Box Fill Calculator for Maine
NEC 2020 box fill math for EV charger installers working in Maine.
Every EVSE installation in Maine eventually hits a junction or device box — disconnects, splice points, pull boxes — all of which must satisfy NEC 2020 Article 314.16 fill rules.
Worked example for Maine
A 4-11/16" square × 2-1/8" deep box has a 42.0 in³ volume. Each #6 Cu conductor counts as 5.0 in³. With a 2-conductor + EGC EVSE branch landing in the box plus a device, you consume roughly 15-20 in³, leaving plenty of headroom — but a 60 A multi-port pull box can fill quickly with #4 or #2 AWG conductors.
Code & Utilities
The applicable code in Maine is the NEC 2020, 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.
In Maine, you'll most often interconnect with Central Maine Power, Versant Power, Maine Public Utilities Commission Cooperatives. Each has its own service-upgrade timeline, EV rebate availability, and metering rules — confirm them before quoting commercial work.
Climate & Ampacity
Maine's representative summer design ambient is around 84°F, which yields a 0.94× ampacity correction factor at 75°C terminations per NEC 310.15(B)(1). The correction is mild but still NEC-required; document it on the load calc so your inspector sees that 310.15(B) was applied.
Maine takeaway
Always run box-fill math when the EVSE disconnect lives more than a few inches from the unit itself — that intermediate junction is where Maine inspectors most often catch fill violations.