• • • DATA CENTRE MANAGEMENT • • •
A guide to fire protection for vital cabling in data centres
Alex Smith, technical director at flexible conduit manufacturer, Flexicon explains some of the common myths around cable protection and fire performance for data centres – highlighting why operators should ensure that their cable protection meets all low fire hazard criteria requirements
fire protection for the given installation. Commercial building contractors and data
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installers alike have a legal obligation to ensure that cables are suitably fire performance rated for the application and location and therefore, comply to the European cable fire standard, BS EN 50575. This includes classifications of ‘reaction to fire performance’ and considers heat release, flame spread and propagation, smoke production, flaming droplets and acidity. BS 7671, commonly referred to as the 18th
edition wiring regulations, calls up EN 61386 for flexible conduit performance requirements, including fire. However, this standard for conduit systems, which was first published in 2008, only addresses non-flame propagation (self- extinguishing) – and no other fire performance properties such as enhanced flame retardancy,
n a data centre environment, all power cables seen as possible cause of fire, need to be jacketed in materials that provide the necessary
smoke and toxic fume emission are included. This can give rise to a potentially dangerous
situation where cables can be laid in flexible conduit that, by its standard, only needs to clarify if it is self-extinguishing and does not offer a comprehensive level of fire performance.
Assessing the hazard When assessing the fire hazard, suppliers should work with customers to assess the installation and environment that the conduit system will be used in. For example, in a data centre environment, factors such as high temperatures in confined server rooms should be considered. Also conduit systems containing halogens, such as PVC, will give off chlorine acid gas in a fire that can destroy electronic equipment in another part of the building. Almost all applications will require non-flame
propagating (self-extinguishing) as called for within the UK wiring Regulations (BS 7671) and tested by
means of the flame propagation test in EN 61386 as a bare minimum. Many customers will assume that this basic requirement will be met by any flexible conduit they specify, but this is not always the case.
Low fire hazard specification For a product to be classified as low fire hazard, it must display four clearly defined characteristics. It must be highly flame retardant, have low smoke emission, low toxic fumes and be halogen free. All metal conduit systems are inherently low
fire hazard as there is no plastic to burn, however most conduit systems are now plastic coated or all plastic, so their performance needs to be assessed. Traditionally, Halogen Free conduits have been
specified, often based on the common misconception that they offer comprehensive fire protection performance. Although such a conduit may prevent the generation of toxic gases in some settings, it does not mean necessarily that it is also flame retardant or have low smoke properties and may still be flammable if exposed to a heat source. Add to this the fact that there is no single
European classification standard for low fire hazard cable management products that defines terms, test methods and results expected, and it is easy to see why there is confusion in the industry. Terms are commonly used which suggest that
adequate fire protection is in place, when the product may only meet one of the four required facets. For example, ‘low smoke and fume (LSF)’ rated products may not address toxicity and ‘low smoke zero halogen (LSOH)’ specification may not address flame retardancy. The good news, however, is that there are
numerous flexible conduit solutions available that meet all four requirements for low fire hazard specification.
Flame retardancy First, a supplier must be able to demonstrate appropriate flame retardancy and there are a number of established test methods to prove performance. Flammability – the measure of how difficult it is
to ignite the conduit if it is exposed to a heat source - is often cited here. The minimum requirement is that the product is self- extinguishing, according to conduit system standard EN 61386. Here a vertical sample of
20 ELECTRICAL ENGINEERING • JUNE 2022
electricalengineeringmagazine.co.uk
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