We've had one of these installed in a new downstairs toilet and I must admit it's a lot more convenient and cleaner than using a pull chord.
As long as the floor-to-sensor height is at least 2.4m you won't have to worry about the zones, just the environmental factors (steam etc) but if it's going in the same place it should be OK.
The 3-core & earth cable will replace the existing twin & earth from the light fitting to the switch, purely to get a neutral to the switch terminal. If you're replacing an existing timed fan it should have all it needs at that end.
We didn't bother with a timed fan as the switch sets a time of up to 10 mins delay anyway which was fine for our 2m^2 space.
As long as the floor-to-sensor height is at least 2.4m you won't have to worry about the zones, just the environmental factors (steam etc) but if it's going in the same place it should be OK.
The 3-core & earth cable will replace the existing twin & earth from the light fitting to the switch, purely to get a neutral to the switch terminal. If you're replacing an existing timed fan it should have all it needs at that end.
We didn't bother with a timed fan as the switch sets a time of up to 10 mins delay anyway which was fine for our 2m^2 space.