# Cable Sizing for 2 nos x 400W Floodlight

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
• Could I ask your about your thought process for the 10A MCB rather than a 5A RCBO?  I assume the flood lights will be outdoors?

• Yes, it is outdoor equipment and supposed to have IP65 rating, and in my circuit actually I already have RCCB with 100mA sensitivity .

• This may sound silly but what does the manufacturer recommend for the flood light?  Also what cable will you use, what is that manufacturers recommendation?

• As i said earlier, this design is for learning purpose, hence I haven't consider the brand. But i don't think the brand confirmation is really needed for this kind of general equipment in the early stage. Usually we have to design it first based on our experience and assumption, in order for us to determine the maximum demand and for regulatory application submission etc., since awaiting brand confirming from clients tends to be time-consuming . Our local regulation however has mandate the minimum cable for lighting is 1.5sqmm and should have SIRIM (Malaysia) and IEC standard, but again that is a minimum size (we can increase the size of the cable due to several factor such as derating factor and voltage drop).

• You do not specify in your plan which type of floodlight you are using. Will it be LED? Why not 30ma for your residual current device? Especially if the installation is outdoors.

I have fitted 4 x 40W LED floodlights in a large hall supplied via 1.5mm NYY-J cable clipped direct to 4" tray and connected to a B6 RCBO with no problems whatsoever. Can't recall the length of each run but the longest two were at least 20 metres each.