You're right to question this setup and understand the intent of NEC 230.71(B). Let's break it down

NEC 230.71(B) is about Limiting the Number of Disconnects.

The core purpose of 230.71 is to limit the number of service disconnects at each service. This makes it easier and safer to disconnect all power to a building or a specific service. The rule generally limits a building to no more than six service disconnects for each service.

Scenario Analysis

In your scenario, you have:

One set of service entrance conductors. One MLO (Main Lug Only) panelboard. Four branch breakers in the MLO panelboard, each feeding a sub-panel.

Does this violate 230.71(B)? If the breakers in the MLO panelboard are rated to serve as service disconnects, then YES, this violates 230.71(B). The four breakers, each considered a service disconnect, exceed the limit of six. If the breakers in the MLO panelboard are not rated to serve as service disconnects, then the answer is less clear and relies on the interpretation of the AHJ. Some would argue that the MLO panelboard, in itself, is the service disconnect. In this case, you would be in compliance.

Why the Concern About Compartments?

You mention your concern about separate compartments, and this is a valid point. NEC 230.71(B) requires that where service disconnecting means are grouped, they are located in a readily accessible location and that the disconnects are permanently marked to indicate the load served and the disconnect or overcurrent device that controls it. This requirement is indirectly related to the total number of disconnects allowed. While not explicitly stating "separate compartments," the intent is to ensure that each disconnect can be easily identified and accessed. A jumble of unmarked breakers in a single panel does not fulfill this intent.

Possible Solutions to Comply with NEC


Single Main Disconnect

The best practice is to install a single main disconnect ahead of the MLO panelboard. This single disconnect would serve as the service disconnect, and the panelboard would then act as a distribution panel. The four breakers would then be branch circuit breakers and not service disconnects, making them exempt from the 230.71(B) limitation.
2.

Separate Enclosures with Main Disconnects

Instead of an MLO panelboard, you could have four separate service-rated disconnects, each in its own enclosure, fed by the service entrance conductors. This is less common but acceptable if you are only supplied by one service entrance and will never exceed six disconnects.

Important Considerations



Rating of the Breakers

Check the ratings of the breakers in the MLO panelboard. Are they listed and labeled for use as service equipment? If so, they are service disconnects.

Local AHJ (Authority Having Jurisdiction)

The interpretation of the NEC can vary slightly by location. Always consult with your local inspector to get their opinion and ensure compliance. They have the final say.

Load Calculations

Ensure your service entrance conductors and the MLO panelboard are adequately sized for the total calculated load of all the sub-panels they feed.

Clear Labeling

Regardless of the configuration, clear and permanent labeling is crucial. Each disconnect must be clearly marked to indicate the load it serves and the circuit or breaker that controls it.

In Conclusion:

While your scenario technically could* be compliant in some interpretations, it's generally poor practice and often violates the spirit and intent of NEC 230.71(B). The single main disconnect approach is the safest and most straightforward way to comply with the code and provide a clear and safe method for disconnecting power to the building. When in doubt, consult with your local AHJ for their specific interpretation and requirements. Flag for review