placement of breakers with multiwire circuit

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  #1  
Old 10-29-05, 04:44 PM
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placement of breakers with multiwire circuit

This is a follow up to an earlier thread I had posted about pigtailing, but since that thread sort of strated morphing into a new topic and since I did some new research and thinking about this, I figured I'd post a new thread....

I have a multiwire, 20 amp circuit feeding the kitchen. It starts from the panel as 12/3, splits maybe 20 feet later at a junction box in the cellar into 2 circuits, each of which heads up to feed a few outlets in the kitchen. I was reading a bit more about this kind of multiwire circuit elsewhere, and read that it was not good to have this kind of arrangement if the breakers for each of these circuits are located on the SAME SIDE OF THE PANEL.

In my case, the person who set up these circuits used slots 6 and 8 for the 20 amp breakers--each being on the same side of the panel.

Can someone help me understand what this means? I gather that there is somehow an issue with overloading the circuits here, but I don't know if I am wrongly second guessing whoever set it up that way, or I should get someone in to swap the breakers ASAP, or if I shouldn't turn the light on while the coffee maker is running, and so on and so on....

Thanks
 
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Old 10-29-05, 05:04 PM
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Originally Posted by dweeter
..., and read that it was not good to have this kind of arrangement if the breakers for each of these circuits are located on the SAME SIDE OF THE PANEL.
I don't know where you read this but if you did I would not take any more information from this source. This is blatantly wrong.




In my case, the person who set up these circuits used slots 6 and 8 for the 20 amp breakers--each being on the same side of the panel.
That is just where they should be. Above/below each other, on the SAME side of the panel.

If they are on the same leg of the service then the neutral has the potential to carry twice it's rated current. If they are installed correctly, the neutral only carries the current imbalance of the two circuits. Meaning if one circuit is carrying 12 amps, and the other is carrying 10 amps, the neutral is only carrying two amps.
 
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Old 10-29-05, 05:20 PM
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As Speedy said, slots 6 and 8 are just perfect for this purpose. Note that "same side of the panel" is not the same thing as "same leg of the service". The first is (usually) good, the second is always bad.
 
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Old 10-29-05, 06:31 PM
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As John and Speedy stated, you are confusing legs of the service with sides of the panel. I hope it wasn't my post that confused you.

You can verify that you have two different legs of the service by using a voltmeter or a simple neon tester across the two hot wires. If you get 240 volts or the light lights then you have it correct. If you get 0 volts and light doesn't light then you have the same side of the service.
 
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Old 10-30-05, 04:35 AM
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Got it.

My sense of uncertainty about this stems from my earlier discovery that whoever wired this circuit originally ran 14/2 off of one of the braches of the 20 amp 12/3 multiwire circuit (it ran up to a light and an outlet in the kitchen). Even I know that is a no-no. So since they had done that, I thought I ought to look into double checking to make sure that they had done the other work properly as well.

Another lesson learned: Electrical work is proof of why technical language that seems very ordinary (such as "side" and "leg") matters very much.

Many thanks.
 
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Old 10-30-05, 07:57 AM
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The easiest way to confirm proper breaker installation is to measure the voltage between the two hot wries. You should get 240 volts if properly installed and zero if improperly installed.
 
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