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#95317 09/07/05 07:00 PM
Joined: Dec 2003
Posts: 59
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big guy Offline OP
Member
Am I right in saying if you read 310 15 (B) (4)
A neutral does not have to be derated if it is only serving to carry the laod form one ungrounded conductor.
For Ex

You have 9 # 10 in A 3/4 pipe
4 hot wires
4 neutral wires
1 ground
There would be 4 current carrying conductors in this pipe. The load would be only be recp.

Is this right thanks

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#95318 09/07/05 07:42 PM
Joined: Apr 2002
Posts: 7,323
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Ah, we have to know what the loads are???

Incandescent lighting, fluorescent lighting, motors, etc.

John


John
#95319 09/07/05 07:46 PM
Joined: May 2002
Posts: 1,716
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Member
Big Guy, in a two wire circuit, both conductors are current carrying, there is no neutral.

[Linked Image]

Now if the grounded conductor is shared between legs it becomes a neutral.

[Linked Image]

[Linked Image]

Roger

#95320 09/08/05 04:51 AM
Joined: Dec 2003
Posts: 59
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big guy Offline OP
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The load is just common 120 volt recp.

I want to know if the neutral is a current carrying conductor

If each hot wire has is own neutral.Do you have derate the neutral with the hot wires.
I hope this clears it up better.

thanks

#95321 09/08/05 05:03 AM
Joined: May 2002
Posts: 1,716
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Big Guy, yes in your two wire circuits both wires are current carrying conductors, it wouldn't matter what the voltage is, see the first graphic.

In your question you have 8 current carrying conductors.

Roger

#95322 09/08/05 05:06 AM
Joined: Jan 2003
Posts: 4,391
I
Moderator
The short answer is yes the white wire in these circuits is a current carrying conductor.

You do not have a 'neutral' in that circuit. Look at Rogers upper diagram.

What you have you have in the language of the NEC an ungrounded and a grounded conductor.

Your 3/4" pipe has 8 current carrying conductors for the purposes of derating.


Bob Badger
Construction & Maintenance Electrician
Massachusetts
#95323 09/08/05 05:08 AM
Joined: Sep 2003
Posts: 650
W
Member
Yes and yes.

Look at the diagrams that Roger posted. Any current flowing in a hot wire has to be balanced somewhere. If each hot wire has its own separate neutral, then the current flowing in that neutral _must_ be equal to the current flowing in the hot. Therefore if the hot is counted as a current carrying conductor, the neutral must also be counted.

_Shared_ neutrals under _some_ conditions need no be counted as current carrying conductors. This is because the current flow in the hot will be balanced by the current flow in the opposite hot.

Remember: the current flow in a string of series connected elements is always the same everywhere.

In your example, there would be 8 current carrying conductors.

-Jon

#95324 09/15/05 06:58 PM
Joined: Jun 2005
Posts: 821
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Member
This thread is why I think this forum is good.

Thanks guys!

#95325 09/18/05 01:41 AM
Joined: Jul 2004
Posts: 19
L
Member
While I agree with the ideas posted so far I think the NEC says you do not need to count the grounded conductor as a current carrying conductor for the purpose of derating in this instance. The text of the code reads:

310.15 (B)(4)(a)
A Neutral conductor that carries only the unbalanced current from other conductors of the same circuit shall not be required to be counted when applying the provisions of 310.15(B)(2)(a)

I interpret this to read:
"One hot and one neutral count as 1 CCC when applying 310.15(B)(2)(a)"

A multi-wire circuit would require counting the grounded conductor according to 310.15(B)(4)(b&c)

Have I missed the boat? What do you guys think?

[This message has been edited by Local (edited 09-18-2005).]

#95326 09/18/05 02:47 AM
Joined: May 2003
Posts: 2,876
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e57 Offline
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Local it is talking about at least a 3-wire ciruit. "...unbalanced current from other conductors of the same circuit"

But I think there's something wrong with the wording here. I think it should be balanced current! Otherwise it is a current carrying conductor, right? At least in single phase it would be. Hmmmm. It's late, and I need beer.


Mark Heller
"Well - I oughta....." -Jackie Gleason
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