You're not misunderstanding. The AHJ is likely misinterpreting the code. Let's break down why: 705.12(B)(1) explicitly allows "ONE or MORE power source(s) shall have its own overcurrent device." The "or more" is key. This clearly anticipates the possibility of multiple PV systems (power sources) connecting to a single service panel, each with its own breaker. 705.12(B)(2) and (3) (the 120% rule) provides additional requirements for those power sources connected using the backfed breaker method. The fact that these sections even exist and use the term "power source(s)" implies that multiple PV systems can feed back through the bus bar. If only one were ever allowed, these sections wouldn't need to exist or be phrased as they are. The intent of the NEC is safety and preventing overloading, not arbitrarily limiting the number of PV connections. The 120% rule is precisely how the NEC addresses safe connection of multiple PV systems.

Your position is strong. Here's how to proceed

1.

Politely Request Clarification

First, assume good faith. Contact the AHJ and politely ask them to clarify their reasoning. Ask them to specifically point to the exact language in the NEC that supports their interpretation that only one PV breaker is allowed regardless of the 120% rule.2.

Present Your Argument

Be prepared to explain your understanding of the NEC articles: "Article 705.12(B)(1) states that ONE or more power sources shall have its own circuit breaker or fusible disconnect means. This clearly allows for multiple PV systems." "Articles 705.12(B)(2) and (3), the 120% rule, provide the means for safely connecting multiple power sources by ensuring that the combined rating of all overcurrent devices supplying power to a busbar section doesn't exceed 120% of the busbar's rating." "My design complies with the 120% rule and all other applicable NEC requirements, ensuring the safety of the system." "Requiring only one PV breaker per service panel would severely restrict the adoption of solar energy, contrary to the spirit of promoting renewable energy sources."3.

Bring the Plans Examiner into the Conversation

If possible, involve the head of the permitting department or the plans examiner for electrical systems. A second opinion within the AHJ can sometimes resolve the issue.4.

Refer to the NEC Handbook or a Qualified Electrical Engineer

The NEC Handbook often provides further explanation and examples that can support your interpretation. If needed, consider consulting with a licensed electrical engineer who specializes in PV systems. They can provide a professional opinion letter supporting your design's compliance with the NEC. This carries significant weight with AHJs.5.

Consider an Alternative Interpretation Request

If the AHJ remains unconvinced, you might* consider formally submitting an "interpretation request" to the AHJ, requesting a written interpretation of their policy. This forces them to formally justify their position. This can be a more confrontational approach, so use it as a last resort.

In summary: You are likely correct. The AHJ's interpretation appears flawed. Politely and professionally advocate for your interpretation of the code, providing clear references and, if necessary, expert support. Good luck! Flag for review