Box Fill Calculator for Connecticut
NEC 2020 box fill math for EV charger installers working in Connecticut.
Every EVSE installation in Connecticut 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 Connecticut
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 Connecticut is the NEC 2020, which the state 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 Connecticut include Eversource Energy, United Illuminating, Connecticut Municipal Electric. Always verify the applicable tariff and any utility-specific requirements (CT cabinets, metering enclosures, demand limiters) at design time.
Climate & Ampacity
Connecticut'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.
Connecticut 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 Connecticut inspectors most often catch fill violations.