Service upgrade with outdoor main breaker

[bryant097]

Has anyone had issuses running 4/0 ser cable from outdoor meter/main combo through the inside of a house to a main panel. I have always done this but i was told by another contractor you have size it differently. I have always ran my water and ground rods to outside panel and the ser to the main panel and never had issuses but havent done one in a while and i am curious.

 

[LarryFine]

Standard procedure, no issues.

 

[readydave8]

What size main in meter-main? Does meter-main also have spaces for other breakers?

 

[bryant097]

200 amp and no breakers

 

[infinity]

200 amp and no breakers

No issues with what you've described.

 

[bryant097]

Thanks for replys. Ill have to see what the other conctractor meant by sizing the SER differenly. Maybe he thinks since it in wall or who knows.

 

[Little Bill]

Thanks for replys. Ill have to see what the other conctractor meant by sizing the SER differenly. Maybe he thinks since it in wall or who knows.

I'm guessing he was thinking since you had a meter/main, that you would have circuits ran out of that. Then also have a subpanel inside for other circuits. Since you can't use the reduction in service/feeder size for a dwelling unless the entire load is carried from a single panel, he's probably thinking you needed to use the table for sizing your conductors and not use the allowance for a dwelling.

 

[augie47]

I'm guessing he was thinking since you had a meter/main, that you would have circuits ran out of that. Then also have a subpanel inside for other circuits. Since you can't use the reduction in service/feeder size for a dwelling unless the entire load is carried from a single panel, he's probably thinking you needed to use the table for sizing your conductors and not use the allowance for a dwelling.

Agree. On 4/0 SER it is not normally a problem as the 310.15(B)(16) applies and the 180 amp rating is normally sufficient for the load. As Bill states, if the feeder from your combo does not carry the ENTIRE load of the dwelling then 310.15(B)(7) does not apply and you have to use the (B)(16) ampacities. Where I normally find the problem is on 100 amp- feeders where electricians have the old (B)(7) Table in mind and assume the #2 AL feeder is good for 100 amps where in reality if its not a "whole house" feeder the #2 is a 90 amp feeder. It was a real problem in the '-08 Code when SE had a 60° rating.

 

[bryant097]

I think you are correct a s that possible where the confusion is. I have noticed supply house stopped carrying #2 ser for that reason.

 

[bryant097]

It crazy sonething so simple can make you second guess stuff in this trade

 

[bryant097]

So you if your adding a sub panel off a exsiting main panel you should be running 1/0 not #2 .

 

[Little Bill]

Depends on what size breaker you're feeding it with, also copper or Al.
If you're talking about for 100A, using Al conductors, then #1 would be what you need, not 1/0

 

[infinity]

I'm guessing he was thinking since you had a meter/main, that you would have circuits ran out of that. Then also have a subpanel inside for other circuits. Since you can't use the reduction in service/feeder size for a dwelling unless the entire load is carried from a single panel, he's probably thinking you needed to use the table for sizing your conductors and not use the allowance for a dwelling.

What purpose would it serve to have the feeder conductors larger than the service entrance conductors?

 

[Little Bill]

What purpose would it serve to have the feeder conductors larger than the service entrance conductors?

It wouldn't and I didn't say that. I don't even know what size the service conductors are. I was only thinking of why the OP's friend was saying he couldn't use the 4/0 to the inside, assuming he was talking about 200A. I was pointing out that the guy might have been saying there were circuits in the meter/main and also circuits from the inside panel, which is a subpanel since the main is outside. Because the meter/main didn't serve the entire load, then the feeder to the sub couldn't use the allowance for a dwelling using 4/0 wire for a 200A. I was only guessing at what the guy was thinking.

 

[infinity]

The way I read 310.15(B)(7) whether or not the entire load is served by the feeder is not relevant in this case. Even if the meter main served other branch circuits the feeder conductors are not required to be larger than the SEC's, which can be sized at 83% of the 200 amp OCPD rating. So #4/0's to the meter main and a #4/0 supply the feeder would be compliant.

310.15(B)(7) Single-Phase Dwelling Services and Feeders. For one family dwellings and the individual dwelling units of two-family and multifamily dwellings, service and feeder conductors supplied by a single-phase, 120/240-volt system shall be permitted to be sized in accordance with 310.15(B)(7)(1) through (4). For one-family dwellings and the individual dwelling units of two-family and multifamily dwellings, single-phase feeder
conductors consisting of 2 ungrounded conductors and the neutral conductor from a 208Y/120 volt system shall be permitted to be sized in accordance with 310.15(B)(7)(1) through (3).
(1) For a service rated 100 through 400 amperes, the service
conductors supplying the entire load associated with a
one-family dwelling, or the service conductors supplying
the entire load associated with an individual dwelling unit
in a two-family or multifamily dwelling, shall be permitted
to have an ampacity not less than 83 percent of the serv‐
ice rating.
(2) For a feeder rated 100 through 400 amperes, the feeder
conductors supplying the entire load associated with a
one-family dwelling, or the feeder conductors supplying
the entire load associated with an individual dwelling unit
in a two-family or multifamily dwelling, shall be permitted
to have an ampacity not less than 83 percent of the feeder
rating.
(3) In no case shall a feeder for an individual dwelling unit be required to have
an ampacity greater than that specified in 310.15(B)(7)(1) or (2).

 

[Little Bill]

Let me see if I can explain better. I did not say the way was correct. What I said was that I was guessing at what the guy meant by telling the OP that he couldn't use the 4/0.

 

[augie47]

Just a note from a historical standpoint. As I recall, one of the reasons for the change (from a Table to the 83% rule) was that the Table provided a condcutor size (such a 4/0AL fo 200 amp services/feeders) which did not take ampacity adjustments into account. During the era when SE cable was a 60° conductor, the use of the Taabel allowed you to use a 150 amp conductor on a 200 amp service.