NM-B over Size #1

[rookie4now]

I feel like I should know this, but apparently I don't. I just failed an inspection because I used 2/0 NM-B as the feeder from a main disconnect to a panel that serves an entire residence. I used 315.15(B)(6) which allows 200a for 2/0 in this situation. However, the inspector pointed out that it does not list NM-B in that section, only THHN, and some other types. When you look in the ampacity chart in the 60 degree column (which includes NM-B) there is nothing listed after size #1 Copper. There are kust dashes in the 60 degree column after that. So, the question is, since NM-B is supposed to be in the 60 degree column and there are no ratings in that column after size #2 copper, what is the amperage rating of 2/0 NM-B? I always just jumped over to the 75 degree column, but apparently that isn't correct??? Confused.

 

[LarryFine]

What is the brand and model of that cable?

The next cable of choice is usually SER.

 

[david luchini]

I feel like I should know this, but apparently I don't. I just failed an inspection because I used 2/0 NM-B as the feeder from a main disconnect to a panel that serves an entire residence. I used 315.15(B)(6) which allows 200a for 2/0 in this situation. However, the inspector pointed out that it does not list NM-B in that section, only THHN, and some other types.

Which Code year are you under. I don't believe 310.15(B)(7) lists conductor types any longer.

When you look in the ampacity chart in the 60 degree column (which includes NM-B) there is nothing listed after size #1 Copper. There are kust dashes in the 60 degree column after that.

What ampacity chart are you looking at? They all appear to go up to 2000kcmil in the 60 degree column.

 

[Dennis Alwon]

Where did you get 2/0 nmb. I thought they only made it up to #2

334.104 Conductors. The 600-volt insulated conductors shall
be sizes 14 AWG through 2 AWG copper conductors or sizes
12 AWG through 2 AWG aluminum or copper-clad aluminum

 

[infinity]

Where did you get 2/0 nmb. I thought they only made it up to #2

That's correct #2 is the largest size permitted by the NEC. Must be SE cable.

 

[rookie4now]

What is the brand and model of that cable?

The next cable of choice is usually SER.

It would either be Romex Simpul or Cerro Wire

 

[Dennis Alwon]

It would either be Romex Simpul or Cerro Wire

Is the jacket gray in color or some other color like black, white etc...

 

[Dennis Alwon]

Here is a good look t the different wires. Of course nm-b comes in yellow, white, orange , black