CABLE MANAGEMENT


In July 2018, the 18th Edion of the IET Wiring Regulaons (BS 7671) was


published which comes into force in January. There is already plenty of speculaon as to what exactly the new regulaons mean, leading to many varied and confusing interpretaons about supporng wiring systems. Here, John Brodie, product manager for fastenings and fixings at


HellermannTyton is keen to dispel these misinterpretaons and set the record straight


T


o understand what additional support is required for wiring systems, we must first understand what has changed in the


regulations.


Firstly, there is the location – the scope of where additional support is required, is now much greater than it was previously. Where the previous wiring regulations stated ‘escape routes’ it now states ‘access or egress routes’, meaning both entry routes in and exit routes out of the building are covered.


The 18th Edition is also explicit that plastic clips should not be used as the sole or ‘main’ support for cables. In addition to this, strong reference is made to the spacing of the metallic clips and fixation methods.


Finally, there is specific reference made to cable trays and baskets, stating that these methods of cable management meet the regulations.


What does that mean?


What is clear from these changes is that the scope of the new regulations is wider than in the 17th Edition 3rd Amendment, specifically where reference is made to both entry routes in and exit routes out of the building. This reference combined with explicitly requiring metallic fixing is to reduce the risk of cables causing an obstruction, both to the residents of buildings as well as to first responders.


When fixing cables to exposed surfaces vertically and horizontally, the spacing of metal fixings should be approximately 250 - 400mm. HellermannTyton does not recommend that plastic fixings are used as the only method of fixing and should only be used in addition to sufficient metal fixing.


Where changes have been made to include cable trays and baskets it is recommended that larger cables and cable bundles are fixed within a cable basket or tray. By using metal fixings such as stainless-steel cable ties in conjunction with cable trays and baskets ensures maximum compliance with the 18th Edition to reduce risk of cables causing obstruction in the event of a fire.


BS 7671? What about BS 5839? And BS 5266?


In addition to BS 7671, there are other standards to consider for new installations. BS 5839 gives recommendations for fire detection devices and fire alarm systems for buildings and BS 5266 gives recommendations for emergency escape lighting. Both standards recognise the danger of collapsing cable supports in a fire, a danger which will be decreased with the introduction of the requirement of metal fixings in the 18th Edition. Fire Performance cables must maintain their function for a minimum of 120 minutes at temperatures up to 970 degrees. HellermannTyton recommends that fire resistant cable is supported using exclusively metal fixings.


If in doubt, ask


HellermannTyton has an in-house design team and its own manufacturing capability, so can provide expert advice on cable management as well as bespoke solutions. With this capability, HellermannTyton can create solutions to meet the needs of electrical installation contractors.


uBoth standards recognise the danger of collapsing cable supports in a fire, a danger which will be decreased with the introducon of the requirement of metal fixings in the 18th Edion


www.hellermanntyton.co.uk/competences/cable-ties-and-fixings


uThe scope of where addional support is required, is now much greater than it was previously


BSEE Untangling the latest wiring regulations


Read the latest at: www.bsee.co.uk


BUILDING SERVICES & ENVIRONMENTAL ENGINEER JANUARY 2019 31


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