IS/ISO 7240 : Part 17 : 2020 Fire Detection and Alarm Systems - Part 17 Transmission Path Isolators
NATIONAL FOREWORD
This Indian Standard (Part 17) (First Revision) which is identical to ISO 7240-17 : 2020 'Fire detection and fire alarm systems - Part 17: Transmission path isolators' issued by the International Organization for Standardization (ISO) was adopted by the Bureau of Indian Standards on the recommendation of the Fire Fighting Sectional Committee and approval of the Civil Engineering Division Council.
This standard was first published in 2018 as IS/ISO 7240-17 : 2009. The first revision of this standard has been undertaken to align it with the latest version of ISO 7240-17 to make pace with the latest international practices.
This Indian Standard is published in various parts. The other parts in this series are:
Part 2 Fire detection control and indicating equipment
Part 3 Audible alarm devices
Part 4 Power supply equipment
Part 5 Point-type heat detectors
Part 6 Carbon monoxide fire detectors using electro-chemical cells
Part 7 Point-type smoke detectors using scattered light, transmitted light or ionization
Part 8 Point-type fire detectors using a carbon monoxide sensor in combination with a heat sensor
Part 10 Point-type flame detectors
Part 11 Manual call points
Part 12 Line type smoke detectors using a transmitted optical beam
Part 13 Compatibility assessment of system components
Part 15 Point-type fire detectors using smoke heat sensors
Part 16 Sound system control and indicating equipment
Part 18 Input/output devices
Part 20 Aspirating smoke detectors
Part 21 Routing equipment
Part 22 Smoke-detection equipment for ducts
Part 23 Visual alarm devices
Part 24 Fire alarm loudspeakers
Part 25 Components using radio transmission paths
Part 27 Point-type fire detectors using a smoke sensor in combination with a carbon monoxide sensor and, optionally, one or more heat sensors
Part 29 Video fire detectors
Part 31 Resettable line-type heat detectors
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 (for example, 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 (for example, the control and indicating equipment and detectors) and the transmission path parameters (for example, line impedance and line loads), and they will have to be verified in a system test.
However, this Indian Standard includes:
a) 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 recognised 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.
b) the tests to verify that the transmission path isolator functions in accordance with these manufacturer's specifications; and
c) 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 standard 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 A.
The text of ISO standard has been approved as suitable for publication as an Indian Standard without deviations. Certain conventions and terminologies are, however, not identical to those used in Indian Standards. Attention is particularly drawn to the following:
a) Wherever the words 'International Standard' appear referring to this standard, they should be read as 'Indian Standard'; and
b) Comma (,) has been used as a decimal marker while in Indian Standards, the current practice is to use a point (.) as the decimal marker.