Flow Switch for shower light and fan

[Billmccan]

Can anyone recommend a flow switch to operate a shower fan and light when the shower is in operation? The shower is fed from a boost pump and 15mm Pex

 

[Avo Mk8]

Since you have a boost pump that already senses the shower being turned on, you could implement an electrical solution without interfering with the plumbing to add a flow switch!
If you put the L core of the boost pump through a current sensing switch (CT transformer device), you could use the contacts of that to operate your light and fan. It would require an enclosure and cable strain relief etc, so maybe not so elegant when it comes to wiring it up!
example of the sort of thing I mean: there are others

https://www.amazon.co.uk/dp/B07WJ5LZ3K/ref=sspa_dk_detail_3?

 

[Billmccan]

Thanks for your reply, the pump is at the other end of the house from where the shower is, so It would incur lifting a lot of floorboards again ,If I had thought about it I could have done it the same time the plumbers put their pipes in, every day is a school day but thanks anyway.

 

[DPG]

What about using a humidistat fan. That way it would kick in automatically when needed.
The light can be on a normal pull cord.

 

[littlespark]

The trouble is, the fan would shut off when the shower stops… unless there’s a timer incorporated.
The high humidity remains in the bathroom for some time after the shower is turned off.

 

[mainline]

Can anyone recommend a flow switch to operate a shower fan and light when the shower is in operation? The shower is fed from a boost pump and 15mm Pex

You're going to need to wire a light supply anyway, so adding a timed humidity fan is the best way.