Multiwire Branch Circuit - 15A & #10 wire

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Old 03-03-13, 07:08 PM
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Multiwire Branch Circuit - 15A & #10 wire

Hello, I need some advice on guidance on MWBC.

From the main panel, I have a #10/3 cable wired to my basement, not connected to the main panel though. Now, in the basement, there are two separate branch (not connected to the #10/3 as of now); First branch: lights (#14 wire) and outlets (#12 wire). Second branch: Microwave and couple of outlets (all #12 wire).

Now, I need some guidance to safely connect
1. #10/3 to the main panel
2. connect #10/3 to the 2 separate circuits

Some precautions that I'm aware (& taking seriously) of
1. The 2 hot wires in #10/3 need to be connected to separate legs of the mainpanel - since the shared neutral has to cancel the excess voltage, etc.
2. Planning on using 15A breakers for both the hots as the first of the two branches in the basement has a #14 wire.

Question: 1) Can I use 2 different breakers (15A & 20A respectively) for each of the hot on the #10/3?
2) Any problem with using #10 wire? I would've preferred a #12, but this wiring is already done behind studs and drywalled and would hate to redo it.
3) In the junction box where the #10/3 & the 2 circuits are spliced, all the neutral are spliced together (all 3 - #10/3 neutral, branch 1 neutral & branch 2 neutral); same for the ground too.

Am I missing anything or Am I doing anything wrong? Any help is appreciated.
Thank you, Joel
 
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Old 03-03-13, 08:03 PM
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Given the wiring you have I would suggest a 30 amp subpanel in the basement. That is about the simplest way to use what you have in a code legal way that would not be misunderstood by some future repair person. Any time you mix wire sizes in a circuit there is a danger someone looking at one part of the circuit and not realize the breaker can't be increased. Doing what you suggest would be confusion to the Nth degree even if not exactly non code compliant.
 
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Old 03-03-13, 08:07 PM
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Welcome to the forums!

1) Sort of. A breaker of multiwire branch circuit must disconnect all hots at the same time. So you need to use either a two pole breaker (15/15 or 15/20 if you can find one), or two single pole breakers with an approved handle tie.

2) Code wise, no. The #10 will be a bit tough to work with, but as long as your boxes and wire nuts are large enough for all the wires, your ok.

3) Correct.
 
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Old 03-03-13, 09:57 PM
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agree on the 30A subpanel

I do agree that a subpanel in the basement is a good idea.

I have a "never-used" Siemens sub-panel Catalog # E0408ML1125F (image attached - http://www.homedepot.com/catalog/pdf...a0f44624d4.pdf). It is rated 125A

Now, I have a few more questions.

1. The main panel is a Crouse-Hinds, can I use this subpanel (Siemens)?
2. Assuming that I can use this subpanel, from the main panel, should I be getting a 2 X 20A or 2 X 15A breaker for the #10/3?
3. I'm assuming that I'll have to get a 2-pole breaker for the main panel or a handle ties.
4. The neutral from the #10/3 should be wired to the nut on the right corner of the neutral/ground bus, right?
5. I read somewhere that in subpanels, the neutral and ground wires should not be wired to the same ground bus. However, in the Siemens subpanel, there is only one ground bus. So, is it okay to wire the neutral & ground to the same bus?
6. Assuming everything is good till now, I can put in a 1-pole Siemens QP type 15A (for branch 1) and 1-pole Siemens QP type 20A (for branch 2).

