Results 1 to 4 of 4

Thread: Cable joint

  1. #1
    New Member
    Join Date
    Mar 2015
    Location
    windhoek
    Posts
    2
    Thanks
    0
    Thanked 0 Times in 0 Posts

    Cable joint

    is it wrong to joint 16 mm cable with a 10 mm cable with a scotch cast joint?

  2. #2
    Diamond Member AndyD's Avatar
    Join Date
    Jan 2010
    Location
    Cape Town
    Posts
    4,582
    Thanks
    534
    Thanked 873 Times in 705 Posts
    Er yeah, nah maybe....

    It's an odd question. Not sure how any circuit design could ever result in the need to joint a 16mm cable to a 10mm cable or is this a hypothetical type question?.

    A few issues first followed by a lot of 'if's'.

    Firstly you'd need a joint with ferrules that are designed to have unequal wires sizes in the same ferrule. They do exist but I've never seen them in this country and generally they're bi-metalic and meant for medium and high voltage applications. The logistics of making a satisfactory unequal wiring joint that is permissible by the manufacturers specs of the equipment being used would already be problematic. For example using a 16mm ferrule with a 10mm wire is non-compliant. Likewise using a 10mm ferrule and giving the 16mm wire a short back and sides to make it fit is also non-compliant.

    Secondly I'd say it would be wrong if the cable size is reducing along its route. If the circuit is starting as a 10mm and increasing part way to 16mm it might be less of an issue IF the protective device supplying the circuit is sized to the smaller cable size and IF the CPC (earth wire) is sufficiently sized etc and IF the circuit has adequate labelling at both ends indicating the CSA changes etc etc.

    In a nutshell it's a really bad idea, it's poor circuit design and it's highly unlikely you'll find a compliant way to do it.

    I have to ask the question, why would you want to do it and why is there no better way to design this circuit?
    _______________________________________________
    I am special and so is Vanash.
    _______________________________________________

  3. Thanks given for this post:

    Dave A (02-Sep-17)

  4. #3
    Silver Member
    Join Date
    Sep 2010
    Location
    cape town
    Posts
    298
    Thanks
    3
    Thanked 42 Times in 36 Posts
    i have found it a few times where different size cables had to be joined on existing installations. (by one cable size anyway) for example, the original cable was installed oversize for voltage drop. now years later the db is replaced and relocated a few meters further . the new db has a lower rating and the cable wont physically fit in the db even if it was long enough. the supply breaker is replaced with a lower rating. im not sure if joining 2 different size wires by trimming the larger wire is compliant or not, but i cant see it reducing the rating of the lower rated wire. the other way to join would be an enclosure with busbar insulators.

  5. #4
    Diamond Member AndyD's Avatar
    Join Date
    Jan 2010
    Location
    Cape Town
    Posts
    4,582
    Thanks
    534
    Thanked 873 Times in 705 Posts
    I think reducing CSA part way along the route is definately a non starter. Problem is if someone in future sees a 16mm cable in a DB they're likely to think it okay to size the circuit breaker according to the size of wiring they can see in front of them. Obviously if the cable is jointed to a smaller cable along its route then the smaller cable can now be overloaded.

    Your suggestion of some kind of accessible enclosure or mashalling kiosk with busbars would be the way to go because apart from the connection being much easier to make compliant, there could also be a breaker mounted in there which is sized to the smaller cable to prevent the overload scenario above.

    I'd say it would be non compliant to trim any wire to make it fit into an undersized lug or ferrule, it's definately against manufacturers recommendations and also the resulting crimp joint wouldn't be mechanically satisfactory.
    _______________________________________________
    I am special and so is Vanash.
    _______________________________________________

Similar Threads

  1. [Question] Unincorporated joint venture (partnership) and SARS
    By Zothi in forum Tax Forum
    Replies: 0
    Last Post: 18-Nov-15, 01:32 PM
  2. Joint ventures, VAT and income tax.
    By PieterPan in forum Tax Forum
    Replies: 5
    Last Post: 30-Aug-12, 10:18 PM
  3. JOINT WILL FORMAT
    By Vanash Naick in forum General Chat Forum
    Replies: 1
    Last Post: 11-Feb-12, 02:29 PM
  4. [Question] Joint Ventures and SARS Compliance
    By gac in forum Tax Forum
    Replies: 2
    Last Post: 17-Jan-12, 10:36 PM
  5. [Article] Exe cable glands for braided cable
    By Master Electrician in forum Electrical Contracting Industry Forum
    Replies: 0
    Last Post: 26-Aug-10, 02:47 PM

Did you like this article? Share it with your favourite social network.

Did you like this article? Share it with your favourite social network.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •