The IET is carrying out some important updates between 17-30 April and all of our websites will be view only. For more information, read this Announcement

Rules and Guidelines
Want to participate in the discussions? Please read our Community Rules and Guidelines. Need some help? Visit Support and Answers.

  • State Not Answered
  • Locked Locked
  • Replies 5 replies
  • Subscribers 31 subscribers
  • Views 4813 views
  • Users 0 members are here
Options
You may also be interested in
This discussion is locked.
You cannot post a reply to this discussion. If you have a question start a new discussion

Cables in buried duct - Table 4C3.

ianlloyd
Looking at the Regs, particularly Table 4C3, it would appear that only one multicore cable is allowed in a buried duct (i.e. "single way duct"). The 'Rating Factor' seems to be applied to the number of ducts, not the number of cables.


I've seen numerous installations where more than one cable is installed in a single duct - is this acceptable and, if so, how is the grouping factor applied?
Parents
  • 0
    Apologies, yes you are correct, the wording is as you say, and I admit I missed that when I was reading it.


    I agree, that an approach might well be to apply 4C1, on top of 4C3 should there be more ducts in the vicinity, noting that it's still necessary to apply correction factors using the expression of Equation 2 in item 5.1.2 of Appendix 4
    • Ca for the Assumed ambient temperature

    • Cs for the particular soil thermal resistivity

    • Cd for the specific depth

    • Cf if a semi-enclosed fuse is used

    • Cc (0.9 for a cable laid in the ground where overload protection is required).


    So, basically, follow the example in the EIDG, but apply 4C1 on top in any ducts where there is more than one circuit being served.
Reply
  • 0
    Apologies, yes you are correct, the wording is as you say, and I admit I missed that when I was reading it.


    I agree, that an approach might well be to apply 4C1, on top of 4C3 should there be more ducts in the vicinity, noting that it's still necessary to apply correction factors using the expression of Equation 2 in item 5.1.2 of Appendix 4
    • Ca for the Assumed ambient temperature

    • Cs for the particular soil thermal resistivity

    • Cd for the specific depth

    • Cf if a semi-enclosed fuse is used

    • Cc (0.9 for a cable laid in the ground where overload protection is required).


    So, basically, follow the example in the EIDG, but apply 4C1 on top in any ducts where there is more than one circuit being served.
Children
No Data

Join us to get the best from IET EngX.

Joining EngX lets you personalise your experience so you stay up to date on the topics that interest you, plus you’ll be able to make connections who are looking to collaborate, exchange ideas and more.

Join us Not now

Community Rules & Guidelines