Okay, let's break down the feasibility and code considerations for your project, focusing on the electrical service arrangement you're proposing.

Understanding the Concept

You want to install two separate services: 200A Service

Dedicated solely to the 2500 sq ft shop.

400A Service

Located at the shop but dedicated to the 11,500 sq ft house, with an underground feed.

Code Considerations (NEC - National Electrical Code)

This setup can be permissible under the NEC, but it requires careful attention to several factors:1. NEC 230.2 (Number of Services)

The NEC generally allows one service to a building or premises. However, there are specific exceptions outlined in 230.2(A) through (D). The most relevant exception for your situation is likely 230.2(A)(1).

230.2(A)(1) Special Conditions

This section allows for multiple services when the occupancy is large enough to require more than one service. In particular, your local authority having jurisdiction (AHJ) will make the final decision.

230.2(A)(2) Different Characteristics

Where different characteristics, such as variations in voltage, frequency, or phase, are required.

230.2(A)(3) Capacity Requirements

Where the capacity requirements exceed the service equipment limitations of the AHJ.2.

NEC 230.40 (Number of Service-Entrance Conductor Sets)

This section dictates how many sets of service-entrance conductors can be connected to a service. Since you propose two separate services, this is generally not a problem.3.

NEC 225.30 (Number of Supplies)

This section limits the number of supplies to one building to one. However, exception number one states: "For large buildings, the capacity requirements exceed the service equipment limitation of the AHJ." This would be the exception to follow to allow for multiple services.4.

NEC 225.32 (Disconnecting Means)

This section requires a disconnecting means for each building (house) to be installed at a readily accessible location, either inside or outside.5.

NEC 230.71 (Maximum Number of Disconnects)

This section specifies the maximum number of disconnects permitted in a single service. You'll need to ensure your service equipment complies. Usually, a single service disconnect is preferred.6.

Grouping of Disconnects (NEC 230.72)

The disconnects for both services need to be grouped and readily accessible. This is critical. You can't have one disconnect in one part of the shop and another somewhere else. They must be together, or very close. This makes it clear to emergency personnel and anyone working on the system where all power can be cut.7.

Wiring Methods (NEC Chapter 3)

You'll need to adhere to the NEC's requirements for underground wiring (conduit type, burial depth, etc.) for the 400A feeder to the house. This is covered in Article 300 (Wiring Methods) and Article 310 (Conductors for General Wiring).8.

Overcurrent Protection (NEC Article 240)

Proper overcurrent protection (circuit breakers or fuses) is essential at the service entrance for both the 200A and 400A services, and at the house end of the underground feeder.9.

Grounding and Bonding (NEC Article 250)

This is crucial. Both services must be properly grounded and bonded to the grounding electrode system. The grounding electrode system typically consists of a ground rod, metal water pipe (if properly bonded), and/or a concrete-encased electrode (Ufer ground). The house also needs its own grounding electrode system, bonded to the neutral conductor at the main panel. The path for ground-fault current to return to the source is vital for safety.10.

Load Calculations (NEC Article 220)

Accurate load calculations are essential for both the shop and the house to justify the 200A and 400A service sizes. Over-sizing is wasteful and unnecessary.11.

Local Amendments

Always remember that local jurisdictions can amend the NEC. What's allowed in one area might not be in another.

Practical Considerations Utility Company

The local power company is the ultimate decision-maker. They will have their own requirements and may or may not allow two separate services to a single customer. You must discuss this with them early in the planning process. They may require specific metering arrangements.

Cost

Get detailed quotes for both options (two services vs. one larger service). Factor in the cost of the additional service equipment, trenching, wiring, disconnects, and any additional fees from the utility company.

Space

Ensure you have adequate space in the shop for the service equipment (meter socket, disconnects, panels) for both services.

Future Expansion

Consider potential future electrical needs for both the shop and the house. Could one larger service offer more flexibility in the long run?

Resale Value

While not a code issue, consider how the two-service setup might affect the resale value of the property. Some buyers might prefer a single, larger service.

Recommendations1. Consult with the AHJ (Authority Having Jurisdiction)

This is the MOST IMPORTANT step. Meet with your local building inspector or electrical inspector and discuss your plans before you start any work. Get their approval in writing if possible. Explain the reasoning for wanting two separate services.2.

Consult with a Licensed Electrical Contractor

Engage a qualified and licensed electrical contractor to perform load calculations, design the electrical system, and handle the installation. They will be familiar with local codes and utility company requirements.3.

Contact the Utility Company

As mentioned, talk to the power company early on to determine their policies regarding multiple services.4.

Document Everything

Keep detailed records of all communication with the AHJ and the utility company, as well as all permits, inspections, and approvals.

In Summary

Your plan is potentially acceptable under the NEC, provided you meet the requirements of NEC 230.2 and 225.30, properly size the services based on load calculations, and adhere to all other applicable code requirements. However, the approval of the AHJ and the utility company is essential. Consulting with a licensed electrical contractor is crucial to ensure a safe, code-compliant, and cost-effective installation. Flag for review