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BS 8436 Cable

Jonesy
Hi all I am new to the Forum.


I have a question regarding BS 8436 Compliant Cables. I am aware iof the requirement to protect circuits wired in BS 8436 Cables with "B" Type devices etc due to the requirement to limit fault current in the event of the cable being penetrated by a nail or a screw. However, what if you install the cable clipped direct to the surface and on Cable Tray or basket where the risk of accidental penetration is very low, would it them be acceptable to protect the circuit with "C" Type devices?


I have hunted high and low on the internet for an solution but have failed to find a definitive answer.
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    Of course it matters what they serve, presumably the connected equipment HAS TO BE protected by a a Type C MCB  because it has an inrush current that would trip a Type B MCB.



    But that's a matter of rating as well as type. A B10 can survive the same inrush as a C6. And a B32 isn't much different from a C20 on the same score. So as long as overload protection isn't critical (or provided downstream) there might be some wiggle room that allows the use of a higher rated B-type instead of a C-type if you really need to stick to the letter of the specification.


      - Andy.
  • 0
    Andy


    Thank you for your reply. 


    I am happy to go with the BS 8436 requirement and specify the cable where I can and, as you suggest, design my way around the problem using experience and some "outside the box" thinking.
  • 0

    weirdbeard:




    Keith Jones:



    I am looking to use it as an alternative to SWA cable base on ease of installation and coat in commercial installations.


     




    Hi Keith have you considered A Hituff style cable?


     




     

    Any colour of sheath you like, so long as it’s black?

    Any customer can have a car painted any color that he wants so long as it is black. Henry Ford (July 30, 1863 – April 7, 1947)


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    Sparkingchip:


     


    pww235:

    It doesn't really matter what they serve does it?


    The key constraints are the required circuit breaker type/rating, the limitation on available conductor sizes and the installation method information available from the manufacturer.


    P




     

    Of course it matters what they serve, presumably the connected equipment HAS TO BE protected by a a Type C MCB  because it has an inrush current that would trip a Type B MCB.


    Or are you applying some unwritten rule that in commercial installations Type C MCBs are used, because that’s the way it’s done?


    Also if the cable is in a safe place within the cable tray why does it need any armour or earthed protection at all, unless it needs it when it drops out of the tray to the connected equipment?


    I presume this is going to be some cable choice based on the colour of the sheath available rather than what the cable is actually designed for, in which case you drop the spec done to some white sheathed low smoke twin and earth cable, the customer won’t know the difference when they are stood looking up at it.


    Andy B 

    I agree Andy - if the load requires a Type C or D to deal with its characteristics then that should be what is installed. That would then preclude the use of BS 8436 cable and is part of what I meant by the type/rating of the CPD being a constraint.

    My comment about what it serves was more directed at the listing of applications: power, lighting, air-con, etc.


    If its a commercial job, T&E shouldn't be anywhere near it in my opinion unless it is the only viable option left.


    P

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