ISO 7240-17:2020

INTERNATIONAL ISO
STANDARD 7240-17
Second edition
2020-02
Fire detection and fire alarm
systems —
Part 17:
Transmission path isolators
Systèmes de détection d'incendie et d'alarme —
Partie 17: Isolateurs de court-circuit
Reference number
ISO 7240-17:2020(E)
©
ISO 2020

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ISO 7240-17:2020(E)

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© ISO 2020
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Published in Switzerland
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ISO 7240-17:2020(E)

Contents Page
Foreword .v
Introduction .vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 General requirements . 2
4.1 Compliance . 2
4.2 Integral status indication . 2
4.3 Connection of ancillary devices . 2
4.4 Monitoring of detachable transmission path isolators . 3
4.5 Manufacturer's adjustments . 3
4.6 On-site adjustments . 3
4.7 Requirements for software-controlled transmission path isolators . 3
4.7.1 General. 3
4.7.2 Software design. 3
4.7.3 Storage of programs and data . 3
5 Tests . 4
5.1 General . 4
5.1.1 Atmospheric conditions for tests. 4
5.1.2 Operating conditions for tests . 4
5.1.3 Mounting arrangements . 4
5.1.4 Tolerances . 4
5.1.5 Functional test . 4
5.1.6 Provision for tests . 5
5.1.7 Test schedule . 5
5.2 Reproducibility . 6
5.2.1 Object . 6
5.2.2 Test procedure . 7
5.2.3 Requirements . 7
5.3 Variation in supply voltage . 7
5.3.1 Object . 7
5.3.2 Test procedure . 7
5.3.3 Requirements . 7
5.4 Dry heat (operational) . 7
5.4.1 Object . 7
5.4.2 Test procedure . 7
5.4.3 Requirements . 8
5.5 Cold (operational) . 8
5.5.1 Object . 8
5.5.2 Test procedure . 8
5.5.3 Requirements . 9
5.6 Damp heat, cyclic (operational) . 9
5.6.1 Object . 9
5.6.2 Test procedure . 9
5.6.3 Requirements .10
5.7 Damp heat, steady state (endurance) .11
5.7.1 Object .11
5.7.2 Test procedure .11
5.7.3 Requirements .11
5.8 Sulfur dioxide (SO ) corrosion (endurance) .11
2
5.8.1 Object .11
5.8.2 Test procedure .12
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ISO 7240-17:2020(E)

5.8.3 Requirements .12
5.9 Shock (operational) .12
5.9.1 Object .12
5.9.2 Test procedure .12
5.9.3 Requirements .13
5.10 Impact (operational) .13
5.10.1 Object .13
5.10.2 Test procedure .13
5.10.3 Requirements .14
5.11 Vibration, sinusoidal (operational) .15
5.11.1 Object .15
5.11.2 Test procedure .15
5.11.3 Requirements .15
5.12 Vibration, sinusoidal (endurance) .16
5.12.1 Object .16
5.12.2 Test procedure .16
5.12.3 Requirements .16
5.13 Electromagnetic Compatibility (EMC), Immunity tests (operational) .17
5.13.1 Object .17
5.13.2 Test procedure .17
5.13.3 Requirements .17
6 Test report .17
7 Marking .18
8 Data .18
8.1 Technical documentation for installation .18
8.2 Software documentation .19
Annex A (informative) Examples for the functional test procedure .20
Annex B (informative) Apparatus for impact test .28
Bibliography .30
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ISO 7240-17:2020(E)

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
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
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 documents 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).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www .iso .org/ patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to
the World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see
www .iso .org/ iso/ foreword .html.
This document was prepared by Technical Committee ISO/TC 21, Equipment for fire protection and fire
fighting, Subcommittee SC 3, Fire detection and alarm systems.
The second edition cancels and replaces the first edition (ISO 7240-17:2009), which has been technically
revised. The main changes compared to the previous edition are as follows:
— the title of the document has been changed to “Transmission path isolators” which better reflects
the functionality of the product;
— the whole document has been updated to the latest ISO standard template;
— IEC 62599-2 has been included and replaces the reference to EN 50130-4;
— a new Clause 6 on test report, Clause 7 on marking and Clause 8 on data have been included.
A list of all parts in the ISO 7240 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.
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ISO 7240-17:2020(E)

