Cable Management

Questions at the counter: tackling the fire

performance of PVC-U trunking

Tragedies such as the Grenfell Tower fire have prompted builders, specifiers and electrical installers to re-examine their approach to fire safety. Now, in the midst of a growing debate about the fire performance of trunking solutions, cable management specialist, Marshall-Tufflex, has some pointers for electrical wholesalers.


esearch carried out following the Grenfell Tower tragedy revealed a sharp shiſt in specification stance, with 70% of architects questioned reconsidering how they select and

specify building products. This change in attitude is across the board; it encompasses building

systems and solutions with strong fire performance but is not restricted to them. For an industry accustomed to value engineering and specification switching it can only be a positive move. Its impact, and what it means in practice, has yet to be fully understood but if it drives up quality and the use of the most appropriate building products it will be of benefit to all. It is particularly pertinent to the cable management sector, where the

‘or equivalent to’ rider in specifications has allowed value engineering and product switching, often to the detriment of quality. For the most part, lower quality trunking systems may be more difficult and time-consuming to install, with compromises made on cable management performance, colour fastness, aesthetics and long term performance. Safety isn’t usually under consideration but there is now a growing debate about the fire performance of trunking solutions and this is one area where corners cannot be cut. BS 7671 requires wiring systems to be supported by fire-resistant fixings and fastenings to prevent cables collapsing in extreme heat. More recently the focus has shifted to the performance of PVC-U cable management in the event of a fire, with specific questions asked

about the use of surface mounted plastic wiring systems in older residential buildings. This is where electrical wholesalers can add real value to their offer by

knowing how the products on their shelves and in their order systems behave in fire – and why. Marshall-Tufflex has always been very transparent on this issue.

Charred PVC-U (Polyvinyl chloride unplasticised) consists of an expanded carbonaceous structure which protects underlying material and acts as an effective barrier to the spread of flame from malfunctioning electrical components contained within. PVC-U also has a low rate of smoke production during the early stages

of a fire, does not produce flaming droplets and – importantly – its charring characteristic makes it self-extinguishing. The PVC-U used in the manufacture of Marshall-Tufflex’s cable management systems is afforded Building Regulations Class O rating due being difficult to ignite and doing very little to contribute to the spread of fire. In short, PVC-U is inherently flame retardant, requiring an external heat

source to continue combustion. When subject to a fire situation, the material has low combustion heat and a low burning rate; its resistance to ignition and low rate of heat release means that it makes a minimal contribution to fire development and growth. The release of toxic gases in the event of a fire is of major concern, with carbon dioxide (CO2), carbon monoxide (CO) and hydrogen cyanide (HCN) being the most frequently cited – and dangerous – toxic

June 2018 electrical wholesaler | 23 ●Continued over

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