Adding a switch

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Old 05-28-13, 04:57 PM
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Adding a switch

I am trying to connect a new ceiling fan to an existing line. I want to install a second switch next to an existing light switch and power the fan through the line going to the existing switch. The power source goes to the light first, and then a hot, neutral and ground run to the existing switch. Is there anything wrong with me connecting that hot and neutral to separate pigtails, and then running the hot and neutral separately to the two switches to power the new fan? I couldn't find any wiring diagrams that describe this specific kind of situation.
 
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Old 05-28-13, 05:10 PM
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The power source goes to the light first, and then a hot, neutral and ground run to the existing switch.
If the power goes to the light first then it is more likely you have a switch loop with out a neutral. If there is no red wire and only one white the white wire at the switch is not a neutral therefore you do not have power at the switch. You will need to replace the 2-conductor switch loop cable with a 3-conductor cable or find another source of power.
 
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Old 05-28-13, 09:07 PM
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a hot, neutral and ground run to the existing switch.
It sounds like you mean that there is one 3-wire, 2-conductor cable, with one black, one white and one bare wire in it between the ceiling outlet, where the power comes in, and the switch box on the wall.

If so, the power comes down to your switch on one of the two insulated wires (it should be the white wire) and goes back on the other. Yes, that means you don't have a neutral in the switch box, as Ray said. What's more important is that you only have one return wire, so you can only control one device or function from that switch box.

You can replace the existing cable with a 4-wire, 3-conductor cable, as Ray suggested, to provide two return wires. Or, to control both functions without new wiring, you can leave the switch as it is, install a fan remote control, and do all switching with the remote.

A third alternative is to connect the power feed for the fan motor directly to the power feed from the panel, controlling that with the pull chain, and let the wall switch control the light.

Which would you rather do?
 
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Old 05-29-13, 05:18 AM
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I have since learned that it is not a hot and a neutral coming into the existing switch (as you both point out) - what I have instead is a switch loop. So I'm wondering if a can simply run a second switch loop out of the power going into the light. Can I pigtail into the hot wire coming into the light with new black wire, run that to the new switch, then connect a black wire from the other side of the new switch to the fan. Then run the white wire from the fan back into the switch box and connect it to the white going back into the source light (making sure to put black tape on the ends of both white wires. Does this sound correct?
 
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Old 05-29-13, 08:59 AM
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I think I understand you but let me restate what you wrote to be sure we are on the same page.
  • At the existing light you run a second cable* to the switch box.
  • At the existing light you would run a new 2-conductor cable to the new light.
Is that correct?

*To be compliant with latest national code the new cable to the switch box would have to be 3-conductor and some changes made in the connections.
 
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Old 05-29-13, 10:35 AM
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If the two switches are going to be in the same box you should run a 3-conductor cable instead of a second 2-conductor cable.

In the ceiling, splice the wires in the existing 2-conductor switch cable to the wires in the cable bringing power in, color-to-color. Splice the wires in the 3-conductor cable to the load wires in your fan/light combo: White to neutral, black to the fan motor lead and red to the light lead. Aplice all grounds together. Bond the box if it's metal.

In the switch box, splice all of the grounds together and bond the box if it's metal. Bond each switch to ground. Splice the two white wires together. Add two pigtails to the black wire in the 2-conductor cable and use one to feed each switch. Connect the black wire from the 3-conductor cable to the switch for the fan. Connect the red wire to the switch for the light.

Note: You need to install a fan motor controller in the wall to control that. Not a standard on/off switch.
 
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Old 05-29-13, 12:06 PM
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Nash and I are understanding to different ways, I think. I understand it as you want to put a new box in a different location for a fan, correct? Will the fan have a light. Do you want the new single switch to control both fan and light or just the light on the fan and use pull chain switch to control the fan motor?
 
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Old 05-29-13, 01:28 PM
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OK, clarity needed.

Are you replacing the light with a fan, or are you installing a new fan-rated box that you need to bring power to and would like to control from a wall?

We need the answers to Ray'e questions too.
 
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Old 05-31-13, 07:24 AM
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The light and the fan are physically separated. It is not a normal bathroom installation, but a fan add-on in my office to help boost air conditioning flow during the summer months. I have power coming into the existing light and one black, one white, and one ground running from the light to the switch box. I've already installed the fan with one black, one white, and one ground running out of it. I think what I need to do is to run black from the source power black coming into the light to a new switch for the fan, then connect the white from the fan switch back to the black running to the fan in the light box. The white from the fan should run back to the light box and tie into all the neutrals. Does this sound correct?
 
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Old 05-31-13, 07:54 AM
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I need to do is to run black from the source power black coming into the light to a new switch for the fan,
That is correct but to meet latest code you must also take the neutral down to the switch even if it won't be used. At one time a two conductor cable was used for switch loops but to meet newest code a three conductor cable is used. By standard practice the black carries power down and red carries power up.

If you are adding the new switch to an existing switch box that already has a switch on the same breaker that is connected to a two conductor cable switch loop connection is a bit different. Are you doing that? It seemed so when I first read your post.
 
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Old 06-01-13, 02:24 PM
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I'm still confused, and here's why:

I've already installed the fan with one black, one white, and one ground running out of it.
To the light box or the switch box?

I think what I need to do is to run black from the source power black coming into the light to a new switch for the fan, then connect the white from the fan switch back to the black running to the fan in the light box. The white from the fan should run back to the light box and tie into all the neutrals. Does this sound correct?
No, for several reasons: The power and the neutral must be in the same raceway to avoid overheating. Do you have conduit or are you running cable?

This is the way I would wire this: I would wire the fan-rated box by extending the unswitched power from the light box and connecting the wires color-to-color at the light box. I would mark the white wire going to the switch with black or red electrical tape or permanent marker and add that wire to the splice of the two black wires. I would connect the neutral for the light to the splice of the two white wires, and I would connect the black for the light to the black going to the switch.

When you turn the power back on the switch will control the light and the fan will be controllable with its pull chain. That way, you won't run the risk of turning the power for the fan off and on while the pull chain switch is set on either Low or Medium. Doing that can burn out the fan's motor or its capacitors rather quickly.

If you want to have a wall control for the fan you will need to run more wiring to the wall and install a fan motor control along with the light switch.
 
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