Cabling – getting it right
With an ever-increasing number of cables coming onto the market, and a growing awareness of the need to comply with regulatory standards and ensure best practices it is high time that a number of cable issues are seriously addressed. A vitally important task is to get to a point where installers can confidently rely on manufacturers’ cable ratings and to have absolute confidence that the cable being supplied ‘does what it says on the box’.
In the UK, fire performance cables for alarm systems now fall into two categories; they are classified as either Standard cable or Enhanced cable. These are performance levels that are determined by testing procedures described in BS EN 50200: (Method of test for resistance to fire of unprotected small cables for use in emergency circuits) and BS 8434: (Methods of test for assessment of the fire integrity of electric cables).
Standard cable is acceptable for the majority of installations, while Enhanced cable is called for in clearly defined applications. These can be summarised as: buildings where cables are required to operate longer due to phased evacuation; buildings over 30 metres high that are not protected by sprinklers; buildings with critical signal paths to areas where people may remain for some time during a fire; and buildings where a fire risk assessment identifies the need for Enhanced performance.
The growing international trend for buildings to be designed on fire engineering principles rather than prescribed measures has resulted in the increased use of Enhanced cables. This has prompted a number of major investment programmes that have seen the introduction of pliable cables that attain Enhanced performance.
An entirely new generation of Enhanced fire performance cables has been introduced that offers 60 minutes fire and mechanical protection, followed by 60 minutes of fire, mechanical impact and water protection. It is suitable for use in Zone 1 and Zone 2 hazardous areas, as defined in EN 60079-0 (Electrical apparatus for explosive gas atmospheres – general requirements). Zone I areas are where an explosive atmosphere is likely to occur during normal operations, while Zone 2 areas are those in which explosion hazards do not exist during normal operating conditions.
This particular cable, in common with all Draka’s cables, is verified by BASEC (British Approvals Service for Cables) and LPCB (Loss Prevention Certification Board) independent testing and approval.
Another recent innovation offers contractors ease of preparation, handling and installation. This too is a OHLS (Zero Halogen, Low Smoke) cable, which combines robust construction and the fastest ever sheath removal with minimal installation and preparation damage, due to the cable’s filled supportive sheath. It is a pliable cable that is not prone to deformation or kinking, even when the cable bending radius is tight, which means that it meets the Standard performance of BS 5839-1 (Fire detection and alarm systems for buildings). Code of practice for system design, installation, commissioning and maintenance and BS 5266 (Code of Practice for emergency lighting).
This particular cable exploits the very latest cable materials technology to deliver the ultimate in flame retardancy and consistent circuit integrity, and establishes a new international industry benchmark in terms of flame spread and smoke production, lightness and reduced diameter. It is also suitable for use in both Zone 1 and Zone 2 hazardous environments.
Another recent innovation was the introduction of a cable specifically designed to meet the challenging demand for immunity to electro-magnetic interference (EMI). This is a particular requirement of airport environments, where higher than normal levels of electro-magnetic radiation are present, rendering fire detection and alarm systems vulnerable to false alarms.
The need for approval
Following the introduction of the Standard and Enhanced classifications, there have been a number of instances of incorrect product installation. Whether this has been due to misunderstanding the cable performance rating, or because cables are marked with a rating that testing subsequently fails to corroborate is difficult to say. However, the suspicion must exist that some cable manufacturers are not supplying cables that have the same specification as the samples they supplied for testing.
Even the DTI has expressed concerns regarding unscrupulous manufacturers of wire and cable that are alleged to be cutting down on the copper content. There are allegations that, in some instances, aluminium is being substituted and disguised as copper by anodising or plating, and that there are cases where lower grade copper additives are being used; practices that appear to be restricted to imported cable.
Whether these problems are the result of misunderstandings, or blatant misrepresentation, the only way to put an end to them is through third-party accreditation. This is a policy that Draka has been championing in the cable industry for some years. Specifiers should also seek direct evidence of independent approval, such as listing in Part 3 of Volume 1 of the LPCB Red Book.
Draka’s and the DTI’s concerns are shared by BASEC. Dr Jeremy Hodge, Chief Executive of BASEC, believes the problem is getting worse and is calling for the industry to use only cabling that is BASEC approved. He recently said: “Do not take a supplier’s claim at face value – that is the message from the British Approvals Service for Cables as faulty products become a major industry issue.”
The comment came as BASEC revealed that it has been contacted over recent months by a number of distributors, cable manufacturers and end users with examples of faulty or non-compliant cable. Now it is warning of the severe dangers of buying and installing cables which lack independent third party approval. Dr Hodge said: “A common misunderstanding is thinking that a cable is compliant, or even BASEC approved, just because the supplier claims that it has been produced to a certain standard.”
These issues have grown in importance with the greater awareness of the need to comply with regulatory standards and ensure best practices. This is particularly so in England and Wales, following the enactment of the Regulatory Reform (Fire Safety) Order last October, and Approved Document B (Fire safety) of the Building Regulations that came into force on 6 April 2007.
Even in areas not covered by the Fire Safety Order or the UK Building Regulations, fire engineering solutions rather than the adoption of prescribed measures are becoming increasingly commonplace. All of which places a far greater responsibility on specifiers, system designers and manufacturers, installers, project managers – even the building’s owner and occupier – to ensure that the cabling delivers its expected performance. In other words, to ensure the installation’s full integrity.