Sizing ground wire for 200 amp sub feed service

[Simms]

I am doing a 200 amp sub feed in a residential home. Normally I would run aluminum SER cable which has three 4/O (2 hots, a neutral, and a 2/O ground). For this house I'm running PVC conduit with individual XHHW aluminum wire.

So my question is on the size of the ground. In the manufacturer's SER cable it's a 2/O, but according to the 2005 NEC chart 250.66, it says I need a 2 AWG, and if I use chart 250.122 it says I need a 4 AWG. So why does the SER cable have a 2/0 in it, which is by code much larger than what is needed?

 

[celtic]

Re: Sizing ground wire for 200 amp sub feed service

So why does the SER cable have a 2/0 in it, which is by code much larger than what is needed?

...because that is what you asked for.

You could probably get an AL SER cable with 3 3/0 w/ #4 EGC if you asked for it.

 

[bdarnell]

3 conductor 3/0 SER AL comes with a 1/0 bare ground.

 

[jeff43222]

Table 250.66 in my codebook says that ungrounded 2/0 aluminum calls for #4 aluminum for the GEC.

I don't believe Table 250.122 comes into play here.

 

[bdarnell]

I don't believe Table 250.122 comes into play here.

Sure it does. He's running a feeder, unless I mis-read the post. I thought he said subfeed.

Guess we need to clarify if this is an equipment grounding conductor or the grounding electrode conductor.