Wiring exhaust fan

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Old 07-28-10, 10:45 AM
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Wiring exhaust fan

I'm trying to replace an exhaust fan/light that was on one switch with an exhaust fan/light on two separate switches. I know very little about electrical, so I apologize in advance for my poor description. Below is a diagram.

The two "hot" wires come from the switches into the same Romex cable (so one is white, the other black). So when both the fan and the light are switched on, there will be two "hot" lines inside the cable. This is probably a bad idea, no? I'm trying to avoid opening up the walls to add another line.

Thanks so much for the help.

[IMG]<img src="https://s1.postimage.org/6fEt9.jpg" width="180" height="180"/>[/IMG]
 
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Old 07-28-10, 06:35 PM
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Wait for the pros, but the answer is no. From the switch box you have one hot and one neutral. If you use the neutral as a second hot, you still need a neutral to complete the circuit. You will need to pull a second romex.
 
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Old 07-28-10, 06:47 PM
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You will need to replace the 2-conductor Romex from the switch to the fan with 3-conductor Romex. If you can't you may be able to use a universal remote for a ceiling fan.
 
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Old 07-28-10, 07:44 PM
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exhaust fan

I'm sorry, should have clarified a couple of things. It's an exhaust fan in a bathroom.

I tested it out and the wiring works fine this way. My question is:
Is it safe to have two "hot" wires running inside the same romex cable? (I am pretty sure it's 12-2, but it's not labeled)

Thanks for the help
 
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Old 07-28-10, 10:15 PM
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What are you using for a return, I hope not the ground wire?
 
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Old 07-28-10, 10:23 PM
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So how does the black cable get to the switch? You can't run it outside the cable.

 
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Old 07-29-10, 10:15 AM
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In my highly sophisticated rendering (joking) I neglected to include that the main wire from the panel goes directly to the ceiling fixture. The black "hot" is joined to a romex cable which travels to the switches (this is only shown as a black line to the switch, but it is in fact a romex cable with an unused white wire). I updated the image to reflect this.

I could reverse the setup and have the neutral go to the switches, but i don't think that matters because when both switches are turned on there will still be two "hot" wires in one romex cable.

Is it safe to have two "hot" wires in one 12-2 romex cable?

Sorry again for my poor explanations, and thanks for the help.

[IMG][/IMG]
 
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Old 07-29-10, 11:13 AM
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Won't meet code won't work, not enough wires. You need one wire carrying power to the switch and two to bring it back, one for each function. If the power goes in to the fan/light Jbox then the Romex to the switch needs to be be 3-conductor. The white of the 3-conductor cable would be remarked blue or any color but white, green or gray. Power would go to the switch box by the remarked white. Red would be use for fan and the black would be used for light.

The whites from the fan/light and only the white from the power in 2-conductor cable would be wire-nutted together. All grounds tied togather and if the Jbox is metal pigtailed to the Jbox.

Tech Note: Colors for fan and light could also be black and red. Using red for the light is just common practice not mandatory.
I'm sorry, should have clarified a couple of things. It's an exhaust fan in a bathroom.
But you still may be able to use it if you have room at the fan. Than you could use the existing cable.
I'm trying to avoid opening up the walls to add another line.
There is normally no need to open a wall. You can just fish the cable. Is there an unfinished attic above?
 

Last edited by ray2047; 07-29-10 at 11:32 AM.
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Old 07-29-10, 11:44 AM
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Ray: Thank you very much, this is very helpful.

I also neglected to mention that the two 12-2 romex cables running between the fixture and the switches are already existing.

I don't understand what the difference is between using what you suggested (one three conductor wire) and using the two existing 2 conductor wires (and not using the extra neutral wire)?

Thanks again
 
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Old 07-29-10, 11:47 AM
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oh, and it's on the first floor of a two story house. The holes the drilled in the joists for the romex are just big enough, and I think it will be a pain in the ass to snake a new line through.
 
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Old 07-29-10, 12:10 PM
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Originally Posted by ray2047 View Post
Power would go to the switch box by the remarked white.
So the remarked white (hot) would be split in two inside the plastic box that houses the switches? This is ok?

Thanks again
 
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Old 07-29-10, 01:08 PM
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[QUOTE=kboothe;1752275]So the remarked white (hot) would be split in two inside the plastic box that houses the switches? This is ok?{/QUOTE] Yes. You would wire-nut two pigtails to it and run one pigtail to each switch.
 
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Old 07-29-10, 01:18 PM
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Great! Thank you so much for your help.
 
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Old 07-29-10, 04:24 PM
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The neutral and hot must come into the same box initially. You can't do that. You don't have enough wires. Here is one way to do it.



If instead power comes in at the switch you still need at least one three conductor cable. One wire for neutral and one wire for each function. You could add a second 2-conductor cable but in that case each cable would have to carry both a power wire and neutral. That means four instead of three wires in the rather small fan/light connection box instead of three.

You can't use just one of the neutrals in the two 2-conductor cable setup because code requires both hot and neutral in the same sheath.
 
 

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