Bathroom fan control

Discussion in 'The Projects Forum' started by Key, Aug 22, 2013.

  1. Key

    Thread Starter New Member

    Jun 21, 2013
    14
    2
    Greetings everyone, I have a small problem that I could use your help with.
    Me and my father were building a bathroom for my apartment. During my time in draft, he built walls with cables in them for the shower room, which is all well and good. The devices that consume power are the water heater, the lamp and the fan to suck the moisture out, but there is one problem, he only pulled seperate cables for the water heater and lamp only, unless we destroy the walls we have to run the fan from the lamp wiring. I would hate to have the fan on an "on mode" while the lamp is active, my apartment is rather small and it will surely suck all the air out in no time at all, leaving me to die while i shower.

    Long story short, I came out with a small solution, I would like your input on this. When turning the lamp switch on, some cheapo mains nokia switching charger with a battery will feed power to the mcu. There is a sensor on the mains line that will give input data to the mcu, when I rapidly flip the lamp switch from an on-off-on state in an interval of 1 second or so, the mcu will open the gate of the triac and feed power to the fan. The fan will work only when I flip the lamp switch rapidly and will remain off at other times.

    In your opinion, is this a practical solution, a too complicated way of doing it or is there an easier way ? If this is a feesable way, what kind of a sensor would guys recommend me ? Bathroom moisture could cause some problems, I was thinking of housing the electronics in a small plastic box with decent sealant around it, any input about moisture ?

    Feel free to bash me and this idea (excuse the ms paint aswell)
     
  2. Metalmann

    Active Member

    Dec 8, 2012
    700
    223
    "my apartment is rather small and it will surely suck all the air out in no time at all, leaving me to die while I shower."




    Well, that should get everyone's attention!:D
     
  3. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
    4,771
    971
    Depending on the local building code you can just drill a hole in the top stud and fish the wire down to the wall switch for the lamp. Add one more switch next to the lamp switch and done. No need to destroy a wall..
    Can you just use romex or do you require conduit where you are?
     
  4. LDC3

    Active Member

    Apr 27, 2013
    920
    160
    If you look carefully, you will see spaces where the air can get by the door. Besides, the fan is not strong enough to detect a change in pressure in the room.
     
  5. wayneh

    Expert

    Sep 9, 2010
    12,154
    3,061
    Yes, the vacuum effect is no concern, even for a perfectly sealed bathroom, which is unlikely But the noise of the fan when it's not needed is annoying.

    I'm a little confused why you couldn't pull another wire and add another switch next to the light switch. Or, get a fan that you control with a pull chain.
     
  6. Key

    Thread Starter New Member

    Jun 21, 2013
    14
    2

    See this is what im talking about, me overcomplicating things.

    I did not wish to pull another wire because it was kind of visually unappealing, every single electrical cable I have is hidden in the walls, except for the extra lonely one for the fan.

    Problem solved, pull chain.

    Thanks
     
  7. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
    4,771
    971
    He could easily.. he just doesn't know any better and keeps thinking we mean outside the wall.
    Drill hole in top stud/snake wire down to outlet box..done
     
  8. wayneh

    Expert

    Sep 9, 2010
    12,154
    3,061
    For the adventurous, I think he could use the existing light wire to pull through 2 wires from the light fixture back to the switch box, thus adding an additional wire. There is some risk in this approach if the wires get stuck "halfway" during the pull, leaving you with zero wires.
     
  9. GopherT

    AAC Fanatic!

    Nov 23, 2012
    6,072
    3,844
    Normally the Romex wire needs to be stapled to the stud within 8" of the junction box so, unless they can be detached, it is not feasible.

    The strategy to wire the fan will depend on where the power enters the circuit (at the switch vs. at the light). If power starts at the switch, then the fan can only be turned on with a pull chain when the light is on. There are more options if power enters at the light/fan area and a pull chain s a good idea. Another option is a humidity switch commonly used in attic fans - could automatically turn on the fan if the shower is creating humidity.

    The humidity sensor works only with humidity and will not automatically turn on for toilet odors - if a toilet is near.
     
  10. wayneh

    Expert

    Sep 9, 2010
    12,154
    3,061
    I grew up with all wiring inside conduit. Yeah, pulling Romex is not a likely option.
     
  11. ErnieM

    AAC Fanatic!

    Apr 24, 2011
    7,395
    1,607
    When I moved into a co-op apartment decades back I too had a bath fan that ran whenever the light was on. It didn't leave me breathless, but I couldn't hear the TV when I was in there "reading."

    My solution was to add a switch at the fan. Standard light type switch. You can get electric work boxes for "old work" that just need you to cut a rectangle in the sheet rock. I put my switch just below the fan.

    When I cut that hole I could get to the fan wiring; I don't remember if I had to pull the fan too but that may make this even easier to do. So the original cable to the fan went to the box & switch, and a short length of new cable went to the fan.

    That way I would just run the fan when I was in there taking a shower.
     
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