Conductor Size for a Garage Service

[Chuckster in NJ]

I have a friend of mine who has a stand alone garage with a dedicated single phase overhead service. The electrical contractor used 200 amp SEU Aluminum service cable (4/0) feeding a 200 amp main breaker. I believe this is a violation because you can only "de-rate" service conductors (83%) on a residential DWELLING as per the NEC……. NOT on a "stand alone garage" with a commercial electric rate.
I interpret that service feeder conductors to a "stand alone garage" shall be sized as per the main breaker rating and NOT de-rated like a residential dwelling…….. So I say given that the job is done in order to make it "code compliant" (least expensive way) he should change the existing 200 amp main breaker to a 175 amp main breaker.
The service was inspected and approved by the local inspector and my friend feels the electrical contractor "exceeded" minimum requirements set by the NEC.
What are your thoughts?

 

[alfredeneuman]

4/0 aluminum has an ampacity of 180A which doesn't correspond to a standard breaker size.
When it doesn't the next standard breaker (200) can be used as long as the total calculated load doesn't exceed 180A.
NEC 240.3(B)

 

[Chuckster in NJ]

As per manufacturers spec, they chart says this SEU cannot be used on a stand alone garage. This cable would be approved for use on a residential DWELLING.

 

[wyliesdiesels]

I have a friend of mine who has a stand alone garage with a dedicated single phase overhead service. The electrical contractor used 200 amp SEU Aluminum service cable (4/0) feeding a 200 amp main breaker. I believe this is a violation because you can only "de-rate" service conductors (83%) on a residential DWELLING as per the NEC……. NOT on a "stand alone garage" with a commercial electric rate.
I interpret that service feeder conductors to a "stand alone garage" shall be sized as per the main breaker rating and NOT de-rated like a residential dwelling…….. So I say given that the job is done in order to make it "code compliant" (least expensive way) he should change the existing 200 amp main breaker to a 175 amp main breaker.
The service was inspected and approved by the local inspector and my friend feels the electrical contractor "exceeded" minimum requirements set by the NEC.
What are your thoughts?

What is the calculated load of the building?

Good luck finding a 175a or 180a main breaker.

The 200a main is code compliant as long as the load doesnt exceed 180a

 

[wyliesdiesels]

As per manufacturers spec, they chart says this SEU cannot be used on a stand alone garage. This cable would be approved for use on a residential DWELLING.

Umm where does the chart say that?

 

[alfredeneuman]

As per manufacturers spec, they chart says this SEU cannot be used on a stand alone garage. This cable would be approved for use on a residential DWELLING.

Would you point out where it says that?

NEC 338.10 (B)(4)(b)
Type USE cable installed as underground feeder and branch circuit cable shall comply
with Part II of Article 340.

 

[Chuckster in NJ]

Would you point out where it says that?

Look in the lower right hand corner of the chart….. It says "DWELLING" could I be reading the chart wrong?

NEC 338.10 (B)(4)(b)
Type USE cable installed as underground feeder and branch circuit cable shall comply
with Part II of Article 340.

This is an overhead service.

 

[Chuckster in NJ]

Umm where does the chart say that?

 

[alfredeneuman]

Look in the lower right hand corner of the chart….. It says "DWELLING" could I be reading the chart wrong?

This is an overhead service.

Yes you're reading it wrong. It doesn't exclude any other uses.
USE=SEU and it only needs to be marked as suitable for aboveground use to be used overhead

 

[wyliesdiesels]

Deleted

 

[wyliesdiesels]

Look in the lower right hand corner of the chart….. It says "DWELLING" could I be reading the chart wrong?

This is an overhead service.

Youre totally misreading or misinterpreting the code

Code doesnt prohibit use of SEU in non dwelling buildings

I suggest you grab a code book and read through the applicable code sections a couple times

SEU can be used for connection to the overhead service drop. Its done all the time.

 

[Chuckster in NJ]

Youre totally misreading or misinterpreting the code

Code doesnt prohibit use of SEU in non dwelling buildings

I suggest you grab a code book and read through the applicable code sections a couple times

SEU can be used for connection to the overhead service drop. Its done all the time.

TRUE! I understand where you can use the cable however the 200 amp rating on the chart is for a "dwelling" and not a stand alone garage.….. I have always been taught that you can only de-rate service conductors on a dwelling.
NOT to "beat this to death" but I just wanted to get an opinion from others.

 

[wyliesdiesels]

TRUE! I understand where you can use the cable however the 200 amp rating on the chart is for a "dwelling" and not a stand alone garage.….. I have always been taught that you can only de-rate service conductors on a dwelling.
NOT to "beat this to death" but I just wanted to get an opinion from others.

there is no derating going on. #4 AL good for 180a however there is no 180a breaker so code allows upsizing of the breaker to the next standard size as long as the load is 180a or less.... but this is the third time explaining this....