You've hit upon a very sharp observation and a likely unintended consequence of the code changes in the 2023 NEC. Your understanding is correct: by moving the minimum lighting load calculations from Part II to Part III of Article 220, and explicitly stating that the Optional School Calculation in 220.86 is "in lieu of Part III," you are technically correct in that the minimum lighting load is no longer required in the Optional School Calculation.

Here's a breakdown of why you're right and why it feels so wrong: Explicit Exclusion

The language "in lieu of Part III" is pretty clear. It creates an entirely different method of calculation that bypasses everything in Part III, including the minimum lighting load requirements now found there.

Reliance on Connected Load

The optional method focuses on connected load and demand factors tailored to schools. This is why it's intended to be a simplified method, but in the case of lighting, it creates a potentially bizarre outcome.

Why It Feels Wrong (And Probably Is)

The minimum lighting load is intended to ensure adequate capacity for basic lighting needs, regardless of the actual installed lighting. It is a minimum safety factor. Removing it creates a vulnerability: A designer could theoretically specify very low wattage lighting throughout the school initially, then later, upgrades could overload the service. The school might initially install energy-efficient lighting to minimize the calculated load, but could later replace it with less efficient (higher wattage) lighting.

Why This is Likely an Oversight



No Stated Intent

Code changes are usually accompanied by explanations from the Code Making Panels (CMP) in the Report on Proposals (ROP) and Report on Comments (ROC). There's likely no explicit intent stated to eliminate the minimum lighting load from the optional school calculation. This strongly suggests it's an unintended consequence.

Potential Safety Implications

As mentioned above, the removal of the minimum could lead to undersized services in the long run, potentially creating safety hazards.

Lack of Awareness

As you pointed out, most electricians, engineers, and inspectors might miss this subtle but significant change.

What You're (Probably) Not Missing

You're not missing anything from a strict interpretation of the 2023 NEC. You've accurately identified the conflict and the potential consequences.

What To Do


AHJ Interpretation

The first step is to consult with your Authority Having Jurisdiction (AHJ). Explain your concern and ask how they interpret the code in this situation. The AHJ's interpretation is the one that matters.2.

Document Your Reasoning

If the AHJ agrees that the strict interpretation removes the minimum lighting load, document your calculations thoroughly, and include a note indicating the potential limitations and concerns.3.

Conservative Design

Even if the AHJ allows the connected load calculation without a minimum, strongly consider applying the minimum lighting load requirements anyway. It adds a safety factor and provides a more robust design that can handle future lighting changes. You can document this as an "over-sizing" or "safety factor" added to the calculation.4.

Code Change Proposal

Consider submitting a code change proposal to the NEC for the next code cycle (2026). The proposal should clearly state the problem, the unintended consequences, and suggest a solution to re-integrate the minimum lighting load requirements into the optional school calculation (e.g., a specific reference back to Table 220.42(A), or a statement that the general lighting load shall be no less than that required by 220.42).
5.

Clarification Request

You can also submit a formal interpretation request to NFPA (National Fire Protection Association, the publisher of the NEC). While they don't issue formal opinions, they can provide guidance and insights from the CMP members.

In Conclusion:

You've discovered a very real and potentially problematic issue in the 2023 NEC. While the code technically supports your interpretation, the practical implications and potential safety concerns suggest it was likely an oversight. By documenting the issue, consulting with your AHJ, designing conservatively, and considering a code change proposal, you can help ensure safer and more reliable electrical installations in schools.Your "chills" are justified! It's precisely this kind of critical thinking that keeps the NEC evolving and electrical installations safe. Good catch! Flag for review