Nope, we can use Table 310.15(B)(6) only if the conductors are installed in a raceway or cable. Sorry, you gotta use Table 310.16.
(of course, I am assuming NJ has adopted the NEC without amending this part)
What is your computed load? Are you feeding these panels through a main distribution center or a disconnect and OC device? Or, are you paralleling the panels, using a 150 amp main breaker for each panel?
#98031 - 04/27/0604:59 PMRe: 310.15(B)(6) for underground conductors
It is a pair of 150-amp panels, but the computed load is less than 200-amps. I hope to use 230.90(A) exception 3. Also 240.4(B) seems to permit 250 kcmil copper, which has an ampacity of 255 amps @ 75 deg.C to be protected at the next standard size OCPD, which is 300 ammps.
#98032 - 04/27/0605:00 PMRe: 310.15(B)(6) for underground conductors
If these are service conductors (a service lateral), then I would say you can use it. It depends on how you parse the wording, but to me the cable or raceway restriction only applies to main power feeders. Here's the exact words (at least the first part):
For dwelling units, conductors, as listed in Table 310.15(B)(6), shall be permitted as 120/240-volt, 3-wire, single-phase service-entrance conductors, service lateral conductors, and feeder conductors that serve as the main power feeder to a dwelling unit and are installed in raceway or cable with or without an equipment grounding conductor. For application of this section, the main power feeder shall be the feeder(s) between the main disconnect and the lighting and appliance branch-circuit panelboard(s).
[This message has been edited by markp (edited 04-27-2006).]
Mark Kent, WA
#98033 - 04/27/0608:00 PMRe: 310.15(B)(6) for underground conductors
If they intended the raceway or cable clause to cover all the different wire classes listed at the beginning, they should have put a comma between "dwelling unit" and "and are". Also, why would there be an equipment grounding conductor in a service lateral? That is further evidence to me that the "and are installed in raceway or cable with or without an equipment grounding conductor" clause only applies to feeders and not service entrance conductors or service laterals.
Mark Kent, WA
#98038 - 04/29/0606:19 AMRe: 310.15(B)(6) for underground conductors
I have to admit that if the code writers are well versed in punctuation, markp makes a valid point. The more I read it, the more i agree with him. Of course, I'm not sure an inspector would be patient enough to discuss proper grammer.
I hope I know where you were going when you asked me about the computed load.