Okay, let's break down this situation with the code requirements, your arguments, and potential solutions.

Understanding the Code (NEC 230.79) NEC 230.79 is about the Minimum Size of Service Disconnecting Means. It specifies the minimum amperage ratings for the main disconnect that controls the entire service. The rule is not necessarily referring to your apartment sub panels. (D) One-Family Dwelling. For a one-family dwelling, the service disconnecting means must have a rating of not less than 100 A, three-wire. (C) Other Installations. For all other installations, the service disconnecting means shall have a rating of not less than 60 A.

Your Scenario



Problem

An inspector is interpreting NEC 230.79(C) to require you to upgrade the apartment subpanel feeder (from the meter to the apartment panel) to 60A when replacing Zinsco or FPE panels, even if the existing service is 40A.

Your Position

You believe that this requirement only applies to new installations and not replacements of existing equipment like-for-like. You also highlight the significant disruption and cost of upgrading the wiring in older apartments.

Arguments and Considerations


"Like-for-Like" Replacement vs. New Installation

This is the crux of the issue.

Your Argument is Strong

In general, electrical codes aim to improve safety and are typically

not retroactive unless there's an explicit mandate. Requiring a full service upgrade for a panel replacement goes beyond a "like-for-like" repair. Like for like means replacing equipment with the same thing without making changes to anything else. Inspector's Perspective

The inspector might be taking a stricter interpretation, arguing that any panel replacement triggers a review of the entire service to ensure it meets current code minimums. Their argument may also stem from a concern about the safety of undersized services in older buildings.

Important: Check Local Amendments

Los Angeles County or the specific city may have local amendments to the NEC that further clarify or modify this requirement. This is critical to your case. Contact the County of Los Angeles Department of Building and Safety.2.

Existing Load vs. Potential Load



Existing Load

Do the apartments actually need 60A? Has the actual load on these 40A services ever been close to the limit? If you have data showing the actual load is well below 40A, this weakens the inspector's argument. Documenting the existing load is important.



Potential Load

The inspector might be looking at the potential for increased load. If someone installs a large window AC unit, electric heaters, etc., the 40A service could be overloaded.

California Energy Code (Title 24)

This code dictates energy efficiency requirements, and that may influence load considerations.3.

Safety Implications



Your Position

Replacing a known hazard (Zinsco/FPE) with a safer panel is a significant improvement in safety, even if the service isn't upgraded.

Inspector's Position

An undersized service can lead to overloaded circuits, overheating, and potentially fire hazards.4.

Practicality and Cost

Rewiring the entire complex is a massive undertaking, both financially and logistically. The cost to the owners will be very significant.

Steps to Take


Research Local Amendments

This is the most important step. Contact the Los Angeles County or the city's building department and ask if there are any local amendments or interpretations regarding panel replacements and service upgrades, referencing NEC 230.79. Find out if it's just this inspector's opinion or an official policy.
2.

Document Existing Loads

If possible, use a clamp meter to measure the actual current draw on the service feeders during peak usage times. This data can be presented to the inspector to show that the 40A service is adequate.3.

Prepare a Written Explanation

Prepare a written explanation of your position, citing the following: The "like-for-like" replacement principle. The lack of local amendments requiring service upgrades. The measured existing load. The significant cost and disruption of rewiring. The enhanced safety from replacing the Zinsco/FPE panel, even without a service upgrade.4.

Meet with the Inspector (and their Supervisor)

Schedule a meeting with the inspector, and if possible, their supervisor, to discuss the issue. Present your written explanation and supporting data. Be professional and respectful, but firmly advocate for your position.5.

Consider an Independent Electrical Engineer

If the inspector remains firm, consider hiring a licensed electrical engineer to review the situation and provide an independent assessment. Their professional opinion can carry significant weight.6.

Seek a Formal Interpretation

If all else fails, you can request a formal interpretation of the code from the relevant authorities (e.g., the Los Angeles County Department of Building and Safety, or even the ICC (International Code Council, which publishes the NEC)). This process can be time-consuming, but it provides a definitive answer.7.

Alternative Solutions (Compromises)

Explore options that improve safety without a full rewire:

Load Calculation

Perform a formal load calculation (using NEC Article 220) to justify the adequacy of the existing 40A service.

Oversized Neutral

Check the neutral conductor size. If it's significantly oversized (common in older installations), that can help mitigate potential issues.

Consider a 60A Sub-Panel on the Existing 40A Service

While counterintuitive, you could replace the existing 40A panel with a 60A panel and label it clearly: "Max. Breaker Size = 40A". This allows for future expansion if a service upgrade is done later. This is not allowed and considered to be bad practice.

Important Considerations



Liability

If you proceed with the panel replacement without upgrading the service and the inspector insists it's a violation, you may be exposed to liability if a problem arises later.

Communication with Building Owners

Keep the building owners informed of the situation and the potential costs involved. Explain the pros and cons of upgrading the service versus a like-for-like replacement.Good luck navigating this situation. It's a common challenge in older buildings. Remember to be thorough in your research, documentation, and communication.
Disclaimer: I am an AI chatbot and cannot provide professional electrical engineering or legal advice. Consult with qualified professionals for specific guidance on your project. Flag for review