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Old 06-22-2010, 07:37 PM   #1
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Need Help using 12/3 to do 2 Runs in 1 Cable


Hi everyone, I'm hoping someone can help me with a unique question. I've finished most of my work; and I rewired the entire house with the exception of the laundry room and a rough in basement bathroom and bedroom project i'm working on.

I have a LOT of 12/3 left over, but I'm out of 12/2 wiring. I can go buy more, but I was curious if I could run two independent lights off of the red conductor and bypass a couple of outlets with the red; and then bypass the lights and switches with the black conductor, but then use it to power the two outlets I need to install near those switches. I'll use two circuits at the box.

I've tried to draw it out briefly at the dinner table of what I'm planning. I looked through all the stickies, and I've checked some good wiring books I have as well as this and other websites, but I couldn't find a template for my unique request.

Can anyone double check my work? Take a look at the following picture.

I know it's totally crude, but I'm just mapping it out. Blue is the Neutral (white) conductors, and the big circles are supposed to be Wire Nuts, and I've numbered everything if you look close. Here's my points I'm curious about:

Between Outet 2 and Switch 2: Am I missing an extra white conductor?

Point #3: I have a wire nut from the 2nd switch (#7) going all the way back to *before* the first switch, this should prevent the first light from switching off the light and everything after it on the red conductor, correct?

Point #5: Should I wire the Neutral to this spot or bypass it?

Points 1, 2, 4, 5, 6, 7 and 8 are all the wire nuts bypassing everything. Did I miss something? I know something looks off, but I'm just completely blind to it.
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Old 06-22-2010, 09:29 PM   #2
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Your diagram will not work by daisy chaining one 12-3 cable through the items in the order shown. You don't have enough wires for the functions:
1. Hot 1
2. Hot 2
3. Neutral (white)
4. From wire nut #3 to #7

Here is what you need to do:

Disconnect the silver (or white) terminal of Light 1 from #6 and use a white wire to connect that light terminal to the neutral at #5.

Disconnect the neutral from Outlet 2 to #8 atSwitch 2.

Disconnect the red from #7 to Switch 2.

(Your point 3) Run another cable from the panel to Switch 2 without stopping at #7. While you might run the cable from Switch 1 to Switch 2, using 3 wire cable will likely have too many wires crowded into Switch 1. Use the neutral in the new cable and not the neutral from Outlet 2 to connect to #8.

Yes you are still doing two runs with one cable but the project needs three runs hence the added cable.

Important! To connect the red and black to different breakers at the panel they must be connected to breakers on opposite sides, namely 240 volts between the breakers (there will still be 120 volts between each breaker and neutral).

Since the picture was dark enough I took the liberty of filling in real white for the neutral. Nothing has been deleted except where an X is shown.
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Last edited by AllanJ; 06-22-2010 at 10:30 PM.
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Old 06-22-2010, 09:56 PM   #3
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you need a neutral at light 1

the wire that has the connection 6 and 7 needs to simply go away. What needs to happen is that connection point on light 1 is where you would connect the neutral

other than that I see no functionality problems with it.

Oh, and per code, this must be on a 2 pole breaker or have two adjacent breakers and using a handle tie so the will both be turned off if either of them is turned off.
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Old 06-22-2010, 10:10 PM   #4
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Hahah i'm so glad an extra set of eyes looked at it.... how could I miss the white wire on the first device!

Great point about making sure i use two circuits, the 240 volt mistake could be a big one. I'm using a double breaker 20 amp breaker and will use one (say the top) for lights), and the other (bottom) for outlets. I'll "weave" for a better term, the white neutrals between the two sets of hot lines; so it'll be shared.

Thank you both for your great answering guys... awesome... I got such a headache trying to think it through without actually wiring it.. and then when I wrote it down, it wasn't much better (wait, was blue the neutral, or the ground? was the pen the black conductor and the markerthe whole 12/3 outline, or vice verca? lol).

Can't believe I missed it right off the bat

Thanks again!!!
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Old 06-23-2010, 08:03 AM   #5
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Here's the one I fixed; let me know if I missed anything!

I was going to draw in the grounds, but it was just complicating the drawing.

** Edit**

Wow, Allan thank you for the picture. I just redrew mine, posted it, then when I refreshed I saw you had already done the same for me. That's great, I really appreciate your help!
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Last edited by jdm001; 06-23-2010 at 08:07 AM. Reason: Saw other diagram!
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Old 06-23-2010, 08:15 AM   #6
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Just make sure to make the proper connections at all the devices. On the receptacles you show mixed hot and neutral connections on the same side of the device.

Be sure to watch your box fill also.
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Last edited by Jim Port; 06-23-2010 at 09:53 AM. Reason: added box fill comment
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Old 06-23-2010, 11:52 AM   #7
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About the red wire shown looping up and over Switch 1 and Light 1, don't forget that you may not buy a single red wire and wrap it around the outside of the 12-3 cable serving the outlets.

