Breaker Sizing Calculator for South Carolina
NEC 2017 breaker sizing math for EV charger installers working in South Carolina.
Every EVSE branch in South Carolina is treated as a continuous load per NEC 2017 Article 625 — the OCPD must be sized at 125% of the EVSE's listed maximum draw.
Worked example for South Carolina
A 40 A continuous EV load requires a breaker rated 50 A (40 × 1.25 = 50.0 A, rounded up to the next standard size). The conductor downstream must carry that 50 A after South Carolina's 0.88× ampacity correction.
Code & Utilities
The applicable code in South Carolina is the NEC 2017, which the state adopted in 2018. That includes Article 625 EVSE rules and the 125% continuous-load factor on charging branch circuits, though some 2020-cycle changes (like expanded EMS provisions) are not yet enforced statewide.
Major electric utilities serving South Carolina include Duke Energy Carolinas SC, Dominion Energy South Carolina, Santee Cooper. Their make-ready, time-of-use, and demand-charge structures vary widely; pull the specific tariff before sizing service equipment.
Climate & Ampacity
South Carolina's representative summer design ambient is around 94°F, which yields a 0.88× ampacity correction factor at 75°C terminations per NEC 310.15(B)(1). Because the correction is below 0.9, conductors that "look fine" on a 30°C ampacity table will not carry their nameplate current here — always derate explicitly.
South Carolina takeaway
Use a 100%-rated breaker only when the panel and breaker are both listed for 100% continuous duty — otherwise the 125% rule applies. South Carolina inspectors enforce this rigorously on Article 625 work.