The Chief Engineer's statement about the 2017 NEC is incorrect, or at best, a serious oversimplification. While the NEC is complex, and interpretations can vary, the scenario he describes doesn't generally hold true, especially to the extreme he outlines.Here's a breakdown of why, and how the 2020/2023 change makes a real difference

Why the 2017 NEC Statement is Problematic:
Overcurrent Protection

The core principle of electrical code is to protect conductors and equipment from overcurrent. Installing a 60-amp breaker on a circuit wired with #12 wire (which is only rated for 20 amps) is a

severe violation of the NEC, regardless of the load connected. It creates a fire hazard. The 60-amp breaker would allow much more current than the #12 wire can safely handle, potentially causing it to overheat and start a fire before the breaker trips. Nameplate Rating vs. Adjustable Settings

Under the 2017 NEC (and even before), the nameplate rating of the appliance is important, but so is the actual load it presents. If an EVSE can be configured for up to 60 amps, but is set to draw a maximum of 20 amps, the circuit needs to be sized accordingly.

Practicality and Common Sense

If the Chief Engineer's interpretation were universally true, many electrical installations would be absurdly oversized and unnecessarily expensive. You wouldn't install a 200-amp service to a house just because the range could draw 50 amps even if it typically draws much less.

What likely caused this misunderstanding of the 2017 NEC



Confusion with Continuous Load

EV chargers are considered continuous loads (operate for 3 hours or more). This means the circuit must be rated for 125% of the charger's continuous current draw. For example, if the charger is set to 20 amps, the circuit needs to be rated for 25 amps (20 1.25 = 25). This would typically require #10 wire and a 30 amp breaker.

Initial Interpretation of Adjustable Chargers

Early interpretations of the 2017 NEC may have been overly cautious regarding chargers with adjustable amperage. The wording wasn't as explicit as it is in later editions. Some inspectors and engineers might have leaned toward the highest possible amperage to avoid any ambiguity, especially if the charger lacked clear and easily accessible amperage adjustment mechanisms.

The Difference with the 2020/2023 NEC

The 2020 and especially the 2023 NEC revisions have clarified the rules surrounding adjustable EVSEs (Electric Vehicle Supply Equipment). The key change is the inclusion of language like

625.42(B) EVSE with Adjustable Settings. This section explicitly allows for wiring the EVSE based on the adjusted current setting as long as certain conditions are met: Restricted Access

The amperage adjustment setting should not be easily accessible to unqualified users. This prevents someone from accidentally turning up the amperage beyond the circuit's capacity.

Labeling

The EVSE must have a clear and durable label indicating the adjusted current setting.

Manufacturer's Instructions

Adjustments must be made according to the manufacturer's instructions.

In summary



2017 NEC

While interpretations could vary, the extreme scenario described by the Chief Engineer is unlikely to be correct for most situations. Sizing the circuit based on the actual continuous load was generally permissible. However, there was room for misinterpretation, especially with adjustable chargers.

2020/2023 NEC

The revisions provide a much clearer path for wiring adjustable EVSEs based on their set amperage, making installations more efficient and cost-effective. But you MUST adhere to the restrictions about accessibility and labeling.

Important Considerations



Local Codes and AHJ (Authority Having Jurisdiction)

Always consult with your local electrical inspector or AHJ. They have the final say on code interpretations in your area.

Manufacturer's Instructions

Always follow the manufacturer's instructions for the EVSE and any related equipment.

Professional Installation: Have a qualified electrician perform the installation. They can ensure that the wiring, breaker, and EVSE are properly sized and installed according to code.It's crucial to clarify the Chief Engineer's interpretation with more details, but based on the information provided, the 2017 NEC was not as restrictive as portrayed in his example. The 2020/2023 NEC revisions significantly improve clarity and allow for more sensible installations with adjustable EV chargers. Flag for review