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Old 07-07-2010, 05:36 PM   #1
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Split 220v in a junction box into 2x 110v


I see a couple of similar posts, but want to be sure I'm doing my job correctly:

At the panel, I have a 10/3 wire which served an upstairs dryer which has been decommissioned. When we removed the dryer, I put a 4" square junction box in a lower cabinet, and dead-ended the wire there. I'm doing some remodel work on the lower level just below this box, and wish to split the 220v out into two 110v circuits.

Presently, the 10/3 wire is connected to two unconnected 30A breakers at the panel. I assume that since I will be coming out of the junction box with # 12 wire, I should replace these breakers with 20A. The breakers are in the same row, one on top of the other, red to one, black to the other. The white wire in connected to the bar at the bottom of the panel. Is there some reason to move one of the breakers to the other row? I've seen something about this mentioned in another forum, but don't understand why it would make any difference since the breakers are totally independant of one another, and each is already drawing 110v from the panel.

At the junction box, I will join the #10 white with the two #12 whites, and one of the black #12 wires to the red #10. The other #12 black will connect to the black #10. Ground wires will of course all be connected

Any problem with this plan?

Thanks!
DFS

Last edited by dsoelter; 07-07-2010 at 05:38 PM. Reason: mis-stated wire size
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Old 07-07-2010, 05:55 PM   #2
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Split 220v in a junction box into 2x 110v


No problem at all.
Replace the 2 pole 30 amp breaker with a 2 pole 20 amp breaker and make sure that all grounds are connected.
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Old 07-07-2010, 07:58 PM   #3
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Split 220v in a junction box into 2x 110v


Because the 110 volt circuits coming out of your junction box share the neutral of the 10-3 cable coming in, you need a double wide breaker with handles tied together so when you kill one circuit to do work on it, the other goes dead too.

Because there is no additional max 20 amp breaker (such as in a subpanel) between the 10-3 feed and the lights and receptacles that will be installed downstream, the entire 10-3 cable can carry no more than 20 amps on the red and 20 amps on the black.

While you will always get 110 volts hot to neutral, the double breaker must be positioned in the panel to feed the 10-3 red and black from opposite sides of the line, that is, with 220 volts betwen them.
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Last edited by AllanJ; 07-07-2010 at 08:05 PM.
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Old 07-08-2010, 12:31 AM   #4
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Split 220v in a junction box into 2x 110v


Something it did click on my mind did the OP did have 6.0mmX3w/G { 10-3W/G } with bare ground conductor ??

If so that will work fine but if no bare conductor then no the OP only can get one circuit due the way cable set up { this is true if you have small SE cable }

Merci.
Marc
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Old 07-08-2010, 12:38 AM   #5
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Split 220v in a junction box into 2x 110v


First, thanks jbfan...from one Parrothead to another.

AllanJ, Understand everything you say until the last part of your last sentence. What do you mean by "the double breaker must be positioned in the panel to feed the 10-3 red and black from opposite sides of the line, that is, with 220 volts betwen them?"

Let me tell you where I think I'm confused, and you can correct me if I'm wrong. You talk about a double wide breaker. All of the breakers in my panels are single breakers, with the 220V circuit breakers joined at the handles. That's two joined 50A breakers for the combo range/oven, two joined 30A each for the oven, cooktop, dryer. The remainder is filled with the individual 15A and 20A for the plugs and lights. The two 30A breakers presently carrying the 10/3 wires are not a double breaker, but two individual breakers joined at the handle. My thinking is that the replacement will duplicate that configuration, just switching out the 30A breakers for 20A. Red wire to one, black to the other. Panel is one of two 70's vintage GE 200A, sitting atop a CT can. Each panel has two rows of breakers top to bottom. I don't know why there aren't any double wide breakers in the panels. Perhaps it was a contractor's choice, or perhaps they weren't available for these panels.

Assuming I will be using two separate breakers, does this satisfy issues you raise in that last sentence? As I see it, there is only one way the new breakers will go into the panel which allows the handles to be joined, just like the 30A breakers they will replace, one above the other in the same row on the same side of the panel.

Thanks again, DFS
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Old 07-08-2010, 12:42 AM   #6
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Split 220v in a junction box into 2x 110v


Bonjour frenchelectrician,

Yes, the circuit to be split is 10/3AWG

DFS
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Old 07-08-2010, 12:48 AM   #7
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Split 220v in a junction box into 2x 110v


Ok then you are good to go and all you have to replace that 30 amp duex pole breaker with 20 amp duex pole breaker then you are good to go.

Merci.
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Old 07-08-2010, 07:36 AM   #8
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Split 220v in a junction box into 2x 110v


Double wide -- The breaker unit takes up two slots in the panel.
(They also make 120 volt only breaker units that have two handles, control two circuits, and fit in one slot; you may not use one of these for the 10-3 feed.)

If the clip on fins under the chosen breaker slots both go to the same bus bar, you may not put the breaker unit there. If that was the case, usually positioning the breaker unit up one slot or down one slot will land it on fins connected to both (to opposite) bus bars. The double breaker is properly positioned when you measure 220 volts between the two poles, even though you will use it for (two) 110 volt circuits.

Two single pole breakers, even with handles tied together, are sometimes not satisfactory because tripping of one breaker, which may not jerk the handle as far as manual turn off, might fail to turn off the matching breaker.
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Last edited by AllanJ; 07-08-2010 at 07:46 AM.
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Old 07-08-2010, 07:42 AM   #9
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Split 220v in a junction box into 2x 110v


What you have been calling "Joined at the handle" others have been calling "double wide". Make sure your new 20 amp breakers are "joined at the handle". Put them in the same slots as the 30 amp breakers you are removing. Do not use what are often called "piggy-back" breakers where you have two breakers in one slot since they will not provide 220V. Also, depending on where your outlets will go you may need AFCI breakers. On the 05 code they were only required in bedrooms. On the 08 code they are required pretty much everywhere that doesn't require GFCI.
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Old 07-10-2010, 09:18 PM   #10
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Split 220v in a junction box into 2x 110v


I am not understanding why it would be bad to have a pair of standard 20 amp breakers?

what would be the problem if 1 half was live while the other was cut off? assuming you'd be working on it after it splits in the juction box, it would be like 2 completely seperate circuts independant of each other only sharing the neutral and ground, but then all the circuts in the house share thier neutrals and grounds.

if you are working on before it gets to the split in the junction box, you'd either be ripping apart the cover or be at the pannel. either way, you'd see you are dealing with more than 1 circut's wires.
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Old 07-10-2010, 09:25 PM   #11
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Split 220v in a junction box into 2x 110v


As I understand new code requires the handle ties or the 2 pole breaker

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All multi-wire branch circuits must be simultaneousy disconnected as per NEC 2008 210.4
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