125 amp sub panel wire size

[Stevenfyeager]

House has outside 125 amp disconnect. House sub panel cannot use the typical residential service cable size because inspectors here say it’s not a ‘service’. Please help me determine which column to use for my cable size. I need a 4 conductor cable. Existing is 3 wire #2 Cu cable so I have to replace it. If I am reading the correct column, even their #2 was too small. Thanks!

 

[augie47]

Is there just the one 125 amp service disconnect feeding this one panel ?
If so, a #2 Cu or 1/0 AL will work.

 

[retirede]

I think as long as the feeder serves the entire load, it can be sized just like service conductors, no?

 

[Stevenfyeager]

I’m sorry, my inspector says it is still considered a service. I was confusing times when I have to add a 100 amp sub panel and I can’t use my usual residential service size #2 AL. Sorry.

 

[Little Bill]

If the house panel serves the entire load of the dwelling, then you can use the ruduced table for a dwelling and the #2 is sufficient.

 

[Little Bill]

The applies even if they are feeders as long as the entire load is served by them.

 

[Stevenfyeager]

Thank you !

 

[infinity]

I’m sorry, my inspector says it is still considered a service. I was confusing times when I have to add a 100 amp sub panel and I can’t use my usual residential service size #2 AL. Sorry.

It's a feeder to the sub-panel not a service.

For a 100 amp sub-panel that is not carrying the entire load then the feeder conductors are sized according to T310.15(B)(16) so #2 Al is only good for 90 amps.