Q: The calculated load for an apartment building is 665 amperes, 120/240 volts. May the service-entrance conductors be two sets of parallel 350 Kcmil Type THWN copper conductors in separate raceways? I am using Table 310.15(B)(6) and doubling the ampacity of 350 Kcmil copper conductors to obtain an ampacity of 700?
A: The special or elevated ampacities of conductors permitted by Table 310.16(B)(6) stops at 400 amperes. It does not include elevated ampacities for service-entrance conductors in parallel.
The minimum size service-entrance conductors for a calculated load of 665 amperes is two sets of 400 Kcmil Type THWN copper or other copper insulated conductors with 75°C or 90°C insulation in two separate raceways. These conductors may be protected by a 700-ampere overcurrent protective device.
Grounding in Apartment Building
