Shower Flow Sensor + Extractor

[jshailes]

I'm thinking of installing a water flow sensor on the shower to control an extractor fan in the bathroom. I've attempted to draw a diagram of the wiring and I was wondering if anyone would mind having a quick look over it (and probably point out all of the mistakes I've made!).

I feel a bit uneasy about the rcd. The flow sensor has COM, NO and NC terminals.. am I right in thinking the NC isn't required to be connected? And is it ok to have no neutral and earth connections between the rcd and the flow sensor?

 

[James]

Is there a reason why you don’t have/want an rcd supplying the whole upstairs lighting circuit instead of just the fan?

The arrangement shown above will not work, live and neutral have to pass through the same rcd.

I think this is a little out of the realms of a diy job.

 

[jshailes]

Is there a reason why you don’t have/want an rcd supplying the whole upstairs lighting circuit instead of just the fan?

Thanks. That sounds a good idea. I'd read that it was important to put an rcd in because it was in the bathroom and hadn't considered it could protect the whole of the upstairs lights. I've updated the diagram.

I think this is a little out of the realms of a diy job.

Thanks for the concern, I think you're right. I suppose there's a couple of reasons I'm doing it - if I didn't attempt the job I wouldn't have opportunity to learn, and secondly it helps with coordinating the tradesmen. My plan is to run all the cables whilst the plasterboard is off, potentially connect it up but leave the circuit off, and then get an electrician in to connect/test.