Yesq. All neutral lines are common at the main breaker box. However, some contractors may not follow standards and loop the neutral lines.



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For lighting points, normally 6 lighting points (if not mistaken) will share 1 MCB (mini circuit breaker) of 6A. One single N wire is looping to all these points and return to the DB. The 20A switch will have its own N wire going back to the DB. This is because it is meant to carry the 20A load back to DB from L wire.

Even though it is a single phase wiring where the N is common throughout the house, the N wire to devices are separated throughout the house because of the current load wires have to bear. So, when you loop the N from the switch to the 20A switch, it will work for single phase usually, but now the load from smart switch will now share the load of the 20A switch.

If I understood the smart switch with N requirement right, the N will just carry very small current just to power the smart switch, not the load from light points because they have their own N at the ceiling. Therefore, I think this will not be a problem. No, it will not cause any damage to house wiring anyway. The 20A MCB still protect the wiring of the 20A switch.

This is looping. Eg in your bedroom you have 1 breaker for lights and 1 breaker for Aircond. By right the contractor needs to pull 2 neutral wires to that bedroom.  But some contractors want to save wire costs, they loop the neutral for both breakers.

So if you are working on the 20A and your lights are ON, you can get shocked if there is looping. because the current will flow to the 20A neutral line.

To be sure turn off all breakers in the room you are working on.

You can loop the neutral from the 20A double pole to use with your multigang neutral switch. However, there’s some safety concerns with that. Assuming that neutral cabling is not looped, meaning each and every circuit is connected directly from the respective DB to the fitting (in this case the 20A double pole), then whenever you want to carry out maintenance on your multigang switch or change the multigang switch to another switch, then you need to turn off your 6A lighting MCB and also the 20A MCB (for the double pole) before you carry out maintenance. Because if you just turn off the 6A MCB, the neutral from the 20A double pole that was looped over is still live, and may electrocute you.

I think, you can consider to install the non-neutral multigang switches that use the zigbee 3.0 protocol, and they are cheaper when you go with brands under the TUYA OEM umbrella. They can be wired up without neutral, do not require capacitor (so far no issue with mine) and just required a zigbee hub to pair to.

Brands such as Aqara are pricier. Wifi only switches may clog up your 2.4Ghz network. And brands like sonoff, require neutral.

Edit: if you want a one to one replacement for the 4 gang switch, you may still require neutral (some 4-gang switches are sold online, but only wifi, no zigbee). Because zigbee switches are only 3-gang, No 4-gang zigbee switches as of yet. I have a 4-gang switch that i am still thinking of how to settle. I dont want to settle for a 4-gang wifi switch and have to deal with capacitors, rather have zigbee.

Why is it bent? Because each of seitches had protrusions on the screw holes, such that if I installed as-is with the spacer bracket, it will leave a gap between the wall/spacer and the switch's frame. So I had to saw off a bit of the spacer's screw holes, but I had sawed off too much of the spacer's screw hole in earlier installations. To re-fill back the space left vacant from sawing off too much of the spacer, I used nuts.

Now the switches are flush with the spacers without any gap between wall, spacer, and switch; and no more flickering since the switches are no longer bent from tightening too much over empty, sawed off screw holes.