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Discuss Metal cable tie distance in the Commercial Electrical Talk area at ElectrciansForums.co.uk.

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  1. Daniel Mills
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    Daniel Mills New EF Member

    Location:
    Bromley
    I’m working on a commercial construction site and I’ve been requested by he client to install metal cable ties to all inverted tray runs for my beldon and SWA cables.

    I’ve looked through BS7671 and I can’t seem to find the distance required between each metal cable tie.

    Does anyone know where I can find this distance and what distance it is?

    Additionally PVC cable ties are installed, this is just incase of a fire.
     
  2. buzzlightyear
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    buzzlightyear Electrician's Arms

    Location:
    star command
    personally I would space them out for cable trays 10inches apart approx.
     
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  3. Andy78
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    Andy78 Trusted Advisor

    Location:
    Kingston upon Hull
    I think the OSG has tables for maximum distances for cable support if you need them, but what Buzz suggested seems right.
     
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  4. Wilko
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    Wilko Electrician's Arms

    Location:
    Berkshire
    Business Name:
    Wilko Electrics
    OSG Appendix D Table D1 has the spacings :)
     
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  5. Murdoch
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    Murdoch Electrician's Arms

    Location:
    Woking
    Where is it in the BYB?
     
  6. Andy78
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    Andy78 Trusted Advisor

    Location:
    Kingston upon Hull
    I think the regs say something vague and all encompassing like "cables must be adequately supported" then the OSG expands on this with distances for sizes of cables.
     
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  7. Wilko
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    Wilko Electrician's Arms

    Location:
    Berkshire
    Business Name:
    Wilko Electrics
    The next question is - do all of the supports need to be metal to comply with 521.11.201 ?
    I haven't read advice on that, but I've seen some where every clip is metal, some every second clip and some looking retro fitted at 1m.
     
    Last edited: Oct 11, 2017
  8. Richard Burns
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    Richard Burns Trusted Advisor

    Location:
    Cambridgeshire
    Business Name:
    Richard Burns
    I think I would concur with wilko that the general approach is that there must be some metallic or fire resisting clips at 1m intervals, the remaining supports can be plastic or such like.
    The regulation is as usual for BS7671 fairly vague on wording as Andy78 says it cannot be the sole means of support and must be adequate??
    The intent of the regulation is to prevent cables dropping in a fire and causing a restriction to someone trying to traverse the route.
    Therefore on a high ceiling above 3m a cable that drops one meter down will not impede the majority of people. If the ceiling is low then a smaller drop could be a problem, so a risk assessment of the amount that cables could drop would be a good idea to ascertain the frequency of fixing.
    Having said that if the cable is metallically intact then it should not drop far even if the insulation and sheathing are gone so long as there are regular intact supports.
     
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  9. Murdoch
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    Murdoch Electrician's Arms

    Location:
    Woking
    Which is just madness. That table should be in theBYB....
     
  10. Andy78
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    Andy78 Trusted Advisor

    Location:
    Kingston upon Hull
    The way the regulations are worded for cable supports allows for experience and good workmanship to figure out what is adequate. The OSG takes the "dummies guide" approach though I suppose.

    The regs are 522.8.4 and 522.8.5
     
  11. stevethesparks
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    stevethesparks Electrician's Arms

    Location:
    Northampton
    But if common sense were applied, there would be no need to sell both books to us mugs.
     
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  12. Risteard
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    Risteard Electrician's Arms

    Location:
    Derry, Ireland
    Business Name:
    Walsh Electrical Services
    SWAs secured with cable ties is not great to be honest (although fairly common). They should really be cleated to the tray.
     
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