Introduction
Short-circuit isolators have been renamed transmission path isolators reflecting that the isolators
considered are intended to limit the consequences of low parallel resistance faults between the
lines of the transmission path(s) of a fire detection and fire alarm system. This is normally achieved
by connecting the transmission path in a loop configuration, separating sections of the loop with
transmission path isolators and introducing a means of detecting the presence of a fault if its
consequences (e.g. reduction in the line voltage) jeopardises the correct operation of components
on the transmission path. The faulty section of the loop can then be switched out, between a pair of
transmission path isolators, allowing the rest of the loop to continue to function correctly.
It is recognised that it is not possible for this component standard to specify all of the requirements
for the function of a transmission path isolator in a system. The requirements for the functioning of a
transmission path isolator are dependent on the system operation, the other components associated
with the transmission path (e.g. the control and indicating equipment and detectors) and the
transmission path parameters (e.g. line impedance and line loads), and they will have to be verified in a
system test.
However, this document includes:
— a requirement that the manufacturer gives all of the specifications, for the transmission path
isolator, needed by system designers to use the device correctly, in accordance with the system
requirements;
NOTE It is recognized that the system designer needs to ensure that only those transmission path isolators
having the necessary performance are chosen to meet the specific requirements of a given system design.
— the tests to verify that the transmission path isolator functions in accordance with these
manufacturer’s specifications;
— the tests to verify the stability of the transmission path isolator with respect to environmental and
electromagnetic compatibility (EMC) conditions.
Due to the many different concepts that can be used for the operation of transmission path isolators, it is
not possible to define a precise functional test procedure applicable to all types. Instead, this document
requires that a functional test procedure is developed to verify the manufacturer’s specification and
lists the most important points that have to be verified. To assist in developing such test procedures,
some example procedures are given in an informative annex (Annex A).
In view of the above, it is important that, in addition to meeting the requirements of this document,
transmission path isolators are shown to operate correctly within the types of systems with which
they are intended to be used.
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INTERNATIONAL STANDARD ISO 7240-17:2020(E)
Fire detection and fire alarm systems —
Part 17:
Transmission path isolators
1 Scope
This document specifies the requirements, test methods and performance criteria for transmission
path isolators for use in fire detection and fire alarm systems for buildings (for general requirements
and definitions, see ISO 7240-1).
Means of isolation or protection incorporated within control and indicating equipment are not covered
by this document.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 209, Aluminium and aluminium alloys — Chemical composition
ISO 7240-1, Fire detection and alarm systems — Part 1: General and definitions
IEC 60068-1, Environmental testing — Part 1: General and guidance
IEC 60068-2-1, Environmental testing — Part 2-1: Tests. Tests A: Cold
IEC 60068-2-6, Environmental testing — Part 2-6: Tests — Test Fc: Vibration (sinusoidal)
IEC 60068-2-27, Environmental testing — Part 2-27: Tests. Test Ea and guidance: Shock
IEC 60068-2-30, Environmental testing — Part 2-30: Tests. Test Db and guidance: Damp heat, cyclic
(12 + 12-hour cycle)
IEC 60068-2-42, Environmental testing — Part 2-42: Tests — Test Kc: Sulphur dioxide test for contacts and
connections
IEC 62599-2, Alarm systems — Part 2: Electromagnetic compatibility — Immunity requirements for
components of fire and security alarm systems
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 7240-1 and the following apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
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ISO 7240-17:2020(E)

