310.15 (b) (4 ) (a)

[donnie]

Am I looking at this right, or am I just having an off day.


I'm reading this to say , that if you have one hot wire and one neutral wire , that you don't count the neutral as a current carrying conductor.
But if you have two or three hot wires to one neutral, then you would count the neutral as a current carrying conductor.

Any comments welcomed.

 

[bphgravity]

Re: 310.15 (b) (4 ) (a)

You pretty much got the right idea. The grounded conductor only becomes a neutral conductor when it carries the unbalance of any load or loads. In most cases, a multi-wire branch circuit will meet this condition. However, if you have to completely balanced loads that share a grounded conductor, the conductor will not carry current and would not need to be considered for adjustment factors.

 

[don_resqcapt19]

Re: 310.15 (b) (4 ) (a)

Donnie,
You have it backwards. If you have only two wires, one hot and one grounded, they are both current carrying conductors. If you have two hots that share a grounded conductor, in a single phase 120/240 volt system, the grounded conductor is not a current carrying conductor. If you have 3 hots sharing a grounded conductor in a 3 phase 208Y\120 vor a 480Y\277 volt system the grounded conductor is a not a current carrying conductor. If you are only using two hots from a 3 phase system, with a common grounded conductor, then all three are current carrying conductors. Note: this assumes that a majority of the load is not nonlinear.
Don

 

[ronaldrc]

Re: 310.15 (b) (4 ) (a)

Hey Don?

If I have a hot tub 230 VAC. single phase and the heat is say 10 KW. and 120 volt pump motor. Since the heater is 230 volts the neutral is not counted as just carring the unbalanced load is it?

In this case wouldn't I have to count the neutral as a current carring conductor because it will pull the motor current load either way wouldn't it?

I always counted the neutral as a current carring load with 230 volt equipment. I think the unballance load just applies to what we refer to as split circuit doesn't it?

The reason I bring this up is where someone might think just because they have two legs of opposite polarity they can count the neutral as a noncurrent carring conductor which is not true.

Just want to get this straight.
Thanks" Nick
Ronald

[ March 31, 2003, 09:14 PM: Message edited by: ronaldrc ]

 

[Nick]

Re: 310.15 (b) (4 ) (a)

Ronald,
"1000KW"!

 

[ronaldrc]

Re: 310.15 (b) (4 ) (a)

Okay I meant 10 KW, Thanks" :roll:

 

[don_resqcapt19]

Re: 310.15 (b) (4 ) (a)

Ron,
Your circuit does not have a common grounded conductor as there is only a load between one hot and the grounded conductor, not two hots and a grounded conductor. In this case the grounded conductor is really part of a two wire circuit and is a current carrying conductor.
Don

 

[ronaldrc]

Re: 310.15 (b) (4 ) (a)

Don thats my point.I thought the statement a neutral with two others ungrounded lines run with it ruled out the neutral being a current carring conductor was miss leading.


Ronald