On 02/06/2019 02:21, Fredxx wrote:
On 01/06/2019 23:16, ss wrote:
I am changing an extraction fan with timer.
The old fan has 2 red and a black wire but no indication as to what
one is live switch, how do I determine what one of the reds is live
switch, with the power switch off at mains.

I would be tempted to make a guess knowing there's a 50% likelihood of
it being right!

+1

Timer works, job done.
Timer does not work - then swap the reds over.

--
Adam