NEMA 14-50 receptacles (or outlets) have been a popular choice for EV charging for years because of their convenience, low installation cost, and increased charging speed over a standard 120V connection.
This is what a NEMA 14-50 receptacle looks like:
While NEMA 14-50 charging remains a good choice in some situations, hardwired wall chargers (or EVSEs) generally provide a better experience. In addition to offering faster-charging speeds, hardwired chargers are more reliable.
What are the main reliability concerns?
Recently, the electrical code in most of the country has been amended to require ground fault circuit interrupter (GFCI) protection for NEMA 14-50 receptacles. Most charging equipment already has GFCI protection. The interaction between the two GFCI systems often causes what's known as nuisance tripping.
Nuisance tripping is the unintended shutdown of a circuit that halts charging on your vehicle. The unintentional shutdown is usually unpredictable and often occurs in the middle of the night. This causes headaches for many homeowners who must continually reset the tripped GFCI breaker.
In addition to nuisance tripping, NEMA 14-50 receptacles can be subject to wear and tear from EV charging. NEMA 14-50 receptacles are most often used for devices that are infrequently plunged and unplugged (e.g., clothing dryers). The receptacle can become loose or wear out if the user frequently plugs and unplugs their EV charging device. A loose connection can lead to safety issues.
Why does nuisance tripping happen?
An often simple explanation of nuisance tripping is that a GFCI can't protect a GFCI. Although this is a convenient explanation for why a nuisance might occur, it does not accurately describe what issues are causing the GFCI to trip.
A GFCI works by measuring the amount of electrical current flowing through the conductors. When an issue occurs, the GFCI senses the current flowing through to "ground" as an imbalance from hot to neutral. In a normally functioning circuit, there is a balance between the conductors. As soon as the GFCI senses an imbalance or "leakage" of power, it trips the circuit.
EV Chargers are complicated electronic devices that have intricate circuitry. Their built-in circuitry is likely creating small amounts of "leakage" current. A 50amp GFCI breaker can measure as little as five milliamps of "leakage" and will trip once the leakage is detected.
All UL-certified level 2 chargers will have GFCI protection built-in. Manufacturers typically place the chargers' GFCI downstream of the "leak" to prevent unnecessary internal trips.
We suggest investing in a hard-wired charger, as these types of units provide a higher rate of charge when compared to a NEMA 14-50 charger. Ultimately, installers will have to wait and see how GFCI technology plays out. One question remains, will the electrical "powers that be" revise the current code, or will the EV charger manufacturers eventually have to fix this "leakage" problem?