Bathroom fan turning on via PIR

[vala]

Hi all,
Looking to have my bathroom extractor fan turn on via a PIR instead of on with the light switch.
Main reason for this is the bathroom gets lots of light in during the day and if showering at that time there's no need for the light, and so an extractor fan wouldn't turn on.
I also have a fan isolator mounted above the bathroom door outside the bathroom.

The extractor fan is this
https://www.extractorfanworld.co.uk/envirovent-silmv250100t-ultra-quiet-inline-fan--timer-4358-p.asp

And I was thinking of this
https://www.cef.co.uk/catalogue/pro...VEc53Ch3-jQP4EAQYBCABEgLbF_D_BwE&gclsrc=aw.ds

to trigger it.

Can anyone confirm if this would work?

 

[flameport]

That will work, but you don't need a timer in the fan - the PIR already has a timer in it.

 

[vala]

@flameport any issues with having a fan with timer? I’ve already got the fan.

Also can anyone help with wiring this up? Done extractor fans in the past off the lighting circuit but never had one run off a PIR.
I’ve got the extractor fan isolator at the moment of the lightning circuit and then from the forwards I’m a bit lost. I know I’ll have a permanent feed to the PIR then come off this to switch on the extractor, and by the looks of it 4 core cable will be used. But that’s about as far as I can make out at present?
Also could I bring the cables back to the fan isolator and make the connections in the back box using wago’s? Rather then having a load of cables buried under 250mm of insulation.

 

[flameport]

The problem with using both is how it will work - if the PIR had a 10 minute delay and the fan a 15 minute delay, the PIR would keep the fan running for 10 minutes, and when that switched off then fan would continue for another 15 minutes on it's own timer.

Wiring is L,N,E to the PIR, and then SL,N,E from the PIR to the fan.
A PIR sensor is just a switch that also needs a neutral connection.
Basic on/off switch = L, SL.
PIR = L, SL, N.

 

[vala]

@flameport
Just checked the spec on the PIR and looks like the minimum time I can set is 10s, so m I could set it for that and then base the length of time I require on the fan.
I'll check through the fan specs tomorrow when back on site.
Also to throw something else in the mix.....could I have my 2 mirror demister off that PIR?
Thinking if possible this would definitely mean making all connections in the fan isolator back box. I did install a 47mm back box just in case this was a possibility.

 

[vala]

Managed to get some pics of the isolator I'll be using and the wiring diagram Scolmore provide.

Am I correct in thinking, L1 on the load (top row) is live feed in from my lighting circuit, then L1 on the supply (bottom row) is my permanent live to the PIR?
I can confirm tomorrow but I think the extractor fan also has a permanent live in which case this goes into L1?
Then switch live from the fan, and live from the mirror demister all go into L2?
Neutral from feed into N on top row and all neutrals from PIR, fan and mirror demister into N on supply?
And finally all earths into earth terminal.

 

[vala]

Revising this thread as I’ll soon be able to make all connections for my PIR controlled extractor fan and mirror demister.

Does this wiring diagram look correct?

 

[EFLImpudence]

You haven't marked which terminals are which on the PIR nor fan.

You do not need a three-pole isolator if you are not using the light switch to turn on the fan.

Do you intend to connect all the wiring to the isolator switch for a specific reason?

Would it not be better to wire:
supply > isolator >>> PIR >>> fan - connecting the mirror at the easiest/nearest position.

 

[EFLImpudence]

 

[EFLImpudence]

If you want all the connections in isolator box:

 

[vala]

@EFLImpudence could I still use the fan isolator now that I have already got it?
If so would I be correct in thinking I can just run a twin and earth to L2 (permanent live) and N. And leave out L1 (switched live) on the supply side.
And then from that head off to the PIR, fan and demisters?
I’ve re done the drawing but want to check if this is ok before posting it here for confirmation.

 

[EFLImpudence]

could I still use the fan isolator now that I have already got it?

Yes, of course. Do you not think my diagrams show that?

If so would I be correct in thinking I can just run a twin and earth to L2 (permanent live) and N.

Yes.

And leave out L1 (switched live) on the supply side.

Yes, but it does not matter whether you use L1 or L2.

And then from that head off to the PIR, fan and demisters?

Yes. Again - what do you think my diagrams show?

I’ve re done the drawing but want to check if this is ok before posting it here for confirmation.

I cannot see any new drawing.

 

[Taylortwocities]

I can see a drawing that shows it.
Post #10.

 

[vala]

Hi @EFLImpudence ,
Here is my updated drawing.

I didn’t include it earlier as I was waiting on your responses to my questions so I could amend the drawing if needed.
One question I have is with regards to the PIR & fan switch lives. Am I correct in thinking that although it’s the PIR that will activate the fan, they both are connected to live and switch live at the isolator as they both will continue to run on a timer function after movement is no longer detected by the PIR?

 

[aptsys]

Why confuse the matter with the fan timer? Just connect the permanent line and switched line from the fan together, and connect this to the switched line from the PIR.

This leaves the PIR in control of the timing for all items.

Your assumption was generally correct though with your diagram - the fan will overrun after the PIR timer had expired which didn't sound like your original intention.