You've identified a tricky situation that hinges on how the NEC interprets and allows for equipment with internal overcurrent protection devices (OCPDs). Here's a breakdown of the issues and a possible solution, along with NEC references

Understanding the Issue
Your Understanding is Correct

You are correct in noting that Table 210.24(B) dictates the permissible loads and outlet ratings on a given branch circuit. Generally, a 20A circuit must have 20A rated receptacles and can't feed more than 16A of continuous load.

UPS Internal Breaker

The UPS manufacturer's argument is that the 25A internal breaker provides the necessary overcurrent protection for the receptacles connected to the UPS output.

NEC Concerns

The NEC generally requires that the branch circuit breaker provides overcurrent protection for the wiring and the connected receptacles. Relying solely on the internal UPS breaker can be problematic under certain NEC interpretations.

NEC Considerations & Potential Conflicts1. Article 400.8 (Uses Not Permitted)

Hardwiring multiple receptacles from a UPS output could be interpreted as creating a permanent wiring system that is not permitted, as the UPS and receptacles are not typically designed to be a permanently installed distribution system.2.

Article 210.20(A) (Overcurrent Protection - Conductor Protection)

This article requires that the overcurrent protection device (in this case, the upstream breaker) must protect the branch circuit conductors. Your 30A breaker and #10 AWG are fine for feeding the UPS, but they don't necessarily protect the receptacles connected to the UPS output.3.

Article 210.21(B) (Receptacle Ratings)

This article dictates that a 20A branch circuit must have 20A-rated receptacles. You meet this requirement.4.

Article 240.3(D) (Small Conductors)

This is not necessarily applicable in your situation since you are running #10 AWG wire, but if you had used smaller wire, this article would further reinforce that the OCPD must protect the wire as well as the receptacle.5.

Article 645.5(A) (Supply Circuits and Interconnecting Cables)

Equipment in Information Technology Equipment (ITE) and Data Rooms may be subject to alternative requirements.

Possible Solution(s) and NEC References Using a Power Distribution Unit (PDU)

This is often the cleanest and most NEC-compliant solution. Install a PDU specifically designed for UPS output. PDUs often have: A single input connection to the UPS. Multiple 20A output receptacles. Individual overcurrent protection for each receptacle (e.g., 20A breakers).

Why this works

The PDU becomes a listed sub-assembly. Its internal breakers provide the required overcurrent protection for the downstream receptacles. The 30A breaker upstream of the UPS provides protection for the UPS's input wiring and the #10 AWG feeder conductors.

Dedicated Branch Circuit for Each Receptacle

Run individual 20A branch circuits from your electrical panel to each 20A receptacle near the UPS. This is less practical and potentially more expensive, but it's a very clear-cut NEC-compliant solution.

Important Considerations & Recommendations Listing and Labeling

Ensure all equipment used (UPS, PDU, receptacles) is properly listed and labeled by a recognized testing laboratory (UL, ETL, etc.). The labeling will provide valuable information about the equipment's intended use and compliance with relevant standards.

Local AHJ (Authority Having Jurisdiction)

This is crucial. Contact your local electrical inspector to discuss your proposed setup. They have the final say in how the NEC is interpreted and enforced in your area. They may have specific requirements or interpretations that you need to follow.

Manufacturer Documentation

Carefully review the UPS manufacturer's installation instructions and any supporting documentation regarding overcurrent protection and branch circuit requirements. Get their documentation in writing, if possible.

In summary, while the UPS manufacturer's claim might* seem logical, relying solely on the internal UPS breaker to protect the receptacles on its output can be problematic under the NEC. Using a PDU with its own internal OCPDs is generally the most compliant and practical solution. Always consult with your local AHJ to ensure your installation meets all applicable codes and regulations. Flag for review