Instead you must run another cable with both hot and neutral. In addition, things served by this new cable (Switch 2 and Light 2) must be served by the neutral in that new cable, not by the neutral in the first cable going through Outlet 1. So you cannot tie in before Outlet 1.

Come to think of it, it would be much easier if you could run light #2 off of the black side, namely the subcircuit that serves the outlets.

Another reminder, be sure to connect the white wires to the silverish screws on the outlets (receptacles) and the colored wires to the gold screws.
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Stick to your lawn watering schedule until it really starts to pour. After the storm you have only the same number of rest days you always had and then you need to start watering again.

Last edited by AllanJ; 06-23-2010 at 12:09 PM.
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Old 06-23-2010, 07:44 PM   #8
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Quote:
Originally Posted by AllanJ View Post
About the red wire shown looping up and over Switch 1 and Light 1, don't forget that you may not buy a single red wire and wrap it around the outside of the 12-3 cable serving the outlets.
Aah I see the confusion. My apologies, I wasn't refering to a seperate red wire, i drew it going around the light to show that it was byassing the light.

See, I'll ONLY be using 12/3 even on the parts that only need 12/2 -- because I only have 12/3 left over. I'm using oversize boxes and I'm using wirenuts that i'll also tape on the unused black or red on each outlet.

To draw the drawing, I had to show that the power from the red has to pigtail on the first light to it's switch, but ALSO to the 2nd light otherwise the 2nd light would turn off (or anything else on the red hot line) after the switch unless I pigtail it.



Quote:
Originally Posted by AllanJ View Post
Come to think of it, it would be much easier if you could run light #2 off of the black side, namely the subcircuit that serves the outlets.

Another reminder, be sure to connect the white wires to the silverish screws on the outlets (receptacles) and the colored wires to the gold screws.
Yes, my crude drawing was just to make it easier to see, i'll get the brass/silver wiring correct; it's just tougher to draw.

I'm curious about the 2nd light on the black hot... here's my setup:

I have a light that goes to a switch. Directly below the switch I have an outlet I need to add.

I have a second, unrelated light that goes to another switch. Below it will be another outlet also. The outlets are to suffice the 12 foot "lamp" rule.

I was trying to do Red for Lights and have them on their own circuit; and then Black for Outlets only on it's own circuit.

Do you think it'd be better to do each room on it's own circuit. IE Light 1, Switch 1, and Outlet one all on RED, and L2, S2 & O2 all on BLACK?

Your thoughts?

At first glance it'd seem like it'd be easier-- but if I trip a circuit the light goes out in that room... only downfall I can see. Neither outlet will have much on it, they are just spare outlets for lamps or something small since this is for a small unfinished space in the basement.
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Old 06-24-2010, 07:49 AM   #9
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I suggested connecting the second light to the black in order to avoid running a second 12-3 cable following the route of the single red line going up and over.

Running the second red (an entire cable), that has to come back down after outlet #2, not before outlet #1. The way you had it, Light 2 gets its neutral through outlet #2 which may not be done when it gets its hot from the cable with the second red.

It is your choice to have each room on its own circuit. In a project I did recently I had each wall (receptacles in the rooms on both sides) on its own circuit.

Quote:
... for a small unfinished space in the basement ...
This adds some complications.

You need a ground fault circuit interrupter and the cheapest way is to install a GFCI receptacle unit as Outlet 1 with cable continuing to Outlet 2. When you do this you must leave unused the red wire going between outlets 1 and 2. And so long as the neutral from Outlet 2 goes to Light 2 you must feed Light 2 with the black from Outlet 2.

Both my doctoring of your first diagram and my doctoring of your second diagram work with the GFCI at Outlet 1.

Quote:
I have a light that goes to a switch
For connecting up an outlet under the switch, you need to run the cable from the outlet box to a box with a neutral as well as a hot. Sometimes the power goes to the switch first in which case you can run the cable from the outlet up to that switch box. This does not work when there is only one cable with two wires entering the switch box originally and the white is connected to one of the switch terminals.
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Last edited by AllanJ; 06-24-2010 at 08:20 AM.
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Old 06-25-2010, 09:21 AM   #10
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Allen, yes correct. I didn't do a full diagram, but I've put GFCI's on all outlets in my home. I've also done Arc Fault circuit breakers in the main panel for all bedrooms and each bathroom. A bit more expensive (about $100-200 more for the whole small house) but it's an investment as I've heard of possible new code changes for new construction are possibly going to require all GFCI's in the future.

