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Old 08-14-2010, 08:31 PM   #1
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Two cables in Junction Box


Hello,
I recently removed a light fixture in a room that was connected to a dimmer switch on the wall. In the junction box there were two cables. Each cable had a white, a black and a ground. The way it was set up was the two grounds were connected to the ground on the light, the two blacks (from the ceiling) were connected to each other and nothing else, and one white from the ceiling was connected to the white from light and the other white from the ceiling was connected to the black from the light. The dimmer switch on the wall only turned the old light on (no dimming) while a switch next to the dimmer controlled nothing that I can find. I think a fan was here a long time ago (before I bought the house) but I cant be sure. Can anyone help me wire a new fan to this wiring configuration?

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Old 08-14-2010, 08:59 PM   #2
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Two cables in Junction Box


Sure. First, how do you want this wired up? Are you going to have a light on the fan? If so, do you want the fan to have power all the time and the light to be switched from the switch on the wall? Or do you want both the fan and light to be switched by the switch on the wall?

FWIW, the second switch on the wall doesn't do anything with this box and won't be able to work on the fan.

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Old 08-14-2010, 09:22 PM   #3
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Two cables in Junction Box


Proby,
thanks for the quick reply. Yes, there will be a light on this fan. I think it will be okay if the light and fan are both switched on from the wall, I will still be able to control them individually from the separate pull strings right? Pretty much, I am for whatever doesnt require me to install any additonal switches or wiring if possible and just work with what I currently have. I am a new homeowner and I just dont want to burn my house down, by doing something poorly. Thanks again.
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Old 08-14-2010, 09:35 PM   #4
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Two cables in Junction Box


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Proby,
thanks for the quick reply. Yes, there will be a light on this fan. I think it will be okay if the light and fan are both switched on from the wall, I will still be able to control them individually from the separate pull strings right? Pretty much, I am for whatever doesnt require me to install any additonal switches or wiring if possible and just work with what I currently have. I am a new homeowner and I just dont want to burn my house down, by doing something poorly. Thanks again.
In this instance, you have the choice. You could either:

A) Have both the fan and light controlled by the switch. This means that when you use the switch to turn the light off, the fan will no longer spin.

B) Have the switch control only the light. This will allow you to use the switch to turn the light on/off when you enter/exit the room, but it will allow the fan to stay on. I personally like this configuration since I usually spend time in the bedroom or living room with the fan on but the light off (I'll use a table lamp or no light at all when sleeping).

Pick whatever one you like and I'll help you wire it.

Did you completely disconnect the light fixture? Did you mark the wires before doing so? It will make it easier if you did. You have two cables up there each containing a black and white wire. One of them is the feed and the other is a switch loop. The feed cable has a hot and neutral. The switch loop as a constant hot and a switch leg, no neutral.

When you get back to me I'll help you wire it up in the configuration that you choose.
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Old 08-14-2010, 10:04 PM   #5
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Two cables in Junction Box


Proby,
I guess we will go with config "B", that makes the most sense to me. Unfortunately I didn't label the wires when I disconnected the old light. I only noticed this config after I disconnected the wires and thats what got me confused and to the point I am at now. I have connected several fans in other rooms of the house and none of them were like this, so I never gave it a second thought. All I know for sure is that I havent touched the two blacks that were hiding connnected to each other in the back of the box. I appreciate your help.
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Old 08-14-2010, 10:23 PM   #6
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Two cables in Junction Box


Alright. First you can unsplice those two wires connected in the back of the box. If we are going to do this, we are going to do it right.

Second, we need to find out which cable is the feed and which is the switch loop as I defined above. To do this, you need some type of tester. You are either going to have to use a continuity tester to find out which cable runs down to the box, or you are going to have to turn the circuit on and use some type of tester to see which cable becomes hot when the power is on. If you need more help with this process, let me know.

Once you know for sure which cable is which we can move on.

In the switch box you are simply going to put each wire on a screw of the switch, you really can't go wrong. The only thing you need to do is wrap some black tape around the white wire since it is hot. That's all for the switch box.

Up in the ceiling box you are going to do the following:

Connect the white wire from the feed cable to the white wire on the fan.
Connect the black wire on the feed cable to both the black wire on the fan and the white wire on the switch loop cable. You will also put black tape around this white wire.
Finally, connect the black wire from the switch loop cable to the blue wire on the fan.

I haven't mentioned grounding because I assume you know what to do. Bond all ground wires together and to the box and the fan.

Finally, to hang a fan from this box it is required to be a fan rated box. If it isn't they make a kit for about $12. You will have to cut out the existing box and install a new bracket and fan rated box.
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Old 08-15-2010, 02:15 PM   #7
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Two cables in Junction Box


Proby,
The fan is up and everything seems to be working fine. Thanks again for taking the time to walk me through it.
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Old 08-15-2010, 02:42 PM   #8
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I'm glad it works.

Out of curiosity, how did you find out which cable was the feed and which was the switch loop?
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Old 08-15-2010, 03:31 PM   #9
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I'm glad it works.

Out of curiosity, how did you find out which cable was the feed and which was the switch loop?
I pulled all the wires out of the box, pointed them in different directions, turned on the breaker and then used a non-contact voltage tester and found the only one that was giving off voltage. Not sure if there was an easier way, but this worked for me. Thanks again.
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Old 08-15-2010, 03:35 PM   #10
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I pulled all the wires out of the box, pointed them in different directions, turned on the breaker and then used a non-contact voltage tester and found the only one that was giving off voltage. Not sure if there was an easier way, but this worked for me. Thanks again.
That was the easiest way and what I would have done.
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Old 08-16-2010, 11:57 AM   #11
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Two cables in Junction Box


Nitpicking. The wiring was incorrect when you started; the wire connected to the black or blue of the fan has to be colored (and not green).

The color mismatch will then occur as mentioned above, between the hot wire of the feed (black) and the raw hot down to the switch (white).

If you have a multimeter, you can also use the ohms setting to test continuity (with the circuit power off). Measuring between the two wires in a cable, you get continuity (at or near zero ohms) with the switch on and no continuity (near infinite ohms) when the switch is off.
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Last edited by AllanJ; 08-16-2010 at 12:00 PM.
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Old 08-16-2010, 01:19 PM   #12
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Nitpicking. The wiring was incorrect when you started; the wire connected to the black or blue of the fan has to be colored (and not green).

The color mismatch will then occur as mentioned above, between the hot wire of the feed (black) and the raw hot down to the switch (white).

If you have a multimeter, you can also use the ohms setting to test continuity (with the circuit power off). Measuring between the two wires in a cable, you get continuity (at or near zero ohms) with the switch on and no continuity (near infinite ohms) when the switch is off.
I'm finding a alot of things are incorrectly done in this house, that is why I find this forum so helpful.
Thanks everyone.
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Old 08-16-2010, 02:20 PM   #13
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Two cables in Junction Box


Quote:
Originally Posted by AllanJ View Post
Nitpicking. The wiring was incorrect when you started; the wire connected to the black or blue of the fan has to be colored (and not green).

The color mismatch will then occur as mentioned above, between the hot wire of the feed (black) and the raw hot down to the switch (white).
In the Op's situation, one wire of the cable assembly had to be spliced to the black wire of the fan and the other wire of the cable assembly had to be spliced to the blue wire of the fan, there is no escaping that. I felt that the re-marked white was best spliced to the black wire of the fan and the constant hot because at the switch box the re-marked white would be hot like normal, if anyone came in after the fact they wouldn't be surprised.

Originally whoever setup this switchloop used the black wire to run constant hot down to the switch, which is why in post #6 I wanted him to unsplice that and do it the right way.

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