service conductors protection

[thetacon]

I am reviewing a one line diagram for a job I will be starting soon. the residential portion calls out for a 3 phase 1600 amp service feeding the meter pack. the feeders from the utility transformer are 4 - 500 kcmil xhhw (310 amps 1240 amps total) aluminum per phase. My question are the feeders from the utility to the gear required to comply with 240.4(c). Do the feeders and the over current protection need to match each other with no rounding up. The way i read it is does, but my boss seems to think that all that is required for the utility feeders is for them to match the load. any clarification would be appreciated .
thanks

 

[iwire]

First off they do not sound like feeders, feeders always have over current protection on the supply end.

These sound like service conductors.

Is there a single over current device protecting the conductors or 2 to 6 over current devices?

 

[thetacon]

i worded it incorrectly, they are service conductors they are coming directly from the utilities transformer room.

 

[thetacon]

does any one have any suggestions?

 

[augie47]

one suggestion.. answer Bob's question on the main (post #2)
who is supplying the service conductors, you are POCO ?

 

[George Stolz]

My question are the feeders from the utility to the gear required to comply with 240.4(c). Do the feeders and the over current protection need to match each other with no rounding up.

I would agree with you.

230.90(A) requires that the OCPD not be higher than the rating of the conductor.

Exception 2 to that allows us to use 240.4(C).

240.4(C) states that the conductor ampacity shall be equal to or greater than the OCPD.

 

[thetacon]

i did answer the question they are service conductors coming directly from the utility transformer, they are landing on the main breaker in my gear. are those conductors required to match the main breaker in the my gear as far as 240.4 (c) i concerned?

 

[shepelec]

As Augie said

"Who is supplying the cables?"

 

[George Stolz]

I think what these fellows are getting at is, that the serving utility may allow smaller cables per the NESC, and if the utility owns them then the NEC does not necessarily apply.

 

[iwire]

I think what these fellows are getting at is, that the serving utility may allow smaller cables per the NESC, and if the utility owns them then the NEC does not necessarily apply.

I am getting at the fact that if these service conductors supply more than one OCPD that they only need to be rated as much as the calculated load.

 

[don_resqcapt19]

i did answer the question they are service conductors coming directly from the utility transformer, they are landing on the main breaker in my gear. are those conductors required to match the main breaker in the my gear as far as 240.4 (c) i concerned?

If these are customer owned, and there is a single main, then, yes, the ampacity of the conductors must equal or exceed the rating of the main breaker. If there are multiple main breakers, then they only have to have an ampacity equal to or greater than the calculated load.
If they are utility owned conductors they can be any size that the utility wants to install.

 

[George Stolz]

I am getting at the fact that if these service conductors supply more than one OCPD that they only need to be rated as much as the calculated load.

Ah, ok. Do you expect me to read the last sentence of all of your posts?

 

[shepelec]

He did state "main breaker".

I guess thats all we get.

 

[iwire]

Ah, ok. Do you expect me to read the last sentence of all of your posts?

:grin::grin:

I am guilty of that with emails sometimes.

 

[thetacon]

sorry for the delay. It is a 3 phase residential 120/208 service for a 36 unit housing complex. it has one 1600 amp main disconnect in the middle section with 18 meters on each side. It will have 4- 3" conduits run into the center pull section where the disconnect is located. each conduit will have 3- 500 kcmill xhhw aluminum and 1- 250 kcmil xhhw aluminum. the conduits will run directly to the utilities transformer. I am responsible for installing the conduit and and wire but once it is install the utility company owns it. The utility company terminates in the vault. we terminate at the disconnect. I looked thru Section 230 to see if i could find a code reference stating that the service conductors must comply with section 240.4(c) but was unable to find it in the code book. if some one could offer a code reference for it i would a appreciate it

thanks

 

[George Stolz]

I already did, look above.

 

[don_resqcapt19]

sorry for the delay. It is a 3 phase residential 120/208 service for a 36 unit housing complex. it has one 1600 amp main disconnect in the middle section with 18 meters on each side. It will have 4- 3" conduits run into the center pull section where the disconnect is located. each conduit will have 3- 500 kcmill xhhw aluminum and 1- 250 kcmil xhhw aluminum. the conduits will run directly to the utilities transformer. I am responsible for installing the conduit and and wire but once it is install the utility company owns it. The utility company terminates in the vault. we terminate at the disconnect. I looked thru Section 230 to see if i could find a code reference stating that the service conductors must comply with section 240.4(c) but was unable to find it in the code book. if some one could offer a code reference for it i would a appreciate it

thanks

If the utility owns it and is responsible for it, then they get to tell you what size the cable will be.

230.90 specifies the required overcurrent protection for service conductors when the are covered by the rules in the NEC. To comply with the NEC, this installation would require six sets of 500kcmil aluminum.

 

[thetacon]

got it thanks for your help