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Regulatory change “intensifies focus” on ‘fire-resistant’ cable performance

23 September 2021

ONE MANUFACTURER of mineral insulated copper cables is urging specifiers and designers to consider the stresses real-life fire scenarios place on ‘fire-resistant’ cables, such that they can then select products that will truly withstand a critical situation.

As the focus on building safety intensifies, Wrexham Mineral Cables has voiced its approval of recent amendments to Approved Document B (Fire Safety) of the Building Regulations. Those amendments mean that all new residential buildings over 11 metres in height must be fitted with sprinkler systems.

With the proposed Building Safety Bill addressing the need for greater accountability at every stage of the construction process, Wrexham Mineral Cables’ commercial manager Steve Williams firmly believes that understanding the performance capabilities of different types of ‘fire-resistant’ cable is particularly important for specifiers and designers with whom the responsibility of product specification ultimately rests.

True fire test

Currently, only ‘fire-resistant’ cables that are greater in diameter than 20 mm must undergo testing for direct impacts and water testing with any significant pressure on a single test sample. For ‘fire-resistant’ cables under 20 mm, different stages of the test are carried out on different samples of cable, while exposure to water is minimal.

This means that most fire performance cables used to power fire alarms, emergency lighting, smoke detection systems and even smoke extraction systems in high-rise buildings would not have undergone any true fire test to reflect the recommended changes.

Williams commented: “The tests to which construction products are subjected need to be relevant and relied upon, especially so in tall buildings that require extended evacuation times. Regardless of size or construction, if a cable is required to function in the event of a fire, each single cable sample must have to pass a true fire scenario test.”

Certification system

With the Government set to review the certification system for testing construction products to examine how it can be strengthened, Williams has suggested that the system needs to be extended to cover ‘fire-resistant’ cables.

He added: “We’ve been calling for more stringent testing standards for ‘fire-resistant’ cables that reflect real fire scenarios. We believe that all ‘enhanced fire-resistant’ cables should undergo a minimum of three hours of fire testing, a water test that involves a fire hose or high-pressure jets similar to a sprinkler system and also direct impact testing on the cable, not on the test rig supporting it. All three of these test formats should be conducted on one single cable sample. Only then can a cable be classed as ‘enhanced fire-resistant’ for use in critical circuits.”