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Bath fan controls

davidmeiland | Posted in Mechanicals on

As part of a remodel project I’ve been asked to install new fan controls for two bathrooms, each with its own fan. The existing controls are simple toggle switches, and apparently at least one occupant (a teenager who is otherwise a straight-A student) cannot be persuaded to switch the fan on during lengthy showers. In the past I have installed 5-10-20-30 timer switches, and like those in my own house, but I’ve been able to get people in the household to use the fans every time.

I’m aware that there are various types of humidistats and occupant-sensing controls on the market. I think what is needed here are controls that automatically exhaust the humid air during and after a shower, without the user doing anything. The fans themselves are Panasonic inline models and are very quiet. I have not done a blower door test on this house but for now I am assuming that these fans do not need to run other than during bathroom use. What are folks out there using successfully?

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  1. craig kosman | | #1

    use a 24 hour digital timer and set it according to the ventilation requirements for the bathroom. Try 1 hour in the AM and 1 hour in the PM to start. If the bath fan is the only ventilation for the building you may want to increase the run time.

  2. wjrobinson | | #2

    Panasonic makes great fans.


    I am moving to non bath central fan to reduce sound levels and to automate.

    Panasonic does make such. ERV/HRVs if you are using them will do the job also.

    Oh.. .on a small cottage... we just spec'ed the Panasonic Whisper comfort ERV.

    The switch is from Lutron and runs the fan for time period per occupancy.

    Lutron Electronics MA-T5 Maestro Timer Control Lightswitch. Many more to choose from.

  3. Garth Sproule | | #3

    This switch from EFI might work well for you if the bathroom light needs to be on when the shower is in use...

  4. Jesse Smith | | #4


    Stick with Panasonic, but go with occupant sensing, optional continuous-duty. I've used the switched version of these, which has a programmable delay. I'm pretty certain that the occupant sensing also has programmable delay. EFI has great tech support, so it's a good question for them. This feature would allow you to eliminate the delay function from the switch which opens the door to something other than EFI's toggle switch linked by Garth above. Also, it sounds conceivable that you'd require some quantity of make-up air, which makes the optional continuous-duty function convenient.

    I've used the Lutron switch that AJ recommends, because it's the only Decora switch I've found with a delay. Too much user autonomy, which, as implied by your initial post, is pretty much the opposite of what you want.

    Finally, if you're exhausting through the roof, I'd anticipate about a 15%-20% drop from the rated fan flow. I know, Panasonic's aren't supposed to do that. But I've installed and tested about a dozen of them in the past year, and it just hasn't been my experience. Great fans though.

  5. David Meiland | | #5

    Thanks for the input so far--many good ideas.

    Stick with Panasonic, but go with occupant sensing, optional continuous-duty

    Jesse, are you saying that the fan itself has the occupant-sensing built in? If so I hadn't come across that yet. The fan I had planned on is the FV-10NLF1 which doesn't appear to have any control functionality built in. The exit points are on a gable end and I'm going to have as much as 20 feet of straight, rigid duct from the furthest bathroom, so there will be some loss but it shouldn't be too bad.

  6. Daniel Ernst | | #6

    Panasonic Model FV-08VKM2 has the Smart Action motion sensor.

    It's a long link; hopefully it comes through . . . .

  7. davidmeiland | | #7

    The link worked fine for me. That type of control setup would probably work well for my customer, but I was hoping to install inline fans near their exit points on the gable wall. That places most of the ductwork under negative pressure and keeps the source of noise as far from the occupant as possible. I like the idea, though--the fan comes on anytime there is someone in the room, and stays on for a preset time after they leave. That makes a lot of sense. If someone is in the house, they will hit the bathroom every so often, and the fan will run. In no one is in the house, no fan needed.

  8. Jesse Smith | | #8

    Daniel's link was the fan I had in mind. Although I couldn't find it on that page, EFI's catalog puts it at .3 sones, which is marginally audible.

    Conceptually, the fans are a great idea, especially for remodelers like us. You could do a bath reno tomorrow, siding and windows next year, and finish the basement the year after that. The siding and window job might put you perilously close to/below whatever building air-tightness limit you're using. But the basement work provides you with the best opportunity to install proper ventilation. In the interim you can just ramp up the CFM's on the bath fan.

  9. Anonymous | | #9

    Remote fan will be quieter. Some contractors use one fan for multiple rooms . (Wire switches in parallel.) Some switches hide the timer adjustment from user under cover plate assuring no change to setup.

  10. Anonymous | | #10

    Problem with Panasonic fan/lights. Can't dim that type of fluorescent. Put other lights in the bathroom if dimming is desired.

  11. GBA Editor
    Martin Holladay | | #11

    Who dims bathroom lights? What's that about? Setting a romantic mood when there are candles around the edge of the bathtub?

  12. MICHAEL CHANDLER | | #12

    Martin, dimming bathroom lights (typically the mirror lights, not the fan light) is about being able to use the WC in the middle of the night without blasting your eyes. Just more comfortable to have dim light at 4 am after playing tunes in a smoky club all night but to have bright lighting at 11 pm when putting on the glitter and eyeliner before heading out to said smoky club.

    In reference to the original question Lutron and both offer affordable time-delay occupancy sensors that are robust enough to supply a bath fan. Lutrons programming ritual is a little more complex than R.E.Williams dials under the face plate strategy but the Lutron is more tamper resistant. (I've had problems with customers defeating the occ sensors after move in because they don't like the idea of leaving the fan running when they walk out of the bathroom)

    I do like the Panasonic Whisper Green fan with Occ sensor the best if you have it in the budget to replace the fan instead of just the switch.

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