Dual input switched live

[i_am_fubar]

Andy,

Desire to have this arrangement comes from not wanting the fan to be able to stay on permanently if the lights are off. A visual indicator that the fan is running via the lights.

The light switch for the main bathroom will be outside the door.

If I were to have a shower in the day, I wouldn't necessarily switch the lights on before going in the bathroom.

The additional mom. switch gives the option to turn the extractor on for it's timed duration without having to leave the bathroom to flip the lights on. But without allowing the fan to inadvertent be left on without the lights on.

Extra cable isn't really a concern as it'll all be in 1.5mm run through conduit from the loft.

Bernard,
Are you essentially saying that when the mom. switch is pressed, you dis-connect the lighting live, while enabling the switched live to the fan?

Cheers,
Fubar.

 

[bernardgreen]

The switched live to the lamp remains as is. Permanent live remains connected to the fan

The switched live for the fan is moved from the switched live for the lamp and connected to live while the button is pressed, this will start the timer without connecting live to the lamp.

Untitled

• bernardgreen
• 7 Jan 2014
• 1

 

[SimonH2]

Thanks for the replies guys. Some good ideas, and with a chat I had with a mate last night, I think I've got it sussed.

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• i_am_fubar
• 7 Jan 2014
• 1

Except that what you've got would make the light flash on if the neutral weren't switched, and switching the neutral is a no-no as it can leave the whole circuit live when someone might expect it to be off.

If you're going to use a DP light switch, then use one pole to switch the light, and the other to switch the live to the fan SL. That will allow the momentary switch to trigger the fan without flashing the light, but without having a circuit that's neutral switched.
You can connect the momentary switch however the wiring suits, but a logical and simple way to do it would be to wire it across the pole of the light switch that controls the fan SL - so just a T&E from light switch to momentary switch. No JB required.

One option would be to use a momentary push button change over switch to switch the switched live to the fan.

Wake up at the back, already discussed several posts ago

 

[AndyPRK]

Andy,
The additional mom. switch gives the option to turn the extractor on for it's timed duration without having to leave the bathroom to flip the lights on. But without allowing the fan to inadvertent be left on without the lights on.

I suspect the timer would be too short for the shower duration.
And having a long timer setting every time the light is turned on can be annoying.

Its where I find a humidity sensor good. It will turn the fan on even with the lights off and run on until the humidity has dropped.
Although its still good to trigger the fan on its timer at the start of the shower.

 

[bernardgreen]

Wake up at the back, already discussed several posts ago

Sorry teacher

So why hasn't it been accepted. it is the ideal solution.

 

[i_am_fubar]

So many options... Well, I'll have access to all these cables in the loft, so I can add a humidity sensor at a later date.

Other option I guess is to have a 2 way switch with a neon (visual fan indicator) for the fan next to the light switch (maybe use grid, then I can have a dimmer for the main light for bath time) and another by the sink. Then I have interior and exterior access.

Fubar.