Light switch with overrun timer...

tony9i9i9i · 2025-02-28T11:39:01+0000

I went to swap a fan for a customer, they wanted a humidistat one. When I dropped the old fan I found it was wired with T&E.
I explained there was no permanent live so no overrun was possible, and that I'd either have to make a lot of mess running a three-core or they'd be best off leaving the light on after using the shower, they said to put it back for now.
Then I thought, could the switch act as the overrun timer leaving the live live after switching off for a period of time? I've looked on live and can only see the push button on for a certain time switches, for hallway lights etc.
You'd probably want two switches, one to isolate the supply to the the timer switch and hence the light (and FIS), the other to be the timer switch.
Does anyone know is a switch like that exists?

UNG · 2025-02-28T11:56:43+0000

Could you not use a delay to off relay to switch the fan

littlespark · 2025-02-28T12:07:59+0000

where does the fans t&e come from? The switch, the light or a joint box above?

You could put in a second switch for fan, or a timer module or occupancy sensor where you have a live and neutral.

tony9i9i9i · 2025-02-28T12:25:57+0000

Four cables in the switch, all neutrals in a connector, so feed in, feed out, 2 Sw/L's 1 going to the light, one to the FIL, I assume.
I could move the Sw/l to the FIS to the perm live side of the light switch.
Don't suppose you have a link to an example of a timer module?
And would a sensor have a built-in overrun?