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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?  



Parents

  • Perhaps it is related to power loss. Using a larger cable will have a higher initial cost, but in the long run, you will recover it by reducing the energy loss over the years. You can use Ohm’s law, hours of usage, and copper resistance values to calculate the kWh lost per year and the cost per year. You can then calculate the payback period by dividing the initial cost by the annual savings. Appendix 17 of Bs 7671 is expected to become a new part in the near future.

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  • Perhaps it is related to power loss. Using a larger cable will have a higher initial cost, but in the long run, you will recover it by reducing the energy loss over the years. You can use Ohm’s law, hours of usage, and copper resistance values to calculate the kWh lost per year and the cost per year. You can then calculate the payback period by dividing the initial cost by the annual savings. Appendix 17 of Bs 7671 is expected to become a new part in the near future.

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