Your time and suggestions are well appreciated. Thank you, Joel
 
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Old 03-03-13, 10:53 PM
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1. The main panel is a Crouse-Hinds, can I use this subpanel (Siemens)?
Sure.
2. Assuming that I can use this subpanel, from the main panel, should I be getting a 2 X 20A or 2 X 15A breaker for the #10/3?
It's a 30A subpanel. Assuming you're using the #10AWG wire to feed it - and only the #10 AWG wire, I would use a 30A 240V breaker to protect the panel feed.
3. I'm assuming that I'll have to get a 2-pole breaker for the main panel or a handle ties.
See 2. This is a subpanel feed, not a MWBC. No handle tie.
4. The neutral from the #10/3 should be wired to the nut on the right corner of the neutral/ground bus, right?
Yes, the neutral from the 10/3 should be connected to the neutral bus. That lug looks too big to secure it though. I would just terminate it under one of the regular screws.
5. I read somewhere that in subpanels, the neutral and ground wires should not be wired to the same ground bus. However, in the Siemens subpanel, there is only one ground bus. So, is it okay to wire the neutral & ground to the same bus?
In a subpanel, The grounds must be bonded and the neutrals must be isolated. Do a continuity test to insure that the installed bus is not bonded to the enclosure and terminate the neutrals there. Buy a separate ground bar, mount it directly to the enclosure, and terminate all of the grounds to that.
6. Assuming everything is good till now, I can put in a 1-pole Siemens QP type 15A (for branch 1) and 1-pole Siemens QP type 20A (for branch 2).
Yes, assuming that type QP is one of the breaker types listed for use with this panel.
 
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Old 03-04-13, 06:12 PM
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To be a little more clear on #2/3, you need to use a 30 amp, two pole breaker.

#4 The screw holes on the right side of the panel in the picture are for the installation of a ground bar.
 
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Old 03-04-13, 07:13 PM
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1. The main panel is a Crouse-Hinds,
3. I'm assuming that I'll have to get a 2-pole breaker for the main panel
You have already been told you need a 30 amp 2 pole breaker to feed the subpanel, but what kind of breaker do you have or are getting (what brand?) for the Crouse-Hinds panel?
 
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Old 03-06-13, 03:50 PM
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Casualjoe, I bought Murray breakers - MP230, MP115 & MP120 as I couldn't find any crouse-hinds breakers in the market. Hopefully, this will work? Right?
 
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Old 03-06-13, 07:17 PM
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Casualjoe, I bought Murray breakers - MP230, MP115 & MP120 as I couldn't find any crouse-hinds breakers in the market. Hopefully, this will work? Right?
To find new Crouse-Hinds breakers would be a rarity. Are Murray breakers U.L. Listed for use in the Crouse-Hinds panel? Did you check the information label inside the panel door to see if they are approved for use in that panel? I believe there are a couple approved choices including Bryant or Westinghouse (now Cutler-Hammer) Type BR and GE Type THQL. I'm not sure if any others are approved, but if they are, they'll be listed inside the panel door.
 
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Old 03-07-13, 07:24 AM
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Yes, you are right that the panel lists Bryant BR, BRO type breakers. Since Bryant is now Cutler-Hammer, can I use the Cutler-Hammer BR type from HD (Eaton 15 Amp 1 in. Single-Pole Type BR Circuit Breaker-BR115 at The Home Depot)?
I thought about this before ordering the Murray MP115, MP120 & MP230 as the existing Crouse-Hinds panel breakers have the MP115/MP120 ones, with a Crouse-Hinds marking... I thought since Murray bought CH, I will be okay. Your thoughts?
 
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Old 03-07-13, 05:45 PM
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Yes, you are right that the panel lists Bryant BR, BRO type breakers. Since Bryant is now Cutler-Hammer, can I use the Cutler-Hammer BR type from HD (Eaton 15 Amp 1 in. Single-Pole Type BR Circuit Breaker-BR115 at The Home Depot)?
I thought about this before ordering the Murray MP115, MP120 & MP230 as the existing Crouse-Hinds panel breakers have the MP115/MP120 ones, with a Crouse-Hinds marking... I thought since Murray bought CH, I will be okay. Your thoughts?
I'd use the Cutler-Hammer BR breakers. The change from the old Murray to Crouse-Hinds and then to the new Murray is a blur. Siemens owns the new Murray now and their breakers aren't even approved in a Murray panel and they are the same breaker with a paper Murray label on them, explain that! I'd still use the C-H BR breakers.
 
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