Hi,

Currently, my bathroom has a fan which switches along with the light and
stays on on a timer afterwards. Most of the time, this is unnecessary -
if I fill up a glass of water before going to bed I don't need a fan
waking up everyone else in the house.

As part of my bathroom refit, I'm planning to disconnect the fan totally
from the lighting, and instead switch it via a flow switch on the shower
supply. I also want a manual button strategically positioned next to the
toilet flush :-). This would be a momentary switch so that the fan
starts and then runs-on on the timer.

My question is how to handle the wiring of this switch. I currently have
a nice brushed-steel button that would look the part. It happens to be
rated to 250v/5a, but AFAIK is not IP-rated. I also have a relay that
will switch a mains supply from a 6-12v signal current. One approach
would be to have the relay in a suitable enclosure in the roof space
above the bathroom, with the button controlling the low-voltage side
from below. This keeps mains out of the bathroom, but is it acceptable
from a regs point of view? I'm confident that I can built it safely, but
these aren't quite the same thing :-)

Alternatively, I could buy an IP-66 button (eg MP0031, http://is.gd/fdko
) and wire it directly. Would this be OK? The back of the button would
be inside a substantial piece of boxing-in, effectively a stud wall.
This would have access points in it, but not routinely openable (ie
require cutting sealant).

Cheers,

Pete