200a service cable/100a panel

[kwired]

IMO, the size would depend on where the connection was made. If you connected the GEC at the meter, I would say you would size it per the service conductors supplying the meter. If you connected at the service disconnect means, I would say size per the service conductors supplying the disconnect.
Again, my opinion.

The SEC's begin at the drop. IMO you need to use the largest size SEC's for sizing the GEC even if they terminate in the 100 amp service panel.

You may already done this but I mention it for benefit of everyone else:

Read art 100 defintions of service entrance conductors.

If supply is overhead the service entrance conductors start at the connection to the service drop.

If supply is underground the service entrance conductors start at point of connection to the lateral - sometimes there is no splice or other connection separating the service entrance conductors and the lateral conductors and is generally considered the point of entrance in that case. If the lateral ends at a meter socket the load side conductors are the service entrance conductors.

 

[infinity]

I don't see why we need to redefine the word largest. The OP mentioned drop which indicates an overhead service, the SEC's begin there. T250.66 says to base the GEC off of the largest SEC's. Seems simple to me.

I do realize that there are other places in the NEC that allow the GEC to be based on the conductors going to the service disconnect means and although it makes perfect sense I fail to see how that applies here.

 

[Dennis Alwon]

I don't see why we need to redefine the word largest. The OP mentioned drop which indicates an overhead service, the SEC's begin there. T250.66 says to base the GEC off of the largest SEC's. Seems simple to me.

I do realize that there are other places in the NEC that allow the GEC to be based on the conductors going to the service disconnect means and although it makes perfect sense I fail to see how that applies here.

I have to agree with Rob here

 

[jxofaltrds]

You may already done this but I mention it for benefit of everyone else:

Read art 100 defintions of service entrance conductors.

If supply is overhead the service entrance conductors start at the connection to the service drop.

If supply is underground the service entrance conductors start at point of connection to the lateral - sometimes there is no splice or other connection separating the service entrance conductors and the lateral conductors and is generally considered the point of entrance in that case. If the lateral ends at a meter socket the load side conductors are the service entrance conductors.

I agree that is what it sounds like. So why the figure then?

Service-Entrance Conductors are not defined in 100. The system is which includes the service conductors.

What is it with all the changes in 230 adding "service" everywhere?

 

[Smart $]

I don't see why we need to redefine the word largest. The OP mentioned drop which indicates an overhead service, the SEC's begin there. T250.66 says to base the GEC off of the largest SEC's. Seems simple to me.

I do realize that there are other places in the NEC that allow the GEC to be based on the conductors going to the service disconnect means and although it makes perfect sense I fail to see how that applies here.

I would bet that when considering the stipulation, it was assumed the SEC's, for a single disconnect, were the same size for the entire length. Change in SEC size for a one disconnect service is atypical.

What if, at the service head, we used 100A conductors, changed somewhere in the middle to 200A conductors, then back to 100A conductors at the disconnect. What would be the purpose of sizing the GEC(s) to the 200A conductors?

 

[kwired]

I agree that is what it sounds like. So why the figure then?

Service-Entrance Conductors are not defined in 100. The system is which includes the service conductors.

What is it with all the changes in 230 adding "service" everywhere?

Service entrance conductors are defined in 100, one definition for overhead system, one definition for underground system.

I have no idea what you even mean with the rest of what you said in this post.