The Data Cabling Industry has always been closely coupled to the Electrical Industry and practicing professional installers will be familiar with BS7671: Requirements for Electrical Installations aka the 17th Edition Wiring Regulations. From January 1st this year the 18th Edition came into force following publication last July. Wiring systems includes ELV cables such as data cables so it is important to be aware of changes in the regulation that can affect data cabling design and installation.
One important change relates to the design of wiring systems support in fire escape routes. This has major implications for the use of non-metallic support and containment for cabling.
In the 17th Edition regulations, high-level non-metallic cable support systems e.g. plastic was not permitted where there was a risk of collapse into the path of evacuees or firefighters. This gave rise to uncertainty over what path the escape route included or even if it was relevant to data cables. In practice, this meant it was often ignored.
In the 18th Edition, this uncertainty has been removed because fire escape routes apply to ALL locations within a building. In the event of a fire, cables and their support systems should not collapse prematurely* such that it would hinder **, evacuation or firefighting.
The 18th Edition is explicit that plastic clips should not be used as the sole or “main” support for cables. In addition to this, a strong reference is made to the spacing of the metallic clips and fixation methods. When fixing cables to exposed surfaces vertically and horizontally, the spacing of metal fixings should be approximately 250-400mm.
What does this mean in practice? Here are a couple of examples:
It will no longer be acceptable to clip cables to the underside of overhead metallic cable tray using plastic cable ties.
It will no longer be acceptable to use high-level plastic trunking, conduit or hangers e.g. ‘J’ hooks if not affixed to the building substrate by metallic supports. These will need to be suitably spaced to prevent the premature* collapse of the wiring system. Therefore plastic clips e.g. conduit saddle clips, cable ties etc. are not going be acceptable if in the event of a fire the cabling could fall into the path of people.
Many data cabling installers do not install the containment systems but there are often instances in existing buildings where the cable path containment is full. In these situations, the installer will need to be mindful of the 18th Edition Wiring Regulations or they may incur additional costs associated with providing metallic support systems or re-routing. Ignorance of regulations does not excuse responsibility.
*Premature is defined as to hinder evacuation and firefighting activity.
**The word hinder is open to some interpretation. There are very small cables e.g. alarm sensor cables that are designed to be glued to a building substrate for example. Firefighting authorities have given rulings on a case by case basis so there will be a few exceptions.
Article based mainly on an FIA report for members by Mike Gilmore published 7 Jan 2019.
https://www.fia-online.co.uk/