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Cable Sizing for 2 nos x 400W Floodlight

Qaslun

I'm trying to design one single line diagram (just for learning session) and one of my circuit is having 2 nos. x 400W Floodlight with 1.5sqmm Cu/PVC cable, with 30m cable length, MCB rating 10A all the calculation such as load current Ib, MCB rating In, derating factor, cable carrying capacity and voltage drop is shown in the above photo.

Based on my calculation, my Ib < In < Iz is  3.9A < 10A < 17.5A respectively, with voltage drop of 3.933V @ 1.147% from 230V, 

However, after discussing this with several knowledgeable individuals and referring to previous single-line diagrams that I've encountered, they've indicated that 1.5sqmm might not be sufficient, instead they requested me to change it to 2.5sqmm. (I do understand 2.5sqmm is better than 1.5sqmm in terms of cable-current carrying capacity, and voltage drop).

My query is, where might my calculation have gone wrong in this context?  



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  • In England we require 30ma (RCD) Residual Current Device for outside lighting that could be accessed by the public, I take this to mean all outdoor lighting .

  • in reply to Newfutile

    In England we require 30ma (RCD) Residual Current Device for outside lighting that could be accessed by the public, I take this to mean all outdoor lighting .

    I'd suggest that's being  little over-enthusiastic. Anything on private property often isn't accessible to the general public (invited guests etc aren't "the public"), section 714 overall doesn't apply to lights fixed to the outside of a building and supplied from the building's internal wiring (714.1 (v)) and 714.411.3.4 has a stack of exceptions itself, including street lighting.

       - Andy.

Reply
  • in reply to Newfutile

    In England we require 30ma (RCD) Residual Current Device for outside lighting that could be accessed by the public, I take this to mean all outdoor lighting .

    I'd suggest that's being  little over-enthusiastic. Anything on private property often isn't accessible to the general public (invited guests etc aren't "the public"), section 714 overall doesn't apply to lights fixed to the outside of a building and supplied from the building's internal wiring (714.1 (v)) and 714.411.3.4 has a stack of exceptions itself, including street lighting.

       - Andy.

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