Hi,
If you are installing as per the diagram below, you only have to run 3 (possibly 4 see note) extra wires from the wall switch to the unit.
Looking from the bottom, the white wire and the ground are already (or should be) at the existing light socket. You will need to connect a wire between the white wire terminal point for the lights and the white wire terminal point for the fan/humidity at the unit as well, as connecting the existing white wire(s)(house wiring multiple) to one of the white wire terminal points.
The black wire going from the new switch to the blue (light) should also be there, as it is already running from the existing light terminal to the existing switch.
The black going into the new switch is also there as it is the other wire going from the existing house multiple wiring terminal point at the existing light socket to the existing wall switch.
Therefore all you should have to run is what is shown as the red to red (night light), the blue to brown (humidity control) and the red to orange (humidity control) from the wall switch to the ceiling unit.
Note : You also have to run a ground wire to the switch box (from the existing light as there should be a ground connection available there), as it shows that the switch has an earth wire coming out of it which needs to be attached to the switch box which is earthed by the wire that you have to run. (Unless your existing switch box is already earthed and therefore you don't need to run one in).
Not sure if I read it right somewhere but I think that you need a 2 gang switch box for the switch.
Please observe all safety precautions when dealing with electric wiring. If in doubt, don't.
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