Ceiling Fan/Light Wiring


Old 05-15-04, 03:41 PM
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Question Ceiling Fan/Light Wiring

I am instlling a Hunter fan with a light. The fan is to be controlled by a wall switch. The light is to be controlled by a separate three way wall switch that also controlls another ceiling fixture in the room.

Each of these two wall switches is separately wired. That is, a white/black/green wire runs to the outlet box and is controlled by one switch, while a second white/black/green wire runs to the outlet box and is controlled by the other switch. This was done purpously based on the configuration of fans/lights that I had earlier installed that had separate switches for the fan and the light.

My problem is that the fan/light that I am installing is wired differently. The current fan has a black wire and a white wire for the fan control, and a single blue wire for the light contol. I know that the will switches can be wired this way, but mine are not, and the result is that I have an "extra" wire, the white one controlled by the designated light switch, that is in the ceiling outlet box and I do not know what to do with it.

I thought about rewiring the fan so that the "light" switch wires were directly hooked up to the light on the fan, but the wiring configuration in the fan is too complicated for me to change without the possibility of fouling up the entire unit. Likewise, all of the wiring in the wall and to the ceiling outlet box is already in, and it would be difficult to change it around to have the appropriate number of wires (three) in the outlet box. Besides, I do not know how to rewire the wall switches to accomplish this.

Therefore, my question is, can I wire this fan correctly with the configuration that I have? Or, to put it another way, what do I do with the "extra" white (neutral) wire?

Any help would be greatly appreciated.
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Old 05-16-04, 07:12 PM
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Just connect one of the White (Neutral) wires to the fan and then connect the 3-way to the Blue and the Single to the fan. You should cap off the other Neutral wire too.

I'm not familiar with electrical panel wiring, but if I remember correctly the Neutral is common to the whole house - John, confirm? deny?

Either way, more than likely, your 2 switches mentioned above are probably on the same circuit anyway.

Good luck!
Old 05-16-04, 08:33 PM
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If the two cable up to the fan are on different circuits, this could be very dangerous. If they are on the same circuit, then is is just moderately dangerous. Both are violations of the National Electrical Code.

The only way to do this properly is to run 14/3 cable (black/red/white/bare) from the same source.

Here are the potential problems:

(1) If these two cables are on different circuits, then the neutral wire may overheat and cause a fire since you will be diverting current from one circuit on to another circuit's neutral, causing it to carry up to twice its designed maximum in certain circumstances.

(2) Even if both cables are on the same circuit, there is increased risk by running the current flowing "out" via a different route than the return current. I can't explain the physics of it all, but it has to do with the magnetic field caused by current flowing in a wire. This is why the National Electrical Code does not allow it.

Each circuit has its own neutral, and that is extremely important. The hot wire is protected by a breaker, but the neutral wire is not. The only way we get away with this is because we know that the current on the neutral of a circuit cannot exceed the current on a hot. If current flowing on the hot of one circuit is allowed to return on the neutral of another, the safety of the breaker is gone, and a fire can result.
Old 05-17-04, 06:30 AM
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There you go, makes sense to me.

Of course, the other option is to use just one of the switches for both fan and light - then you could just use the pull chains to control the light (since you would want the fan on all the time anyway.) That's probably the easiest thing to do.

There are other ways to make it work - but I know they are against code.

Good luck!
Old 05-17-04, 07:49 AM
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Ceiling Fan/Light Wiring

Thanks for the information.

First, both switches are on the same circuit. The original cable was simply divided into two cables at a box (not the box where the switches are located nor the ceiling outlet box where the fan is to be hung), and the hot wire on each of these two cables was run through a separate switch, and each of the now switched cables was run to the outlet ceiling box to be hooked up to the fan. Obviously, each of the cables running into the ceiling outlet box has its own hot and neutral wires, but they each go back to the same source - the original cable at the box where they were originally divided.

As I say, this was done this way because earlier fans that I have had did not have this white/black/blue (or in the case of my fan, the second hot wire is a black and white wire) - the fan hook up had a black (hot) and white (neutral) wire and the light had its own separate black (hot) and white (neutral) wire.

Anyway, given the configuration that I have, is it possible to simply hook up both of the neutral wires coming into the ceiling outlet box to the single neutral wire in the fan? If not, any alternatives short of running completely new cable?


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