When to count a neutral as a conductor

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KWH

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When derating conductor ampacity for a conduit run would there be a situation where you would count the neutral as current carrying if you install a neutral for each hot conductor . I am working on a job where the conduit runs are going to be extremely difficult and trying to eliminate some conduits.

Thanks
 
KWH said:
When derating conductor ampacity for a conduit run would there be a situation where you would count the neutral as current carrying if you install a neutral for each hot conductor .
Thanks
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In that case (two wire circuits) all grounded conductors must be counted since they carry the same current as their ungrounded counterpart.

Roger
 
conduit fill

conduit fill

I will have to check code book but a 2 wire branch has no imbalance. If you run multi wire where you share neutral then neutral carries un balanced load and must be carried.
Don't forget to check ampacities when de rating, sometimes the larger wire needed makes it easier to run more conduits.
 
310.15 4 (a) what is this referring to

310.15 4 (a) what is this referring to

I was taking this as one neutral per ungrounded conductor
 
Len said:
I will have to check code book but a 2 wire branch has no imbalance.
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Correct, it is balanced and it carries the same current as the ungrounded conductor.

Len said:
If you run multi wire where you share neutral then neutral carries un balanced load and must be carried.
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The neutral would almost never need to be considered a current carrying conductor in a MWBC.


Roger
 
Here's an illustration that may help.

not_a_neutral.JPG


Roger
 
Thanks Roger

Thanks Roger

Balanced versus Unbalanced with one ungrounded and one grounded conductor, what would be a common occurance of unbalanced in this scenario concerning your typical office building.
 
KWH said:
Balanced versus Unbalanced with one ungrounded and one grounded conductor, what would be a common occurance of unbalanced in this scenario concerning your typical office building.
Click to expand...

You would never have an imbalance in a two wire circuit, a neutral that carries only imbalanced current can only exist in a MWBC.

Here's another illustration of a single phase neutral.

unbalanced__neutral.JPG


Roger
 
While in a three wire circuit of a single phase system the neutral would not be counted.
In a Three wire circuit (two phase's and a grounded conductor) of a three phase four wire wye system that grounded conductor would be counted.
Probably don't have to mention about nonlinear loads of three phase systems as noted in 310.15(B)(4)
There is no mention of counting nonlinear on single phase systems.
 
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