International and National standards are important in setting down good practice and providing a basis for product and system definition to ensure safe and effective operation. This is particularly true in the area of fire performance where incorrect functioning could have life safety implications.
Fortunately in this field in the UK, we are well served by a number of respected British Standards, be they system codes of practice, product standards or test method standards. Similar, although not identical, Irish Standards are also available. Such standards are a valuable basis against which products and systems may be assessed and their performance verified.
Recent changes to standards affecting the choice and installation of fire resistant cables
BS5839-1
BS5839-1 ”Fire detection and fire alarm systems for buildings. Code of practice for system design, installation, commissioning and maintenance” which provides recommendations for the planning, design, installation, commissioning and maintenance of fire detection and fire alarm systems in and around buildings, other than dwellings is perhaps the single most important standard governing the use of fire resistant cables in the UK and UK influenced markets.
This standard was fully revised for the 2002 edition and at that time extensive changes were made to the cable requirements, including the introduction of the concept of “standard” and “enhanced” fire performance depending upon the application. Whilst conducting their 5 year review, the responsible BSI Committee considered that the 2002 edition was still relevant to market needs and only small changes by way of amendment were needed. The amended BS5839-1:2002 + A2:2008 was published in March 2008.
There are no major changes regarding cables but the following are worthy of note:
- Strengthening of the advice regarding the necessity to use suitable fire resistant fixings
- Advice in the commentary regarding clause 522.6 of the new 17th Edition IEE Wiring Regulations and the need to choose both "standard" and "enhanced" cables that will provide an adequate level of mechanical protection when concealed in a wall or partition.
- A change of reference for the requirement for standard cables from BS8434-1 to the equivalent BS EN 50200 Annex E.
BS5839-8
A companion document to BS5839-1, BS5839-8 “Fire detection and fire alarm systems for buildings. Code of practice for the design, installation, commissioning and maintenance of voice alarm systems” which gives recommendations for the design, installation, commissioning and maintenance of voice alarm systems which automatically broadcast speech or warning tones, in response to signals from their associated fire detection and alarm systems which are covered by BS5839-1.
This standard has been fully revised for the 2008 edition which was published in May 2008 and replaces the previous 1998 edition. Extensive changes have been made to the requirements for cable and their installation. Generally these changes have been introduced to ensure greater alignment with BS5839-1 requirements:
- All cables on critical signal paths, ELV supply and final LV mains supply are now required to be fire resistant types
- Cables should comply with BS7629, BS7846 or BS EN60702-1 and also with fire test requirements for "standard" and "enhanced" as in BS5839-1. Previously there was only a requirement to meet BS7629 or BS EN60702.
- Specific areas of application are given for "standard" and "enhanced" types but
loudspeaker and ANS circuits in areas where devices are fitted and loop or diverse routed network cables are only required to meet the requirements for "standard" cables - Certain large and complex buildings need "enhanced" cables as in BS5839-1
- Appropriate methods of support and jointing as given in BS5839-1 are required
- Optical cables may be used but they must satisfy the same fire test conditions as given for "standard" and "enhanced" copper cables
Many cables approved to these new requirements of BS5839-8 are available on the market. Some product ranges, such as Prysmian FP200Gold (“standard”) and FP PLUS (“enhanced”) offer designs with similar installation related features ensuring that there are no new or special procedures to be followed when installing “enhanced” cables in applications where their use is required.
BS7671
The issue of the new 17th Edition IEE Wiring Regulations / BS 7671:2008 which was published in January 2008 and comes into effect in July 2008 has also impacted UK fire alarm installations. BS5839-1 requires that the installation of the entire system should conform to the requirements of BS 7671. Reference has already been made to the new series of Regulations given in clause 522.6 concerning cables concealed in a wall or partition. These are specifically aimed at the issue of penetration of concealed cables by nails, screws and the like. A number of solutions are allowed by BS7671 but not all are appropriate for fire alarm installations.
For the mains supply to the fire alarm system, BS5839-1 warns that not all cable types complying with its requirement will provide an adequate level of mechanical protection to meet the clause 522.6 requirements. Most fire alarm cables employ a thin foil screen which cannot meet the nail penetration test given in BS8436 necessary to prove adequate protection. Cables with a more robust screen such as FP200Gold or FP PLUS which comply with the requirements of the nail penetration test should be selected for such applications.
Although one may question the necessity, ELV circuits are not excluded from the clause 522.6 requirements. In order to ensure complete compliance with BS7671, the same consideration needs to be given to all fire alarm cabling including the ELV circuits.
The Irish Wiring regulations differ from BS7671:2008 in this particular area.
BS8491
Another new standard affecting the choice of fire resistant power cables is BS8491:2008 “Method for assessment of fire integrity of large diameter power cables for use as components for smoke and heat control systems and certain other active fire safety systems”. This is a new standard publication from January 2008 which essentially extracts the test method given in BS7346-6:2005. The two test methods are technically identical.
A main reason for its issue was to ensure visibility of the test method so that it can be called up for appropriate applications besides the smoke and heat control systems included in BS7346. Cables approved to the requirements of BS8491 including the maximum 120 minute rating are already listed and are subject to growing interest for use in large and complex buildings where the superior level of resistance to fire with direct impact and water jet is appropriate.
The growing problem of “fake” fire resistant cables
The growing problem of sub standard and “fake” cables has been widely reported and the campaigns by BASEC and other organisations are doing an important job in raising awareness. A most concerning recent activity has been the targeting of the fire resistant cable markets with “fake” cable which has no fire resistance at all.
One recent example of cable taken from a fire alarm installation and examined in the Prysmian laboratory illustrated the steps some manufacturers and their suppliers will take to increase their profits with no regard to the lives they are potentially putting at risk due to the lack essential performance of their product:
- Cable marking included “BS5839-1:2002 26.2d BS6360/BS6387 CWZ BS EN50200 PH30 British Made Cable” which would suggest a fire resistant cable
- Conductor actually copper clad aluminium instead of copper
- Insulation actually pvc which would quickly soften and degrade in a fire instead of a fire resistant type
- CPC actually copper clad aluminium instead of copper and not full size
- Screen not in contact with the CPC so there would be no automatic earthing of the screen
- Sheath made of polyethylene which would melt, drip and readily propagate flame
Never has the warning “caveat emptor” been so necessary. Use of such a cable would potentially put lives at risk due to non functioning of the fire alarm system and under the UK Regulatory Reform (Fire Safety) Order 2005 or even the Manslaughter and Corporate Homicide Act of 2008 could lay the installer open to serious penalty.
It is not sufficient to look only for the necessary standards to be marked on the product but also to ensure that the product is from a reputable manufacturer and backed by verifiable approval from an independent body.
Standards are important – ensuring compliance with the necessary standards even more so.