Rating Current for Switch & Cable

@ 12.5A yes, but with a big BUT. The striking current when 40 lamps turn on at the same time will be X1.8 load. The cable is undersized so you will get appreciable volt drop making starting the lamps worse.

Time for a rethink.

The key factor you've omitted is the nominal voltage and phases of your power grid that this switch and cable will be handling. The fluorescent lamps will be drawing nearly 3kW of power. (At a nominal 80 lumen per watt you're at almost a total of 1/4 million lumen. That's a lot of light.) If you have a 120 VAC single phase grid this is an inadequate switch and cable. If the grid is 480 VAC three phase then you will not have to worry about in rush currents.

Yeah, I know lo of light. Voltage here is 220V.

Normally, we use this switch to control less than 10 sets of 72w lamp. But the reason I post the question here is I want to find the truth behind the current rating given by supplier especially commercial sockets and switches.

Why didn't you say so in the first place?

I've noticed that and will do it in the first place. Thank you very much for your suggestion.

The 16A switch rating is for a resistive load, but you will be switching a capacitive load which will result in very large inrush currents. This will cause arcing and may result in the switch contacts welding together. My experiance is to use these everyday commercial switchers at about 50% of their rating and this seems to work well.

British Standard 7671.

Just noted that these lights are being installed underground, as the cable rating you are using, indicates that it will not be in a roof space or in conduit above ground.

If the 1.5mm cable is being used as a control circuit to switch a contactor, rated at 16amp AC3, and your 40 lamps have been split into 3 groups, and wired with 2.5sqmm cable, then you are getting there.

Cheers.

Mark N.