Shared neutral?

[winayetun]

I have three switches. They each control two to three lights.

switch A: A1, A2, A3 (3 lights)
switch B: B1, B2, B3 (3 lights)
switch C: C1, C2 (2 lights)

The other day, I was working on A2 and got a shock while A was off. I was puzzled. I then disconnected all six wires (2 each of live, neutral, and ground) of A2 and found that the three B lights and the two C lights all stopped working. I assume this is a case of shared neutral, in which all lights share the same neutral. Correct? Is this allowed by the code?

 

[Marvo]

I'm not familiar with the Myanmar regulations but if circuits are sharing a neutral they should all be supplied by the same single phase or 3-phase circuit breaker so they all become isolated together if there's a fault or if they're manually isolated.

Working on any light fittings and relying on the light switch for safe isolation is not ever acceptable. Always isolate the entire circuit at the circuit breaker.