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) ================(neutral)----------------
c) ----------------(blue)------------------


Knowing which country you reside in would help. ^_^


I didn't think it matters. I'm in Myanmar if this helps.


Translating 'downlight' into common English is a start. I assume you are
talking about a switch rather than a small, recessed spotlight. Assuming
the switch is configured so both black and blue are hot in one position,
why wouldn't they both work?


..... it has a fan .. and a light.

https://www.1000bulbs.com/pdf/fanima...stallation.pdf

John T.