You're right to be cautious and question this design. Let's break down the NEC 230.2 and its implications for your situation in Tulsa (2023 NEC).

Your Analysis is Correct

Based on the information provided, you are correct in identifying this as likely violating the intent of a single service as defined by the NEC. Here's why: 230.2 Number of Services

The general rule in 230.2 states that a building or other structure shall be supplied by only one service.

Exceptions 230.2(A) through (D)

These exceptions outline very specific circumstances where multiple services are permitted. From your description, none of these seem to apply:

(A) Fire Pumps

Not applicable (no fire pump)

(B) Emergency Systems

Not applicable (no emergency system)

(C) Parallel Power Production Systems

This is often used for solar or wind systems connected in parallel with the utility grid, which isn't mentioned in this case.

(D) High Rise Buildings

Not applicable (not a high rise building)

230.2(E) Special Occupancies

Since your building is single occupancy and exceptions (A) through (D) do not apply, you are not able to consider this option.

Why Two Service Laterals Aren't Allowed Here

The key factor is that you have two separate service laterals coming from the transformer to two distinct service disconnects. This establishes two completely separate services, and none of the exceptions to the single service rule seem to apply.

Potential Problems & Concerns NEC Violation

This is the most immediate concern. If the electrical inspector views it as a violation of 230.2, they can reject the installation.

Confusion and Safety

Having two services, even with the same voltage and single occupancy, can create confusion for maintenance, troubleshooting, and emergency responders.

Metering Issues

While the CT's are at the transformer, the billing may not be correct for a single occupancy building

Redundancy Questionable

This set up is intended to improve redundancy, but the transformer is still the only power source.

Future Modifications

Adding more power in the future becomes more complicated.

What to Do1. Consult the Local Authority Having Jurisdiction (AHJ)

This is crucial. Reach out to the Tulsa electrical inspector and specifically ask about the two service lateral situation and why they're allowing it if exceptions A-D don't apply. Get their interpretation in writing if possible.2.

Request a Written Justification

Ask the designer/engineer for a written explanation of why they believe this installation meets the requirements of the NEC, specifically addressing 230.2 and the relevant exceptions. They should provide code references and a clear rationale.
3.

Consider Alternatives

If the two-service approach isn't defensible, explore alternatives that would comply with the NEC:

Single, Larger Service

The most common solution is to install a single service with a capacity sufficient for the entire building (existing + addition). This would involve a larger service lateral, a larger service disconnect, and potentially an upgrade to the distribution panel(s).

Sub-Metering

If the utility has specific reasons for the CT location at the transformer, consider a single service and then sub-meter the addition for internal accounting or tenant billing (if applicable - which it doesn't seem to be).

Load Calculations

Ensure a thorough load calculation is performed for the entire building (existing + addition) to accurately determine the required service capacity. This is critical to avoid undersizing the service.4.

Documentation

Keep meticulous records of all communications, code interpretations, and design justifications related to this issue. This will be essential if questions arise later during inspection or operation.

In summary:

Your initial assessment that this likely violates NEC 230.2 is well-founded. Before proceeding, you must* get clarification from the AHJ and a clear, code-compliant justification from the design team. Don't rely on assumptions; get it in writing. Flag for review