I'm in the process of trying to add a smart relays to my light switches across the house. In most cases I've managed fine and I understand how the circuit works, to me that is critical before I make any changes.
In one case, the bathroom, i'm struggling to understand what's going on. I've attached a picture of the existing setup below. The main question I have is why are there 2 connections out of common so I can understand what impact adding to this circuit will have.
For reference, the left hand side currently controls 3 downlights. The right hand side controls an extractor fan within the bathroom (which can stay powered on after the switch is turned off if the humidity is high). The extractor fan also has an isolating switch separate from this double gang switch, could this be something to do with it?
Right hand side is the standard neutral block. Colours are accurate for UK wiring.