Amp load of multi-circuit neutral

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  #1  
Old 02-25-05, 02:12 PM
kevlarus
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Amp load of multi-circuit neutral

I was going through some older posts and come across a thread talking about the return load (balance?) of a neutral in a multi-circuit (2 hots) and whether the hots are from the same side or from each side (A & B) in the panel.

If I understand correctly, given 2 circuits, 20A each which power lights or receptacles (as 120V), the return could potentially be carrying up to 40A if the 2 hots are from the same side instead of apposing phases.

I'm comparing this to how the main breaker panel is wired. A #12/3 wg (might be #10, can't tell) is run from the panel to a jbox which seperates into 2 individual runs of the neutral + 1 of the hots. However, both hots are from the same side (vertical, #1 & #3 in a square D panel).

Doesn't this mean the neutral could have to carry up to 40A ?

Thanks
 
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  #2  
Old 02-25-05, 02:26 PM
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Same side of the panel is not the same as same leg of the service. Breakers #1 and #2 are on the same leg. Breakers #1 and #3 are on opposite legs. Next time you're at the home center, look at the panels on display. You'll see these fingers that alternately come off of the two main buses. The finger off one bus serves breakers #1 and #2, and the finger off the second bus serves breakers #3 and #4, and so forth. Without this scheme, double-pole breakers could not hit both buses and thus could not supply 240 volts.

Bottom line--you're good.
 
  #3  
Old 02-25-05, 02:31 PM
kevlarus
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Thanks John... no, I haven't looked at an empty one. But I will the next time I'm in :-) Does make sense with regard to 240V for dryer and A/C.
 
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