at the nominal heat input
Replace the second
...