Grounding Conductor Calculator for Massachusetts
NEC 2023 grounding conductor math for EV charger installers working in Massachusetts.
EGC sizing in Massachusetts follows NEC 2023 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 Massachusetts
For a 200 A EVSE branch, Table 250.122 calls for a minimum #6 Cu equipment grounding conductor. If you upsize the phase conductors for voltage drop in Massachusetts's long runs, NEC 250.122(B) requires the EGC to be upsized proportionally.
Code & Utilities
The applicable code in Massachusetts is the NEC 2023, which the state adopted in 2023. 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 Massachusetts include Eversource Energy, National Grid, Unitil Massachusetts. Each has its own service-upgrade timeline, EV rebate availability, and metering rules — confirm them before quoting commercial work.
Climate & Ampacity
Massachusetts's representative summer design ambient is around 88°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.
Massachusetts takeaway
On DCFC sites with parallel feeder sets, each parallel raceway needs its own full-size EGC — a detail inspectors in Massachusetts catch frequently on commercial submittals.