CCC or Not?

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Depends on what type system it's fed from. Omn a 240/120 single-phase, it is not a CCC. On a 3 phase system it would be.
 
augie47 said:
Depends on what type system it's fed from. Omn a 240/120 single-phase, it is not a CCC. On a 3 phase system it would be.
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I have to disagree. I would say no for both cases - 310.15(B)(4)(a) for single phase, and (b) for 3 phase.

Steve
 
curt swartz said:
Steve, 310.15(B)(4)b says it must be counted as a current carrying conductor.
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You are right, I didn't read that paragraph carefully enough. The neutral does count under 310.15(B)(4)b.

But if we go back to the original post, we had a "4 wire range". Doesn't that imply a 3 phase system? And if it is 3 phase, that means the neutral is not a CCC per 310.15(B)(4)a.

Steve
 
After a little more thought, maybe I didn't understand what was meant by "4 wire". Now I think I do.

4 wire means (2) hot wires, a neutral, and a ground. Is that right?? Now Augie and Raider's comments make sense.

I was thinking about 3 hot wires, and a neutral.

Steve
 
dcspector said:
What is the intent? Is it due to the fact it is carrying unbalance from multiple phases?
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If the neutral is only carrying the imbalance from 2 of the 3 phases of a 3 phase system, then the neutral will carry almost the same current as the ungrounded conductors, therefore you must count it as a current carrying conductor.

Chris
 
steve66 said:
After a little more thought, maybe I didn't understand what was meant by "4 wire". Now I think I do.

4 wire means (2) hot wires, a neutral, and a ground. Is that right?? Now Augie and Raider's comments make sense.

I was thinking about 3 hot wires, and a neutral.

Steve
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That is what I understood when the original poster said "4 wire range" 2 hots, 1 neutral and 1 EGC. I always think of a 3 wire range as a range that uses the neutral for bonding purposes.

Chris
 
Yes, my intent was to reference a typical residential range circuit consisting of 2 phase conductors, 1 grounded conductor and 1 grounding conductor. I still have a hard time rationalizing the three phase scenario where the grounded conductor would be counted as a CCC. You still have a single phase load with 2 phase conductors and 1 grounded conductor.
 
You still have a single phase load with 2 phase conductors and 1 grounded conductor.
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But when you are dealing with a 3 phase system, the neutral conductor is connected to the common point of 3 ungrounded conductors. The only time the neutral will not count as a CCC on a 3 phase system is when it is carrying the unbalanced between all 3 phase conductors. If the neutral is carrying only the imbalanced current from 2 of the 3 phases the current on the neutral will be very close to that of the highest ungrounded conductor.

Here is the formula for finding neutral current for a 3 phase system.
ry400k.jpg


As you can see if Phase a was 10 amps and Phase b was 12 and Phase c 0 then the neutral would carry 11 amps.

Chris
 
raider1 said:
If the neutral is only carrying the imbalance from 2 of the 3 phases of a 3 phase system, then the neutral will carry almost the same current as the ungrounded conductors, therefore you must count it as a current carrying conductor.

Chris
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A/A Fuel GTX said:
Yes, my intent was to reference a typical residential range circuit consisting of 2 phase conductors, 1 grounded conductor and 1 grounding conductor. I still have a hard time rationalizing the three phase scenario where the grounded conductor would be counted as a CCC. You still have a single phase load with 2 phase conductors and 1 grounded conductor.
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You have to be careful when you use the term 3 phase system. The system that Chris is talking about is a 3 phase Wye system where the neutral would be a CCC. In a 3 phase, 4 wire Delta system the neutral would not be a CCC.
 
infinity said:
You have to be careful when you use the term 3 phase system. The system that Chris is talking about is a 3 phase Wye system where the neutral would be a CCC. In a 3 phase, 4 wire Delta system the neutral would not be a CCC.
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Good point, I am talking about a 3 phase Wye connected system. The answer I gave was in regards to 310.15(B)(4)(b) which is talking about a 4 wire, 3 phase Wye connected system.

Chris
 
raider1 said:
Good point, I am talking about a 3 phase Wye connected system. The answer I gave was in regards to 310.15(B)(4)(b) which is talking about a 4 wire, 3 phase Wye connected system.

Chris
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I knew that's what you meant. :)
 
A/A Fuel GTX said:
So to play it safe, when in doubt, count the neutral as a CCC.....
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You could do that as long as it doesn't adversely impact your installation. The real concern is when using a single phase, 4 wire circuit from a WYE system. For everyday 120/240 volt systems you won't need to concern yourself about the neutral being a CCC.
 
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