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Bathroom fan 2 switches

Discussion in 'Electrics UK' started by Fullmutt, 23 Jan 2012.

  1. Fullmutt

    Fullmutt

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    Hi. I wonder if any of you sparky clever clogs might be able to puzzle my problem. I want to wire a bathroom Fan to my lights in the normal way and have a timer overrun. But the tricky thing in addition to this I would also like to control the fan independently of the lights on a separate switch. Ie be able to turn the fan off when the lights are on or on when the lights are off. Ideally I would have a separate 3 position switch. Position one fan on independent of lights, position 2 fan on with lights only, position 3 fan off independent of light. The reason for this is that my bathroom is next to my bedroom- the whirring of the fan is a distraction from my beauty sleep at night and sometimes when I have a bath I like to have lights low and no fan. I hope it's possible- it would be great if it is and someone could sketch me a wiring diagram. I find it difficult to understand written instructions, take pity on me. Thanks very much.
     
  2. Space cat

    Space cat

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    Using a single pole three-way switch, the wiring is easy enough. Where you stand with respect to building regulations is another matter. I'll let somebody else answer that one.

    Your fan has three terminals (plus earth if it's not double insulated): permanent live, switched live and neutral. The switched live comes from the light. This is the one that brings the fan on when the light is on. The permanent live keeps it running on its timer when the light goes off and neutral is self-explanatory. You insert your three-way switch in the switched live supply with its common terminal connected to the fan. Of the three switched terminals, one goes to the light as before (normal operation), another goes to permanent live (fan always on) and the third goes nowhere (no fan). :cool: :cool: :cool:
     
  3. Fullmutt

    Fullmutt

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    I think I understand. I tried to draw a diagram to clarify. Took a picture of the drawing and then tried to upload it but can't work out how to get it off my phone. I will try to describe what I have drawn. My lighting circuit is done with the junction box method. Inside the junction box I have 4 terminals. One which I use for the earth and I won't mention again. Of the three remaining which I will call neutral, live and switched live. This is how they are wired. The neutral has supply wire, a wire to lamp and the neutral terminal of fan. The live terminal has a supply wire, a wire to the common terminal of the light switch, a wire to the live terminal of the fan and a wire to the second of the three switched terminals of the three way switch. The switched live terminal in the junction box has a wire to the switched terminal of the fan, a wire to the lamp and a wire to the first terminal of the three terminals of the three way switch. The third terminal of the the three way switch is not used. There is also a wire between the l1 terminal of the light switch and the common terminal of the 3 way light switch.

    I hope that explains what I understand, it is complicated in words but quite self explanatory on my sketch. I wonder is this right. I have two questions the two core cable between the light switch is divided one wire going to the junction box and the other to the second switch. What's the best way to do that, that doesn't strike me as usual practice. I certainly have never done that before. The other question is do I need an isolating switch between the junction box and fan or is that uneccasry. That's all
    A bit much from my little brain- does anyone else get an itchy brain when they have to think to hard. Thanks again
     
  4. riveralt

    riveralt

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    Do they make three way single pole switches? Or do you mean three gang switch?

    Thats the theory but how does this arrangement fit in to what you outline next?
    Which switched live? Where are you interrupting it?
    How?
    from where to where ?
    ??

    This doesn't seem to make sense. You seem to be saying you interrupt the switched live but don't say where the switched live comes from. You don't talk about how power gets to the other 'terminals' linking wire maybe - and while you have mentioned it at the beginning the neutral seems to have got lost in the translation.

    To the OP …. To achieve what you want to achieve you only need to separate out the lights and extractor fan and thus only actually need a two gang switch.
    Assuming that the OP does actually mean a three (two) gang switch, then surely the best option is:
    1. From the ceiling rose light bring the live, neutral and earth down to the switch - using three core & earth cable. Use brown as the live which goes into the first gang Common Terminal and the ceiling rose permanent live. The grey cable (with brown sleeving) goes into the first switch terminal L1 and the ceiling rose switched live. - This will give normal light operation with the fan inactive. The black cable (blue sleeving) is connected to the neutral at the ceiling rose and put in a terminal strip at the switch.
    2. Now run an addition three core and earth cable from the light switch to the extractor fan.
    3. To get the fan to work. At the switch connect a small piece of cable from the first gang common terminal to the second gang common terminal. Then the brown from the second three core cable to the second gang terminal common and at the extractor fan the brown to the permanent live. This is your permanent live. Connect the black from the second three core cable to the neutral terminal strip at the switch and the neutral at the extractor fan. This is your neutral. Take the grey from the second three core cable and sleeve it in brown and place it in the L1 terminal of the second gang at the switch and the switched live at the extractor fan. This is your switched live. The second gang at the switch will now operate the fan independently of the light. Ensure continuity of the earth.

    Caution:::: The fundamental problem with this and other approaches suggested is that you do not have a means of isolating the fan for maintenance and thus you would need to interupt the second three core cable with a three pole isolator. I am also certain that most manufacturers instructions for fans say a 3Amp FCU should be used as well.
    Oh and don't forget you can only do this work if you notify your Local authority building control first.
     
