Service Entrance

[sharan]

600 amps, 120/240V, 1 phase, 3 wire service requires - (2) sets of #350kcmil in 3"c.
We have to run portion of this under DOT highway and if we go directionally bored conduit, can we run this in (1) 6"c under highway?

 

[david]

600 amps, 120/240V, 1 phase, 3 wire service requires - (2) sets of #350kcmil in 3"c.
We have to run portion of this under DOT highway and if we go directionally bored conduit, can we run this in (1) 6"c under highway?

Four 310 amp current caring conductors in conduit @ 80% would give you just shy of 500 amps.

The next standard breaker or fuse would be 500 amps. It depends on the actual calculated load of the service and if your service equipment is a 600 amp main or if the service equipment is a MDP using the max of six disconnects

Edit: Four current caring conductors @ 350 amp insulation @ 80% would leave you at 560 amps so again it depends on the actual calculated load

 

[Smart $]

You can... but you'll have to evaluate a change in parameters. Conductors need derated for number in conduit at least to 80%. If 90°C-rated conductors, 350A × 80% puts you at 280A... or 560A for both sets. Is your calculated load 560A or less?

 

[petersonra]

600 amps, 120/240V, 1 phase, 3 wire service requires - (2) sets of #350kcmil in 3"c.
We have to run portion of this under DOT highway and if we go directionally bored conduit, can we run this in (1) 6"c under highway?

quite possibly. the devil is always in the details. if the N wire is not counted as a CCC, you would have 4 CCC in the conduit and have to derate the conductor ampacity to 80%. it would be the same even if you counted the N as a CCC.

350 kcm copper THWN2 is good for 350 A according to the charts so that would give you 560 Amps. if your calculated load is less than that you are OK.

it may not matter much but is it really a service? or is it a feeder?