As for the external cable, there is no external cable. I'm not sure of a good way to draw it out, but here's what I'm doing:

Main panel to first switch using 12/3
(the black will be unused and wire nutted for continuity to the next romex)
(the white conductor used as normal at a switch)

Switch to Light using 12/3 with Red as power
(the black conductor again wire nutted for continuity)
(the white conductor used at normal at the light)

Light to 2nd Switch using 12/3 with Red as power
(same as above except I might have to code white for hot if it's light-switch)

THEN here's the jump. From here on out the BLACK is the power being used, and the RED is now completed circuit at the end of the light, the black moves on but all red 12/3 conductors are wire nutted at the outlet.

Light to First Outlet using 12/3 with BLACK as power
(the white is used on the circuit flowing through the lights and now being used as the neutral for the outlets too)
(the black conductor is used for power with the white)
(the red conductor is wire nutted as short as possible inside the box)

Outlet 1 to Outlet 2 using 12/3 with Black as power
(same as above, but I have to make sure the White flows all the way back to the service panel in this order: Outlet 2, to Outlet 1, to Light 2, to Switch 2, to Light 1, to Switch 1, to Service Panel).

There will be only ONE Romex line used at each device, there is no external cabling. The last two outlet runs will have unused Red Conductors that will not have access to live current, and the first four devices (lights & switch) will have a live Black Conductor with power, just being bypassed to get to the outlets at the end of the line.

I realize I'll be doing a lot of pigtails and I'm using oversize boxes (deep well) to fit. The grounds and whites will be pretty standard hookups; I just have to pay attention to continue the black conductors early on, and to wire nut the red conductors at the end. The last "gotcha" I might have to double-check is where the White starts to go back from between Light 2 and Outlet 1, that's where it goes from being Red's neutral to Black's neutral.

Anything else I should watch out for?

I hope that's a little clearer, as I know my picture probably muddied the water.
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Old 06-25-2010, 08:03 PM   #11
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Your new plan with items in different order, exactly as you described:

Panel - Switch 1 -- Light 1 -- Switch 2 -- Light 2 -- Outlet 1 -- Outlet 2

One problem. Switch 1 will force Light 2 off. Beyond Switch 1 the red wire which daisy chains through everything in order is controlled by Switch 1.
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Stick to your lawn watering schedule until it really starts to pour. After the storm you have only the same number of rest days you always had and then you need to start watering again.

Last edited by AllanJ; 06-25-2010 at 08:06 PM.
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Old 06-29-2010, 08:16 AM   #12
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Quote:
Originally Posted by AllanJ View Post
Your new plan with items in different order, exactly as you described:

Panel - Switch 1 -- Light 1 -- Switch 2 -- Light 2 -- Outlet 1 -- Outlet 2

One problem. Switch 1 will force Light 2 off. Beyond Switch 1 the red wire which daisy chains through everything in order is controlled by Switch 1.
Great catch.

What if I pigtail it at Switch 1? Meaning instead of doing a straight series line, maybe I make it a "Y" with two switch-legs. My first switch is within 10 feet of the second light.

I can work backward and do a Light 2 To Switch Two, then do Light 1 to Switch 1, and have them both meet at a junction box where the power from the panel goes directly to both.

IE I have the panel with a black hot being wire nutted to the next black and that's all (bypassing the whole switch inside the box), and then the red hot which will power each switch will have a wire nut from the red conductor from the panel, to the red on the Switch 1 and the red on Switch 2.

I made a super crude drawing in paint before work, best I could do in 3 minutes; maybe it will explain a bit better? The "X" marks are wire nuts (you can see the bypasses) and blue conductors are the white/neutral lines.



I know this would probably be much easier if I just used the black for the Light/Switch/Outlet in one area and the red for the other Light/Switch/Outlet (I loved that suggestion AllenJ), but I was hoping to avoid the light going out in a room if an outlet was tripped.

I also think I may have been better off getting more 12/2 and just doing two independent runs, but I didn't want to notch the joists anymore, as I've already redone all the other electric throughout the house and it's getting pretty crowded near the box.

Hopefully this last plan will work. Really glad I posted on here before I jumped in, very grateful for everyones help!
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Old 06-29-2010, 08:35 AM   #13
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Something went wrong and your last diagram does not appear in your last reply.

Yes you can branch from Switch 1 directly to Light 2 and then over to Switch 2.

When you do this, the cable forming the other half of the Y, from Switch 1 to Light 1, does not daisy chain through Switch 2 or Light 2 on the way to Outlet 1. If the shortest path goes by those boxes, the cable may pass by the outside of those boxes.

Psst! Pigtail refers only to a short length of wire contained wholly in one box. You will need one at Switch 1 when connecting together the incoming red from the panel, the continuing red to Light 2, and the switch itself.
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Last edited by AllanJ; 06-29-2010 at 08:50 AM.
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Old 07-01-2010, 08:24 AM   #14
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Awesome. That's what I meant too; a set of pigtails to "split" the power instead of in a series; thus avoiding light 1 from switching everything off down the line from it.

I really appreciate all your help. I plan on rewiring it this weekend; this was very helpful. Again thanks Allan!
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