Okay, let's break down this fault current labeling conundrum, focusing on your specific points.

Understanding the Code Sections 110.16(B) – Service Equipment Rated 1200 Amperes or More

This section specifically mandates arc-flash hazard warning labels on service equipment rated 1200A or more. It's a distinct requirement, independent of 110.24.

110.24(A) – Available Fault Current

This is the primary rule requiring fault current labeling at the service equipment. It aims to inform electricians (qualified persons) about the potential hazard during an arc-fault condition.

110.24(B) – Modifications

This section triggers a re-evaluation and update of the 110.24(A) labeling when modifications (like your PV installation) could affect the available fault current at the service. This is where your pain point arises.

Addressing Your Questions1. Is 110.24(A) Unenforced, or is the 110.24(B) Exception Used? This is the core of your question and the most variable aspect. The answer is likely a mix of all three: Underreporting

Often the initial labeling is not done. (The original installation predates current NEC requirements, or it was overlooked. )

Exception Usage

The exception in 110.24(B) regarding qualified persons serving the equipment in industrial establishments is frequently used, particularly in larger industrial facilities. These facilities often have comprehensive electrical safety programs, documented procedures, and only qualified personnel working on the equipment.

Inconsistent Enforcement

Yes, this is also true. Enforcement of NEC provisions varies widely by jurisdiction and inspector. Some inspectors are more diligent and focused on specific rules than others. There is often confusion between 110.16 and 110.
24.2.

Can You Argue for the Exception to Apply to Your PV Installations? This is tricky. While the facility might be an industrial facility, the specific service equipment your PV system interacts with might not fall under the exception's intent. Consider this: Who Services the Equipment? The key question is: who will be the exclusive personnel working on the AC disconnect and associated service equipment? If only qualified personnel from the industrial facility will ever work on it, you have a stronger case. Documentation is Key

If you want to argue the exception, you need to provide documentation demonstrating: The facility's electrical safety program. Evidence that only qualified personnel will service the equipment. A signed statement from the facility owner/operator accepting responsibility for maintaining the equipment and fault current labeling, in accordance with the program.

Inspector Discretion

Ultimately, the inspector has the final say. Be prepared to explain your reasoning clearly and respectfully.3.

How to Handle Being Asked to Update a Nonexistent Label? This is a common problem. Here’s a suggested approach: Document the Existing Situation

Take photos of the service equipment clearly showing the absence of a fault current label.

Communicate with the Inspector

Start by politely asking the inspector if they are sure that the service equipment label is nonexistent. Let the inspector explain their point of view.

Offer a Compromise

If the inspector insists on an updated label, suggest one of the following options:

Perform a Fault Current Calculation

Perform a fault current study at the service equipment to determine the available fault current and affix a label reflecting that value. (This will likely require involving a qualified engineer.)

Affix a Warning Label

Place a label that says: "Available Fault Current Not Determined. Contact Qualified Personnel for Information." This acknowledges the requirement while stating that the full information is not currently available.

Reiterate the Exception

Make your argument as above.

Escalate if Necessary

If you can't reach an agreement with the inspector, escalate the issue to their supervisor or the local electrical authority.

Additional Considerations PV System Contribution

While the fault current contribution from most PV systems is often negligible, this is a calculation issue. You can make that argument, backed up with calculations, but inspectors may still be required to ask for the labeling regardless.

NFPA 70E

You are correct that NFPA 70E is not enforceable unless it's adopted into law or regulation by the jurisdiction. However, many companies adopt it as a best practice for worker safety. The inspector might be referencing it as a rationale, but they should be basing their requirements on the NEC.

2023 NEC

Make sure you are aware of the newest 2023 NEC requirements in this area, including the expansion of the definition of "qualified person."

In summary: Document everything. Communicate clearly with the inspector. Be prepared to perform a fault current study if necessary (or at least provide a basic calculation). Make your argument for the exception based on the facts of the installation and the facility's electrical safety program.* Understand that you might have to compromise.It's also worth noting that some AHJs (Authorities Having Jurisdiction) have developed their own specific interpretations and requirements related to fault current labeling, so research your local requirements as well.Good luck! Flag for review