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Old 09-25-2013, 04:01 PM   #1
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Need help wiring 2 new circuits


Installing an over the range microwave (draws 13.85A) and a fridge (draws 8.50A). I know you dont have to have the fridge on a dedicated circuit, but I would prefer it.

Trying to find the cheapest solution here. The run from the panel to the desired location is about 80ft.

1. Should I just get 12-3 romex and install each circuit to its own individual breaker?

2. Use 12-2 and connect to a 20A tandem?

3. Go with 14-2 romex and use a 15Amp tandem breaker?

4. Use 14-3 romex with two single pole breakers?

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Old 09-25-2013, 04:15 PM   #2
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Need help wiring 2 new circuits


Use 12/3 with a 2 pole 20 amp breaker (This is called a MWBC- Multi Wire Branch Circuit). This runs to the first location, then run 12-2 to the second.

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Old 09-25-2013, 04:31 PM   #3
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Need help wiring 2 new circuits


Does a 2 pole switch count as 2 different circuits?
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Old 09-25-2013, 06:23 PM   #4
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Need help wiring 2 new circuits


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Does a 2 pole switch count as 2 different circuits?
Your question makes no sense. What has a 2 pole switch have to do with this discussion.
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Old 09-25-2013, 06:49 PM   #5
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Need help wiring 2 new circuits


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Your question makes no sense. What has a 2 pole switch have to do with this discussion.
Sorry about that made a typo. I meant does a 2 pole breaker count as 2 different circuits?

The manual for the over the range microwave says it needs a dedicated circuit. I know a single pole breaker connected to a outlet is a dedicated circuit. Since this is a 2 pole breaker Im assuming 240v is delivered to the microwave and fridge? I hope I made sense.
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Old 09-25-2013, 06:54 PM   #6
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Need help wiring 2 new circuits


A MWBC is used to provide 2 120 volt circuits. 1 circuit uses 1 pole of the breaker, the other circuit uses the other pole. The neutral is common to both circuits.
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Old 09-25-2013, 07:53 PM   #7
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Need help wiring 2 new circuits


Awesome thanks for all the help.
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Old 09-25-2013, 10:31 PM   #8
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Need help wiring 2 new circuits


Make sure you understand the difference between a 2 pole breaker and a tandem breaker.
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Old 09-28-2013, 10:24 AM   #9
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Need help wiring 2 new circuits


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Make sure you understand the difference between a 2 pole breaker and a tandem breaker.
Im a little confused by this. Is the difference the voltage they carry? The 2 pole breaker is 240v while the tandem isn't? With the 2 pole breaker you are using 12-3 wire and the tandem is using 12-2.
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Old 09-28-2013, 10:42 AM   #10
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Need help wiring 2 new circuits


A tandem is actually two single pole breakers in the space of one.
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Old 09-28-2013, 12:50 PM   #11
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Need help wiring 2 new circuits


Who ever installed are panel was using 12-3 romex and installed both hots onto a tandem breaker. Thanks for clearing that up for me.
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Old 09-28-2013, 12:56 PM   #12
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Need help wiring 2 new circuits


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Who ever installed are panel was using 12-3 romex and installed both hots onto a tandem breaker. Thanks for clearing that up for me.
The problem with that is that both hots are on the same 120 volt leg. This will cause the neutral to carry the total current from both hot legs which can exceed 20 amps. When connected to a 2 pole breaker, each is on a different 120 volt leg that are 180 degrees out of phase. The neutral only sees the difference in the current on the hots.
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Old 09-28-2013, 01:40 PM   #13
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Need help wiring 2 new circuits


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The problem with that is that both hots are on the same 120 volt leg. This will cause the neutral to carry the total current from both hot legs which can exceed 20 amps. When connected to a 2 pole breaker, each is on a different 120 volt leg that are 180 degrees out of phase. The neutral only sees the difference in the current on the hots.
Sadly when I told the Lowes employee who said he was an electrician said he didn't see a problem with that. Is it ok to use 12-3 and two single pole 20A breakers or does that have to be a double pole?
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Old 09-28-2013, 02:15 PM   #14
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Need help wiring 2 new circuits


With 12-3 you need to use a two pole breaker. If you used two 12-2 cables you could use a tandem.
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Old 09-28-2013, 02:22 PM   #15
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Need help wiring 2 new circuits


Although you technically may use 12/3 and two single pole breakers, the breaker handles should be tied together so that they must both be either on or together...not separately.

It is safer to use a double-pole breaker with a single handle.

And while I'm sure you caught the earlier comments, ensure you know the difference between a double-pole breaker and a tandem breaker.

Never use 12/3 with a tandem breaker where the neutral wire is shared.

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