Electrical Contracting News (ECN) April 2017 - Page 50





It is over four years since an amendment to the Wiring Regulations introduced tougher standards for non-sheathed , single insulated cable trunking installations , yet compliance problems still exist . Tim Brown , national sales manager at Unitrunk , looks at the requirements , examines the reasons for noncompliance and calls for an industry-wide approach to tackle the problem .

Out of sight , out of mind .

Unfortunately , the old adage too often applies to cable management installations in buildings . It ’ s more than four years since an amendment to the latest edition of the Wiring Regulations introduced more stringent standards in terms of trunking , yet we are still coming across installations that do not meet the regulations . Are specifiers and contractors unaware of the changes , or are they turning a blind eye because they deem it an unnecessary burden and an additional cost without clear safety benefits ?
BS7671:2008 – Amendment No . 1:2011 , which came into force on 1st January 2012 , requires the installation of IP4X trunking for all UK non-sheathed , single insulated cable trunking installations . Previously , the Wiring Regulations had called for trunking solutions for these kind of cables to meet the IP3 standard . Indeed , the IP3 standard is still deemed acceptable for double insulated cabling installations , as well as data cabling trunking .
Section 521.10.1 of the Wiring Regulations states : ‘ Non-sheathed
cables are permitted if the cable trunking system provides at least the degree of protection IPXXD or IP4X , and if the cover can only be removed by means of a tool or deliberate action ’.
An additional note was included as part of Amendment 3 in January 2015 , which reads : ‘ For a trunking system to meet IP4X requirements , IP4X trunking and related system components would need to be installed . If a system includes site fabricated joints the installer must confirm the completed item meets at least the degree of protection IPXXD ’.
The guidance couldn ’ t be clearer but there remains a lack of understanding and compliance on this apsect of the wiring regulations . There is a definite need for an industry-wide approach to address the issue .
An unnecessary change ?
You could , of course , question the need for this change to the Regulations . In my view , there are far more pressing matters worthy of attention if you are looking to improve safety in electrical installations . The change in industry trunking standards certainly doesn ’ t run in tandem with the drivers for ease and speed of installation
‘ IP4X and IPXXD rated trunking systems offer a high degree of protection .’
seen in initiatives such as BIM ( Building Information Modelling ). The requirement for trunking to be rated at IP4X or IPXXD means additional cost on site and cable management solutions that are slower to install , flying in the face of everything we are looking to achieve with BIM . It was an unnecessary change to my mind .
Yet we are where we are . Let ’ s take a look at what is now required in the Wiring Regulations . IP – or ‘ Index of Protection ’– is defined in the standard BS EN60529:1992 as the degree of protection an enclosure provides against a series of external agents . Products with a rated voltage of no more than 72.5kV are given a classification based on their performance in protecting persons against access to the hazardous parts inside the enclosure , and the way the electrical equipment inside is protected from foreign objects .
IP4X and IPXXD rated trunking systems offer a high degree of protection . For example , to achieve the IP4X standard , an enclosure needs to offer full protection against solid foreign objects larger than 1mm . In order to test this , a 1mm probe or wire , measuring 100mm in length , is applied with a force of 1N ± 10 % and it is not allowed to enter the enclosure being tested .
50 | April 2017