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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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  • Other thought was to to fault protection - what's the PFC at the supply end like? Above about 3kA a C10 might have an energy let-though higher than the withstand of a 1.5mm² Cu conductor.

       - Andy.

  • in reply to AJJewsbury

    not an absolute requirement since you have In ≤ Iz you can go down the deemed to comply route of 435.1 but some might prefer the added reassurance.

       - Andy.

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  • in reply to AJJewsbury

    not an absolute requirement since you have In ≤ Iz you can go down the deemed to comply route of 435.1 but some might prefer the added reassurance.

       - Andy.

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