Remember me talking about flow switches and extractor fans recently?
Well, (insert drum roll here) please allow my faithful assistant to demonstrate the use of the hot water tap as an electrical switch (no way I was going to test it mysefl ;o *)
Not an ideal demonstration as having the sink tap turn on a fan and shower light is fairly pointless. In use the fan/light will come on when you turn the shower on (unless having a cold one for some reason) or run a bath and will continue running for ten minutes or so. As a side effect it also comes on when you wash your hands in the sink. To get round this will mean more pipework and I'm yet to decide if I can be bothered. It might be nice to have the extractor fan come on if you're washing your hands after dropping the kids off at the pool. Either way I can't help thinking it's fairly impressive having this interaction between plumbing and electrics.
Anyway, in case some of you want to mimic this setup, here's how. You need a shower extractor fan (I went for the Vent Axia Luminair T (for timer)) and a flow switch (I got the 615 model off this page).
With the flow switch plumbed in to the hot water supply run the cable up to the loft space, where you have the extractor fan installed and a spare wire from the lighting cicuit available. It's now a simple case of connecting the mains, the switch and the fan together. I say simple, but in fact it took me ages to work this out in my head and a phone call to the switch manufacturer. As I expected, it is quite simple, but takes some figuring out. The easiest way to do this is to think of the flow switch as a normal wall light switch. Although the flow switch has three wires - a common and two "neutrals" labbeled N.O and N.C for "normally open/closed". In the diagram below you can see I've connected the open neatral to the live connector on the fan (marked Ls for live from switch).
It's a bit messy as I just wanted to get it up and running to test it actually worked. Hopefully it's clear enough to see how it works though. Any questions let me know.
* This is, of course, a joke. I'd never let my pregnant wife test this without having done so mysefl beforehand. What kind of man do you take me for!?