ISO 23551-8:2023

INTERNATIONAL ISO
STANDARD 23551-8
Second edition
2023-05
Safety and control devices for gas
burners and gas-burning appliances —
Particular requirements —
Part 8:
Multifunctional controls
Dispositifs de commande et de sécurité pour les brûleurs et les
appareils à gaz — Exigences particulières —
Partie 8: Equipements multifonctionnels
Reference number
© ISO 2023
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Published in Switzerland
ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 2
3.1 General terms . 2
3.2 Definitions pertaining to component parts of burner control systems . 3
4 Classes of control . 4
4.1 Classes of controls . 4
4.2 Groups of controls . 4
5 Test conditions .4
6 Construction . 5
6.1 General . 5
6.2 MFC based on combination of controls . 5
6.2.1 General . 5
6.2.2 Interaction between controls . 5
6.3 Components of burner control systems . 6
7 Performance . 6
7.1 Overview . 6
7.2 General . 6
7.3 External leak-tightness of MFC . 6
7.4 Mechanical thermostat function . 6
7.5 Internal leak-tightness of MFC . 6
7.6 Endurance test for combined functions . 6
7.7 Components of burner control systems . 6
8 Electrical equipment . 6
9 Electromagnetic compatibility (EMC) . 7
10 Marking, installation and operating instructions . 7
10.1 Marking . 7
10.2 Installation and operating instructions . 7
10.3 Warning notice . 7
Annex A (informative) Leak-tightness test — Volumetric method . 8
Annex B (informative) Leak-tightness test — pressure-loss method . 9
Annex C (informative) Conversion of pressure loss into leakage rate .10
Annex D (normative) Gas quick connector (GQC).11
Annex E (normative) Elastomers/requirements resistance to lubricants and gas .12
Annex F (normative) Specific regional requirements in European countries.13
Annex G (normative) Specific regional requirements in Canada and the USA .14
Annex H (normative) Specific regional requirements in Japan .15
Annex I (normative) Water-operated gas valves .16
Annex J (normative) Overheating safety devices .18
Annex K (normative) Requirements for components of burner control systems .21
Bibliography .31
iii
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
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ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the
different types of ISO document should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).
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of (a) patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed
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www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 161, Controls and protective devices for
gaseous and liquid fuels.
This second edition cancels and replaces the first edition (ISO 23551-8:2016), which has been technically
revised. It also incorporates the Amendment ISO 23551-8:2016/Amd. 1:2019.
The main changes are as follows:
— the document has been updated to align technically and with the revised format of ISO 23550:2018;
— the document has been updated to align technically and with the relevant latest editions of ISO 23551
series, referenced herein;
— specific regional requirements have been moved from annexes into the main body of the document.
A list of all parts in the ISO 23551 series can be found on the ISO website.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.
iv
Introduction
This document is designed to be used in combination with ISO 23550 and relevant parts of the
ISO 23551 series. Together with both ISO 23550 and the ISO 23551 series, this document establishes the
full requirements as they apply to the product covered by this document.
Where needed, this document adapts ISO 23550 by stating the corresponding clause number and
adding:
— “with the following modification”;
— “with the following addition”;
— “is replaced by the following”; or
— “is not applicable”.
In order to identify specific requirements that are particular to this document, that are not already
covered by ISO 23550, this document contains certain clauses or subclauses that are additional to the
structure of ISO 23550. These subclauses are indicated by the introductory sentence: “Subclause (or
Annex) specific to this document."
To ensure global relevance of this document, the differing requirements resulting from practical
experience and installation practices in various regions of the world have been taken into account.
The variations in basic infrastructure associated with gas controls and appliances have also been
recognized, some of which are addressed in Annexes F, G and H. This document intends to provide a
basic framework of requirements that recognize these differences.
v
INTERNATIONAL STANDARD ISO 23551-8:2023(E)
Safety and control devices for gas burners and gas-burning
appliances — Particular requirements —
Part 8:
Multifunctional controls
1 Scope
This document specifies safety, construction, performance and testing requirements of multifunctional
controls (MFC) intended for use with gas burners, gas appliances and appliances of similar use.
This document applies to an MFC with declared maximum inlet pressures up to and including 50 kPa
(500 mbar) of nominal connection sizes up to and including DN 150 for use on burners or in appliances
using gases such as natural gas, manufactured gas or liquefied petroleum gas (LPG). It is not applicable
to corrosive and waste gases.
An MFC consists of two or more functions, at least one of which is a mechanical control, as specified in
the relevant control standards.
This document is also applicable to construction and performance requirements for components of
burner ignition systems as specified in Annex K. The requirements and test methods in Annex K include
optional type test
...