You are correct in your understanding of the NEC. Here's a breakdown of why, and the relevant NEC sections: NEC Article 430 - Motors, Motor Circuits, and Controllers

This article covers requirements for motors, including disconnecting means.

NEC 430.102(A) Location

The disconnecting means must be within sight from the motor controller location. In your case, the MCB is the motor controller.

NEC 430.102(B) Location

If 430.102(A) is not practical or creates a hazard, 430.102(B) allows the disconnecting means to be remote.

NEC 430.107 - Readily Accessible

The disconnecting means must be readily accessible. Typically, this means not blocked or requiring tools to access.

NEC 430.109 - Type

The disconnecting means must be a switch, circuit breaker, or molded case switch.

NEC 430.109(A)(6) - Stationary Motor of 1 Horsepower or Less

A horsepower rated switch rated in accordance with 430.81(C) or a general use snap switch suitable only for use on ac (not general use ac/dc switches) where the motor full-load current does not exceed 80% of the ampere rating of the switch.

NEC 430.109(E) - Cord and Plug Connected

If the motor is cord-and-plug connected, a horsepower-rated attachment plug and receptacle are permitted to serve as the disconnecting means.

Your Specific Situation

You've stated that the MCB (Motor Control Box) is located adjacent to the 100amp service panel, less than 12 inches away. This means the circuit breaker in the service panel is clearly

within sight of the MCB. Assuming the breaker is readily accessible and meets the requirements of 430.109, the breaker can function as the disconnecting means for the MCB, provided it is rated appropriately for the motor's size and voltage.

Verification

Yes, based on the information you provided, the circuit breaker in the service panel

can serve as the disconnecting means for the MCB, and a separate fused disconnect is not required if the following conditions are met:1. Within Sight

The breaker is clearly visible from the MCB.2.

Readily Accessible

The breaker is readily accessible.3.

Rated Appropriately

The breaker is sized appropriately for the motor connected to the MCB (check the motor's nameplate for its Full Load Amps (FLA) and voltage). The breaker must have an interrupting rating sufficient for the available fault current.4.

Suitable Switch Type

The switch type must be appropriate as noted above in 430.109(A)(6).
5.

Marking: The circuit breaker or switch should be clearly and permanently marked to indicate that it is the disconnecting means for the MCB.

Important Considerations



Local Codes

Always check with your local electrical inspector or authority having jurisdiction (AHJ). Local codes may have stricter requirements than the NEC.*

Manufacturer's Instructions

While the NEC may allow the breaker to serve as the disconnect, always adhere to the pump manufacturer's specific instructions and recommendations, especially if those instructions involve safety procedures. If their manual insists on a separate disconnect, it's wise to follow it for warranty and liability reasons.

In summary, you're likely correct, but double-check the breaker's rating, accessibility, suitability, and consult with your local AHJ and the pump manufacturer's documentation to ensure full compliance. Flag for review