Grounding Conductor Calculator for Arizona
NEC 2017 grounding conductor math for EV charger installers working in Arizona.
EGC sizing in Arizona follows NEC 2017 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 Arizona
For a 40 A EVSE branch, Table 250.122 calls for a minimum #10 Cu equipment grounding conductor. If you upsize the phase conductors for voltage drop in Arizona's long runs, NEC 250.122(B) requires the EGC to be upsized proportionally.
Code & Utilities
EV installations in Arizona are governed by the 2017 National Electrical Code, in force since 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 Arizona include Arizona Public Service, Salt River Project, Tucson Electric Power. Each has its own service-upgrade timeline, EV rebate availability, and metering rules — confirm them before quoting commercial work.
Climate & Ampacity
Plan EV feeders against a 108°F ambient in Arizona — the resulting NEC 310.15(B) correction of 0.75× is what trims a #6 THWN-2 down to its true continuous rating. 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.
Arizona takeaway
On DCFC sites with parallel feeder sets, each parallel raceway needs its own full-size EGC — a detail inspectors in Arizona catch frequently on commercial submittals.