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Temperature rating of C.B's, cables and conduits

Former Community Member
Former Community Member
Question 1: All PVC conduits in market to BS:61386 are rated for 60C operating temp while CU/PVC single core wires to IEC 60228 are rated for 70C. what is the BS 7671 point of view.
Question 2: BS 7671 section 512.1.5 states that :Switchgear, protective devices, accessories and other types of equipment shall not be connected to conductors

intended to operate at a temperature exceeding 70°C at the equipment in normal service unless the equipment manufacturer has confirmed that the equipment is suitable for such conditions, or the conductor size shall be chosen based on the current ratings for 70° C cables of a similar construction. where as NEC 110.14(c): “Conductors with temperature ratings higher than specified for terminations shall be permitted to be used for ampacity adjustment,correction, or both.” Derating factors may be required because of the number of conductors in a conduit, higher ambient temperatures, or internal design requirements for a facility. By beginning the derating process at the ampacity of the conductor based on the higher insulation value, you may not be required to upsize the conductor to compensate for the derating.is there a similar way to apply the exception of NEC using the BS 7671.
  • Former Community Member
    0 Former Community Member
    I tried to apply Thomas Cook's Equation for NEC tables but it useless there.
  • Former Community Member
    0 Former Community Member
    . (I'm not entirely sure what the yanks mean by 'ampacity adjustment' etc.)


     


     

    Kindly check pages 5 and 6 of attached file and give me your opinion.
  • I'm not entirely sure what the yanks mean by 'ampacity adjustment' etc.


    Hmmmm. Just yanks being yanks, invent a stupid name or saying for summat.


    Sames as this phrase "Be advised, at this time, we have a situation"  over here in proper speak land the bloke would come home, take off flat cap and say "there`s been trouble at t`mill" and everbody knows what he means. Nobody here ever says "Be advised, at this time, we have a situation" we would be looked upon as stark raving bonkers

  • Kindly check pages 5 and 6 of attached file and give me your opinion.



    Thanks for that - an interesting read. It does seem that they just mean applying correction factors.


    Curiously they have a concept of a minimum cable temperature rating to suit MCB terminals - e,g, if you're running a conductor at 60 degrees you still need to use a cable with 75 degree insulation to cope with the heat generated by the MCB itself. Maybe we just side-step the issue as all our normal cables have an insulation rating of at least 70 degrees.


       - Andy.