jar546
Forum Coordinator
Service conductors and feeders for certain dwellings are permitted to be sized in accordance with 310.12. How often do you apply the correction factor?
With No Required Adjustment or Correction Factors. If a 175-ampere service rating is selected, a service conductor is then sized as follows:
175 amperes × 0.83 = 145.25 amperes per 310.12.
If no other adjustments or corrections are required for the installation, then, in accordance with Table 310.16, a 1/0 AWG Cu or a 3/0 AWG Al meets this rating at 75°C (167°F).
With Required Temperature Correction Factor.
If a 175-ampere service rating is selected, a service conductor is then
175 amperes × 0.83 = 145.25 amperes per 310.12.
If the conductors are installed in an ambient temperature of 38°C (100°F), the conductor ampacity must be multiplied by the appropriate correction factor in Table 310.15(B)(1)(1). In this case, we will use an XHHW-2 conductor, so we use a correction factor of 0.91 to find the minimum conductor ampacity and size:
145.25/.91 = 159.6 amperes
In accordance with Table 310.16, a 2/0 AWG Cu or a 4/0 AWG Al would be required.
If no temperature correction or ampacity adjustment factors are required, the following table includes conductor sizes calculated using the requirements in 310.12. This table is based on 75°C terminations and without any adjustment or correction factors.
With No Required Adjustment or Correction Factors. If a 175-ampere service rating is selected, a service conductor is then sized as follows:
175 amperes × 0.83 = 145.25 amperes per 310.12.
If no other adjustments or corrections are required for the installation, then, in accordance with Table 310.16, a 1/0 AWG Cu or a 3/0 AWG Al meets this rating at 75°C (167°F).
With Required Temperature Correction Factor.
If a 175-ampere service rating is selected, a service conductor is then
175 amperes × 0.83 = 145.25 amperes per 310.12.
If the conductors are installed in an ambient temperature of 38°C (100°F), the conductor ampacity must be multiplied by the appropriate correction factor in Table 310.15(B)(1)(1). In this case, we will use an XHHW-2 conductor, so we use a correction factor of 0.91 to find the minimum conductor ampacity and size:
145.25/.91 = 159.6 amperes
In accordance with Table 310.16, a 2/0 AWG Cu or a 4/0 AWG Al would be required.
If no temperature correction or ampacity adjustment factors are required, the following table includes conductor sizes calculated using the requirements in 310.12. This table is based on 75°C terminations and without any adjustment or correction factors.