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FP200 Gold and fire resistant cables from Prysmian Cables UK

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FP200 Gold and fire resistant cables from Prysmian Cables UK

Welcome

FP200 Gold and fire resistant cables from Prysmian Cables UK

Fire Resistant Cables - Choice or Confusion?
Posted: 27/03/06 12:49:43

Fire Resistant Cables - Choice or Confusion?

As we enter 2006, it is an opportune time to reflect on the considerable growth in the availability of fire resistant cables on the UK market and some of the problems in selection of the appropriate product for a particular application that this has caused. What is certain is that there are now more manufacturers and fire resistant cable product ranges available than ever before. What is less certain is if this will prove to be to the long term benefit of users.

A quick review of the current LPCB “Red book” shows more than 20 manufacturers and nearly 60 distinct product ranges listed “for use in fire detection and fire alarm systems, and other application where specifications call up cables with specific performance in the event of fire.” Whilst many of the ranges are not listed against the standards needed to comply with, for example, current UK requirements of BS5839-1:2002 “Fire detection and fire alarm systems for buildings – Code of practice for system design, installation, commissioning and maintenance”, even for this particular application, the number of listed “standard” cables has more than doubled and the number of listed “enhanced” cables quadrupled in the last two years.

Comparison with the dire warnings given from some quarters at the time of issue of BS5839-1:2002 that only MICC cables would be able to meet its new requirements is interesting. Three years later, we find an ever increasing number of so called “soft skinned” cables joining the well established brands in the market, listed against both “standard” and “enhanced” requirements.

Whilst such increased choice may appear welcome, it puts a greater responsibility on the user to ensure that a correct choice is made. Important questions need to be asked:

  • Does the product have all the approvals needed for all potential applications?
  • How do the products compare in terms of track record of trouble free installation and performance and ongoing quality of supply?
  • Are the products technically supported by a manufacturer able to give accurate guidance as to the specification requirements for various applications and able to give the required advice on installation issues such as fixing and jointing?

Even within the fire alarm and emergency lighting area it is often overlooked that different applications have different cable test requirements and that one approval listing does not necessarily cover all applications. Historically, when only BS6387 was in use as the test standard, a Category CWZ listing would cover all fire alarm and emergency lighting applications.

Today, with the adoption of new and different test standards driven both by European harmonisation and a more critical examination of the particular application requirements by the BSI Committees responsible for installation Codes of practice, we see a different picture.

  • BS5839-1:2002 “Fire detection and fire alarm systems for buildings – Code of practice for system design, installation, commissioning and maintenance” requires cables for critical signal paths to comply with product specifications BS EN 60702-1 (MICC types), BS 7629 (“soft skin” types) or BS 7846 (armoured types) except that the fire resistance test requirements need not be applied and additionally to comply with the harmonised fire resistance test requirement of 30 min (“standard”) or 120 min (“enhanced”) to BS EN 50200 and the UK only fire resistance test requirement of BS 8434-1 (“standard”) or BS 8434-2 (“enhanced”).
  • BS5839-6:2004 “Code of practice for the design, installation and maintenance of fire detection and fire alarm systems in dwellings” requires cables to comply with the “standard” test requirements of BS5839-1:2002.
  • BS5839-8:1998 “Code of practice for the design, installation and servicing of voice alarm systems” still require cables to meet BS EN 60702-1 (MICC types) or BS7629 (“soft skin” types) including the fire resistance tests. Although BS6387 Category BSWX is actually referenced in BS7629, this requirement is usually taken as the more onerous BS6387 Category CWZ.

This cable requirement has been confirmed by the December 2005 Amendment to the standard and will be considered further for the next revision expected in 2007.

  • BS5839-9:2003 “Code of practice for the design, installation, commissioning and maintenance of emergency voice communication systems” requires cables to comply with the “enhanced” test requirements of BS5839-1:2002.
  • BS5266-1:2005 “Code of practice for the emergency lighting of premises” requires cables to meet the harmonised fire test requirement of 60 min to BS EN 50200.

If the complexity of requirements in the fire alarm and emergency lighting area appears confusing, it can be eased by careful choice of product with all the approvals against the necessary test requirements. However, the situation regarding requirements for power cables required to maintain their circuit integrity under fire conditions and to be used in fire fighting, life safety and property protection systems is also in a state of change.

Although the current version of Approved Document B of the Building Regulations states for “protected power circuits” that “A protected circuit for operation of equipment in the event of fire should consist of cable meeting the requirements for classification as CWZ in accordance with BS6387”, it has for some time been recognised that this test method, particularly in relation to cable size, voltage rating limitation and multistage test protocol, may no longer reflect the level of performance required by today’s fire safety engineered building designs.

Additionally, further refinement of requirements has led to different survival times being required for particular fire fighting and life safety applications.

This greater emphasis on the integrity of electrical circuits which need to maintain the function safe working conditions of such important equipment and systems has led to the development of much more onerous fire survival requirements. These requirements which involve an integrated fire test with the application of radiation by flame, direct impact and water jet onto the cable sample have been incorporated into the recently published BS7346-6:2005 “Components for smoke and heat control systems – specifications for cable systems”. Whilst BS7346-6 is limited such applications as smoke control, motor driven fire shutters and fire barriers and pressurization relief and smoke dampers, it test requirements are being actively considered for other fire fighting applications such as fire-fighting lifts.

Hopefully the current revision of Approved Document B will bring some greater clarity to the situation. Meanwhile, products are available to enable the best practice recommended by the latest British Standards to be implemented.


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