Okay, let's break down your plan and address the electrical considerations.

Understanding Your Current Setup 400 AMP Service

This means the utility company is providing you with a service capable of delivering 400 amps of electrical current to your property.

Two 200 AMP Panels

This is a common way to distribute a 400 amp service. Each panel acts as a separate distribution point within your house, each capable of handling 200 amps. Importantly, these two 200 amp panels likely pull from separate legs of the 240v feed from your service.

Your Proposed Plan: Splitting to the Garage/Barn

You are suggesting:1. Take 100 amps from Panel A (200A)2. Take 100 amps from Panel B (200A)3. Run each 100 amp feed to separate 100 amp panels in the Garage/BarnHere's the analysis



Technically Feasible (With Caveats)

Yes, your plan can work,

IF you carefully calculate the load on each of your existing house panels and ensure you aren't exceeding their individual 200 amp capacity. NEC Requirements

This is the most important aspect. Your plan must comply with the National Electrical Code (NEC) and any local amendments. Specifically:

Load Calculations

You absolutely must perform a load calculation for your entire house and for the planned usage in your garage/barn. This calculation determines the actual amperage draw under various scenarios. You cannot simply assume you have 200 amps available in each panel. Factors to consider include: Square footage of your house and garage/barn Number of circuits and their intended usage (lighting, outlets, appliances, etc.) Large appliances (HVAC, water heater, electric stove/oven, dryer, etc.) Any other loads (e.g., hot tub, electric vehicle charger)

Feeder Size

The wire size for the 100 amp feeders to the garage/barn must be correctly sized to handle 100 amps, per NEC tables.

Overcurrent Protection

You need properly sized breakers in your house panels to protect the feeders to the garage/barn (100 amp breakers).

Grounding and Bonding

Proper grounding and bonding are absolutely critical for safety. You'll need to ensure a proper grounding electrode system at the garage/barn and correct bonding of all metallic components.

Disconnecting Means

A main disconnect (breaker or switch) is required at the garage/barn to shut off all power to the building.

Important Considerations & Potential Problems


Load Balancing

It's crucial to distribute the loads in your garage/barn as evenly as possible between the two 100 amp panels. You don't want to pull 90 amps from one and only 10 amps from the other, defeating the purpose of splitting the load.2.

Future Expansion

Will you need more power in the garage/barn in the future? Running larger feeders (e.g., capable of 125 amps or 150 amps) now, even if you don't immediately use the full capacity, could save you significant cost and hassle later.3.

Demand Factors

The NEC allows for "demand factors" in load calculations. This means you don't necessarily have to account for every possible appliance running at its maximum amperage simultaneously. However, applying demand factors correctly requires expertise.4.

Permitting and Inspection

This is essential! Any electrical work like this requires a permit from your local building department. A qualified electrical inspector will review your plans and inspect the work to ensure it meets code and is safe. Do not skip this step.5.

Alternatives

Depending on your actual load calculations, other options might be better. For example:

Single Larger Feeder

Instead of two 100 amp feeds, could you run a single 200 amp (or 150 amp) feeder from one of your house panels? This might simplify the wiring and panel configuration in the garage/barn. This depends on the load available on your existing 200A panels

Subpanel on the 400A service

Instead of running from the existing 200A panels, perhaps a subpanel that branches off of the 400A service before the two existing panels. This could provide a cleaner separation of loads.

Recommendations


Hire a Qualified Electrician

This is not a DIY project for most homeowners. Electrical work is dangerous and must be done correctly to ensure safety and code compliance. A licensed electrician can perform the necessary load calculations, design the electrical system, obtain permits, do the wiring, and ensure the installation passes inspection.2.

Detailed Load Calculations

Work with the electrician to create very detailed load calculations for both your house and the garage/barn. Be realistic about your current and future needs.3.

Get Multiple Bids

Obtain quotes from several reputable electricians to compare pricing and ensure you're getting a fair deal.4.

Plan for the Future

Consider your future power needs in the garage/barn when designing the system. It's often cheaper to oversize the wiring now than to upgrade it later.

In Summary

Your plan can* work, but it critically depends on accurate load calculations and compliance with all applicable electrical codes.

Consult with a qualified and licensed electrician for professional guidance and to ensure the safety and legality of your installation. Don't take shortcuts or make assumptions – electricity is not something to gamble with. Flag for review