  5. Fullmutt

    Fullmutt

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    Thanks for your response. Your instructions are clear but I need todraw it out before it makes perfect sense to me. It does appear though that this wiring makes the fan and light independent from eachother. What I was looking for was a fan that comes on with light but can also be turned on and off independently of the lights. What I
    Was firstly suggesting was a two one gang switches. One controlling the light and fan, and the other switch controlling the fan ( that being the three position switch 1 fan on 2 fan off 3 fan on with lights. I did a few sketches , could in theory get the fan and lights working independently, the fan working with the lights but couldn't work out how to turn fan off without turning lights off. Is this what your solution does? The reason I wanted two separate switches was I was hoping to have the lights on dimmer and fan control on rocker. What a pain. Sorry.
     
  6. riveralt

    riveralt

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    That is correct.
    The problem is that to achieve the first objective (light and fan together) you use the lights switch live to activate the fan - as Space Cat correctly stated the lights switch live turns the fan on. When the switch live is turned off (to meet your second objective) the permanent live kicks in for whatever time the over run timer is set for.

    As outlined above it would appear to be only way.
    If you use Grid switches from the likes of MK here..

    http://www.tlc-direct.co.uk/Main_In...nu_Index/Grid_System/Grid_System_1/index.html
    http://www.tlc-direct.co.uk/Main_In...nu_Index/Grid_System/Grid_System_3/index.html
    http://www.tlc-direct.co.uk/Main_In...nu_Index/Grid_System/Grid_System_4/index.html
    and wire it as I suggested then you can have both the dimmer for the lights and the fan on off switch in the same single gang switch. You can even have the fan switch with its own name 'fan' ;)
     
  7. Fullmutt

    Fullmutt

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    It seems like it is impossible to have the switches as I
    First thought. I have had a rethink. Because the most annoying part of the fan is the noise- the only function I really need is to be able to turn it off whilst still leaving the lights on. Can this be done with a three pole isolating switch. If I wired a junction box as you would a normal light and the run 3 core and earth wired to the switches , live , switched live and neutral terminals in the junction box to a isolating switch and then on to the fan. Would I atleast be able to turn the fan off at the isolating switch whilst leaving the lights on. When the isolating switch was not isolating the circuit the fan would come on with the lights as usual. I hope that makes some sense. Much appreciated for your help thus far. Cheers
     
  8. riveralt

    riveralt

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    If you want to turn the fan off immediately and leave the light on then wire as I have explained but exclude the permanent live from the switch to the extractor fan.
     
  9. Fullmutt

    Fullmutt

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    I am super confused now. My other half warned me against posting to this forum. She said that I am not bright enough and I will be turned into knots. She is not wrong often. The way I understood you was that the wiring you explained would leave me with two switches. One for the light and one for the fan. If I wanted to turn the lights on I would flip one switch and the other switch would need to be flipped to turn the on the fan. I am not sure how not connecting the permanent live to the fan helps( I realize that this will stop the overrun) but if I don't want the fan on - I just dont turn it on. What I was suggesting was wiring the fan to come on with the lights (this will be the default position, otherwise the fan won't get turned on enough and end up with a manky bathroom) but using an isolating switch to turn the fan off and leave lights on if the fan is annoying. Would this work or will your method turn fan on with lights and I have the wrong end of a very dirty stick. Apolgies once again
     
  10. ban-all-sheds

    ban-all-sheds

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    As long as you're happy to have the fan run on when you switch it directly, not via the lights, then it's all easy to do.

    You need a 2-way centre off switch as your master fan control.

    Take switched live from the light into L1, permanent live into L2, and connect common to SL on the fan. The fan's permanent live and neutral are connected as normal.

    Your 2-way centre-off switch has 3 positions.

    1) Connects the lighting switched live to the fan switched live as per normal.

    Off - the fan never gets a SL poke, so it never comes on

    2) The fan gets a switched live independent of the light switch.

    As for dimming, you can get dimmer switches which are double pole - they have an undimmed output for fan use, and a dimmed one for the light.

    Whether you can get a grid system with both that type of dimmer and a 2-way centre off I don't know....
     
  11. Fullmutt

    Fullmutt

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    I have sketched that out and it is clear how that works. The only down side is that you have to set position of switch before turning light on. Because if the fan comes on with the light and you dont want it there is no way of turning it off. Which defeats the purpose. But if it works I guess that's a small price to pay. Thank you everyone for your help. Its a great resource. Cheers.
     
  12. ban-all-sheds

    ban-all-sheds

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    You would need to learn to have the switch set to what was the best default for you.


    There's always the 3-pole fan isolator....
     
  13. Aragorn84

    Aragorn84

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    Perhaps a third (momentary?) switch to kill the permanent live to the fan as a "cancel overrun" option?
     
  14. Fullmutt

    Fullmutt

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    How funny. It's only a 1 bed flat. 3 switches? That's more knobs and buttons than the bridge on the starship Enterprise. Thanks again that's really helped a bunch.
     
  15. ban-all-sheds

    ban-all-sheds

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    Let's try going back to the start.

    Is the situation that you have a shower, and sometimes you turn the lights on but don't use the shower so don't need the fan, and sometimes you have a shower but don't turn the lights on but still need the fan?
     
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