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Old 02-08-2012, 05:17 PM   #1
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Default Paralleled Conductors - Correction factor?

I looked but could not find it addressed specifically. Technically, there are 6, though they function as 3.

When sizing conductors per 310.16, must a correction factor be applied if running a paralleled circuit resulting in 6 current carrying conductors rather than 3?




I will reference this quote regarding a 600a service.
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Originally Posted by Dennis Alwon View Post
Totally wrong. The panel may work fine without much load but as others have said if the load gets up there you will have issues.

You need to have parallel 300kcm copper conductors if the calculated load on the panel is 570 amps or less. Art. 240.4(B) allows us to use the next size breaker -- 600 amps.

Your egc needs to be based on the 600 amp breaker from T. 250.122. This means you need a #1 copper conductor in both raceways.

When you say 4/0 for ground and #1 for ground are you meaning neutral or the EGC (equipment grounding conductor)?


Was Dennis correct(285a x 2 = 570), or should there be a 20% correction factored in?

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Old 02-08-2012, 05:35 PM   #2
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Are all the conductors in the same raceway or are there two separate raceways?

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Old 02-08-2012, 06:01 PM   #3
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Well, that has been a question sometimes I struggle with. I would say the same.


The reason I struggle is that when the conductors reach the load, regardless of how they get there, in this case they will be entering through a common conduit or opening. So even if the conductors are in "free air", there is no way that they could remain so for 100% of the distance.

But I am flexible in order to minimize cost.
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Old 02-08-2012, 11:14 PM   #4
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what is the difference of 6 conductors paralelled pulling their rated amps and 6 branch circuit conductors pulling their rated amps? Same heat is generated from each so i would say derating applies.
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Old 02-09-2012, 06:49 AM   #5
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That's what I was thinking, but I guess I expected it to be mentioned at least as a foot note to the code.
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Old 02-09-2012, 09:18 AM   #6
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Here is the applicable section.

310.10(H)(4) Ampacity Adjustment.
Conductors installed in parallel

shall comply with the provisions of 310.15(B)(3)(a).

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Old 02-09-2012, 10:18 AM   #7
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Thanks - wasn't in my NEC. Looks like it was a 2011 update.
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Old 02-09-2012, 10:26 AM   #8
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310.4(D) Ampacity Adjustment. Conductors installed in parallel shall comply with the provisions of 310.15(B)(2)(a).

This is from the 2008 NEC.

The 2011 moved the requirement.

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Old 02-09-2012, 10:43 AM   #9
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