On 15/03/2018 19:22, wrote:
On Thursday, March 15, 2018 at 7:58:01 AM UTC-4, Dean Hoffman wrote:
On 3/15/18 6:27 AM, trader_4 wrote:
On Thursday, March 15, 2018 at 6:09:18 AM UTC-4, Oumati Asami wrote:
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)------------------


first lets clarify your picture

does a represent TWO blacks wires and only one is energized when the fan is on? what about the other black wire? are the two black wires connected together?

does b represent TWO white? are they connected together?

and c looks like it is ONE blue wire that is on when the light is on?

Yes. Only one black is energized when fan is on. The two black wires are
connected together. The parentheses represent a connector. It is like
[]=[]=[] where wires go into the [] from top and bottom
(https://uae.souq.com/ae-en/mega-pvc-...70-7557028/i/).
To put the connector into the top diagram, turn the connector ([]=[]=[])
90 degrees. So, from left to right is a, b, and c.

In this part of the world, ground is yellow/green. They are connected
together.

There is only one blue wire and it is on when light is on.

So, when both fan and light are on, both a and c are energized.