Neutral (grounded) conductor in a subpanel

[jjseabra]

I would like some clarification on this. I was always under the assumption that the neutral (grounded) conductor in a subpanel had to be the same size as the ungrounded conductors. Is there a code reference related to this? Or did they change this in the 2008 code?

If you have a code reference that would be great. Ive been racking my brain trying to find this in the code.

 

[augie47]

220.61 provides for feeder neutral calculations.

 

[jjseabra]

220.61 provides for feeder neutral calculations.

But if im reading that article correctly - that is referencing main service feeders, not subpanels. Is there a section that covers services in other buildings that references the size of the grounded and ungrounded conductors?

 

[augie47]

..........- that is referencing main service feeders, not subpanels....

I don't see such a reference. To me, that section is reference to any feeder.
Also look at 215.2, which references Art 220. Note that the grounded conductor shall not be smaller than required by 250.122.

 

[jjseabra]

Here is the reason for the question. In every subpanel I have ever set ie in houses or for garages etc, I will always run 4 wire with the neutral the same size as the ungrounded conductors. Now im being told you dont have to do that by an inspector. I find that hard to believe.

Is not a subpanel in the home or a subpanel to the garage treated the same as a branch circuit? In reality it is if you thing about it. Or is my thinking way off base here.

 

[raider1]

Here is the reason for the question. In every subpanel I have ever set ie in houses or for garages etc, I will always run 4 wire with the neutral the same size as the ungrounded conductors. Now im being told you dont have to do that by an inspector. I find that hard to believe.

Is not a subpanel in the home or a subpanel to the garage treated the same as a branch circuit? In reality it is if you thing about it. Or is my thinking way off base here.

The inspector is correct, you don't have to have a full sized neutral for a feeder, you only have to size it for the maximum unbalanced load in accordance with 220.61.

Chris

 

[augie47]

The inspector is correct, you don't have to have a full sized neutral for a feeder, you only have to size it for the maximum unbalanced load in accordance with 220.61.

Chris

With a few other requirements in mind per 215.2 (minimum size, etc)

also jjs: per NEC "Branch Circuit. The circuit conductors between the final overcurrent device protecting the circuit and the outlet(s)" It's not a branch circuit.

 

[tom baker]

Is not a subpanel in the home or a subpanel to the garage treated the same as a branch circuit? In reality it is if you thing about it. Or is my thinking way off base here.

Yes.
See the definitions of branch circuit and feeder.
A feeder in a seperate building requires a grounding electrode system and disconnect. A branch circuit does not require a grounding electrode system but may require a disconnect.

A feeder does is not required to have a neutral (think of a three phase system). If one if installed, its larger of that required by Art 220 or Section 250.122. Feeders installed prior to the 2005 NEC only had to be size per Art 220.