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Old 07-16-2008, 11:21 AM   #1
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Bathroom electronic dimmer gets reset by exhaust fan switch?


I am no electrician, by trade I'm a software developer, but I am a fairly intuitive person and can usually handle DIY... so bear with me while I sort out the terminology.

Last night, I installed a Leviton Vizia electronic dimmer and coordinating remote switch in the bathroom in a 3-way configuration. All was well (after sorting out what wires were what, as the builder in my condo seems to have used some unorthodox wiring techniques), until I tried to turn on the exhaust fan which is on another set of two switches (not three way, will explain).

What happens is that when the exhaust fan is switched on or off, most of the time but not all of the time, the dimmer turns the lights off, the LEDs on the dimmer all go out for a second or two, and then it "reboots" and turns the lights back on.

The two fan switches are not three way switches, they are normal single pole switches. That is, if you turn the fan on from one side the other switch does nothing and you must turn the fan off from the switch you originally closed. I am imagining that what is happening is that the two switches are wired in parallel with the motor load.

Now, it's important to note that the speed of the fan is not affected by the dimmer (it is a frequency type, so I'm not sure if the fan would work at all if it was somehow using the same hot wire).

There are only two circumstances that I can think of so far that could be the cause:

1) The fan and the lights are simply too close together that turning the fan on causes enough noise on the circuit that it disrupts the electronic dimmer. Is this even possible, if they are NOT sharing any wiring?

2) That the fan and the light are both sharing the same neutral at the load, OR that the the fan is wired from two separate hots and the neutral on the romex that is connected to the light load is being tied also to the neutral leading to the fan load. Actually it sounds more likely now that I typed it that they must be sharing the same neutral in the single romex entering the room and that the brown wire must be going to the other side of the room and being used by the fan on both switches in parallel. In this case, I have no idea how to isolate the neutral from the lights.

That is, the romex on one side has a white, brown, and red wire. The red wire (hot) is fed into the 3 way switch that leads to the lights eventually. The brown wire (hot) is fed to the Fan Switch, and the White (neutral) wire is tied together to the neutral on both the fan and the lights. Is this even a plausible situation?

If the fact that both loads are tied into the same neutral is the problem, what can be done about it. I imagine, I could just give up one of the fan switches completely and disconnect the spare hot that isn't used from the first romex from the breaker from the fan switch, and then determine which of the white wires leads to the fan on that side of the wall and untie it. My other possibility would be to simply remove the neutral from that leg of the circuit but I am not familiar if it is a code violation or otherwise dangerous to wire a load to two separate hot wires and only one neutral.

3)* It occurred to me that perhaps if I installed a fan control module on the fan load that it might protect the circuit from the voltage surge/drop by electronically ramping up and down the voltage or forcing the user to start the fan at a lower voltage. I would rather not bother with this approach though if I could just remove one of the switches if my theory about the fan switch wiring turns out to sound plausible.

The reason I'm not sure about the shared neutral etc. is that I am no longer at the location where the install was done and I'm just brooding over it at work right now.

Any help massively appreciated! I don't really want to go back to the old non dimmed setup.


Last edited by BinaryJay; 07-16-2008 at 11:38 AM.
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Old 07-16-2008, 04:17 PM   #2
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Bathroom electronic dimmer gets reset by exhaust fan switch?


There might be a manu's recall or they may have a Technical Service Bulletin published on this problem.

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Old 07-16-2008, 10:06 PM   #3
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Bathroom electronic dimmer gets reset by exhaust fan switch?


I had called the manufacturer (Leviton) and they told me I just can't use an electric dimmer on my circuit.

I seeked some advice from the guy that seemed to know the most about electrical equipment at home depot, and he told me I was wasting my time trying to get this type of dimmer working.

I decided to buy the Lutron Maestro 3-way kit anyway, against all the advice I had received and I swapped them out tonight... and guess what, it works fine with the Lutron switches.

Lesson is, don't listen to Leviton's tech support, or Home Depot. The Lutron kit is more expensiive by 50% but it works and they've earned my future business as they seem to build residential devices with higher tolerances for fluctuations/line noise.

Turns out, that my fan and lights were indeed fed by the same neutral on the single 3-wire romex coming into the bathroom with the lights using the red wire and the fan on the black (brown) wire.
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Old 07-16-2008, 10:57 PM   #4
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Bathroom electronic dimmer gets reset by exhaust fan switch?


Quote:
Originally Posted by BinaryJay View Post
Lesson is, don't listen to Leviton's tech support, or Home Depot.
For god's sake, don't ever listen to the morons as the Borg!
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