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Metal Cable Ties

Stuart Urban
I have been told that "BS 7671 States that the use of metal cable ties is required for cables of certain gauges". Is there anything somewhere like this in the regs?
  • 0
    Stuart.

    Refer 521.10.202

    Wiring systems shall be supported such that they will not be liable to premature collapse in the event of a fire. 

    NOTE 1: 
    Wiring Systems hanging across access or egress routes may hinder evacuation and firefighting activities. 

    NOTE 2. 
    Cables installed in or on steel cable containment systems are deemed to meet the requirements of this regulation. 

    NOTE 3: 
    This regulation precludes, for example, the use of non-metallic cable clips or cable ties as the sole means of support where cables are clipped direct to exposed surfaces or suspended under cable tray, and the use of non-metallic cable trunking as the sole means of support Of the cables therein. 

    NOTE 4. 
    Suitably spaced steel or copper clips, saddles or ties are examples that will meet the requirements of this regulation. 

    MRF

  • 0
    I just use an occasional wire armour strand or two from old S.W.A. twisted around a steel screw. Works a treat.


    Z.
  • 0

    Zoomup:

    I just use an occasional wire armour strand or two from old S.W.A. twisted around a steel screw Works a treat.


    Z.




    How many twists would be required?

  • 0
    A sufficient number of twists held under a penny washer creates a good solid fixing.


    Z.
  • 0

    mrf:

    Stuart.

    Refer 521.10.202

    Wiring systems shall be supported such that they will not be liable to premature collapse in the event of a fire. 




    NOTE 1: 
    Wiring Systems hanging across access or egress routes may hinder evacuation and firefighting activities. 

    NOTE 2. 
    Cables installed in or on steel cable containment systems are deemed to meet the requirements of this regulation. 

    NOTE 3: 
    This regulation precludes, for example, the use of non-metallic cable clips or cable ties as the sole means of support where cables are clipped direct to exposed surfaces or suspended under cable tray, and the use of non-metallic cable trunking as the sole means of support Of the cables therein. 

    NOTE 4. 
    Suitably spaced steel or copper clips, saddles or ties are examples that will meet the requirements of this regulation. 

    MRF


     




    Yes thanks, and this:

    “522.8.4 Where conductors or cables are not supported continuously due to the method of installation, they shall be supported by suitable means at appropriate intervals in such a manner that the conductors or cables do not suffer damage by their own weight.

    522.8.5 Every cable or conductor shall be supported in such a way that it is not exposed to undue mechanical strain and so that there is no appreciable mechanical strain on the terminations of the conductors, account being taken of mechanical strain imposed by the supported weight of the cable or conductor itself.”

     

  • 0

    I have been told that "BS 7671 States that the use of metal cable ties is required for cables of certain gauges"



    You've been ill informed! There's no requirement for metal cable ties as such - although some kinds of steel ties would be suitable for meeting the fire resistance requirement in some circumstances, as mrf said. Note that not all steel ties are suitable for the high temperatures likely during a building fire - some common types (perhaps with plastic components in the locking mechanism) have very modest temperature rating and would likely not be suitable. Likewise there's no prohibition on using plastic ties if the cable wouldn't fall if they melted - e.g. they're just used to keep things tidy in a horizontal cable basket.


    As for the cable gauge - that's nonsense. The requirement applies equally to all cables (or other kinds of wiring systems) regardless of size.


      - Andy.
  • 0
    The swizzle of SWA armour meets the requirements as written, I rather suspect it was not in the inner eye of the authors of BS7671 as an example of best practice while they earnestly sucked their collective pencils at the drafting stage.


    If you are rolling your own, give it (or perhaps better a test one along side rather than the real cable) a damn good pull to be sure that it won't come undone.


      builder's band looks a bit less of a hack  and can be over sleeved in heat shrink if need be so as not to dig into softer cables like TV coax and so on . It can also be formed  to make P or W saddle clamps. You will however need tin snips or patience.
  • 0

    Zoomup:

    A sufficient number of twists held under a penny washer creates a good solid fixing.




    Clearly not a Yorkshireman, else it would be a ha'penny washer. ?

  • 0
    Hoy, not just Yorkshire, us Lancashires do likewise, reet! now think on
  • 0

    mapj1:

    The swizzle of SWA armour meets the requirements as written, I rather suspect it was not in the inner eye of the authors of BS7671 as an example of best practice while they earnestly sucked their collective pencils at the drafting stage.




    Hello Mike,

                         I was running some S.W.A. over two vertically hinged rear domestic garage doors yesterday for a garden hot tub. Whilst fixing the cable with S.W.A. cleats I suddenly remembered the requirement to prevent premature collapse of the cable in case of fire. I had some lengths of the steel armour strands to hand and used then in just two positions to make  "fire proof" supports. The method is reliable and solid in design. The method complies to Z's standard (133.1.1) and will do the job if required to.


    As the location was just an untidy domestic garage, the appearance did not matter too much. But for an OMS upmarket smart city job he would not approve.


    Z.

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