On 15/03/2018 09:38, trader_4 wrote:
On Wednesday, March 14, 2018 at 10:38:55 PM UTC-4, Oumati Asami wrote:
How does this circuit work?

This house has 3 phase power.

I was replacing a downlight and found it having two black, two neutral,
and one blue incoming wire.

If the light switch was on, the blue wire was energized.
If the ceiling fan was on, one of the incoming black wire was energized.

Why/how do both light and fan work when both are on?

incoming downlight
a) ================(black)------------------
b) ================(GROUND)----------------
c) ----------------(blue)------------------

IDK why a house anywhere would have 3 phase power. But there is a wire for the light, a wire for the fan, two neutrals, so what's the issue?

Sorry, the diagram was wrong. I mistakenly labelled ground as neutral.
It is now corrected.

When both fan and light are on, both the blue and black wires are
energized.