Service entrance Wire

[mannyb]

for a 320/400a residential service wire. if running in

IF IF Aluminum Im lost need help 320amp SVC = 315a @ URD 4/0 AL and 400amp SVC = 415 @ URD 350 AL

A residential home that requires either a 320/400a service would these service entrance wiring? Would it be easier to parallel either conductor type to meter can? or just one conduit? just trying to determine the best solution for this type service type.

 

[iwire]

for a 320/400a residential service wire. if running in

IF IF Aluminum Im lost need help 320amp SVC = 315a @ URD 4/0 AL and 400amp SVC = 415 @ URD 350 AL

A residential home that requires either a 320/400a service would these service entrance wiring? Would it be easier to parallel either conductor type to meter can? or just one conduit? just trying to determine the best solution for this type service type.

Is it a 320 amp or a 400 amp service?

What is the calculated load? You can do it without the calculated load but you will likely end up with bigger conductors without it.

 

[mannyb]

Is it a 320 amp or a 400 amp service?

What is the calculated load? You can do it without the calculated load but you will likely end up with bigger conductors without it.

this is purely educational. I wanted to see what the conductor size would be under these to two type services. i remember a few codes back that the NEC had a table for residential. Where it show amperage and size wire. NOW it says i believe in 310.15 B 7 i can size per use 310.15.B 7 1-4. and it says I am permitted to use 83% of ampacity of service rating.

MY question really is, before i complicate it any more, how is the Service entrance wire for 320/400a is ran? AS FAR AS size wire and conduit? URD? These residential jobs dont give alot information like commercial. Residentiial guys must really know the code to be successful and not miss anything I am trying to get an understanding using both methods on this type services. Thats basically it. i have never run URD and cant believe the ampacity for 4/0 is 315Amps direct burial

 

[augie47]

I don't wish to confuse the issue but, how are you arriving at those numbers ?
(FWIW, true URD (with only that insulation designation) is a utility covered conductor and not a NEC recognized insulated conductor so any "URD" ampacity Tables are not relevant).

 

[mannyb]

I don't wish to confuse the issue but, how are you arriving at those numbers ?
(FWIW, true URD (with only that insulation designation) is a utility covered conductor and not a NEC recognized insulated conductor so any "URD" ampacity Tables are not relevant).

The ampacity is from URD wire chart. Is URD not allowed or am I misapplying the wire ampacity? This is why I am hear getting educated. What wire would i use for for service underground? I really appreicate the comments

 

[augie47]

The ampacity is from URD wire chart. Is URD not allowed or am I misapplying the wire ampacity? This is why I am hear getting educated. What wire would i use for for service underground? I really appreicate the comments

The utility is not governed by the NEC so they can install URD in any size they determine is applicable.
IF you are installing an underground conductor you can use USE-2 direct bury or any "W" conductor
in conduit (XHHW-2, THWN-2, etc). Your base ampacity would come from 310.15(B)(16)keeping the termination limitation of 110.14 in mind.
In that regard, the ampacity of a 4/0 XHHW-2 would be 205 amps but, if terminated at 75° it would be limited to 180 amps, so your calculated load based on the 83% could not exceed 180 amps.

 

[mannyb]

The utility is not governed by the NEC so they can install URD in any size they determine is applicable.
IF you are installing an underground conductor you can use USE-2 direct bury or any "W" conductor
in conduit (XHHW-2, THWN-2, etc). Your base ampacity would come from 310.15(B)(16)keeping the termination limitation of 110.14 in mind.
In that regard, the ampacity of a 4/0 XHHW-2 would be 205 amps but, if terminated at 75° it would be limited to 180 amps, so your calculated load based on the 83% could not exceed 180 amps.

i understand I have never installed URD BUT i have seen many jobs where EC pull URD for services risers and laterals. . I want to do it per NEC. IM not saying its legal Im just mentioning what i see, I guess thats where i get to use URD.

 

[augie47]

i understand I have never installed URD BUT i have seen many jobs where EC pull URD for services risers and laterals. . I want to do it per NEC. IM not saying its legal Im just mentioning what i see, I guess thats where i get to use URD.

Note that some conductors are dual-rated such as URD/RHW, etc. in which case they would be legal and subject to their respective 310.15(B)(16) ampacities.
For NEC installs simply ignore any "URD" ampacity Tables.

 

[mannyb]

Note that some conductors are dual-rated such as URD/RHW, etc. in which case they would be legal and subject to their respective 310.15(B)(16) ampacities.
For NEC installs simply ignore any "URD" ampacity Tables.

10-4. Thanks for help