Yes, your understanding is correct. The NEC does allow a feeder tap of 10 feet or less to supply multiple overcurrent protective devices (OCPDs), provided the conductor sizing and other requirements are met. The critical difference lies in the explicit wording of 240.21(B)(2) which imposes the "single circuit breaker or single set of fuses" limitation on 25-foot taps. This restriction is absent in 240.21(B)(1) for 10-foot taps.Here's a breakdown: 240.21(B)(1) - 10-Foot Tap Rule

This section allows for greater flexibility. The tap conductors can supply multiple OCPDs as long as the tap conductors meet the following requirements: The ampacity of the tap conductors is: Not less than 10% of the rating of the overcurrent device protecting the feeder. Not less than the sum of the calculated loads on the circuits supplied by the tap conductors. Not less than the rating of the OCPD at the termination of the tap conductors. The tap conductors are enclosed in a raceway or otherwise protected from physical damage. The tap does not extend beyond 10 feet.

240.21(B)(2) - 25-Foot Tap Rule

This rule is more restrictive. The tap conductors must terminate in a single circuit breaker or single set of fuses that will limit the load to the ampacity of the tap conductors.

Example and Considerations for your Specific Scenario

Your example of a tap from a feeder to a circuit breaker, then continuing with the same wire size and double wire ferrules to another breaker, can be permissible under the 10-foot tap rule IF all the requirements are met:1.

Tap Length

The total length of the tap conductor (from the feeder to the farthest overcurrent device) must not exceed 10 feet.2.

Ampacity

The tap conductor ampacity must be adequate: At least 10% of the feeder overcurrent device's rating. Sized to carry the sum of the loads on both circuit breakers (the loads connected to each breaker downstream). The ampacity must also be equal or greater than the overcurrent protective device connected to the downstream side of the tap conductors.3.

Proper Terminations

The connections with double-wire ferrules must be properly rated and installed for the application. They must maintain the integrity of the connection and be suitable for the conductor size and ampacity. The method of connecting multiple breakers to a single tap conductor is the critical part of this scenario. Using listed and labeled connectors, such as power distribution blocks, is more common and reliable.4.

Protection

The tap conductors must be properly protected from physical damage (e.g., in conduit, raceway).

Important Considerations and Cautions



Local Amendments

Always check for local amendments to the NEC. Some jurisdictions may have stricter rules regarding tap conductors.

Engineering Judgment

It's generally better practice, whenever feasible, to avoid taps, especially if they are supplying multiple loads. A dedicated feeder is often a cleaner and safer design.

Coordination

Ensure proper overcurrent protection coordination between the feeder breaker and the branch circuit breakers.

Documentation

Document the tap design thoroughly, including conductor size, ampacity calculations, and the basis for meeting all NEC requirements. This is especially important if the design is complex.

AHJ Approval: It's always a good idea to discuss complex or unusual tap applications with the Authority Having Jurisdiction (AHJ) for their input and approval before installation.In summary, while the NEC does allow a 10-foot tap to supply multiple OCPDs, it's crucial to ensure that all requirements are meticulously met. Always prioritize safety and code compliance. The example you provided is possible, but requires careful consideration of the connection methods and all relevant requirements. It's often best practice to use a power distribution block or similar device for distributing power from a tap to multiple OCPDs rather than relying on double-wire ferrules directly connected to breakers. Flag for review