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Wiring regulations and their application to optical fibre in the home.

Timothy Durkin

I understand that telecoms wiring is subject to section 521.10.202 of BS7671:2018. Cat 5 ethernet cable is just as capable of causing entanglement of emergency service personnel as a mains power cable. I wanted to know if the tensile strength of the cable in question may be taken into consideration or if any provision is made for very light cable?  Some of the single core buffer fibre I am working with has the tensile capacity of sewing cotton and crumbles in fire.  Even very small metal clips do not offer the clamping force needed to support the vertical runs and I wanted to use some intumescent caulking.

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  • 0 in reply to Timothy Durkin

    Why would wiring regulations apply to glass fibres that don't even conduct electricity?

  • 0 in reply to Simon Barker

    well the signals are carried electromagnetically in the glass -it is a waveguide after all, just unlike coax and UTP, not one that goes down to DC. And more prosaically, as the OP notes, being garotted by a fallen bundle of optic fibres is much the same as it being copper,  and CAT whatever and optic fibres are often put in the same routes by the same folk, so a one size fits all approach makes sense.

    Now it is less clear if most network installers read or care what is in BS7671, but the authors of the standard think they should.

    to the OP, as far as BS7671 is concerned there is no de-minimis cable size below which the rules relax, but the decision to worry about compliance with the standard or not, may involve such a thought.

    M,

  • 0 in reply to Simon Barker

    Why would wiring regulations apply to glass fibres that don't even conduct electricity?

    Well they do - see 110.1.2 (vi). I guess the thinking is that entanglement can in theory happen with any kind of cable, so lacking anywhere else to put the requirement, it fell to BS 7671 by default.

    I do notice that OpenReach etc still seem to be using plastic clips on the outside of buildings...

    I can see an argument that if a cable disintegrates before the fixings in a fire, then it's not liable to collapse as such, so meeting the requirement.

       - Andy.

  • 0 in reply to Timothy Durkin

    I genuinely thought I deleted this post. It was the first time using this forum and I posed the question in the wrong box. I reposed the question in the correct boxes here.

     

    https://engx.theiet.org/f/questions-about-iet-engx/30830/wiring-regulations-and-their-application-to-optical-fibre-in-the-home

     

    I hope this clears up the discussion as the full question is available.

  • 0 in reply to Timothy Durkin

    Hi Timothy, I've merged the two threads into this one and moved it to the Wiring Regs forum which should clear up any confusion Slight smile

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