Okay, let's break down the requirements for feeding the second building from the first. Based on the information you provided, here's a breakdown of the code and considerations

Key Considerations (NEC 2023):

1. Feeder Calculation: You need to calculate the total load that the second building will draw. This will determine the required ampacity of the feeder conductors and the overcurrent protection (OCPD). NEC Article 220 outlines the requirements for calculating loads. Don't just guess; do the math. Consider lighting, receptacles, any appliances, and any future expansion.2. Feeder Overcurrent Protection

The size of the feeder overcurrent protection device (circuit breaker or fuses) must be sized to protect the feeder conductors based on their ampacity. The overcurrent protection device

cannot be larger than the ampacity of the conductors. (NEC 240.4(B))3. Building Disconnect The building which gets power must have a disconnect. NEC 225.314. Conductor Size

The conductor sizes must be large enough to carry the calculated load to the second building. Use NEC Table 310.16 (or appropriate tables for the conductor type) to determine the ampacity of the conductors.
5.

Grounding

Proper grounding is crucial. You'll need a grounding electrode system at the second building (if it meets the criteria in 250.32). This generally involves a grounding electrode conductor (GEC) connected to a ground rod, ground ring, or other approved grounding electrode.

Addressing Your Specific Questions



MCB (Main Circuit Breaker) at the Second Building

NEC 225.31 says the second building must have a disconnect.

The need for an MCB in the second panelboard depends on its design and intended use, and the rating of the panelboard itself. The panelboard must be rated for the available fault current at its location.

In many cases, you will need an OCPD (like a circuit breaker) at the point where the feeder enters the second building. This is because: It acts as the required disconnect for the second building, and It can provide additional overcurrent protection specifically for the branch circuits in that building.

Feeder from the First Panelboard

You'll need to install a new circuit breaker in the first panelboard to feed the second building. The size of this circuit breaker is determined by the calculated load of the second building and the ampacity of the conductors you choose.

Example Scenario (Illustrative - Requires Accurate Calculations)

Let's say your calculated load for the second building is 30 amps. You might choose:

First Panelboard

Install a 30 amp circuit breaker.

Feeder Conductors

Use #10 AWG copper THHN conductors (rated for at least 30 amps in most installations - verify based on the installation conditions).

Second Panelboard

Install a 60 or 100 amp panelboard with a 30 amp main breaker.

Grounding

Install a ground rod at the second building and connect it to the panelboard's grounding busbar with a GEC of the appropriate size.

Critical Warnings & Recommendations



DO NOT guess at the loads! Accurate load calculations are essential for safety and code compliance. Consult NEC Article 220.

Bonding and Grounding

Proper grounding and bonding are crucial for safety. Review NEC Article 250 carefully.

Professional Assistance

Given the potential hazards of electrical work, it is strongly recommended that you consult with a qualified and licensed electrician for this project. They can perform the necessary load calculations, ensure code compliance, and safely install the wiring and equipment. Improper electrical work can lead to fire, electrocution, and property damage.

Permits

Check with your local building department about required permits for this type of electrical work.

In summary, while an MCB is not strictly required in the second panel if it's rated to the size of the feeder breaker and serves as the main disconnect and the load calculation is small, you will likely want an OCPD in the second building to serve as the building disconnect. Always perform proper load calculations, adhere to the NEC, and consider professional assistance. Flag for review