Grounding Conductor Calculator for New Hampshire
NEC 2020 grounding conductor math for EV charger installers working in New Hampshire.
EGC sizing in New Hampshire follows NEC 2020 Table 250.122, indexed off the upstream OCPD rating, with parallel rules for parallel sets and increased-conductor adjustments under 250.122(B).
Worked example for New Hampshire
For a 100 A EVSE branch, Table 250.122 calls for a minimum #8 Cu equipment grounding conductor. If you upsize the phase conductors for voltage drop in New Hampshire's long runs, NEC 250.122(B) requires the EGC to be upsized proportionally.
Code & Utilities
New Hampshire 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.
New Hampshire's primary EV-relevant utilities are Eversource New Hampshire, Unitil, New Hampshire Electric Cooperative. Each has its own service-upgrade timeline, EV rebate availability, and metering rules — confirm them before quoting commercial work.
Climate & Ampacity
New Hampshire's representative summer design ambient is around 87°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.
New Hampshire takeaway
On DCFC sites with parallel feeder sets, each parallel raceway needs its own full-size EGC — a detail inspectors in New Hampshire catch frequently on commercial submittals.