3.1
transmission path isolator
device, which may be inserted into a transmission path of a fire detection and fire alarm system, to
limit the consequences of low parallel resistance faults between the lines of this transmission path
Note 1 to entry: A transmission path isolator may be a physically separate device or it may be incorporated into
another device (e.g. integrated into a smoke detector or detector base).
3.2
closed condition
condition of the transmission path isolator which allows the normal signals and the supply currents to
pass through the transmission path isolator
Note 1 to entry: This is the correct condition for the transmission path isolator when there is no short circuit.
3.3
open condition
condition of the transmission path isolator which prevents the passage of short circuit currents through
the transmission path isolator
Note 1 to entry: This is the correct condition for the transmission path isolator when it is protecting part of a
circuit from the effects of a short circuit.
3.4
field device
device, which is located remotely from the CIE and may be subject to a more severe environmental
condition
Note 1 to entry: Detectors, MCP, and alarm devices are always considered as field devices whereas PSE, input/
output module, and routing equipment may be field devices.
3.5
non-field device
device which is specified to be located in the same conditions as the CIE
4 General requirements
4.1 Compliance
In order to comply with this document, the transmission path isolator shall meet the requirements of:
a) Clause 4, which shall be verified by visual inspection or engineering assessment, shall be tested as
described in Clause 5 and shall meet the requirements of the tests;
b) Clauses 7 and 8, which shall be verified by visual inspection.
4.2 Integral status indication
If the transmission path isolator incorporates an integral visual indication of its status, then this
indication shall not be red.
4.3 Connection of ancillary devices
Where the transmission path isolator provides for connections to ancillary devices (e.g. remote
indicators), open or short circuit failures of these connections shall not prevent the correct operation of
the transmission path isolator.
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ISO 7240-17:2020(E)

4.4 Monitoring of detachable transmission path isolators
If a transmission path isolator is detachable (i.e. it is attached to a mounting base), then a means shall
be provided for a remote monitoring system (e.g. the control and indicating equipment) to detect the
removal of the device from the base, in order to give a fault signal.
4.5 Manufacturer's adjustments
It shall not be possible to change the manufacturer's settings except by special means (e.g. the use of a
special code or tool) or by breaking or removing a seal.
4.6 On-site adjustments
If there is provision for on-site adjustment of the transmission path isolator, then for each setting, the
transmission path isolator shall comply with the requirements of this document. Access to the means of
adjustment shall only be possible using a code or special tool.
4.7 Requirements for software-controlled transmission path isolators
4.7.1 General
The requirements of 4.7.2 and 4.7.3 shall apply to transmission path isolators that rely on software
control in order to fulfil the requirements of this document.
4.7.2 Software design
To ensure the reliability of the transmission path isolator, the following requirements for software
design shall apply.
— The software shall have a modular structure.
— The design of the interfaces for manually and automatically generated data shall not permit invalid
data to cause error in the program operation.
— The software shall be designed to avoid the occurrence of deadlock of the program flow.
4.7.3 Storage of programs and data
The program necessary to comply with this document and any pre-set data, such as manufacturer's
settings, shall be held in non-volatile memory. Writing to areas of memory containing this program
and data shall be possible only using some special tool or code and shall not be possible during normal
operation of the transmission path isolator.
Site-specific data shall be held in memory that will retain data for at least two weeks without external
power to the transmission path isolator, unless provision is made for the automatic renewal of such
data, following loss of power, within 1 h of power being restored.
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ISO 7240-17:2020(E)

5 Tests
5.1 General
5.1.1 Atmospheric conditions for tests
Unless otherwise stated in a test procedure, carry out the testing after the test specimen has been
allowed to stabilize in the standard atmospheric conditions for testing as described in IEC 60068-1 as
follows:
a) temperature: (15 to 35) °C;
b) relative humidity: (25 to 75) %;
c) air pressure: (86 to 106) kPa.
If variations in these parameters have a significant effect on a measurement, then such variations
need to be kept to a minimum during a series of
...