Transformer Sizing Calculator for Kentucky
NEC 2020 transformer sizing math for EV charger installers working in Kentucky.
DCFC and large workplace EV deployments in Kentucky typically need a dedicated 480 V three-phase service, which means sizing a pad-mount or dry-type transformer against the connected charger load plus the NEC 2020 continuous-load multiplier.
Worked example for Kentucky
A 180 kW DC fast charger draws roughly 217 A at 480 V three-phase. Applying the 125% continuous-load factor (180 × 1.25 ≈ 225 kVA), then rounding up to the next standard transformer rating gives a 225 kVA minimum. Kentucky's 92°F summer ambient does not directly derate the transformer, but it does push the secondary feeder ampacity down by 0.88× — so the secondary copper has to be sized accordingly.
Code & Utilities
Kentucky currently enforces the NEC 2020 edition, adopted in 2022. That includes Article 625 (Electric Vehicle Power Transfer System) requirements: 125% continuous-load sizing on EVSE branch circuits, GFCI protection at outdoor receptacles, and provisions for energy management systems on shared circuits.
Major electric utilities serving Kentucky include LG&E and KU, Kentucky Power, East Kentucky Power Cooperative. Each has its own service-upgrade timeline, EV rebate availability, and metering rules — confirm them before quoting commercial work.
Climate & Ampacity
Kentucky's representative summer design ambient is around 92°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.
Kentucky takeaway
Coordinate primary-side voltage, impedance, and fault-current specs with LG&E and KU early — interconnection lead times for new pad-mounts in Kentucky can run 6-12 months on commercial DCFC sites.