Last edited 05 Nov 2019

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Data cables and the CPR

ECA CPR reaction to fire large.jpg
**In addition to the flame propagation classes for cables outlined in the table above, there are three other sub-categories of cable fire performance for the classes B1ca to Dca. More information about these is available in the application guide, Cable and CPR, available exclusively to ECA Members.

Contents

[edit] The CPR and cable reaction in a fire

More than ever, data communications and control cables are built into the fabric of homes and offices, alongside traditional power cables. But with more connectivity comes a larger number of conduits along which a fire could spread. Data comms, power and control cables come under the Construction Products Regulation (CPR), designed to consider the reaction of cables in a fire. As such, they must be selected carefully before an installation.

[edit] Stopping fire in its tracks

Government statistics show that, in England, in 2017/18, almost 31,000 fires involving fatalities, casualties or rescues occurred in homes, and over 15,000 occurred in other buildings (offices, shops, hospitals, schools, etc). In about seven per cent (approximately 3,400) of these fires, wiring insulation was identified as the main material responsible for the fire propagating.

The same statistics also concluded that “the most commonly identified cause of death from a fire incident is being overcome by gas or smoke.”

Clearly, the type of cable installed, and the way it reacts to fire, is a critical consideration for designers and installers.

Data communications cables currently available in the UK are insulated, bedded or sheathed with materials such as PVC, TPE, Nylon, metal weaving and mercerised cotton. Each reacts differently to fire and will have a different EuroClass rating.

In the event of a fire, these materials may, to different degrees, produce toxic smoke and acidic gases. They might also act as a fuel, helping to propagate flames along cables and through a building and its voids. This danger is further exacerbated by falling flaming droplets caused by melting.

The smoke and gases given off by burning cables can hinder a building’s occupants from escaping a in event of a fire. It can also inhibit firefighters by blocking their vision and reducing the effectiveness of emergency lighting.

Another less immediately obvious side effect of acidic gases may be corrosion of other metallic components – often within electrical and electronic equipment.

[edit] What about Brexit?

Despite Britain’s intention to leave the European Union, it is understood that CE marking will remain a pre-requisite for any manufacturer, importer or distributor wishing to sell their cables within the EU. What we know for certain is that CPR will still apply to all construction sales, both in the EU and in the UK.

[edit] Top of the class

Under CPR, European Classification replaces IEC 60332-1-2:2004, which was the previous benchmark for assessing the flammability of cables. Because methods of testing cables have changed drastically, direct comparisons to the old standard are not exactly straightforward. The table at the top of this page clarifies the classes.

Some readers may notice that these seven classes broadly align with classes Aca to Fca used for other construction products, and which are already referred to in UK Building Regulations.

It is clear that a cable in class Aca would be the best in terms of fire performance, and an Eca cable would be seen as the worst. Class Fca cables should be used with caution or avoided entirely if possible, as it would be of unknown origin with no identification markings or labelling.

[edit] Selecting and designing with CPR

In all cases, the designer or cable specifier will be ultimately responsible for selecting the appropriate classification of cable.

Best practice’ would dictate that safety should always be the first consideration, especially for buildings where vulnerable people may be restricted in their ability to escape a fire, such as care homes or hospitals.

Similarly, high-rise buildings, buildings with high fire risk or buildings with high traffic, such as offices, shopping centres or conference centres, would also warrant higher levels of safety from the hazards of burning cables.

[edit] About the CPR

The CPR covers all construction products and classifies them by their reaction to fire. It is also the reason behind the CE marks seen on many construction products.

To keep up with the new ways cables in buildings are made, installed, used and maintained, the CPR was updated and became a legal requirement in 2017*.

This development was met with some confusion, particularly over the new European Classification (or EuroClass) system which replaced the old Construction Products Directive (CPD).

An obvious benefit of the CPR is that it enables designers, specifiers and other industry professionals, as well as consumers, to compare the safety performance of products that may have come from different manufacturers. In other words, it allows easy like-for-like comparison between products.

  • Since 1 July 2017, it has been a legal requirement in the UK for manufacturers, distributors or importers to make a Declaration of Performance (DoP) and apply CE marking on relevant cables (i.e. those intended to be permanently installed within a building).

[edit] About this article

This article was written by Gary Parker. It previously appeared in the Autumn 2019 issue (pp 28-29) of ECA Today, the magazine of the Electrical Contractors Association and can be accessed HERE.

More articles by ECA on Designing Buildings Wiki can be accessed HERE.

[edit] Related articles on Designing Buildings Wiki

--ECA