2 lighting circuits & extractor fan in bathroom: possible?

[linze]

Hello all,

I'm new to the Forum (and not an electrician, as you'll see below!)

I've been hunting around for hours online to find answers to my bathroom wiring conundrum, but so far haven't found the answer. Any pointers would be very gratefully received

I'm having my bathroom rewired soon by a professional electrician. Currently the bathroom has a single ceiling light, switched outside the room.

Ideally I would like to keep that ceiling light, and install some wall sconces on a separate lighting circuit, so there is a choice of 'practical' or 'atmospheric' lighting (or both). Presumably this is easily done, just by having two switches outside the bathroom?

I also need to install an extractor fan, and ideally want it switched separately again. (The bathroom has a window, so I understand that this is within regs?) So in theory, I'm now talking about 3 switches outside the bathroom.

What I'm not clear on is two things:
1. Is the timer in an extractor fan timed from when the light is switched on, or when it's switched off?
2. Would it be possible to have my third switch as a two-way switch, so that you would just flick it to the opposite position, the fan would come on, and then turn itself off after the timer has run its course?

I know this probably seems hugely complicated, but any advice would be much appreciated.

Thank you!

 

[SirKit Breaker]

Hi mate,

Yes you can have your lights as you intend on 2 switches.
with regard to your extractor fan, you will need a 3 pole fan isolator switch, even though you have a window, the fan must be able to be isolated for maintenance or other scenarios like if it burns out. so you will need to have it wired into your lighting so it comes on with the light, then runs on for 15 mins after the light is switched off, the isolator will turn it off permanently whether the light is on or off.

Cheers..........Howard

PS make sure your sparky is Part p redg as this is notifiable work.

 

[linze]

Thanks Howard, for replying so quickly.

So - just to be clear - even if I had a separate isolator switch, I can't switch my extractor fan separately to my lights?

 

[pn125]

Agree with above - Also depending upon where these lights are based - there will be 'zone' implications for the type used, but a registered electrician should be able to advise you of this.

 

[pn125]

Linze,
Yes, you could use a separate switch to engage the fan - but it would still need to be fed from the 3 pole isolator switch which ensures all 3 circuits have been isolated at the same time.

 

[linze]

Hiya,

Yep, am sorted on lighting zones. Thanks for the tip.

Hmm - so there doesn't seem to be much point putting the lights on separate circuits, does there, if you always have to switch one of them on to get the fan working.

I'm surprised that other people don't have this problem... or perhaps they do?!

 

[linze]

Sorry pn 125 - I think my last post crossed over with yours

Ok, so I can have the three switches (plus the isolator switch). Great.

Can my third switch - the one for the fan - be a two-way?

 

[Des 56]

Just read the thread,but you have lost me on the two way fan switch
A two way operation requires that there is another switch elsewhere to energise or de energise

What do you want to achieve ?

By the way
I personally never fit a fan that is operated by the lighting,always seperate control
Why have a means of ventilation controlled by the need for light

 

[JUD]

...with regard to your extractor fan, you will need a 3 pole fan isolator switch, even though you have a window....

I disagree. See page 65 of the Electricians guide to the building regs

An extractor fan supplied from a lighting circuit for a bathroom without a window should have it's own means of isolation, as otherwise replacement or maintenance would have to be carried out in the dark.

Personally, I always fit one (usually above door outside bathroom) wheather there's a window or not so it can be switched off at night if required.

 

[linze]

Hi Des 56,

Thank you. Hmm, yes, I've probably not understood how 2-way switches work.

What I'd assumed was that if I have the timer extractor fan on a separate circuit with an ordinary switch:
1. I'd turn the switch on, and the fan would come on
2. I'd leave the bathroom without turning the switch off, and the fan would switch itself off after the timed period
3. Next time I went to the bathroom, the switch would be in the 'on' position, so how do I switch it on again?

 

[JUD]

Hi Des 56,

Thank you. Hmm, yes, I've probably not understood how 2-way switches work.

What I'd assumed was that if I have the timer extractor fan on a separate circuit with an ordinary switch:
1. I'd turn the switch on, and the fan would come on
2. I'd leave the bathroom without turning the switch off, and the fan would switch itself off after the timed period
3. Next time I went to the bathroom, the switch would be in the 'on' position, so how do I switch it on again?

Extractor fans with timer over-runs have 2 live feeds...a permanent live and a switched live. The switched live acts as a signal for the fan to come on.

When the light is switched on the fan (fed from the permanent live) will come on and will keep running until the light is switched off.

When the light is switched off the fan timer will keep the fan running for a pre-set time (usually 15 mins) and then switch off.

 

[glynnis]

The timer comes into play when the light/fan is switched off. You have a perm line and a switched line and neutral at the fan hence the 3 pole isolation switch for the fan.

 

[Des 56]

A standard way of controlling a timed fan may be the person enters the room.switches on the fan,the fan triggers and runs in triggered mode,the person leaves the room and turns off the fan,the fan continues to run until the time setting has expired
The next person enters switches on the fan and repeat the above

There are many ways of controlling the fan examples are, as above,via the light,an occupancy sensor,a de humidifier.
thats why I asked what you wanted to achieve
If its a case of switch control,the most basic switch is a non latching type that triggers the fan and returns to an off position when you take your finger off the switch and the fan just runs for the timed peiod
There are so many ways of controlling, you need to state what you require of the ventilation